Prevalence of extended spectrum beta-lactamase-producing enterobac-teriaceae by phenotypic and genotypic methods in intensive care units in Tehran, Iran

ABSTRACT

The occurrence of Extended Spectrum beta-Lactamase [ESBL]-producing Entrobacteriaceae has been steadily increased in recent years, resulting in limitation of therapeutic options. The purpose of this study was to determine prevalence of ESBL-producing Entrobacteriaceae isolated from Intensive Care Units [ICUs] and to investigate their phenotypic and genotypic characteristics. A total of one hundred fifty isolates were collected from urine and urinary catheter, sputum, blood, wound and other clinical samples from patient admitted in ICUs. All isolates were identified by biochemical tests and then were screened for ESBL production by Disk Agar Diffusion [DAD] according to the Clinical and Laboratory Standards Institute [CLSI] guideline. The species that met screening criteria were further tested for the effects of clavulanic acid by confirmatory method. ESBL-positive species were tested for bla[TEM] and bla[SHV] genes by PCR assay. Of total of 150 bacterial isolates, 133 [89.3%] isolates were positive in the resistance to all tested cephalosporin indicators; and 89 [59.3%] isolates were confirmed as ESBL producer. Klebsiella pneumoniae, Escherichia coli and Entrobacter spp. were the most ESBL-producing species. All isolates were sensitive to imipenem. The bla[TEM] [55.5%] was the most common gene detected in ESBL phenotypic-positive isolates using PCR method. The present study shows high prevalence of ESBL-producing Entrobacteriaceae from ICU patients. The increased rate of these species is mainly due to the inadequate and unnecessary antimicrobial therapy. Rational administration of beta-lactams and appropriate infection control policies may reduce prevalence of ESBL-producing bacteria in ICUs