Bacterial plasmid genome analysis and the mechanism of resistance gene transfer in the clinical Shigella sonnei isolate 1173

Abstract:

[Objective] To sequence and analyze plasmid p1173-CTXM from the clinical multidrug-resistant Shigella sonnei isolate 1173 with the aim of investigating the mechanism of bla_CTX-M-64resistance gene transfer. [Methods] A double-disk synergy test was conducted to determine if strain 1173 produced extended-spectrum beta-lactamase (ESBL), then antibiotic resistance genes were PCR-amplified and sequenced. Conjugation experiments were used to verify the transferability of plasmids carrying ESBL genes. The transconjugant was detected to certify the production of ESBL and the existence of corresponding resistance genes. Strains 1173 and 1173-CTXM-EC600 underwent testing for antimicrobial drug susceptibility. Plasmid p1173-CTXM-EC600 was sequenced by high-throughput genomic sequencing to illustrate the mechanism of resistance gene transfer. [Results] The multidrug-resistant isolate Shigella sonnei 1173 was shown to be an ESBL-producing strain and to carry the antibiotic resistance genes bla_CTX-M-64 and bla_TEM; however, only bla_CTX-M-64 was horizontally transferred to the recipient strain EC600 which endowed the corresponding antibiotic resistant profiles to EC600. Sequencing and bioinformatics analysis revealed that the resistance gene bla_CTX-M-64 was carried by the ISEcp1-bla_CTX-M-64-Δorf477 transposition unit. [Conclusion] The resistance gene bla_CTX-M-64 carried by plasmid p1173-CTXM mediated the resistance of Shigella sonnei isolate 1173 to multiple antibacterial agents. Horizontal transfer of bla_CTX-M-64 was mediated by the ISEcp1-bla_CTX-M-64-Δorf477 transposition unit.

Key words:Shigella sonnei;plasmid;multidrug resistance;transposition unit;mobile element;bla_CTX-M-64