The canonical Brucella species-host dependency is changing, however, the antibiotic susceptibility profiles remain unchanged

Brucellosis is a chronic disease caused by Brucella species with a wide range of hosts, from marine mammals to terrestrial species, but with strict host preferences. With the zoonotic character, the prevalence of human brucellosis cases is a reflection of animal infections. This study aimed to identify 192 Brucella isolates obtained from various sources by Bruce-ladder PCR and to determine their antibiotic susceptibilities by gradient diffusion method (E-test). As a result of the PCR, all human isolates (n = 57) were identified as B. melitensis. While 58 (82.9%) of the cattle isolates were identified as B. abortus, 59 (90.8%) of the sheep isolates were identified as B. melitensis. In addition, 12 (17.1%) of the cattle isolates and 6 (9.2%) of the sheep isolates were determined as B. melitensis and B. abortus, respectively. The primary host change behavior of B. melitensis was 1.9 times higher than that of B. abortus. While gentamicin and ciprofloxacin susceptibilities of Brucella isolates were 100%, tetracycline, doxycycline, streptomycin, trimethoprim/sulfamethoxazole and rifampicin susceptibilities were 99%, 99%, 97.4%, 91.7% and 83.9%, respectively. The lowest sensitivity of the isolates was determined against to cefoperazone as 26%. A triple-drug resistance was detected in 1 B. abortus isolate that included simultaneous resistance to cefoperazone, rifampicin, and trimethoprim/sulfamethoxazole. The high susceptibility profiles we found against to antibiotics such as tetracycline, doxycycline gentamicin and ciprofloxacin, used widely in treatment, are encouraging. However, the change in the canonical Brucella species-primary host preference suggests the need to reconsider eradication program, including updating vaccine formulations.