Clostridium species (Clostridium perfringens, C. butyricum, C. clostridioforme, C. innocuum, C. ramosum, C. septicum, C. sordellii, C. tertium)

Authors: Itzhak Brook, MD, MSc

Among more than 200 known Clostridium spp. at least 30 are associated with human disease. They usually appear as gram-positive rods, however many strains may appear gram-variable or gram-negative. Loss of gram-positive appearance occurs with direct stains of clinical material or in cultures after prolonged incubation or in species with terminal spores. Clostridium perfringens is the most important of the species and accounts for 20-40% of all isolates. Speciation is based mostly on cellular morphology, spores location (central, terminal or sub terminal), biochemical reactions, gas liquid chromatography for fermentation products; and the demonstration of production of lecithinase (or alpha toxin by C. perfringens ) and lipase (by Clostridium sporogenesClostridium novyi and Clostridium botulinum (14).


Organisms of the genus Clostridium are important members of the humans’ anaerobic gastrointestinal and cervical-vaginal flora. Clostridia are ubiquitous and are found in the soil, marine sediment, decaying vegetation and intestinal tract of humans, other vertebrate and insects. Human infections with clostridia can result from endogenous or exogenous infection (5).

Clinical Manifestations

Infections caused by these organisms range from a variety of localized wound contamination to overwhelming systemic disease (5, 7, 29). Clostridial histiotoxic syndromes are mediated by toxins and include soft tissue infections such as gas gangrene (caused by  C. perfringens), enteric diseases such as clostridial food poisoning, enteritis necroticans, antibiotic associated colitis (caused by C. difficile ), discussed elsewhere, and neutropenic enterocolitis (caused by C. septicum) and neurological syndromes such as tetanus and botulism (both discussed elsewhere).

C. septicum can cause spontaneous, non-traumatic gas gangrene, and C. sordellii can induce gas gangrene of the uterus, as a consequence of spontaneous abortion, normal vaginal delivery and traumatic injury. (29).  Clostridial bacteremia account for clinically significant anaerobic bacteremia second only to Bacteroides spp. Clostridia are also often isolated from polymicrobial intraabdominal, biliary, pleuropulmonary, central nervous system, genitourinary and skin and soft tissue infections (5).

Laboratory Diagnosis

Isolation of Clostridia from wound, pus, blood or faeces, along with toxin and serological assays aid in the diagnosis of clostridial infections. The significance of clostridia in polymicrobial isolates is unknown. Clinical diagnosis is especially important in infections such as gas gangrene in which demonstration of clostridial myonecrosis is critical in the diagnosis.


Toxins mediate the Clostridial histiotoxic syndromes. Toxins are biologically active proteins that are antigenic and capable of neutralization by specific antisera. C. perfringens produces 4 major lethal toxins, based on which it is classified into 5 serological types classified A to E. Additional virulence factors include enterotoxin, neuraminadase and haemolysins. The role of clostridia in the pathogenesis of polmicrobial infections is unclear (28, 29).

Clostridium perfringens is the most common clinical isolate of the genus. It is a ubiquitous bacterium associated with several exotoxin-mediated clinical diseases. There are 12 recognized toxins, and the species is divided into types A through E on the basis of the spectrum of toxins produced (16).  The disease syndromes caused by C. perfringens are food poisoning, necrotizing enteritis, and gas gangrene.

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C. perfringens.

C. perfringens, as well as most other Clostridium spp. are generally, but not universally susceptible to penicillin-G, amoxicillin, ticarcillin, piperacillin, cefazolin, cefoxitin, cefotetan, third generation cephalosporins, chloramphenicol, clindamycin, macrolides, metronidazole, imipenem, meropenem, tetracycline, tigecycline, fluoroquinolones, vancomycin, daptomycin, quinupristin-dalfopristin, rifampin, and the combinations of penicillins and beta-lactamase inhibitors (1, 2, 4, 8, 17, 19, 21, 24, 26, 37).
Antimicrobial susceptibilities were determined for 275 C. perfringens isolates of bovine, chicken, porcine, and turkey origin in Ontario Canada. Reduced susceptibility to bacitracin was identified in chicken (64%) and turkey (60%) isolates. Swine isolates had predominantly reduced susceptibility to clindamycin (28%) and erythromycin (31%), whereas bovine isolates had reduced susceptibility to clindamycin (10%) and florfenicol (10%). Reduced susceptibility to tetracycline was spread across all species. No clear reduced susceptibility, but elevated MIC (50) for virginiamycin was found in chicken isolates in comparison with isolates from other species  (25).

Resistance of  C. perfringens isolates to tetracycline was found in strains isolated from poultry in Sweden (76%), Denmark (10%) and Norway (29%) ( 13) Resistance to tetracycline and lincomycin was observed in most C. perfringens isolates recovered from piglets with or without diarrhea in Brazil (23), and 18% of isolates recovered from dogs in Switzerland showed resistance to tetracycline and 54 % showed decreased susceptibility to metronidazole (11). Lincomycin, erythromycins, and tilmicosin showed very high minimal inhibitory concentration (MIC) 50  of > 256 ug/ml recovered from broiler chickens in Jordan n (9) . However, tylosin, amoxicillin, ampicillin, penicillin, florfenicol, danofloxacin, enrofloxacin, chlortetracycline, doxycycline, and oxytetracycline had variable MIC50 of 64, 0.5, 1, 1, 8, 4, 8, 4, 8, 0.5 μg/ml, respectively. Twenty-six (66%) and 24 (61%) out of the 39 tested C. perfringes isolates from broiler chickens in Belgium showed resistance to tetracycline and lincomycin, respectively (10).

Other Clostridium spp.

With some exceptions, strains of Clostridium have been found to express resistance by one or more of the beta-lactamases. Beta–lactamase producing Clostridium spp. express enzymes that are generally inhibited by clavulanic acid (2)  Rifampin and chloramphenicol occasionally lack bactericidal activity against C. perfringens  (36). Cefoxitin is less effective against Clostridium spp. than most other cephalosporins. There is increasing resistance of C. perfringens as well as other clostridia species to antimicrobials (1, 3); C. ramosum,and  C. innocuum, show increased resistance to penicillin (16-57%), cefoxitin (22-48%), other cephalosporin (20%), clindamycin (5-50%), flouroquinolones, and metronidazole (11-12%). C. innocuum is resistant to cephalosporins, and only moderately susceptible to penicillin (90%) and vancomycin (90%). C. clostridioforme resistance was noted to penicillin (26-90%), cephalothin (17%), cefoxitin (29-48%), cefotetan ( 17-29%), ceftriaxone (21%) ,chloramphenicol (33%), clindamycin (7-30%) and tetracycline (55%) (121, 35).

Clostridium sordellii and C. septicum posses susceptibility similar to C. perfringens, although there are occasional strains resistant to extended spectrum penicillins and clindamycin. Clostridium tertium displays resistance to third generation cephalosporins (83% resistance to ceftriaxone) (3, 21, 27).  Resistance was also found to cefoxitin (17%), cefotetan ( 17%), and clindamycin (7%) (21).  Decreased affinity for penicillin-binding proteins was found for strains of C. perfringens and beta lactamase production has been observed with C. ramosum, C. butyricum and C. clostridioforme. A  transferable plasmid mediated resistance to tetracycline, chloramphenicol and erythromycin-clindamycin was observed with C. perfringens.
In vivo studies demonstrated that drugs other than penicillin were more effective in treatment of Clostridial infection. Clindamycin, metronidazole, rifampin and tetracycline were more efficacious than penicillin in the treatment of fulminate gas gangrene in mice caused by C. perfringens (32). Protein synthesis inhibitors (tetracycline, metronidazole, rifampin, clindamycin and chloramphenicol) were found to be better inhibitors of toxin synthesis than cell wall active agents (penicillin).  A combined superior rapid bacterial killing and ability to suppress toxin production was noted with clindamycin, rifampin and metronidazole, as compared to penicillin (30-32).

Additionally clindamycin down modulatated the production of cytokines involved in shock and organ failure (34). The lower efficacy of penicillin may be due to ongoing toxin production by organisms that survive in filamentous form, due to the action because of penicillin’s limited effect only on cell wall formation.

Combination Drugs

The combination of penicillin and clindamycin was found to be more efficacious in vivo than single therapy with metronidazole, clindamycin, rifampin or penicillin. In contrast the combination of penicillin and metronidazole was deleterious (30).

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The current recommendations for treatment are based on many retrospective studies in humans and several studies in animal models. Penicillin-G in a dose of 20 million units a day in adults and 100-250,000 unites/kg/d IV q 4 hr in children, is the treatment of choice for serious infections due to C. perfringensClostridium sordellii and C. septicum such as bacteremia, intra-abdominal, gall bladder, genital tract, pulmonary, central nervous system, and soft tissue infections. In cases of penicillin allergy or concern about resistance other antibiotics should be considered. All isolates of serious infections should be tested for in vitro efficacy because of the possible recovery of resistant strains.

Alternative Therapy

Alternative drugs to penicillin are chloramphenicol 12.5-25 mg/kg q 6 hr for adults and children (PO, IV, IM), (maximal dose 4 gram/d for adults); clindamycin 150-450 mg q 6hr (PO/ IV/IM) for adults, and 25-40 mg/ kg/d q 6-8 hr for children; metronidazole 7.5 mg/ kg q 6hr (PO/ IV/IM) for adults and children (maximal daily dose of 4.0 gm q d in adults); Tetracycline 250-500 mg/q 6 hr (PO/IV/IM) for adults (maximal dose 2 grams), and for children > 9 years 15-20 mg/kg/d (IV) q 6 hr or 25-50 mg/kg/d PO q 6 hr; Vancomycin 15 mg/kg q12 hr or 6-8 mg/kg q 6 hr (IV) (maximal daily dose 2 gm in adults) and 10 mg/kg q 6 hr (IV) in children; Imipenem, 0.5-1 gr q 6-8 hr (IV/IM) in adults (maximal daily dose 2 gram) and 15-25 mg/kg q6 hr (IV/IM) in children; Meropenem 0.5-1.0 gm q 8 hr (IV) for adults, and 40 mg/ kg/ d q 8 hr (IV) for children; Doripenem, 0.5 gr q 8 hr (IV) for adults. Since C. ramosum, C. butyricum and C. clostridioforme can produce beta-lactamase, penicillin cannot be the drug of choice for these organisms. Similarly third generation cephalosporins should not be used for Clostridium tertium. Even though cephalosporins and clindamycin are effective in vitro, their clinical efficacy is uncertain, and clinical failures have been noted with cephalosporins (18). Although clindamycin showed superior efficacy in animal models, Clostridia including some strains of C. perfringens showed increased resistance (1, 3, 4, 6).  Penicillin is still the drug of choice for clostridial infection that does not involve skin and soft tissue.

Combination Therapy

The impact of the animal studies that show improved efficacy of combination therapy of penicillin and clindamycin is not obvious. However, utilization of such a combination in serious Clostridial myonecrosis (gas gangrene) should be considered because of clondamycin’s ability to inhibit toxins production (6, 30).

Special Situations

In clinical situations that involve polymicrobial infections, coverage against the other potential pathogens, aerobic as well as anaerobic, should be included. This can be achieved by choosing single therapy with an antimicrobial that possesses wider coverage (i.e. imipenem, meropenem), or by additional agents that cover other organisms (i.e an cefipime, an aminoglycoside or quinolone for Enterobacteriacae, or a penicillinase-resistant penicillin, or vancomycin for Staphylococcus aureus).

Gastrointestinal Infections

Enteric diseases due to histotoxic clostridium include: C. perfringens food poisoning, enteritis necroticans. Therapy of clostridial food poisoning generally does not require antibiotic therapy. The antibiotics preferred in enteritis necroticans and neutropenic enterocolitis are Piperacillin-tazobactam, cefepime plus  metronidazole or a carbapenem (i.e. Imipenem-cilastatin, meropenem).


Clostridial bacteremia may not always require therapy, as it may be transitory or may only represent specimen contamination (12, 20). However, there are instances of clinically significant clostridial bacteremia without toxin involvement. This usually occurs in gynecological, intrabdominal (including biliary and intestinal), soft tissue (i.e. decubitus ulcer, myonecrosis) infections where the organisms originate from the flora of the infected site.

CNS Infection

Treatment of central nervous infection requires the use of antimicrobials with good penetration through the blood brain barrier (i.e. metronidazole).

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Surgery and debridements, and fluid management are important and integral part of any therapy of clostridial infection. Surgery is important in treatment of clostridial myonecrosis or gas gangrene. Amputation may be required in rapidly spreading infection of a limb. Repeated debridement may be required. Antitoxin for gas gangrene is on longer commercially available in the United States, as it was not found to be effective and was associated with severe allergic reactions (28). However it is still recommended by some authorities. The use of hyperbaric oxygen in the treatment of gas gangrene is also controversial.


Improvements and resolution of the infections are determined through a variety of clinical and laboratory tests. In the case of bacteremia, the lack of recovery of organisms from the blood is an important end point. The disappearance of hemolysis and reduction in the number of white blood cells are important signs of improvement. Improvement in intra-abdominal, biliary tract, genital and pulmonary infections can be judged through clinical and radiographic resolution of the infection - returns the gastrointestinal and pulmonary system to normal function, and disappearance of purulence. Central nervous system infection can be followed by repeated lumbar punctures and radiography. In the cases of subcutaneous tissue infection, return of the tissue to normal color and blood perfusion and resolution of the purulent inflammation are desired. The disappearance of the gas formation in the inflamed tissue (determined clinically or radiographically) are important clues.


There are currently no vaccines for these bacteria. A polyvalent vaccine against C. histolyticum, C. novyi, C. septicum and C. perfringens was developed in the 1930th (SB).   Because the toxoiding alpha toxin from C. perfringens was incudedonly low titers of anti-alpha toxin antibody this approach was abandoned. were elicited. However , several recent studies demonstrated that active immunization with crude toxoid preparations were protective in experimental infections (33).


Debridement of devitalized tissue, removal of foreign material and vascular repair are the key elements in prevention of gas gangrene.  Recent insights regarding the genetic regulation of toxin production, the molecular mechanisms of toxin-induced host cell dysfunction, and the roles of newly described toxins in pathogenesis suggest that novel prevention, diagnostic, and treatment modalities may be on the horizon for these infections (6).

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