Clinical and Molecular Epidemiology of Healthcare-Associated Infections Due to Extended-Spectrum β-Lactamase (ESBL) Producing Strains of Escherichia coli and Klebsiella pneumoniae That Harbor Multiple ESBL Genes

OBJECTIVES. To characterize healthcare-associated infections due to extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia coli and Klebsiella pneumoniae that harbor multiple ESBL genes, as opposed to a single ESBL gene. METHODS. All patients with a confirmed healthcare-associated infection due to an ESBL-producing strain of E.coli or K. pneumoniae were enrolled in the study. Molecular typing of isolates was performed, and the comparative risks and outcomes of patients were analyzed. RESULTS. Among 71 patients with healthcare-associated infection due to an ESBL-producing strain of E. coli or K. pneumoniae, the gene for CTX-M, with or without other ESBL genes, was identified in all 51 (100%) of the patients infected with an E. coli strain and in 18 (90%) of the 20 patients infected with a K. pneumoniae strain. Of these 71 patients, 17 (24%) met the definition of healthcare-associated infection due to an ESBL-producing strain that harbored multiple genes; in multivariate analysis, previous exposure to 3 or more classes of antibiotics (adjusted odds ratio, 4.5 [95% confidence interval, 1.7-75.2]) was the sole risk factor for healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes. Isolates recovered from patients with healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes were more resistant to various antibiotic classes, and, compared with patients with healthcare-associated infection due to an ESBL-producing strain that harbored a single ESBL gene, they were more likely to have ineffective initial empirical antimicrobial therapy (52% vs 94%; odds ratio, 5.1 [95% confidence interval, 1.04-14.5]). CONCLUSIONS. CTX-M ESBL is highly prevalent in Thailand. Patients with healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes were more likely to have had ineffective initial empirical antimicrobial therapy, and, given that antibiotic selection pressure was the only associated risk, we suggest focused antimicrobial stewardship programs to limit the emergence and spread of healthcare-associated infection due to ESBL-producing strains in this middle-income country.