Brucella species (Brucellosis)

Authors: Edward J. Young, M.D.

Brucellosis is a zoonosis that exists worldwide and is caused by bacteria belonging to the genus Brucella. Humans are accidental hosts who contract the disease from direct contact with infected animals, their blood, or secretions, or by ingestion of their milk.


The brucellae are small gram-negative coccobacilli that lack flagellae, endospores or native plasmids. They belong to the alpha-2 subgroup of Proteobacteria, phylogenetically closely related to plant pathogens and symbionts such as Agrobacterium and Rhizobium and other intracellular animal parasites such as Bartonella and Rickettsia (125).  The organism is an intracellular pathogen capable of replicating within phagocytic and non-phagocytic cells of the host. The genus brucella is considered monospecific on the basis of nucleic acid homology and gene sequencing (42); however, because of differences in natural hosts, differences in pathogenicity, and evolutionary history, the traditional (named) nomen-species classification has been largely retained. Among the ten organisms that comprise the genus, those most commonly causing human infection and their natural hosts are: B. melitensis(goats and sheep), B. suis (swine), B. abortus (cattle), and B. canis (dogs). The role in causing human infection of brucellae isolated from marine mammals:


Brucellosis exists worldwide but is especially prevalent in the Mediterranean basin, the Arabian peninsula, the Indian subcontinent, and in parts of Mexico, Central and South America.  Since the control of bovine brucellosis in the United States, the incidence of human brucellosis has declined to approximately 100 reported cases annually (139142).  Once a disease associated with animal husbandry, the epidemiology of human brucellosis has changed in recent years to one associated with food primarily with the importation of dairy products from areas where the disease remains enzootic (43).  In the southern United States, feral swine remain a reservoir for Brucella suis and hunters should use barrier precautions when field dressing these animals (41). Human to human infection is rare but sexual transmission has been documented (120) and the organism can be a risk for laboratory personnel ( 33122132154).


Brucellosis in humans is a systemic infection with protean clinical manifestations (138216). Characteristically patients present with fever, sweats, fatigue, and back pain.  Abnormal physical findings are few with the exception of occasional hepato-splenomegaly. When the disease manifests primarily in a given organ system, eg. osteoarticular, cardiovascular, neurologic, etc. it is termed complicated or localized; however, the course of illness varies little whether localized or generalized (4571114).  On rare occasions localized disease becomes chronic with periodic relapses of symptoms.

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The diagnosis of brucellosis is made with certainty by isolation of a Brucella species from blood, bone marrow or other tissue.  A presumptive diagnosis can be made by demonstrating high or rising titers of specific antibodies in serum (8).  A variety of serologic tests have been applied to the diagnosis of brucellosis including Rose Bengal agglutination (54), serum agglutination or Wright’s test (214), enzyme-linked immunosorbent assay (ELISA) (65) and a rapid lateral flow assay (170).  Brucella ELISA is generally a reliable assay (65), however, due to problems with the IgM test, it is recommended that ELISA results should be confirmed using agglutination tests (3952201). A variety of polymerase chain reaction (PCR) techniques using a variety of primers have been applied to the diagnosis of brucellosis (128); however, the sensitivity, specificity and issues of quality control must be validated before PCR can be used in routine clinical practice (129149219).


Brucella species are facultative intracellular pathogens that have the ability to survive within phagocytic cells of the host. Following inoculation into the body via ingestion, inhalation, or by direct contact with skin abrasions or the conjunctiva, the bacteria localize within cells of the mononuclear phagocytic system including lymph nodes, liver, spleen and bone marrow. Humoral antibodies directed primarily against cell wall lipopolysaccharide (LPS) appear to play some role in resistance, however recover appears to be principally mediated by cellular immune factors (211).  A variety of antimicrobial drugs have activity against Brucella, however, the results of in vitro susceptibility tests do not always correlate with clinical efficacy.  This is believed in part to be the result of the intracellular location of the organism which provides some protection against host defenses and antimicrobial drug effects. For this reason prolonged treatment with several drugs is usually required to achieve a cure (176).


Working with Brucella species is a risk to laboratory personnel and level 3 biohazard precautions are recommended. Periodic serologic testing of those handling brucellae is advisable (159).  Brucella species have relatively simple nutritional requirements, however, they grow slowly in vitro.  They can be cultured on any peptone-based media supplemented with serum, including blood and chocolate agar. Some strains of Brucella require supplemental CO2 especially for primary isolation. Historically, a variety of media, inoculum, incubation times and atmospheric conditions were used in susceptibility testing. An acceptable approach is the National Committee for Clinical Laboratory Standards (NCCLS) method modified to substitute trypticase soy broth (TSB) for Mueller-Hinton broth (MHB) supplemented with 6% CO2 (126127). By convention a test inoculum of 5 X 105 to 1 X 106 CFU of bacteria incubated at 350C for 48 hours is generally used. Alternatively, the bacteria can be suspended in MHB to turbidity equal to that of a 0.5 McFarland standard after which 10 uL is spread on Mueller Hinton agar plates supplemented with 5% sheep blood and E-test strips are applied.  Following incubation for 48 hours, the results are evaluated according to the manufacturer’s instructions with MIC50 and MIC90 (MICs for 50% and 90% of the organisms respectively).

To test for synergy between combinations of antimicrobial agents, most authors recommend conventional checkerboard techniques using reagents, inocula, and conditions of incubation similar to those used for standard MIC tests (102). The nature of the ensuing interaction between antimicrobial agents is determined by the fractional inhibitory concentration index (FIC index) with antagonism defined as an FIC index > 2.0, indifference  as FIC index 0.5-2.0, and synergy as FIC index < 0.5 (131). The E-test method of synergy employs a strip of the antibiotic applied to the surface of 5% sheep blood agar plates and left for 1 hour at room temperature. Next the strip of drug A is removed and another strip (drug B) is applied onto the imprint of strip A.  The plates are then incubated at 35C for 48 hours under anaerobic conditions and the MIC levels of each drug and combinations are recorded.  Although not standardized, the E-test method has been compared to the checkerboard method for determining synergy with agreement between them of varying from 55% (135) to 100% (79).

Another method of testing antimicrobial susceptibility of brucellae singly or in combinations, uses the rate of in vitro bacterial killing (156). The antibiotics at a concentration four times their respective MIC are incubated for 48 hours in tubes of broth containing 105 CFU of brucellae. Aliquots are removed at timed intervals (0 – 96 hrs) and mixed with warm molten agar in 103 to 105 dilutions and the number of CFU determined by the pour plate method. 

Finally a variety of laboratory animal models have been used to test the benefit of antimicrobial agents against Brucella species in vivo.  Although animal models have been no more predictive of clinical success than in vitro tests (57145), they have been used to study novel delivery systems such as liposomal encapsulation (70) and to confirm the superiority of combination drug therapy (109164).

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Single Drug Susceptibility


As early as 1944 crude penicillin was shown to be active against Brucella species, but the effect was least against strains of B. melitensis (192). When crystalline penicillin G was tested against various Brucella species the MIC50 was 12.5 ug/mL and the MIC90 was >100 ug/mL (84). Ampicillin was found to be more active than penicillin G by several investigators (8284126164). The inhibitory concentrations for ampicillin ranged from 0.5 ug/mL to 8 ug/mL with the MIC50 between 0.5 ug/mL and 1.0 ug/mL.  Since it is estimated that serum concentrations of ampicillin can range between 4 – 5 ug/mL the drug should be therapeutic for some but not all Brucella strains.  Consequently, it is not surprising that clinical results with ampicillin and amoxicillin have been disappointing (85118). The semisynthetic penicillins (methicillin, nafcillin, oxacillin) and the ureido-penicillins (carbenicillin, piperacillin) are much less active than ampicillin against Brucella with MIC90 values of 12 ug/mL and 32 ug/mL respectively (84126). Other penicillin analogues including carboxypenicillins and ureidopenicillins have little activity against brucellae. Among the carbapenams, ertapenem has been shown to inhibit Brucella in vitro (188), but it has not been studied clinically.


There are wide variations in the activities of cephalosporin antibiotics against Brucella species. The first generation cephalosporins are similar to penicillin G with generally high MIC values; however, third and fourth generation drugs have better activity and are better able to penetrate the blood/brain barrier.  Among third generation cephalosporins cefotaxime, ceftizoxime and ceftriaxone were found to have good activity against Brucella melitensis (137157) Table 1. These drugs achieve reasonably good levels in CSF in the presence of inflamed meninges suggesting they might have a role in treating neurobrucellosis (140).  However, cephalosporins are never first line treatment regardless of in vitro susceptibility, since clinical results with ceftriaxone, for example have been disappointing (107). Moreover, whereas brucellae showed little resistance early on to ceftriaxone (2730), recent reports indicate increasing MIC values for the drug in some regions (1187).


The  macrolide antibiotic erythromycin was shown to have activity in vitro against Brucella with over one-half of 27 strains of various species inhibited by 0.15 ug/mL and 100 % inhibited by 2.5 ug/mL (84). Another study found a range of inhibitory concentrations between 0.5 ug/mL to 8 ug/mL (126), while a third study yielded a MIC range of 0.5 ug/mL to 256 ug/mL (4). Thus it is not surprising that monotherapy with erythromycin resulted in unacceptably high rates of relapse (37198). Even when used in combination with streptomycin, the response was poor and gastrointestinal side effects were magnified (67). In an extensive review of treatments for human brucellosis, Hall reported an overall rate of relapse of 27% with erythromycin alone or in combination (85).

In contrast, azithromycin and clarithromycin are significantly more active against Brucella species than erythromycin (MIC range 0.1 ug/mL to 4 ug/mL and 0.06 ug/mL to 8 ug/mL respectively) (105146). These drugs achieve good serum levels after oral administration and their tissue concentrations exceed serum levels by as much as 100-fold.  Furthermore, azithromycin is concentrated within phagocytic cells (neutrophils and macrophages) without interfering with the bactericidal activities of the cells (117). Despite these favorable characteristics, azithromycin was found to be less effective than doxycycline in eradicating brucellosis in a mouse model (57).  Moreover, there was a 50% failure rate among patients treated with azithromycin for 21 days plus gentamicin for 7 days (178). One possible contributing factor to the discrepancy between in vitro and in vivo results is the potential loss of activity of azithromycin at acid pH (4).


Chloramphenicol is mentioned only because it has some activity in vitro against Brucella species and it found limited use in human brucellosis during the 1940s and 1950s (85).  The activity in vitro of chloramphenicol against Brucella species is variable with a range of MIC values from 1.25 ug/mL to 5 ug/mL (84126).  From the literature, among 47 patients treated with chloramphenicol the rate of relapse was 32%.  In view of this high failure rate, the potential for serious hematologic side effects, and the availability of safer and more effective agents, chloramphenicol cannot be considered appropriate therapy for human brucellosis.


The tetracyclines remain the most active and clinically effective antibiotics for the treatment of brucellosis and they are the standard against which all other drugs are measured.  Although differences in the in vitro activities of tetracycline analogues against Brucella species have been reported, since 1955 tetracycline HCl has been the most frequently prescribed drug for treating human brucellosis (85).  Tetracycline achieves a serum level of about 4 ug/mL after an oral dose of 500 mg whereas, the long-acting analogues (doxycycline and minocycline) achieve a prolonged serum level of 2.5 ug/mL following a dose of 200 mg (158). Doxycycline is almost completely absorbed and has a prolonged half-life due to its slow rate of renal excretion.  In addition, doxycycline is the only tetracycline compound that can be used in patients with renal insufficiency since it is excreted from the gastrointestinal tract under that condition (203). The low MIC values against Brucella species, the convenience of once daily dosing, and the low rate of side effects makes doxycycline the preferred tetracycline analogue for treating human brucellosis (Table 2).  These factors not withstanding, the use of tetracyclines as monotherapy is complicated by a relapse rate between 8% and 39%.  The high relapse rates are dramatically reduced when doxycycline therapy is combined with other drugs, such as streptomycin (relapse rate 4.5%) or rifampin (relapse rate 8.4%) (85). A major drawback to the use of tetracyclines is permanent staining of teeth in young children. Consequently, tetracyclines are contraindicated for brucellosis during pregnancy or in children less than 8 years of age (Table 8).

Tigecycline, a semisynthetic derivative of minocycline, is the first glycylcycline in clinical use and has a broad spectrum of activity against both Gram positive and Gram negative bacteria (62). Tigecycline must be administered parenterally but achieves high levels in the tissues and within phagocytic cells (185). Currently tigecycline is approved for complicated intra-abdominal and skin/skin-structure infections in adults at an initial dose of 100 mg intravenously followed by 50 mg every 12 hours, but dosing guidelines have not been established for children. It has good activity against Brucella species (2855188195), and some have suggested that it should replace doxycycline as the preferred tetracycline analogue for the treatment of human brucellosis (141). However, the requirement for parenteral administration, its usefulness against multi-drug resistant bacteria, and the lack of trials using the drug clinically make this recommendation premature.


Streptomycin was shown to have activity against Brucella species in vitro with MIC values of 1 ug/mL to 5 ug/mL (85) however when used as monotherapy for human brucellosis it was ineffective (92). In addition, occasional streptomycin-resistant strains were isolated from patients treated with streptomycin alone (218). Consequently, streptomycin was always used in combination with other drugs, initially sulfadiazine and later tetracycline (85).  For many years the recommended therapy for human brucellosis was tetracycline (500 mg four times daily by mouth) given for 4 to 6 weeks plus streptomycin (1 g daily intramuscular) for the first two weeks (206). The discrepancy between in vitromethods for evaluating antibiotic efficacy is illustrated by bacterial killing studies showing that streptomycin exhibits the most rapid rate (complete killing of log10 CFU at 4 times MIC in 8 hours) against B. melitensis (156).  Studies comparing the activity of other aminoglycosides to streptomycin in vitro showed that gentamicin was more active, kanamycin and tobramycin were equivalent, and amikacin was less active (Table 3). Netilmycin, an aminoglycoside derived from sisomycin, was reported to have an MIC value of 0.6 ug/mL againstBrucella species, however, when used in combination with doxycycline to treat brucellosis the rates of failure and relapse were unacceptably high (174).  Spectinomycin was also shown to have activity in vitro (MIC range 1 ug/mL to 5 ug/mL), but it has not been used clinically (48).  Although highly effective when used in combination with tetracyclines (see section on combinations of drugs), monotherapy with aminoglycosides is not recommended. Although they concentrate within phagocytic cells, aminoglycosides are extremely pH susceptible and may be effected by the low pH within the lysosomal cell compartment in which they concentrate (116).

Trimethoprim/Sulfamethoxazole (Co-trimoxazole)

Trimethoprim, a 2,4-diamino-5-(3’,4’,5’-trimethoxy benzyl) pyrimidine, is a potent inhibitor of dihydrofolate reductase. The antimicrobial action of trimethoprim is potentiated by combination with sulfamethoxazole.  The synergistic action of trimethoprim/sulfamethoxazole (TMP/SMX) depends somewhat on the sensitivity of the organism to each compound. Co-trimoxazole is available in a fixed combination in a ratio of 1:5 (80 mg trimethoprim, 400 mg sulfamethoxazole).  Double-strength tablets, quarter-strength (pediatric dose) tablets, and an intravenous preparation (16 mg/mL trimethoprim, 80 mg/mL sulfamethoxazole) are also available.  After oral administration of a single-strength tablet, the peak level of trimethoprim is 3.5 mg/mL after about 2 hours.  The CSF concentration of trimethoprim is approximately 40% of the serum concentration (221).   In vitro susceptibility of Brucella   species to TMP/SMX individually or in combination has been reported with variable results (Table 4). Although some patients have been treated successfully with co-trimoxazole (189), relapse rates in excess of 40% have been reported in open trials (17) and in a prospective comparative study (18). Among 143 blood isolates of B. melitensis in Saudi Arabia over a twelve year period, 29% were resistant to TMP-SMX but the rate of resistance did not increase over time (121). Regardless, co-trimoxazole is a useful alternative in the treatment of brucellosis when the use of tetracyclines is contraindicated (eg. in children and in pregnancy) (110); however it is best used in combination with other drugs such as rifampin (86155).


Rifampin is a semisynthetic derivative of rifomycin B, a macrocyclic antibiotic produced by the mold Nocardia mediterranei (formerly Streptomyces mediterranei).  The drug is remarkably lipid soluble and accumulates in eukaryotic cells.  It exerts its antimicrobial effect by inhibiting DNA-dependent RNA polymerase.  Rifampin is almost completely absorbed after oral ingestion and reaches a peak serum concentration of 7 ug/mL to 10 ug/mL after a 600 mg dose.  Rifampin penetrates tissues well and levels of 1.3 ug/mL are found in the CSF in the presence of inflamed meninges (36). Since plasma clearance is via the enterohepatic circulation, rifampin can be given to patients with renal insufficiency; however drug-induced hepatitis and cholestatic jaundice have been reported especially in alcoholics or patients treated with isoniazid.  Rifampin induces hepatic microsomal enzymes which can result in accelerated metabolism of some other drugs such as warfarin, oral contraceptives, glucocorticoids, digoxin, quinidine, and oral hypoglycemic (26). The in vitro susceptibility of Brucella species to rifampin has been documented by numerous investigators (Table 5).  Corbel reported that rifampin was bactericidal at concentrations four times the MIC however rifampin resistant variants occurred frequently irrespective of the antibiotic concentration (49).  Although rifampin has been used as monotherapy, relapses and the emergence of resistant strains (194) have led to its use primarily in combination with other drugs (96).


Quinolones are derivatives of nalidixic acid, an oral agent introduced in 1963 to treat urinary infections.  Nalidixic acid was only weakly active against Brucella species (MIC90 64 ug/mL) and serum concentrations were too low to be effective in human brucellosis (85108). In the 1980s, the development of fluorine- and piperazinyl-substituted derivatives with greater antimicrobial activities and expanded spectra, renewed interest in this class of drugs.  Quinolones block bacterial DNA synthesis by inhibiting the enzymes DB+NA gyrase and topoisomerase IV (89).  With the proliferation of fluoroquinolones since the early 1990s they have been classified into generations in a manner similar to the cephalosporins based on their spectrum of antibacterial activity (1690).  Quinolones are well absorbed after oral administration and following a 400 mg dose, serum levels range from 1.5 ug/mL for norfloxacin to 5.8 ug/mL for perfloxacin. The drug is concentrated in macrophages and neutrophils but penetration into CSF is low except for perfloxacin (40% of serum level) and ofloxacin (90% of serum level).

The quinolones have greater activity against Brucella species than nalidixic acid, but the MIC values vary for each compound and to some extent for Brucella isolates and several studies showed that activity was decreased at low pH (72).  The in vitro activity of various quinolones and their use clinically has been thoroughly reviewed through 2004 by Falagas and Bliziotis (66). Recent selected studies of quinolones against Brucella spp. are listed in Table 6.  A major issue with the quinolones is the emergence of resistance that can be both chromosomally induced or via plasmids (95). Despite good in vitro activity of some quinolones, especially ciprofloxacin and ofloxacin, when used alone for human brucellosis, relapse rates were unacceptable (1256). Consequently monotherapy of brucellosis with quinolones is not recommended and they should be used in combination with other antimicrobial agents (66216).

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Combinations of Drugs

Penicillin and Sulfathiazole

Of historic interest T’Ung reported that penicillin combined with a small amount of sulfathiazole inhibited some strains of Brucella more effectively than either drug alone (192). Although these drugs are no longer used to treat brucellosis, this early study suggested that combinations of drugs might be synergistic against Brucellaspecies.

Tetracycline and Streptomycin or Gentamicin

Tetracycline and streptomycin were reported to act synergistically in inhibiting the intracellular replication of B. abortus in primary cell cultures. Tetracycline, bacteriostatic at concentrations of 0.5 ug/mL to 1.0 ug/mL became bactericidal when combined with 10 ug/mL of streptomycin (152). In vitro synergy between tetracycline and streptomycin was also reported in a murine model of brucellosis (88), however using BALB/c mice infected with B. melitensis Domingo et al. found the combination of doxycycline and streptomycin to be no more effective than doxycycline alone (5859).  Attempts to demonstrate synergy in vitro have been less successful.  Robertson et al studied 25 strains of B. abortus and were unable to show synergy between tetracycline and streptomycin (153). Using conventional checkerboard microdilutions of combinations of tetracycline and streptomycin Mortensen et al. were unable to show synergy for 5 of 8 strains of Brucella species (126).  In three cases the combination was actually antagonistic as calculated by the fractional inhibitory concentration (FIC) index, whereas, combinations of tetracycline and gentamicin were indifferent for eight strains tested.  Ariza studied antimicrobial sensitivities of B. melitensis recovered from patients with bacteriologic relapse and found no difference between the original isolates and the relapse strains (20). Synergy for the antibiotic combinations could not be assessed because of the very low MIC values for tetracycline and doxycycline among these isolates.  Rubinstein et al. used the agar plate and broth dilution methods to study combinations of antibiotics against 15 strains of B. melitensis. They found that combinations of minocycline, ciprofloxacin, rifampin and streptomycin exhibited synergy against any of the strains tested. However, when bacterial killing rates were compared, streptomycin combined with minocycline, rifampin or ciprofloxacin showed the faster killing than the drugs alone (156). Recently, Orhan et al. compared five different antibiotic combinations using both checkerboard and E-test methods against 16 strains of B. melitensis (135).  The results by both methods were in agreement in 44 (55%) of 80 tests and was most marked for the combination of streptomycin plus doxycycline (synergy = 7/16 by microdilution and 11/16 by E-test). In contrast, using the E-test method, Dizbay found no synergy with the combinations of doxycycline plus streptomycin or tigecyclin plus streptomycin against 16 strains of B. melitensis (55).

Tetracycline and Rifampin

Using the checkerboard microdilution method Mortensen et al. reported that the combination of tetracycline and rifampin was synergistic for 6 of 8 strains of Brucella species and indifferent for 2 strains (126). Orhan et al. using both microdilution and E-test methods found synergy between doxycycline and rifampin in 10/16 and 15/16 strains of B. melitensis respectively (135) whereas, Dizbay et al. using the E-test method reported 100% synergy in the combinations of doxycycline plus rifampin and tigecycline plus rifampin against 16 strains of B. melitensis (55). In contrast, using the checkerboard method, Aliskan et al. found some synergy between tigecycline and rifampin, gentamicin and levofloxacin but none when tigecycline was combined with minocycline, streptomycin or co-trimoxazole (15).

Trimethoprim and Sulfamethoxazole

Co-trimoxazole is compounded as a fixed combination containing 80 mg of trimethoprim and 400 mg of sulfamethoxazole, however each component has been tested against Brucella species alone and together.  Lal et al. reported that MIC values against two strains of B. abortus declined from 15 ug/mL for trimethoprim and 3 ug/mL for sulfamethoxazole individually to 0.05 ug/mL and 0.1 ug/mL respectively when combined (104).  Using an agar dilution method and a heavy inoculum of B. abortus Robertson et al. reported that 25 strains had MIC values of 32 ug/mL for trimethoprim and 2 ug/mL for sulfamethoxazole individually. When combined the MIC values were reduced to 2 ug/mL for trimethoprim and 0.125 ug/mL for sulfamethoxazole indicating a 16-fold synergy (153). Shir and Michel also reported synergy between trimethoprim and sulfamethoxazole against 31 strains of Brucella species in Israel (167).  Using both checkerboard (CB) dilutions and E-test methods, Orhan et al. found the combinations of TMP/SMX plus doxycycline and TMP/SMX plus rifampin to show synergy in 4/16 and 2/16 respectively by CB and in 6/16 and 6/16 respectively by E-test (135).

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In 1958 the Expert Committee on Brucellosis of the World Health Organization concluded that treatment of human brucellosis (a) shortened the clinical course of the disease, (b) lessened complications, and (c) reduced fatalities (204). Spink likened brucellosis to tuberculosis, another facultative intracellular pathogen, that produces an illness characterized by the persistence of organisms in the tissues of a host rendered hypersensitive to antigens of the bacteria (183). In a murine model, Spink showed that infection with B. melitensis could not be eradicated with tetracycline alone even after months of treatment (184). Such experimental data plus clinical reports showing rates of relapse of 15% to 30% with single drug therapy led to the conclusion that prolonged treatment with combinations of drugs was required to achieve a cure in human brucellosis (85).  Similarly, single drug therapy with other antimicrobial agents including ceftriaxone (107), co-trimoxazole (18), rifampin (194), and ciprofloxacin (106) have indicated that monotherapy of brucellosis is at best unwise and generally not recommended in most cases (180). The recommendation against single drug therapy for human brucellosis was also confirmed by three recent reviews including two meta-analyses of the published literature (2451169).

Combination Therapy

In 1965 the WHO recommended a regimen consisting of tetracycline (500 mg four times daily by mouth) for 4 to 6 weeks plus streptomycin (1 gram daily intramuscular) given for the first 1 to 3 weeks for the treatment of brucellosis in humans (205).  When doxycycline became available, it had the advantage of twice daily dosing with fewer side effects (mostly gastrointestinal) and it soon replaced tetracycline HCl as the preferred tetracycline analogue.  Subsequently, studies comparing the aminoglycoside component of the combination (gentamicin versus streptomycin) generally favored gentamicin Table 7.

In 1986 the WHO attempted to simplify the treatment of brucellosis by recommending totally oral therapy with the combination of doxycycline and rifampin with both drugs administered for 45 days (206).  Although this therapy had some success, when the oral regimen was compared in controlled trials with the previously recommended treatment that included an aminoglycoside, it became apparent that it was inferior (44173) Table 7. The cause of this difference is not known with certainty, however, several investigators produced evidence that rifampin (a potent inducer of hepatic microsomes) resulted in lower serum levels of doxycycline (172). In the 28 years since the publication of the WHO Report, there have been numerous studies from a variety of countries where brucellosis remains enzootic reporting on various regimens of antimicrobials in the treatment of human brucellosis.  It is not always possible to make direct comparisons because of differences in the cases studied; for example, studies of patients with spinal complications (5), differences in drug doses, differences in duration of therapy and differences in study design (prospective vs retrospective). In addition to traditional combinations of drugs, recent studies have included combinations of quinolones and rifampin, co-trimoxazole and rifampin, and even triple regimens with doxycycline, rifampicin and amikacin (150). In addition, there are three current reviews of the subject with meta-analyses of the data (2451169). Overall, from the published data certain facts have emerged: (a) longer duration of treatment is preferable to short duration, (b) gentamicin is equivalent to or better than streptomycin when combined with doxycycline, (c) a regimen of doxycycline plus an aminoglycoside is associated with less failure/relapse than doxycycline plus rifampin, and (d) current data do not support the use of quinolones as primary therapy.  With respect to the comparisons between doxycycline plus streptomycin versus doxycycline plus rifampin, a Cochrane review concluded that the two regimens were comparable in the short term, however, when data were compared long term (> 6 months), the rifampin containing regimen was associated with more treatment failures (217).

Concerns that have been raised regarding the treatment of human brucellosis include the need for prolonged therapy, and the cost of antimicrobial agents, especially in developing countries where the disease remains enzootic (186).

Drug of Choice

On the basis of available data, the treatment of choice for human brucellosis is the combination of doxycycline (200mg daily by mouth) administered for 45 days plus streptomycin (1 gram daily intramuscular) for 14 days or gentamicin (5mg/kg daily intramuscular or intravenous) for 7 days (Table 8). The alternative is combined doxycycline and rifampin in uncomplicated cases without focal involvement. Some clinicians prefer to begin with the doxycycline plus aminoglycoside regimen and after the 14 days of streptomycin (or 5 days or gentamicin) continue doxycycline plus rifampin for the remaining 45 days, however, this approach has not been studied in clinical practice.

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Special Situations


Depression and mental inattention are common complaints of patients with brucellosis, however direct invasion of the central nervous system (CNS) is said to occur in less than 5% of cases (60165). A variety of nervous system complications have been reported involving the CNS, peripheral nervous system (PNS) and a combination of the two (13). These include meningitis/meningoencephalitis (32119), myelitis/reduculoneuronitis (119), brain abscess (161), demyelinating syndromes (77), spinal epidural abscess (197), and meningovascular syndromes (3). Rare cases of recurrent episodes of migraine-like headaches with or without isolated cranial nerve palsies have been reported (199212). Meningitis is the most frequent CNS complication and it can be acute or chronic (32). CSF findings in brucellar meningitis include lymphocytic pleocytosis, elevated protein, decreased glucose and the presence of brucella-specific antibodies (81, 46).

Treatment of neurobrucellosis poses special problems because of the need to achieve high concentrations of antimicrobial drugs in the CSF.  Unfortunately, some of the most commonly used drugs, especially the aminoglycosides, do not penetrate the blood/brain barrier in sufficient concentrations to treat Gram-negative meningitis effectively.Doxycycline, but not all tetracyclines, and rifampin both traverse the blood/brain barrier especially in the presence of inflammation. Ceftriaxone, a third-generation cephalosporin often used as empiric treatment of bacterial meningitis (193) has some activity against Brucella species (Table 1), and its use in combination with other antimicrobial agents is recommended by some authors without objective evidence of superiority over other combinations (63140).  A variety of antibiotic combinations have been used for varying periods of time but there is still no consensus for choice of drugs, dose, or duration of therapy for neurobrucellosis (81).  Most authorities recommend doxycycline, rifampin and a third agent, either TMP-SMZ or ceftriaxone given for periods that range from 6 weeks to 18 months. Generally clinical and serologic responses and CSF parameters are used to monitor the course of treatment (77). Another point of disagreement is the value of administering corticosteroids in addition to antimicrobial agents in neurobrucellosis but no firm recommendation either for or against is possible at this time (98).

Cardiovascular Complications

Infective endocarditis occurs in less than 2% of patients with brucellosis, however, in countries where the disease is enzootic, 4% to 8% of cases of endocarditis are caused by Brucella species (69).  In the pre-antibiotic era infective endocarditis was the most frequent cause of death from brucellosis (43).  Infection can occur on native and prosthetic heart valves with the aortic valve involved most often (93151). Mycotic aneurysms of the brain (10), the aorta, and other blood vessels are secondary complications, especially when infection is caused by B. suis (91). Vascular thrombosis is a rare complication of an intense vasculitis (133220). Pericarditis complicating brucellosis is rare, but it can occur apparently distinct from endocarditis (75). Although rare, patients who reside in, or travel to areas where brucellosis is enzootic can have implantable cardiac device infections due to brucella (5053).

Infective endocarditis presents a special problem because of the need for bactericidal concentrations of drug within the vegetations. Although there are reports of successful treatment of brucella endocarditis with antibiotics alone, most patients have required drug therapy combined with valve replacement surgery (94151136162). Although tetracyclines are considered only bacteriostatic, combination with an aminoglycoside results in rapid killing of Brucella species (156).  Currently the medical therapy of Brucellaendocarditis is not clearly established, however, cures have been reported with combinations of tetracycline plus streptomycin, and doxycycline plus rifampin.  The use of rifampin in addition to the combination of doxycycline plus streptomycin (or gentamicin) is advocated because of its excellent tissue distribution and penetration into valvular vegetations (151). Most authorities recommend antibiotic treatment prior to surgery for several weeks if possible followed by surgery and post-operative antibiotics for periods ranging from 2-6 months (136162).

Osteoarticular Complications

Bone and joint involvement is especially common in brucellosis, occurring in up to 66% of patients in some series.  Although any bone or joint can be involved, sacroiliitis and spondylitis account for more than 80% of cases (45). Sacroiliitis is more likely to occur in younger patients (22) whereas, spondylitis and osteomyelitis occur more frequently in older patients (47177). Most patients respond to antimicrobial therapy alone, however some authorities recommend that patients with spondylitis receive therapy for 3 months or more (47). Surgical intervention is rarely necessary except for drainage of large paravertebral abscesses, in patients with neurologic deficits from epidural abscess, or when spinal instability threatens serious neurologic injury (19177).

A number of cases of bone or joint prosthesis infections due to Brucella species have been reported (35200). A variety of antibiotic combinations have been used and treatment times ranged from six weeks to twenty-six months. In some cases treatment with antibiotics alone was curative, in others the prosthesis was removed followed by one-stage or two-stage re-implantation. Not enough cases have been studied to provide a standardized guideline.

Brucellosis in Children

Brucellosis was once considered rare in children, and when it occurred, the symptoms were said to be mild (83). This belief was based on studies with B. abortus infection which is principally occupation related, occurring mainly in working adults.  In contrast, infection with B. melitensis is primarily foodborne (43213), and in countries where this nomen species is enzootic childhood brucellosis is common (1168).  Reports of complications in children with brucellosis prove that the disease is similar for patients of all ages. Similar to adults, osteoarticular involvement is common in childhood brucellosis manifested most often as monoarthritis of large weight bearing joints such as hips, knees and ankles (31166).

Tetracycline compounds are contraindicated in children less than 8 years of age owing to the risk of permanent staining of teeth. Consequently other drug combinations and other lengths of treatment have been tested (76111).  Lubani et al. studied 1100 children at three hospitals in Kuwait using different drugs and drug combinations for periods of 3-, 5-, and 8-weeks. Excluding monotherapy, all other regimens showed similar results irrespective of their duration and they recommended TMP/SMX for 3 weeks plus gentamicin during the first 5 days for children under 8 years and doxycycline or tetracycline for 3 weeks plus gentamicin for the first 5 days in children over 8 years (111).  In contrast, Al-Eissa et al. reported different combinations or TMP/SMX or tetracyclines with streptomycin or rifampin in 102 children and found that 3-week regimens resulted in unacceptably high rates of relapse (9). Gottesman et al. found that combination therapy administered for 4 weeks or longer yielded better results than monotherapy or shorter courses of treatment (76).  Other studies have confirmed that regardless of the drugs used, monotherapy and short-course therapy are associated with high rates of relapse and should be avoided (2160).  Hasanjani Roushan et al. compared treatment of 140 children with brucellosis using TMP/SMX plus rifampin for 6 or 8 weeks without an aminoglycoside and found failure/relapse rates of 10.9% and 4.5% respectively (86).

On the basis of available data (180) children 8 years of age or older with brucellosis can be treated like adults with doxycycline (200 mg daily) by mouth plus gentamicin (5 mg/kg daily intramuscular or intravenous) for 7 days or the combination of doxycycline (200 mg daily) plus rifampin (15-20 mg/kg daily) both drugs administered for 45 days. For children less than 8 years of age the current recommendation is oral rifampin (15-20mg/kg daily) for 45 days plus oral TMP/SMX (80/400 mg/kg twice daily) for 45 days plus intramuscular or intravenous gentamicin (5 mg/kg daily) for 7 days (Table 8).

Brucellosis During Pregnancy

Brucella species are known to cause spontaneous abortion in animals, and there is evidence that brucellosis can induce abortions in humans as well (63,100103). It is reported that brucellosis during pregnancy can lead to spontaneous abortion, premature delivery, congenital or neonatal infection, or in some cases a normal full-term delivery (14).  To that should be added the risk of transmission of infection to the obstetrician and other hospital personnel (122). A variety of antimicrobial drugs have been used in pregnant women with brucellosis including rifampin, TMP/SMX, alone and in combination, and rifampin plus ceftriaxone (78), however, most authorities recommend the combination of rifampin plus TMP-SMZ administered for 45 days (87).

Underlying Diseases

AIDS and other Immune Deficiency Syndromes

In view of the importance of  cellular immunity in recovery from brucellosis it is surprising that the disease has not been reported more often in patients infected with the human immunodeficiency virus (HIV-1). Moreno et al reported 12 HIV-infected patients with brucellosis and reviewed another 5 cases from the literature (124). The course of infection did not differ from that of HIV-negative individuals, including favorable responses to the usual regimens of antimicrobial drugs. It should be noted that most of these patients had relatively preserved immune function and were asymptomatic with respect to their HIV infection. Even in countries with a very high rate of HIV disease, the incidence of brucellosis in this population is low (112). Therefore, from the evidence available, brucellosis does not appear to be an opportunistic infection and it does not pose special problems in treatment. In countries where brucellosis is enzootic, rare cases have been reported among patients with malignant disorders or from immune suppression of tissue transplants (67).

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Regardless of the severity of clinical symptoms the vast majority of patients with brucellosis are cured with antimicrobial therapy alone.  Heart valve replacement may be necessary in patients with brucella endocarditis (94). Occasionally percutaneous or open surgical drainage of localized foci of infection (eg. pleural or pericardial effusions, tissue abscesses, etc.) is necessary for diagnosis or therapy. Epidural abscess is often a neurosurgical emergency and may require prompt surgical intervention to prevent permanent neurologic injury (197). Acute or chronic hepatosplenic abscess is another indication for surgical intervention when a course of antimicrobial therapy fails to resolve the condition (23). In addition, patients with brucella epididymoorchitis may require orchiectomy when antimicrobial therapy fails or when the diagnosis is in question and the risk of testicular cancer is high (130).


Routine laboratory tests such as white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) are of little value in diagnosing brucellosis or monitoring the outcome of therapy (215). Therefore, the principal indicator of a good therapeutic response is the resolution of clinical symptoms without their recurrence after stopping treatment. Serologic tests are also useful, but it should be noted that the titer of specific antibodies declines very slowly over time (214). Buchanan et al. studied 200 patients treated for brucellosis using agglutination assays. Over time, the proportion of patients with positive titers progressively declined so that at 2 years post-treatment, only 1% were still seropositive (34).  Using the brucella ELISA to follow patients treated for brucellosis, a successful outcome was characterized by a progressive decline in IgM, IgA, and IgG antibodies, whereas, a persistent elevation of IgG antibodies presaged relapse or chronic infection (74144). Using quantitative polymerase chain reaction Navarro et al. showed that both patients who relapsed and patients that did not relapse had detectable levels of specific brucella DNA in their serum even after successful antimicrobial therapy (129). The authors point out that finding bacterial DNA persisting in the serum of patients lacking symptoms of active infection is not an indication for re-treatment, however, it can be an indicator of relapse in patients with persistent symptoms.


Currently the only licensed brucella vaccines are veterinary products for use in domestic and semi-domestic animals. Brucella abortus strain S19 and Brucella melitensis strainRev.1 are live attenuated smooth bacteria that have proved effective against infection in cattle and sheep or goats respectively, but they can cause brucellosis in humans and are therefore unsuitable for human immunization (29163). In the United States the use of S19 vaccine has been supplanted by the live rough attenuated strain of Brucela abortus RB-51. This vaccine lacks the polysaccharide O-chain and therefore does not induce circulating antibodies used to detect brucellsis in cattle while still inducing a strong cell-mediated immune response. While its virulence for animals is reduced, strain RB-51 is a potential hazard to humans and being rough, it is not detectable by serologic assays that employ O-polysaccharide antigen. Furthermore, it is rifampin-resistant, hence limiting antibiotic treatment of potential vaccine-associated infections. Fortunately, strain RB-51 appears to have low virulence for humans and few cases of vaccine-associated infections have been reported (25).  There are no vaccines for B. suis or other nomen species, however the threat of brucellosis as a bio-weapon has stimulated the search for an effective human vaccine (134).

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When brucellosis is suspected the laboratory should be notified in order to expedite recovery of the organism and to alert personnel to employ biohazard 3 precautions when handling samples (168190208).  Person-to-person transmission is extremely rare and when it does occur it appears to be sexually transmitted (120). In the routine care of patients with brucellosis, standard precautions are adequate. In countries where brucellosis is endemic serologic testing of bone marrow and other tissue donors may be warranted.

Postexposure Prophylaxis

There are no definitive guidelines for the use of post-exposure prophylaxis in persons suffering laboratory accidents with brucella samples or to accidental inoculation with live brucella vaccines. Nevertheless, based on largely anecdotal evidence, some authors have recommended antibiotic prophylaxis especially for individuals considered at high risk (154,159191209). Because of differences in determining levels of risk and the high rate of significant side effects of the antibiotics, other authors have questioned the role of post-exposure prophylaxis (101113). A variety of antibiotics and regimens have been proposed with CDC recommending the combination of doxycycline plus rifampin for 3 weeks (191). High risk exposure included direct exposure to brucellae such as sniffing bacteriologic cultures, direct skin contact, pipetting by mouth, inoculation or spraying into eyes, nose or mouth or exposure to aerosols outside a level 3 containment cabinet (40).


Chronic Brucellosis

Perhaps no aspect of brucellosis engenders more controversy than chronic illness. The problem is not whether the condition exists, but rather obtaining a consensus on a definition and how to make the diagnosis. Spink and associates showed that the majority of patients with brucellosis recovered within 12 months of receiving antimicrobial chemotherapy, but some patients continued to have clinical manifestations (181). Those patients with clinical complaints for greater than 12 months could be divided into those with objective signs of infection, such as elevated levels of antibodies and focal disease, and those lacking objective signs of disease whose complaints resembled the chronic fatigue syndrome (182). Patients with objective signs of infection, like patients with relapse, benefit from additional specific therapy, whereas those lacking objective signs of infection do not.  In addition to objective signs of disease, patients with chronic infection, like patients with relapsing brucellosis have persistently elevated levels of IgG antibodies in their serum (21).  With the development of polymerase chain reaction (PCR) technology, it became apparent that some patients with relapsing brucellosis also had persistent Brucellaspecies DNA in their serum as well (123). Subsequently, it was shown that some patients with acute brucellosis, despite apparently adequate chemotherapy, have detectable Brucellasp. DNA in their serum and some remain asymptomatic while others have symptoms typical of chronic brucellosis (38).   Others have reported that antibodies directed against a variety of Brucella sp. proteins might be useful in defining chronic brucellosis, but these studies are preliminary and require further analysis (207).

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Table 1. Minimal Inhibitory Concentration (ug/mL) of selected Cephalosporins against Brucella species






Drug MIC50 MIC90 MIC50 MIC90 (range) MIC50 MIC90 (range) MIC50 MIC90 (range)
Cephalothin 12.5 >100 8 32 (1-64) NTa NT NT NT
Cephalexin 12.5 >100 NT NT NT NT NT NT
Cefoxitin NT NT 4 16 (2-16) NT NT NT NT
Cefamandole NT NT 16 32 (4->64) NT NT NT NT
Moxalactam NT NT 8 16 (1-16) 16 16 6.26 50 (0.75-50)
Cefotaxime NT NT 1 2 (<0.5-4) 1 2 (0.5-2) 25 100 (12.5->100)
Ceftizoxime NT NT NT NT 0.5 1 (0.5-1) NT NT
Cefuroxime NT NT NT NT 32 32 (8-64) NT NT
Ceftriaxone NT NT NT NT 0.5 1 (0.25-1) NT NT
Ceftazidime NT NT NT NT 32 32 (16-32)   100 (25-100)
Cefprozil NT NT NT NT NT NT   100 (12.5->100)


Brucella species and no. tested
  Hall84 Mortensen126 Palenque137 Safi157
B. abortus 7 4 0 NRb
B. melitensis 2 7 83 NR
B. suis 10 2 0 NR
B. canis 4 2 0 NR

a NT = not tested

b NR = not reported

Table 2.  Minimal Inhibitory Concentrations (ug/mL) of Tetracyclines Against Brucella Species

Drug No. strains tested MIC90 (MIC range)a Reference
Tetracycline HCl 27 0.03 (0.001 – 0.07) Hall & Manion84 1970
98 0.39 (0.1 – 0.5) Gutierrez etal.80 1982
15 0.25 (<0.13 – 0.25) Mortensen etal.126 1986
95 0.25 (0.06 – 0.25) Bosch etal.30 1986
47 0.04 (0.001 – 0.6) Khan etal.99 1989
358 0.25 (0.06 – 0.5) Landinez etal.105 1992
105 0.25 (0.06 – 0.25) Quadri etal.148 1993
62 0.20 (0.01 – 0.20) Garcia-Rodriguez73 1995
11 0.5 (0.032 – 1.5) Turkmani etal.196 2006
Minocycline 27 0.30 (0.01 – 0.30) Hall & Manion84 1970
86 0.40 ( NR ) Rubinstein etal.156 1991
85 0.04 ( NR ) Al-Sibai MB etal.12 1992
Doxycycline 27 0.30 (0.01 – 0.30) Mortensen etal.126 1986
95 0.12 (0.06 – 0.25) Bosch etal.30 1986
16 0.25 (0.047 – 0.25) Dizbay etal.55 2007
82 0.047 (<0.016 – 0.125) Turan etal.195 2007
20 0.064 (0.064 – 0.125) Marianelli115 2007
56 0.064 (0.023 – 0.125) Bayram etal.28 2011
Tigecycline 16 0.094 (0.064 – 0.125) Dizbay etal.55 2007
82 0.125 (<0.016 – 0.125) Dizbay etal.55 2007
38 0.25 (0.25 – 0.5) Tanyel etal.188 2010
56 0.094 (0.019 – 0.25) Bayram etal. 2011

a NR = not reported

Table 3. Minimal Inhibitory Concentrations (ug/mL) of Aminoglycosides Against Brucella Species

Drug No. strains tested MIC90 (Range)a Reference
Streptomycin 27 2.5 (0.02 – 5.0) Hall & Manion84 1970
8 4.0 (1.0 – 4.0) Mortensen etal.126 1986
95 0.5 (0.12 – 1.0) Bosch etal.30 1986
47 2.5 (0.15 – 5.0) Khan etal.99 1989
86 3.1 ( NR ) Rubinstein etal.156 1991
146 1.0 (0.5 – 2.0) Quadri & Ueno148 1993
62 0.2 (0.01 – 0.2) Garcia-Rodriguez73 1995
11 2.0 (0.125 – 4.0) Turkmani etal.196 2006
16 0.75 (0.25 – 0.75) Dizbay etal.55 2007
56 1.0 (0.064 – 1.5) Bayram etal.28 2011
355 2.0 (0.125 – 3.0) Abdel-Maksoud1 2012
Gentamicin 27 0.4 (0.02 – 2.5) Hall & Manion84 1970
15 1.0 (0.25 – 2.0) Mortensen etal.126 1986
105 0.25 (0.12 – 0.5) Quadri etal.147 1993
146 0.25 (0.12 – 0.5) Quadri & Uneo148 1993
11 2.0 (0.032 – 1.5) Turkmani etal.196 2006
355 1.0 (0.094 – 3.0) Abdel-Maksoud1 2012
Kanamycin 27 2.5 (0.02 – 5.0) Hall & Manion84 1970
Tobramycin 15 2.0 (0.5 – 4.0) Mortensen etal.126 1986
Amikacin 15 2.0 (1.0 – 4.0) Mortensen etal.126 1986

a NR = not reported

Table 4. Minimal Inhibitory Concentration (ug/mL) of Co-trimoxazole Against Brucella Species

Drug No. strains tested MIC90 (Range)a Reference
Co-trimoxazole 98 32 (8 – 128) Gutierrez Altes80 1982
15 1/19b (<0.25/4.5-1/19) Mortensen etal.126 1986
95 0.25 (0.06 – 0.5) Bosch etal.30 1986
47 5.0 (5.0 – 25) Kahn etal.99 1989
86 6.3 ( NR ) Rubinstein etal.156 1991
105 1.0 (0.12 – 1.0) Quadri etal.147 1993
146 1.0 (0.12 – 1.0) Quadri etal.148 1993
62 4/76b (0.1/1.9 – 4/76) Garcia-Rodriguez73 1995
11 0.75/14.2 (0.032/0.61 – 1.5/28.5) Turkmani196 2006
20 0.032 (0.012 – 0.064) Marianelli115 2007
56 0.125c (0.064 – 0.25) Bayram etal.28 2011

a NR = not reported

b values shown for trimethoprim/sulfamethoxazole components

c values shown for trimethoprim component only

Table 5. Minimal Inhibitory Concentrations (ug/mL) of Rifampin Against Brucella Species

Drug No. strains tested MIC90 (Range)a Reference
Rifampin 27 1.25 (0.02 – 12.5) Hall & Manion84 1970
107 <2.5 (0.018 – 1.0) Corbel49 1976
98 0.5 (0.06 – 1.0) Gutierrez-Altes etal.80 1982
8 1.0 (0.06 – 1.0) Mortensen etal.126 1986
95 0.5 (0.12 – 4.0) Bosch etal.30 1986
47 1.25 (0.02 – 2.5) Khan etal.99 1989
86 4.0 ( NR ) Rubinstein etal.156 1991
105 1.0 (0.12 – 1.0) Quadri & Ueno148 1993
62 1.0 (0.1 – 4.0) Garcia-Rodriguez etal.73 1995
146 1.0 (0.12 – 1.0) Quadri etal.147 1993
82 1.5 (0.25 – 2.0) Turan etal.195 2007
20 1.0 (0.75 – 2.0) Marianelli115 2007
56 2.0 (0.5 – 2.0) Bayram etal.28 2011
355 2.0 (0.25 – 6.0) Abdel-Maksoud1 2012

a NR = not reported

Table 6. Minimal Inhibitory Concentration (ug/mL) of Selected Quinolones Aagainst Brucella Species

Drug No. strains tested MIC90 (Range) Reference
Ciprofloxacin 44 2.0 (0.25 – 16) Yamazhan etal.210 2005
74 0.5 (0.016 – 0.75) Turkmani etal.196 2006
50 1.0 (0.25 – 1.0) Tanyel etal.187 2007
82 0.19 (0.047 – 0.25) Turan etal.195 2007
20 0.25 (0.094 – 0.5) Marianelli115 2007
34 1.0 (0.25 – 1.0) Kaya etal.97 2012
355 0.38 (0.125 – 0.75) Abdel-Maksoud1 2012
Levofloxacin 44 2.0 (0.25 – 16) Yamazhan etal.210 2005
74 0.5 (0.064 – 0.75) Turkmani etal.196 2006
50 1.0 (0.25 – 1.0) Tanyel etal.187 2007
34 0.5 (0.25 – 1.0) Kaya etal.97 2012
Moxifloxacin 44 8.0 (0.5 – 16) Yamazhan etal.210 2005
Norfloxacin 74 3.0 (0.125 – 4.0) Turkmani etal.196 2006
Ofloxacin 50 1.0 (0.25 – 1.0) Tanyel etal.187 2007

Table 7.  Selected Studies of Combination Drug Therapies for Brucellosis

Drugs (doses) and Duration (days) No. treated No. Failed or Relapsed Rate (%) Reference
DOX (200mg x 30) + GM (5mg/kg x 7) 35 8 (22.8) Solera175 1997
DOX (200mg x 45) + GM (5mg/kg x 7) 17 1 (5.9)
DOX (200mg x 30) + GM (240mg X 7) 73 15 (20.5) Solera179 2004
DOX (200mg x 45) + GM (240mg x 7) 73 9 (12.3)
DOX (200mg x 45) + SM (1g x 14) 94 7 (7.4) Roushan155 2006
DOX (200mg x 45) + GM (5mg/kg x 7) 97 5 (5.2)
DOX (200mg x 45) + SM (1g x 14) 94 7 (7.45) Solera173 1995
DOX (200mg x 45) + RIF (900mg x 45) 100 26 (24)
DOX (200mg x 45) + RIF (600mg x 45) 14 2 (14.2) Karabay96 2004
OFL (400mg x 30) + RIF (600mg x 30) 15 2 (13.3)
DOX (200mg x 42) + RIF (600mg x 42) 45 6 (14.3) Ersoy64 2005
OFL (400mg x 42) + RIF (600mg x 42) 41 5 (12.8)
DOX (200mg x 42) + SM (1g x 21) 32 3 (9.7)

DOX = doxycycline

GM = gentamicin

SM = streptomycin

RIF = rifampin

OFL = ofloxacin

Table 8. Currently Recommended Therapies for Human Brucellosis

Condition Antimicrobial Agents Dose Rout Duration of Therapy
Adults (Acute brucellosis or Relapse) Doxycycline 200 mg daily PO 6 weeks
+ Streptomycin 1 g daily IM 2-3 weeks
or Gentamicin 5 mg/kg IM or IV 5-7 days
Alternative Doxycycline 200 mg daily PO 6 weeks
+ Rifampin 15-20 mg/kg daily PO 6 weeks
Children > 8 yrs Same as adults
Children < 8 yrs TMP/SMX 2 DS tablets daily PO 45 days
+ Rifampin 15-20 mg/kg daily PO 45 days
+ Gentamicin 5 mg/kg daily IM or IV 7 days


Pia Franco M, et al.  Human Brucellosis. The LANCET Infectious Diseases 2007; Vol.7, Issue 12, 775-786.

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Benedek T.  Brucellosis Therapy: A Historical Overview.

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