Escherichia coli encoding blaNDM-5 associated with community-acquired urinary tract infections with unusual MIC creep-like phenomenon against imipenem.

OBJECTIVES: Carbapenemase-producing Escherichia coli are a major clinical concern. The current study aimed to identify NDM-5-producing E. coli associated with community-acquired urinary tract infections (UTIs) co-harbouring extended-spectrum ß-lactamases (ESBLs) and showing a phenomenon of imipenem minimum inhibitory concentration (MIC) creep. METHODS: A total of 973 urine samples were collected from females aged between 18-49 years diagnosed with UTI in Northeast India (June 2014-July 2016). Isolates were identified by standard microbiological methods. The presence of blaNDM and ESBL genes was determined by PCR and sequencing. PCR-based replicon typing was performed. Plasmid stability of all ß-lactamase-producers and their transformants was analysed by serial passage, and the MIC creep phenomenon was analysed by studying revertants. RESULTS: Among 34 blaNDM-5-positive E. coli isolates, 21 (61.8%) co harboured blaCTX-M-15, followed by multiple combinations of genes. This study revealed diverse plasmid types (HI1, I1, FIA+FIB, FIA and Y). The strains showed progressive plasmid loss after 31 passages. Most if the isolates had MICs of 0.5µg/mL and 1µg/mL to imipenem, ertapenem and meropenem. However, on studying the MIC creep phenomenon, the MIC was found to be elevated from 0.5µg/mL to 64µg/mL and from 1µg/mL to 128µg/mL. Analysis of revertants shows that the MIC of most NDM-positive isolates was reduced to 16µg/mL after the 30th serial passage. CONCLUSION: This study observed a unique phenotype of NDM-producers that has not been reported previously. The observed phenomenon poses a global threat as these pathogens may evade phenotypic screening by routine laboratories.

The First Report of Phenotypic and Molecular Characterization of Extended-Spectrum Beta-Lactamase-Producing Uropathogens in Sikkim and Darjeeling Hills of India.

Extended-spectrum ß-lactamase (ESBL)-producing bacteria are a global health threat both in hospital and in community settings. The emergence of these organisms poses major difficulty in treating infections. This study was carried out to assess major ESBL-producing uropathogens in female patients of Sikkim and Darjeeling by phenotypic and genotypic methods. Out of 1,516 urine samples, 454 uropathogens were isolated with a prevalence rate of 29.94%. Among them, Escherichia coli (74.3%) was the predominant type followed by Klebsiella pneumoniae (20.1%), Pseudomonas aeruginosa (2.4%), and Proteus mirabilis (1.98%). Four different ESBL genes were detected in 63 isolates, which included CTX-M (n = 32), CTX-M+OXA-2 (n = 15), CTX-M-15+OXA-2+TEM (n = 6), OXA-2 (n = 5), TEM+CTX-M-15 (n = 2), TEM+OXA-2+SHV-76 (n = 2), and TEM (n = 1). All ESBL genes (bla genes) were found on a plasmid, which was mostly of HI1, I1, FIA+FIB, FIA, and Y types and was horizontally transferable. Among all ESBL genes, blaCTX-M-I5 group was the most prevalent. The study of urinary tract infection (UTI) caused by ESBL-producing bacteria needs to be studied in other high-altitude parts of India to understand the actual burden of UTI in the female.