Comparison of Phenotypic and Genotypic Patterns of Antimicrobial-Resistant Bacteroides fragilis Group Isolated from Healthy Individuals in Vietnam and Japan

Abstract

Hanh Vu,1 Masahiro Hayashi,2,3 Thang Nam Nguyen,4 Diep Thi Khong,4 Hoa Thi Tran,4 Yoshimasa Yamamoto,1 Kaori Tanaka1– 3 1United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Gifu City, Gifu, Japan; 2Life Science Research Center, Gifu University, Gifu City, Gifu, Japan; 3Institute for Glyco-core Research (iGCORE), Gifu University, Gifu City, Gifu, Japan; 4Center for Medical and Pharmaceutical Research and Service, Thai Binh University of Medicine and Pharmacy, Thai Binh City, Thai Binh, VietnamCorrespondence: Kaori TanakaUnited Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, 1-1 Yanagido, Gifu City, Gifu, 501-1194, JapanTel [phone]Fax [phone]Email [email protected]: Normal non-pathogenic flora can harm the host by acting as a reservoir of resistance determinants that are potentially transferable to human pathogens. This study aimed to assess the phenotypic and genotypic antimicrobial susceptibility patterns of the Bacteroides fragilis group (BFG) isolated from healthy individuals in Vietnam and Japan in order to elucidate the prevalence of antimicrobial resistance in human flora in the two economically and geographically different countries.Materials and Methods: BFG was isolated from fecal samples of 80 healthy individuals in Vietnam (n=51) and Japan (n=29). Isolated strains were identified using MALDI-TOF MS, and the minimum inhibitory concentration (MIC) of 18 antibiotics was determined using the agar dilution method. Additionally, 20 antimicrobial resistance genes were detected using standard PCR.Results: A total of 139 BFG strains belonging to 11 BFG species were isolated from the two countries, with diversity in the prevalence of each species. B. fragilis was not the predominant species. Isolations from Vietnam and Japan showed some similarities in terms of MIC50 values, MIC90 values, and the percentage of resistant strains. However, isolations from Vietnam showed significantly higher resistance to piperacillin, cefmetazole, clindamycin, tetracycline, and minocycline. ErmB, tet 36, tetM, nim, catA, and qnrA were not found in either country. CepA was more common in B. fragilis than in non-fragilis Bacteroides. In contrast, cfiA, ermG, mefA, msrSA, tetX, tetX1, bexA, qnrB, and qnrS were found only in non-fragilis Bacteroides. There were differences in the prevalence of ermG, linA, mefA, msrSA, and qnrS between isolates from Vietnam and Japan.Conclusion: This study is the first report on the antimicrobial susceptibility patterns in the BFG isolated from healthy individuals in Vietnam and Japan. Compared to isolations from Japan, isolations from Vietnam showed significantly higher resistance to antimicrobial agents. The distribution of various antibiotic resistance genes also differed between the two countries.Keywords: antimicrobial resistance patterns, resistance genes, human flora

Keywords

• antimicrobial resistance patterns
• resistance genes
• human flora