The occurrence of extended-spectrum β-lactamase producing Shigella spp. in Tehran, Iran

Background and Objectives: The emergence of extended-spectrum β-lactamase (ESBL)-producing Shigella spp. is of increasing clinical concern specially in children worldwide. The aim of this study was to investigate the occurrence of extended-spectrum β-lactamase producing Shigella spp. in Tehran, Iran. Materials and Methods: The study included all Shigella isolates recovered from pediatric patients aged less than 12 years admitted to a major pediatric hospital in Tehran, Iran, from 2008 to 2010. Bacterial identification, antimicrobial susceptibility testing, extended spectrum β-lactamases (ESBLs) screening and confirmatory tests were performed according to the standard guidelines. Conjugal transfer experiments and plasmid analysis were also carried out. Polymerase chain reaction and sequencing were used to identify the genetic determinants responsible for ESBL production. Results: Four out of 55 Shigella isolates, including three S. sonnei and one S. flexneri, showed an ESBL-positive phenotype. Plasmid transfer of the ESBL phenotype was successful for the S. flexneri isolate only. By PCR and sequencing, one S. sonnei isolate tested positive for the CMY-59 gene, while the other two S. sonnei and the S. flexneri isolates tested positive for the bla TEM-1 and bl