Coexistence of tigecycline resistance genes with two novel -carrying and -carrying transposons in a plasmid.

INTRODUCTION

Tigecycline and carbapenems are considered the last line of defense against microbial infections. The co-occurrence of resistance genes conferring resistance to both tigecycline and carbapenems in was not investigated.

METHODS

A28 was isolated from hospital sewage. Antibiotic susceptibility testing showed resistance to carbapenem and tigecycline. WGS was performed to analyze the antimicrobial resistance genes and genetic characteristics. Plasmid transfer by conjugation was investigated. Plasmid fitness costs were evaluated in transconjugants including a infection model.

RESULTS

Meropenem and tigecycline resistant A28 carries a 199, 972 bp long plasmid PLA28.4 which harbors seven resistance genes. Sequence analysis showed that the 7113 bp transposon Tn is made up of a class I integron without a 5'CS terminal and a complete module flanked by a pair of 25bp insertion repeats. Additionally, the Tn transposon, 20.24 kp long, with a complete 38-bp Tn IR and an incomplete 30-bp Tn IR, is made up of partial skeleton of Tn, a class I integron harboring , and a Tna transposon. Moreover, one cluster was found in the plasmid and another one in the the chromosome. Furthermore, plasmid PLA28.4 could be conjugated to PAO1, with high fitness cost.

DISCUSSION

A multidrug-resistant plasmid carrying and two novel transposons carrying and -resistant genes was found in hospital sewage, increasing the risk of transmission of antibiotic-resistant genes. These finding highlight the necessary of controlling the development and spread of medication resistance requires continuous monitoring and management of resistant microorganisms in hospital sewage.