[Short communication: Investigation of in vitro antibiotic susceptibility of Brucella melitensis]

The aim of this study was to investigate the in vitro susceptibilities of Brucella melitensis clinical isolates against antibiotics used in conventional treatment regimens and additionally against quinolones. A total of 65 B. melitensis strains isolated from blood and bone marrow specimens of patients who were admitted to an university hospital localized in a region endemic for brucellosis. Minimum inhibitory concentration values (MIC50 and MIC90) of trimethoprim-sulphamethoxazole (TMP-SMX), rifampin, doxycycline, ciprofloxacin, ofloxacin, sparfloxacin and levofloxacin for B. melitensis isolates have been detected by using E-test (AB Biodisk, Sweden). In our study the most effective antimicrobial agent was found to be TMP-SMX (MIC90 = 0.023 mg/L) followed by doxycycline (MIC90 = 0.032 mg/L). With regard to fluoroquinolones, the most active antibiotic was sparfloxacin (MIC90 = 0.064mg/L), followed by levofloxacin and ciprofloxacin (MIC90 = 0.125 mg/L), and ofloxacin (MIC90 = 0.50 mg/L). Rifampin exhibited the highest MIC90 value (1.5 mg/L), and eight isolates yielded intermediate resistance to rifampin. There was no serious resistance problem for TMP-SMX and doxycycline in our study, however, enough care should be taken for the use of rifampin which is frequently used for the treatment of tuberculosis and brucellosis which are endemic in our country. As a result, the antimicrobial susceptibilities of Brucella species should be determined periodically to avoid the possible development of resistance problems in the future.