Background –
Extended-spetrum β-lactamases (ESBLs) producing Escherichia coli (E.coli) is an emerging major pathogen worldwide. It has the ability to hydrolyze and cause resistance to various types of newer β-lactamases antibiotics, including third generation cephalosporins and monobactams. Organisms that produce ESBLs remain an important reason for therapy failure with cephalosporin and have serious consequences for infection control. Those clinical microbiology laboratories detect and report ESBL-producing organism is therefore important. The objectives of this study were to determine the prevalence, genotype and clonal relationship of extended-spectrum β-lactamases (ESBLs) in 209 clinical Escherichia coli strains from Macao, China.

Methods –
Phenotypic detection was used by the standard disk diffusion method, double-disk synergy test and E-test. The genotypic characterization was detected by isoelectric focusing analysis (IEF). The clonal relationship between the different isolates was studies by pulsedfield gel electrophoresis (PFGE).

Results –
The prevalence rate of ESBLs was 30.1% according to the Clinical and Laboratory Standards Institute. By isoelectric focusing analysis, polymerase chain reaction and sequencing, we detected the major genotypic characterization of ESBLs was CTX-M-14 (76.2%). Two strains showed indistinguishable patterns by pulsed-field gel electrophoresis.

Conclusions –
This study documented the CTX-M family as the predominant ESBL type among Macao population. The spread of CTX-M enzymes is concerning and deserves close monitoring in further investigation.