Objective: We aimed to determine the resistance of Bacteroides fragilis group (BFG) bacteria to clindamycin, tetracycline and tigecycline and establish the distribution of related resistance genes.

Method: In total 82 BFG strains, isolated from different clinical samples between January 2017 and December 2018, were identified by MALDI-TOF MS. Their antimicrobial sensitivities to were determined using agar dilution methodology (CLSI; M11-A7). The tetM, tetQ, tetX, tetX1, tet36, and ermF genes were investigated by PCR.

Results: Eighty-two strains of BFG bacteria, isolated from intra-abdominal abscess (n=36), tissue biopsy (n=16), blood (n=14) and other sterile body fluids (n=12), were identified as Bacteroides fragilis (n=48), Bacteroides thetaiotaomicron (n=17), Bacteroides vulgatus (n=5), Bacteroides ovatus (n=4), Bacteroides caccae (n=1), Bacteroides uniformis (n=1) and Parabacteroides distasonis (n=6). The resistance rates to clindamycin, tetracycline and tigecycline were 54.9%, 84.1%, 4.9%, respectively. Non-B. fragilis isolates were more resistant than B. fragilis strains. In total, 57.3% of the isolates were ermF gene positive, while B. thetaiotaomicron had the highest rate (70.6%). The tet gene positivity ranged from 18.8% to 66.7% among species. The tetQ gene positivity was higher than other tet genes. The 92.7% of the isolates were resistant to at least one antibiotic, while 94% had at least one resistance gene.

Conclusion: This study provided data on antimicrobial resistance of our BFG isolates to clindamycin, tetracycline and tigecycline and the related resistance genes. However, our information obtained could also be a starting point for further investigation of the antibiotic resistance mechanisms of Bacteroides species, as well as, resistance transfer among BFG isolates and other bacteria.