In-vitro antimicrobial susceptibility results of Brucella species; Single center study from Eastern Türkiye.

Introduction: Brucellosis is the most common zoonotic infection worldwide. The disease imposes significant economic burdens and public health challenges. Due to documented instances of treatment failures, relapses, and resistance, regular monitoring of antimicrobial susceptibility is essential. This study aimed to evaluate the sensitivity of Brucella spp. against antimicrobial agents.

Methodology: The study was conducted at a tertiary state hospital from January 2023 to June 2024. Species level identification was performed using the VITEK-2 Compact system and 16S rRNA analysis. Isolated strains were cultured on Mueller-Hinton agar supplemented with 5% horse blood and β-Nicotinamide adenine dinucleotide (β-NAD), followed by testing with antibiotic discs. Antimicrobial susceptibility tests were performed according to the EUCAST 2024 version 14 recommendations. Zone diameters were categorized as susceptible, standard dosing regimen; susceptible, increased exposure and resistant.

Results: 45 Brucella species isolated from blood culture were included in this study. Species level determination showed Brucella melitensis in 36 (80%) and Brucella abortus in 9 (20%) patients by 16S rRNA analysis. Antimicrobial susceptibilities were as follows: gentamicin, rifampicin, ceftriaxone, tetracycline, trimethoprim-sulfamethoxazole, and streptomycin all showed 100% susceptibility. Conversely, levofloxacin had a susceptibility rate of 15.5%, and ciprofloxacin had a rate of 4.4%. No resistance was detected for levofloxacin or ciprofloxacin, and there were no significant differences in susceptibility between Brucella melitensis and Brucella abortus.

Conclusions: The study highlights increased exposure patterns for ciprofloxacin and levofloxacin, indicating potential future resistance issues. Regular monitoring of antimicrobial resistance in Brucella isolates is crucial for effective disease management and updating treatment guidelines.