Hospital sewage water: a reservoir for variants of New Delhi metallo-β-lactamase (NDM)- and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae

New Delhi metallo-β-lactamase (NDM)-producing Enterobacteriaceae have become a threat to public health. Hospital sewage is generally unexplored, having the potential to harbour bacteria causing healthcare-associated infections. Hence, this study was initiated to monitor NDM-producing Enterobacteriaceae in hospital sewage water. A total of 32 isolates with blaNDM variants were detected in hospital sewage water, including 17 Escherichia coli, 8 Citrobacter freundii, 4 Shigella boydii, 2 Citrobacter braakii and 1 Citrobacter farmeri, showing resistance to all antibiotics except colistin. All 32 isolates carried blaNDM (9 blaNDM-1, 11 blaNDM-4, 10 blaNDM-5 and 2 blaNDM-7), 24 isolates carried blaCMY variants (1 blaCMY-2, 3 blaCMY-4, 5 blaCMY-6, 11 blaCMY-42, 2 blaCMY-86 and 2 blaCMY-139), 20 isolates carried blaOXA-type (17 blaOXA-1 and 3 blaOXA-48), 19 isolates carried blaCTX-M and 9 isolates carried ampC on conjugative plasmids of IncFIA, IncFIB, IncFIC, IncP, IncY, IncHI1 and IncI1 types. In E. coli, coexistence of blaNDM-1 with blaCMY-6 and blaCMY-139, of blaNDM-4 with blaCMY-6, blaCMY-42 and blaCMY-86, of blaNDM-5 with blaCMY-6 and blaCMY-42, and of blaNDM-7 with blaCMY-6 was observed. NDM-5-producing S. boydii and NDM-7-producing C. freundii were identified as well as detection of an association of blaNDM-4 and blaOXA-48 in C. braakii and C. farmeri. A class 1 integron was also found on a plasmid. ISAba125 and bleomycin genes were found surrounding all blaNDM variants. The emergence and dissemination of blaNDM variants in hospital sewage water is a matter of concern, creating an endemic scenario leading to the level of an outbreak.