RESUMO
To determine the prevalence of extended spectrum b-lactamase [ESBL] among multidrug resistant isolates of enterobacteriaceae and non-fermenting gram-negative bacilli. This study was carried out at the Almana General Hospital, Eastern Province, Kingdom of Saudi Arabia, during the period March 2002 through to June 2003. Multidrug resistant gram-negative isolates from patients admitted to the surgical, medical, pediatric, long-term care and intensive care units were studied for the presence of the ESBL enzyme. A total of 3231 gram-negative organisms were studied for the presence of multidrug resistance and ESBLs. Of these, 197 [6%] isolates were multidrug resistant [MDR], and 156 [4.8%] were positive for ESBL. Seventy nine percent of the MDR strains were positive for ESBL. The most frequent isolates were Escherichia coli [1116] and Klebsiella pneumoniae [687] and ESBL was detected in 72 [6.5%] and 37 [5.4%] of these isolates. The MDR strains that produced ESBL were most commonly isolated from surgical care patients with diabetic fascitis [83%] and patients with indwelling Foley's catheter [79%]. Extended spectrm b-lactamase producing strains showed the highest susceptibility to imipenem and meropenem [86%]. The non-b-lactam antibiotics with greatest activity against these ESBL strains in vitro were ciprofloxacin [72%], amikacin [70%], tobramycin [67%] and gentamicin [56%]. The majority [79%] of the MDR enterobacteriaceae and non-fermenting gram-negative bacilli tested over 15-months were positive for ESBL. Imipenem, meropenem, ciprofloxacin and amikacin showed the highest activity against these ESBL-producing organisms. Due to the growing problem of infection with ESBL-producing bacteria, which are frequently resistant to many classes of antibiotics resulting in difficult-to-treat infections, clinicians need to be familiar with the clinical significance of these enzymes and potential strategies for dealing with them