IncFII plasmid carrying antimicrobial resistance genes in Shigella flexneri: Vehicle for dissemination.

OBJECTIVES

Plasmids harbouring antimicrobial resistance determinants in clinical strains are a significant public-health concern worldwide. The present study investigated such plasmids in clinical isolates of Shigella flexneri.

METHODS

A total of 162 Shigella isolates were obtained from stool specimens in the year 2015. Among the 70 multidrug-resistant (MDR) Shigella spp., 27 S. flexneri isolates were randomly selected for further characterisation. Antimicrobial resistance genes (ARGs) and plasmid incompatibility (Inc) types were analysed.

RESULTS

IncFII plasmids were found in 63% (17/27) of the studied S. flexneri isolates. ARGs such as dhfr1a (81%), sulII (74%), blaOXA (74%), blaTEM (33%), blaAmpC (30%), qnrS (15%) and qnrB (4%) were identified by PCR, whereas blaCTX-M was not detected. Next-generation sequencing of a representative S. flexneri IncFII-type plasmid (pSF470) revealed the presence of blaTEM1-B, blaDHA-1, qnrB10, mphA, sulI, sulII, strA, strB and tetR ARGs along with the intI1 integrase gene. In addition, pMLST analysis showed that the replicon belonged to F2:A-:B- type.

CONCLUSIONS

This study helps to know the prevalent plasmid types in MDR Shigella isolates and will improve our understanding of resistance dissemination among enteric bacteria. ARGs in plasmids further highlight the importance of such studies in enteric bacteria.