مقاومت آنزيمي بتالاكتاماز با محدوده اثر وسيع در گونه هاي كلبسيلا پنمونيه و اشريشيا كلي در بيماران بستري و سرپايي

Extended-Spectrum Beta-lactamase Resistance in Clinical Isolates of Klebsiella pneumoniae and Escherichia coli in In-Patient and Out- Patient Groups

Background and Objectives: Extended-Spectrum Beta-lactamases (ESBLS) are common kind of beta-lactamases in routine causative agents of nosocomial infections. Detection of this kind of resistance in laboratory (in vitro) is difficult, because some resistant strains will present themselves as susceptible, while they express resistance in vivo. This cause inappropriate treatment and may increase mortality rate due to misunderstandings in resistance detection. This study was conducted to evaluate epidemiological and microbiological aspects of ESBLs in two distinct genera involved in nosocomial infections, namely Klebsiella spp. and Escherichia coli. Material and Methods: In a period of one year (from October 2003 to October 2004), 221 and 255 isolates of Klebsiella spp. and Escherichia coli were isolated in medical centers and clinical laboratories of Tehran and Tabriz, respectively. While susceptibility tests were performed, all of the isolates were also examined using double disk synergy test (DDST), three dimensional test (TDT) and ESBL E-test methods for enzymatic beta-lactamase resistance detection. Results: Our finding indicated that prevalence of beta-lactamase resistant species in Tehran is high a compared to Tabriz. Prevalence of resistant species was evaluated as 31.4% and 12.2% for Klebsiella spp. and 6.1% and 1.7% for Escherichia coli in in-patient and out-patient groups respsctively in Tehran. This prevalence rate for Tabriz included 21.4% and 9.1% for Klebsiella spp. and 4.6% and 1.1% for Escherichia coli in in-patient and out-patient groups respsctively. Different patterns of resistance in in-patients and out-patient observed, in which higher levels of resistance were present in in-patients group. Conclusion: Our results revealed high prevalence of ESBL resistance in bacterial isolates from Tehran and Tabriz cities. Thus screening of clinical isolates for ESBL resistance is critical.