الملخص الإنجليزي
Abstract
Extended Spectrum B-lactamases (ESBLs) are plasmid-encoded B-lactamases enzymes which are capable of hydrolyzing the B-lactam ring in a wide range of B-lactam antibiotics including penicillins, oxyimino-cephalosporins and monobactams but do not affect cephamycins or carbapenems. Since their first description in 1983 in Europe, ESBLs dissemination has been reported worldwide. The ESBL plasmids frequently carry genes encoding resistance to other classes of drugs, which results in co-resistance of the ESBL producing bacteria to a wide variety of commonly used antimicrobial agents. Therefore, antibiotic options in the treatment of infections caused by ESBL producing organisms are extremely limited.
A total of 350 clinical isolates of Escherichia coli (n=221) and Klebsiella pneumoniae (n=129) recovered from various clinical samples received at Sultan Qaboos University Hospital were collected. These isolates were screened for ESBL production using ceftazidime (30 ug) and cefotaxime (30 ug). Screen positive isolates were subjected to two phenotypic confirmatory tests viz: Double Disc Combined Test (DDCT) and Double Disk Synergy Test (DDST). Identification of ESBLs in screen positive isolates was carried out by PCR using family specific primers. Susceptibility of ESBL positive isolates to commonly use antimicrobial agents other than cephalosporins was tested. Overall, 130/350 (37.1%) clinical isolates were screen positive for ESBL production by both ceftazidime and cefotaxime. A total of 110/130 (84.6%) of the screen positive isolates showed positive results by both phenotypic confirmatory tests. A total of 125/350 (35.7%) isolates were found to harbour ESBL genes by PCR. As many as 73/221 (33%) isolates of E. coli and 52/129 (40.3%) isolates of K. pneumoniae were found to harbour the ESBL genes. A total of 76.8% of the isolates harboured TEM type of ESBLS, 69.6%, harboured CTX-M genes while 46.4% of the screen positive isolates were found to harbour SHV type ESBL genes. A higher percentage of K. pneumoniae isolates were found to harbour all the three ESBL genes (42.3%) in comparison to E.coli isolates as only 5.5% of these isolates had all the three ESBL genes. The CTX-M ESBL genes detected in 83 isolates were found to belong to CTX-M group-1. CTX-M group-9 genes were not detected in any of the isolates. A high percentage of ESBL producing isolates showed resistance to amoxicillin clavulanate (88%) and ciprofloxacin (76.8%). While as many as 94.5% of the ESBL positive E. coli isolates were susceptible to imipenem only 15.5% of the K. pneumoniae isolates were susceptible to imipenem. This study established a high prevalence of ESBL producing E. coli and K. pneumonia clinical isolates at SQUH. It also showed that both ceftazidime (CAZ) and cefotaxime (CTX) are equally efficient screening substrates for ESBL detection. Both the confirmatory tests were equally sensitive as confirmatory phenotypic tests for detection of EŞBL production. In addition, this study found that PCR could identify ESBL genes in isolates that were negative by phenotypic confirmatory test.
