diversity determination of ctx-m1 producing klebsiella pneumoniae using multilocus variable-number tandem repeat analysis, semnan, iran

Background: ctx-m is the most prevalent and rapidly growing type of the extended-spectrum β-lactamase (esbl) family and ctxm1 is the most common type of blactx-m. objectives: the current study aimed at investigating the genetic diversity of ctx-m-1-producing klebsiella pneumoniae circulating in semnan, iran evaluated by multilocus variable-number tandem repeat analysis (mlva). methods: a total of 110 isolates of k. pneumoniae were collected from different clinical samples. the antibiotic suceptibility and double disk synergy test were determined according to clsi (the clinical and laboratory standards institute) guidelines. the polymerase chain reaction (pcr) method was performed to detect ctx-m-1. the eight loci for mlva genotyping were selected along with the primers previously described. results: imipenem, with 84.7% susceptibility, was themost effective antibiotic against k. pneumoniae. seventy (63.63%) isolates had esbl positive results and 42 (60 %) of them were positive for ctx-m-1 gene. totally, 28mlva genotypes were discriminated, evaluation of diversity indexes (dis) for eight loci showed that six different alleles were the most polymorphic and the most di was 0.807. conclusions: the findings of the current study demonstrated heterogeneity among ctx-m-1-producing k. pneumonia strains. the presence of ctx-m-1 in different mlva types demonstrated that a certain clone is not responsible for spreading the isolates.