Prevalence and molecular characterization of extended-spectrum β-lactamase-producing Klebsiella pneumoniae in Riyadh, Saudi Arabia

BACKGROUND AND OBJECTIVES: Reports on extended-spectrum beta-lactamases (ESBL) production by Enterobacteriaceae, and especially in Klebsiella pneumoniae, are few in Saudi Arabia. Therefore, we determined the prevalence of ESBL in K pneumoniae from Riyadh and characterized the predominant beta-lactamase gene in these isolates. METHODS: A total of 400 K pneumoniae samples were isolated from two hospitals in Riyadh during 2007 and screened for production of ESBL using ESBL-E-strips and combined disk methods. PCR assay was used to detect bla(TEM), bla(SHV), and bla(CTX-M) genes. RESULTS: Phenotypic characterization identified a high ESBL rate of 55% of K pneumoniae isolates. ESBL producing K pneumoniae were PCR positive for SHV, TEM and CTX-M beta-lactamase genes with prevalences 97.3%, 84.1% and 34.1%, respectively. Within the CTX-M family, two groups of enzymes, CTX-M-1 and CTXM- 9-like genes were found with prevalences of 60% and 40%, respectively. CONCLUSIONS: This study confirms the high rate of ESBL in K pneumoniae clinical isolates in hospitals in Riyadh. This study demonstrates the worldwide spread of bla(CTX-M) genes. This first report of the presence of the bla(CTX-M) gene in clincial isolates in Saudi Arabia is evidence of the continuing worldwide spread of this gene.