Objective: To test in vitro susceptibilities of Brucella melitensis (B. melitensis) blood isolates obtained from an endemic region, by broth microdilution susceptibility test.
Methods: Fifty blood isolates were tested with anti-brucella antibiotics, namely, tetracycline, gentamicin, streptomycin, ceftriaxone, ciprofloxacin, levofloxacin, ofloxacin, and rifampin. All of the clinical isolates belonged to the group of B. melitensis biotype-3. This study was performed at the Clinical Microbiology Laboratory of the Medical School of Ondokuz Mayis University, Samsun, Turkey, in 2005.
Results: In terms of minimum inhibitory concentration-90 (MIC90) values, tetracycline (MIC90 0.25 microgram/mL) and rifampin (MIC90 0.5 microgram/mL) still continue to be the most effective antibiotics; however, ceftriaxone and streptomycin demonstrated higher MIC values, although they were still effective in vitro against B. melitensis strains with MIC90 of 8 microgram/mL.
Conclusion: All first line, and alternative antimicrobial agents could be used in various combinations in the treatment of human brucellosis. High MIC values of ceftriaxone and streptomycin are alarming, and should be closely monitored during the therapy.