Antimicrobial resistance pattern of the Bacteroides fragilis group strains isolated at a teaching hospital in China

The study was conducted in the microbiology laboratory of the First Affiliated Hospital of Hainan Medical University, Haikou, China, from January 2019 to December 2023. A total of 316 consecutive non-duplicate isolates were collected and identified, that belonged to the Bacteroides fragilis group. Identification of the isolated strains was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The minimum inhibitory concentration (MIC) of seven antibiotics was determined by agar dilution method. The presence of cfiA, ermF, and nim genes was determined by polymerase chain reaction (PCR). Correlations between the presence of resistance genes and the MIC values of antibiotics were determined using the Pearson correlation coefficient. In the identification process, 214 isolates (67.7%) were identified as B. fragilis, 52 (16.4%) as Bacteroides thetaiotaomicron, 17 (5.4%) as Bacteroides ovatus, 12 (3.8%) as Bacteroides uniformis, 10 (3.2%) as Phocaeicola vulgatus (=Bacteroides vulgatus), 7 (2.2%) as Bacteroides stercoris, and 4 (1.3%) as Parabacteroides distasonis. The presence of cfiA gene moderately correlated with the MIC of imipenem and meropenem (r = 0.34 and r = 0.42, respectively), while resistance to clindamycin and the presence of ermF gene exhibited a very strong correlation (r = 0.72). In the current study, the most active antimicrobial agents against B. fragilis group bacteria were found to be meropenem, imipenem, metronidazole, and piperacillin/tazobactam; however, resistance to clindamycin renders its empirical use inappropriate.