Extended-Spectrum β-lactamase-Producing Escherichia coli Isolated in the Al-Amiri Hospital in 2003 and Compared with Isolates from the Farwania Hospital Outbreak in 1994-96 in Kuwait

Abstract

Extended-spectrum -lactamases (ESBLs) are a major problem in Kuwait and an accurate method for their detection is essential. This study was designed to evaluate the efficacy of the commercial system (Vitek 2) to identify ESBLs in clinical isolates of Escherichia coli and relate this to their identification by agar dilution methods for use in a diagnostic laboratory. The presence of the major ESBLs parental enzyme groups was confirmed by PCR and the similarity of the strains was determined by pulsed field gel electrophoresis (PFGE) on DNA, cleaved using XbaI endonuclease, to identify clonal spread.

Seventy-one separate E. coli isolates from 65 patients were tested. Sixty-two isolates were from 56 patients from the Al-Amiri Hospital and nine isolates from neonates from Farwania Hospital. The isolates were screened for ESBL activity by the Vitek 2 system. Isolates showing positive results were further tested with Etest ESBL strips and by the disc approximation methods. All the isolates were flagged as ESBL-positive by the Vitek 2 advanced expert system (AES). Isolates from all the 65 patients were detected as ESBL positive by the Etest, only if both ESBL strips were used. The double disc approximation test using five different antibiotics could detect ESBL presence in isolates from only 46 patients. In this test, the synergy with cefepime was the most sensitive in ESBL detection, showing their presence in 41 isolates. PCR with primers for bla _TEM and bla _SHV demonstrated that one or both of these enzymes in all isolates. PFGE revealed that many different clones were present amongst the isolates.

The epidemiology of ESBL E. coli in Kuwait is complex. Many distinct strains are already present in the population, as shown by the results of PFGE. Several testing methods may be required to detect all strains harboring ESBLs.

Keywords:

• ESBL
• E. coli
• β-lactamases
• cephalosporins
• PFGE
• PCR