Antibiotic resistance and blaNDM transmission characteristics of bacteria from turtle farms in Zhejiang Province

Abstract:

[Objective] To investigate the antibiotic resistance profiles, resistance genes, and bla_NDM transmission characteristics of bacterial isolates from six turtle farms in two regions (three in Lanxi (LX) and three in Xiaoshan (XS)) of Zhejiang Province. [Methods] Bacterial strains were identified by 16S rRNA gene sequencing. The Kirby-Bauer method was employed to examine the antibiotic susceptibility of isolated bacteria. PCR was employed to detect resistance genes carried by the isolated bacteria. Conjugation transfer experiments were conducted to obtain bla_NDM-carrying plasmids, and the conjugation frequency was analyzed to assess the transfer capabilities of bacterial donors. Additionally, the modified Carba NP test, plasmid replicon typing, and minimum inhibitory concentration determination were carried out to evaluate the transmission of bla_NDM-carrying plasmids among bacteria. [Results] A total of 244 bacterial strains were isolated, with similar distribution between the two regions and Enterobacteriaceae being dominant. PCR amplification of integrons revealed various resistance genes, including those conferring resistance to aminoglycosides and trimethoprim. We identified numerous resistant bacteria capable of integrating additional exogenous resistance genes. All the isolated strains exhibited resistance to at least one antibiotic, with some displaying resistance to carbapenems. PCR detection of resistance genes indicated the dissemination of carbapenem resistance genes within some farms. This study confirmed the presence of bla_NDM on plasmids capable of inter-bacterial transmission. Moreover, the farms in LX exhibited significantly higher conjugation frequency of bla_NDM-carrying plasmids than the farms in XS. [Conclusion] Antibiotic resistance of bacteria in aquaculture environments is becoming increasingly serious. The carbapenem resistance gene bla_NDM has spread within turtle farms.

Key words:turtle farms;antibiotic resistance;antibiotic resistance genes;bla_NDM;transmission