Plasmid-Encoding Extended-Spectrum β-Lactamase CTX-M-55 in a Clinical Shigella Sonnei Strain, China

ABSTRACT

Aims: To characterize a clinical Shigella sonnei strain harboring a conjugatable bla_CTX-M-55-borne plasmid. Materials & methods:S. sonnei strain #1081 was isolated from a dysentery patient in China. A CTX-M-55-encoding plasmid harbored in this strain was transformed to Escherichia coli, and then its complete nucleotide sequence was determined by next generation sequencing. The MIC values of bacterial strains were tested by using Vitec^® 2 (Biomerieux, Marcy l’Etoile, France). Results: Strain #1081 conferred the resistance to multiple beta-lactam antibiotics. bla_CTX-M-55 was the only known antibiotic resistance gene and located in a 3090-bp ISEcp1-bla_CTX-M-55-orf477 transposition unit carried by a conjugatable plasmid p1081-CTXM in #1081. The ISEcp1-mediated transposition provided a sole promoter, which was located adjacently upstream of the inverted repeat right element of ISEcp1, to drive the expression of CTX-M-55. Conclusion: Plasmid p1081-CTXM was a close variant of the IncI2-type plasmid pHN1122-1 that was harbored in a faecal E. coli strain recovered from a dog in China, indicating the potential transfer of CTX-M-55-encoding plasmids from faecal flora E. coli to human pathogen S. sonnei.

KEYWORDS:

• conjugatable plasmid
• CTX-M-55
• ISEcp1
• Shigella sonnei

Financial & competing interests disclosure

This work is funded by the Medical and Technology Twelfth Five-Year Science and Research Key Program (BWS11C073), the National Key Program for Infectious Disease of China (2013ZX10004216), and the National Basic Research Program of China (2014CB744400). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

This work is funded by the Medical and Technology Twelfth Five-Year Science and Research Key Program (BWS11C073), the National Key Program for Infectious Disease of China (2013ZX10004216), and the National Basic Research Program of China (2014CB744400). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.