Detection and molecular characterization of blaNDM−1 in uropathogenic Escherichia coli isolates from hospitalized patients in northern Iran

The emergence of carbapenem-resistant Escherichia coli producing NDM-type metallo-β-lactamases encoded by the bla NDM gene is a serious public health threat. This retrospective laboratory-based study investigated the frequency and molecular characteristics of the bla NDM gene among 179 archived, nonduplicate uropathogenic Escherichia coli isolates originally recovered from urine samples of hospitalized patients with urinary tract infections in Babol, northern Iran. The bla NDM gene was detected in 6 out of 179 isolates (3.35%). Sequencing revealed that all positive isolates carried the bla NDM−1 variant, showing 100% nucleotide identity with the reference sequence. Phylogenetic analysis demonstrated high sequence similarity and compact clustering among the isolates. Phenotypically, 15.1% of isolates showed imipenem resistance by disk diffusion. Although the prevalence of bla NDM−1 (3.35%) was lower than some regional reports, the identification of this globally disseminated carbapenemase is epidemiologically significant. The high similarity among bla NDM−1 sequences reflects conservation of this resistance determinant but does not independently establish clonal relatedness, clonal dissemination, or horizontal gene transfer. ERIC-PCR provided supplementary information on genomic fingerprint similarity, although its limited resolution precludes definitive inference of clonality. Higher-resolution genomic and plasmid-typing methods are needed to clarify transmission pathways and the mechanisms underlying bla NDM−1 dissemination. Continued molecular surveillance and appropriate infection-control measures may help limit its spread.