New Delhi metallo-beta-lactamase (NDM-1) is a novel metallo-beta-lactamase (MBL). Sporadic cases of NDM-1 positive strains have been reported from different countries, suggesting a widespread dissemination. The aim of this study was the detection of MBLs in Enterobacteriaceae isolated from patients in Tehran hospitals. After identification tests, the susceptibility to the antibiotics was done by Kirby–Bauer method and broth microdilution. Carbapenem-resistant isolates were tested for carbapenemase production using the modified Hodge test (MHT). Carbapenem-resistant strains screened for bla _KPC gene and genes encoding MBLs. Twenty-three isolates (6.3%) were resistant to meropenem, eleven isolates (3%) were resistant to ertapenem, and four isolates (1.1%) were resistant to imipenem. MHT was positive in 11 (47.8%) of the carbapenem-resistant isolates. In March 2011, we detected a multiple drug-resistant Klebsiella pneumoniae isolate that was resistant to all tested antibiotics except colistin. PCR confirmed that this isolate contained bla _NDM-1 , bla _TEM , bla _SHV , and bla _CTX-M . This is the first report on the detection of MBL NDM-1 in Iran. The rapid spread of NDM-1-positive bacteria proved to be a major challenge for the treatment and control of infectious diseases.

Despite the fact that the bla_OXA-48 and bla_NDM-1 genes have successfully disseminated among Klebsiella pneumoniae isolates worldwide, outbreaks remain unidentified in Iran. Here we examined the molecular epidemiology of 96 carbapenem-resistant K. pneumoniae recovered from an Iranian hospital. A total of 96 non-replicate carbapenem-resistant K. pneumoniae were recovered from clinical specimens in a university hospital. Detection of ESBLs and carbapenemases produced by studied strains was performed using PCR and DNA sequencing. The bacterial isolates were assigned to clonal lineages by PFGE and MLST. In addition, plasmids were analysed by PCR-based replicon typing and conjugation assays. All isolates harboured bla_OXA-48 and bla_NDM-1 genes together or alone. Almost all strains also carried ESBL genes. Eighty-seven isolates of K. pneumoniae were categorized into seven pulsotypes. The predominant strain clusters/pulsotypes associated with the outbreak corresponded to ST11 (48/96) and ST893 (31/96). Plasmids carrying bla_OXA-48 and bla_NDM-1 were successfully transferred to Escherichia coli K12 as the recipient strain. bla_OXA-48 was located on IncL/M plasmids of ∼39 kb, while bla_NDM-1 was carried by either an IncFII plasmid of ∼50 kb or an untypeable plasmid of ∼4 or 10 kb. We describe two separate outbreaks of bla_OXA-48- and bla_NDM-1-carrying K. pneumoniae strains associated with dissemination of the ST11 and ST893 clones, with the ICU acting as the epicentre. The spread of plasmids carrying carbapenemase genes resulting in fulminant antimicrobial resistance is a severe concern.

Carbapenem-resistant Enterobacterales (CRE) is an increasing problem worldwide. Here, we examined the clonal relatedness of 71 non-repetitive CRE isolates collected in a university hospital in Tehran, Iran, between February 2015 and March 2016. Pulsed-field gel electrophoresis (PFGE) and MLST were used for epidemiological analysis. Screening for antibiotic resistance genes, PCR-based replicon typing, conjugation experiments, and optical DNA mapping were also performed. Among all 71 isolates, 47 isolates of Klebsiella pneumoniae (66.2%), eight Escherichia coli (11.2%), five Serratia marcescens (7%), and two Enterobacter cloacae (2.8%) harbored bla_NDM–1 and bla_OXA–48 genes together or alone. PFGE analysis revealed that most of the OXA-48- and NDM-1-producing K. pneumoniae and all of OXA-48-producing S. marcescens were clonally related, while all eight E. coli and two E. cloacae isolates were clonally unrelated. The predominant clones of carbapenemase-producing K. pneumoniae associated with outbreaks within the hospital were ST147 (n = 13) and ST893 (n = 10). Plasmids carrying bla_NDM–1 and bla_OXA–48 were successfully transferred to an E. coli K12-recipient strain. The bla_OXA–48 gene was located on an IncL/M conjugative plasmid, while the bla_NDM–1 gene was located on both IncFII ∼86-kb to ∼140-kb and IncA/C conjugative plasmids. Our findings provide novel epidemiologic data on carbapenemase-producing Enterobacterales (CPE) in Iran and highlight the importance of horizontal gene transfer in the dissemination of bla_NDM–1 and bla_OXA–48 genes. The occurrence and transmission of distinct K. pneumoniae clones call for improved infection control to prevent further spread of these pathogens in Iran.