Division of Biomedical Food Research, National Institute of Health Sciences, Kawasaki-ku, Kawasaki, Kanagawa, 210-9501, Japan.
Applied Microbiology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo, Hokkaido, 060-8589, Japan.
Curr Microbiol. 2022 Jun 15;79(8):217. doi: 10.1007/s00284-022-02913-6.
Gentamicin is an important antibiotic for the treatment of opportunistic infections in the clinical field. Gentamicin-resistant bacteria have been detected in livestock animals and can be transmitted to humans through the food supply or direct contact. We have previously revealed that gentamicin-resistant Escherichia coli are distributed at a comparatively high rate from beef cattle in Japan, but few studies have focused on the molecular epidemiology of gentamicin-resistant bacteria. To understand these bacteria, this study examined the prevalence of various gentamicin resistance genes in gentamicin-resistant E. coli isolates from beef cattle feces. Of the 239 gentamicin-resistant E. coli isolates, the presence of the aacC2, aadB, or aac(3)-VIa genes was confirmed in 147, 84, and 8 isolates, respectively. All aac(3)-VIa-harboring isolates had an MIC value of 64 μg/mL for gentamicin and exhibited resistance to 11 antibiotic agents. An analysis of the representative aac(3)-VIa-harboring E. coli strain GC1-3-GR-4 revealed that the aac(3)-VIa gene was present on the IncA/C plasmid together with the aadA and bla genes. Furthermore, the upstream region of the aac(3)-VIa gene contained the aadA gene and the class 1 integron-integrase gene (intI1). The aac(3)-VIa gene was detected for the first time in Japan and is expected to be able to transfer between bacteria via the IncA/C plasmid and integron. These results reveal the expansion of the distribution or diversity of gentamicin resistance genes in Japan.
庆大霉素是临床治疗机会性感染的重要抗生素。在牲畜中已经检测到了对庆大霉素具有耐药性的细菌，这些细菌可以通过食物供应或直接接触传播给人类。我们之前已经揭示，日本牛肉牛中庆大霉素耐药大肠杆菌的分布率相对较高，但很少有研究关注庆大霉素耐药菌的分子流行病学。为了了解这些细菌，本研究检测了从牛肉牛粪便中分离出的庆大霉素耐药大肠杆菌中各种庆大霉素耐药基因的流行情况。在 239 株庆大霉素耐药大肠杆菌分离株中，分别有 147、84 和 8 株存在 aacC2、aadB 或 aac(3)-VIa 基因。所有携带 aac(3)-VIa 的分离株对庆大霉素的 MIC 值均为 64μg/mL，对 11 种抗生素均表现出耐药性。对代表性的携带 aac(3)-VIa 的大肠杆菌菌株 GC1-3-GR-4 进行分析表明，aac(3)-VIa 基因存在于 IncA/C 质粒上，同时还带有 aadA 和 bla 基因。此外，aac(3)-VIa 基因上游区域含有 aadA 基因和 class 1 整合子整合酶基因（intI1）。aac(3)-VIa 基因在日本首次被发现，预计可以通过 IncA/C 质粒和整合子在细菌之间进行转移。这些结果揭示了日本庆大霉素耐药基因的分布或多样性的扩大。
