Dissemination of carbapenem resistance and plasmids encoding carbapenemases in Gram-negative bacteria isolated in India

Background Carbapenem resistance in Gram-negative bacteria is an ongoing public health problem of global dimensions leaving very few treatment options for infected patients. Objectives To study the dissemination of plasmid-borne carbapenemase genes in Gram-negative bacteria from a diagnostic centre in Tamil Nadu, India. Methods A total of 151 non-repetitive isolates belonging to 10 genera were collected between January 2015 and December 2016 from a diagnostic centre in Tamil Nadu. The isolates included Escherichia coli (n=57), Klebsiella pneumoniae (n=45), Pseudomonas aeruginosa (n=10), Salmonella Typhi (n=8), Enterobacter cloacae (n=8), Acinetobacter baumannii (n=7), Serratia marcescens (n=5), Achromobacter xylosoxidans (n=5), Proteus mirabilis (n=5), Klebsiella oxytoca (n=5) and Elizabethkingia meningoseptica (n=1). Results Of the 151 isolates, 71% (n=107) and 68% (n=103) were found to be resistant to meropenem and imipenem, respectively. The most prevalent beta-lactamase gene was bla(NDM-1) (n=22), followed by bla(OXA-181) (n=21), bla(GES-1) (n=11), bla(OXA-51) (n=9), bla(GES-9) (n=8), bla(OXA-23) (n=7) and bla(IMP-1) (n=3). We also observed bla(OXA-23) in E. coli (n=4), and three K. pneumoniae were positive for both, bla(OXA-23) and bla(OXA-51). Plasmid incompatibility (inc/rep) typing results showed that the resistance genes (n=11) were present in the isolates carrying plasmid-types IncX, IncA/C, IncFIA-FIB and IncFIIA. The plasmid-borne resistance genes in E. coli and K. pneumoniae were transferred to susceptible E. coli AB1157. Conclusions This study highlights the prevalence of carbapenem resistance and the acquisition of plasmid-borne carbapenemase genes in Gram-negative bacteria isolated at this centre.