ABSTRACT
Increasing resistance due to the production of extended-spectrum β-lactamase (ESBL) in Escherichia coli is a major problem to public health and CTX-M enzymes have become the most prevalent ESBL worldwide. In this study, resistance profiles of E. coli isolated in Korea and the genetic environments of bla(CTX-M) genes were analyzed by PCR and direct sequencing to clarify the mechanisms of spread of CTX-M. Resistance rates of CTX-M-producing E. coli, including β-lactams, fluoroquinolones and aminoglycosides, were significantly higher than that of CTX-M-non-producers (p<0.01). Of 41 tested, 39 (95.1%) isolates of CTX-M-producing E. coli showed resistance transfer by conjugation. All the transconjugants harboured large plasmids of 118~172 megadalton. Insertion sequence ISEcp1B was detected in the upstream of the bla(CTX-M) in 38 (92.7%) isolates with bla(CTX-M). ISEcp1B was disrupted by IS26 in 16 (39.0%) isolates with bla(CTX-M). ISEcp1B carried −35 and −10 promoter components between right inverted repeat (IRR) and the start codon of bla(CTX-M). orf477 or IS903D was observed in the downstream of the bla(CTX-M) in all the isolates with bla(CTX-M-3/15/55) or with bla(CTX-M-14/27), respectively. Sequence similar to IRR of ISEcp1B was located downstream of orf477. Target duplication sequences were detected both upstream of IRL and downstream of IRR. These results showed the involvement of ISEcp1B in the mobilization of the resistance genes. In conclusion, the surrounding DNAs of bla(CTX-M) genes were very diverse, and the spread and the expression of CTX-M may be deeply related with ISEcp1B. These informations will provide important knowledge to control the increase in CTX-M-ESBLs.
Subject(s)
Aminoglycosides , Codon, Initiator , DNA , Escherichia coli , Escherichia , Fluoroquinolones , Korea , Plasmids , Polymerase Chain Reaction , Public HealthABSTRACT
Purpose: The present study was aimed to investigate the genetic context, association with IS26 and horizontal transmission of SHV‑148 among Escherichia coli in Tertiary Referral Hospital of India. Methodology: Phenotypic characterisation of extended‑spectrum beta‑lactamases (ESBLs) was carried out as per CLSI criteria. Molecular characterisation of blaSHV and integron was carried out by polymerase chain reaction (PCR) assay and confirmed by sequencing. Linkage of IS26 with blaSHV‑148 was achieved by PCR. Purified products were cloned on pGEM‑T vector and sequenced. Strain typing was performed by pulsed field gel electrophoresis with XbaI digestion. Transferability experiment and antimicrobial susceptibility was performed. Results: A total of 33 isolates showed the presence of SHV‑148 variant by sequencing and all were Class 1 integron borne. PCR and sequencing results suggested that all blaSHV‑148 showed linkage with IS26 and were present in the upstream portion of the gene cassette and were also horizontally transferable through F type of Inc group. Susceptibility results suggest that tigecycline was most effective. Conclusion: The present study reports for the first time of SHV‑148 mediated extended spectrum cephalosporin resistance from India. Association of their resistance gene with IS26 and Class 1 integron and carriage within IncF plasmid signifies the potential mobilising unit for the horizontal transfer.