Detection of New Delhi Metallo--Lactamase Variants NDM-4, NDM-5, and NDM-7 in Enterobacter aerogenes Isolated from a Neonatal Intensive Care Unit of a North India Hospital: A First Report

A total 402 Enterobacteriaceae isolates were recovered from blood and rectal swabs of 1,000 infants admitted to the Neonatal Intensive Care Unit (NICU) of the Jawaharlal Medical College and Hospital Aligarh, India. Carbapenamase producers were determined by Carba NP phenotype biochemical assay. Out of 402 isolates, it was the first time three of the isolates were identified as Enterobacter aerogenes carrying bla(NDM-4,)bla(NDM-5,) and bla(NDM-7) genes. These genes were identified by polymerase chain reaction (PCR) and sequence analysis. The isolates were further characterized to know the plasmid type and genetic environment features, including integron and IS elements. All the three E. aerogenes isolates (AK-93, AK-95, and AK-96) were resistant to all -lactams, including carbapenems. The -lactamase genes bla(OXA-1), bla(OXA-9,)bla(SHV-1), and bla(VIM-2) were also found to be coassociated with bla(NDM-4) in AK-93, bla(OXA-1), bla(OXA-9,) and bla(CMY-149) were found to be coexisted with bla(NDM-5) in AK-95, and bla(OXA-1;)bla(OXA-9,) and bla(CMY-145) were also found to be coassociated with bla(NDM-7) in AK-96, identified by PCR analysis. Plasmid-based replicon typing revealed plasmids of different incompatibility in E. aerogenes in each of the isolates, AK-93 AK-95, and AK-96, respectively. ERIC-PCR was performed for the analysis of genetic relatedness of the strains. We found bla(NDM-4), bla(NDM-5,) and bla(NDM-7) producing three E. aerogenes strains, which were not clonally related. Genetic environment analysis revealed the presence of bleomycin resistance gene (ble(MBL)) to downstream of bla(NDM) and complete ISAba125 sequence were found upstream of bla(NDM) in all the three variants of these isolates. This is the first time we have identified bla(NDM-4), bla(NDM-5,) and bla(NDM-7) in E. aerogenes species, isolated from the NICU of a tertiary care hospital in India.