Acinetobacter indicus Coharboring Tet(X6) and bla_NDM-1 Isolated From Slaughterhouse Waste

Acinetobacter indicus is an important pathogen of nosocomial infection. The purpose of this study was to analyze the resistance and transmission of A. indicus strain AIBD14 isolated from slaughterhouse environment.

A total of 96 environmental samples were collected from slaughterhouse. The antimicrobial susceptibility test was carried out by microbroth dilution method and E-test. Whole genome sequencing and bioinformatics analysis of the AIBD14 were performed, then S1-PFGE and southern blot verified the location of bla_NDM-1 and tet(X6).

The AIBD14 is resistant to meropenem but susceptibility to tigecycline, and coharboring bla_NDM-1 and tet(X6). The bla_NDM-1 is located on the pAIBD14-NDM-1 that cannot be transferred by conjugation. Specifically, bla_NDM-1 is located on the transposon Tn125, and bla_NDM-1 can be transferred to other species with the help of transposon. The genetic background of bla_NDM-1 is "ISAba125-bla_NDM-1-ble_MEL-dsbD-cutA-groES-groEL-insE-ISAba125". pAIBD14-NDM-1 is classified into the GR31 plasmid based on the homology of the repB. Meanwhile, there are two XerC/D-like binding sites on the plasmid, which can mediate the transfer of resistance genes. The tet(X6) gene is located on the chromosome of AIBD14, its downstream is accompanied by the neglected macrolide resistance gene estT, and there is a single copy of the insertion element ISCR2 around tet(X6) as the genetic background "ISAba4-IS3-hp-hp-tet(X6)-estT-guaA-ISCR2".

This is the first report of the coexistence of tet(X6) and bla_NDM-1 in the A. indicus, and it has the risk of horizontal transfer across multiple species. So strict monitoring the multiple-resistant bacteria in the industrial chain is necessary based on the "One Heath".