Detection of CTX-M-type extended-spectrum-beta-lactamases (ESBLs) in Escherichia coli isolated in UKMMC

Abstract

Extended-spectrum-beta-lactamase (ESBL) is an enzyme produced by Enterobacteriaceae to confer resistance to extended-spectrum cephalosporins. These enzymes were mostly derived from the classical penicillinases (TEM-1, TEM-2 and SHV-1 ß-lactamases). ESBL-producing organisms have spread worldwide and pose a management dilemma when very limited antibiotics are left for treatment of infections caused by these organisms. Infection control also faces a challenge when these plasmid-mediated enzymes are easily transmissible to other organisms. Hence, detection of these organisms is crucial to ensure appropriate antibiotics can be delivered and effective infection control measures can be employed to limit its spread. However, in the last decade, another type of ESBL has been discovered and is not related to TEM- or SHV-type ESBLs. This enzyme has a preference to hydrolyze cefotaxime (CTX) rather than ceftazidime (CAZ), hence the name CTX-M-type ESBLs. Many laboratories have used CAZ as the indicator for ESBL production and with the emergence of CTX-M-type ẞ-lactamase, many CTX-M-type ESBL-producing organisms may be missed if CAZ alone is used for indicator for ESBL production. A cross-sectional descriptive study was carried out in UKMMC from January to June 2009, to determine the prevalence of ESBL-producing ESBLS and to detect the presence of CTX-M-type ESBLS among these isolates by molecular method. A total of 111 E.coli isolates were screened positive for ESBL production, however only 96 were confirmed as ESBL-producers by phenotypic confirmatory test using combination disk diffusion method. Out of these, 76 isolates were subjected for detection of blacTX-M genes using multiplex PCR. From these, 70 (92.1%) were CTX-M-type ESBLS with majority from CTX-M-1 group (77.1%), followed by CTX-M-9 group (21.4%) and one (1.4%) from CTX-M-2 group. No CTX-M-8 or -25/26 groups isolated. These findings were similar to other studies in Malaysia and Asia, which demonstrated CTX-M-type ESBLs were the predominant ESBL types and CTX-M-1 and -9 groups were the majority among the clinical isolates.