Antimicrobial susceptibility and resistance gene profiles of Prevotella spp. isolated in Oita University Hospital, Japan.

Prevotella spp. are anaerobic Gram-negative rods that often cause polymicrobial infections. Data on the prevalence of resistance genes in Prevotella spp. in Japan are limited. We evaluated the antimicrobial susceptibility patterns and resistance gene profiles of Prevotella spp. We retrospectively surveyed 51 Prevotella strains isolated from human clinical specimens collected between March 2011 and March 2025. The antimicrobial susceptibility of the isolates to ampicillin (ABPC), sulbactam-ampicillin (SBT/ABPC), tazobactam-piperacillin (TAZ/PIPC), meropenem (MEPM), clindamycin (CLDM), minocycline (MINO), and metronidazole (MNZ) was determined using the broth microdilution method. All isolates were tested for the presence of cfxA, ermF, nim, and tetQ. The antimicrobial resistance rates of Prevotella isolate rates were as follows: ABPC, 47%; SBT/ABPC, 0%; TAZ/PIPC, 0%; MEPM, 0%; CLDM, 39%; and MNZ, 4%. The minimum inhibitory concentration (MIC)50 and MIC90 values for MINO were 0.25 mg/L and 4 mg/L, respectively. The prevalence of the resistance genes was as follows: cfxA, 61%; ermF, 55%; nim, 2%; and tetQ, 27%. This study revealed the antimicrobial susceptibility patterns and resistance gene profiles of Prevotella spp., characterized by a high prevalence of cfxA and ermF, high rates of CLDM resistance, and the presence of MNZ-resistant isolates not harboring the nim gene. Although the prevalence of tetQ was lower than that previously reported, its presence was associated with high MINO MIC values. Our findings highlight the important epidemiological features in Japan and emphasize the need for continued surveillance to guide the development of appropriate antimicrobial therapies.