High prevalence of CTX-M β-lactamase-producing Enterobacteriaceae in stool specimens obtained from healthy individuals in Thailand

To determine the prevalence of CTX-M beta-lactamase-producing Enterobacteriaceae in stool specimens obtained from healthy individuals in a rural area of Thailand. Bacteria in stool specimens were screened for extended-spectrum beta-lactamase (ESBL) production on McConkey agar with cefotaxime and confirmed by the double-disc synergy test. Genetic detection and genotyping of CTX-M-type ESBL was performed by PCR with bacterial DNA extracted from isolates. A markedly high number (82 of 141, 58.2%) of the specimens showed the presence of CTX-M beta-lactamase-producing Enterobacteriaceae, as confirmed by both phenotypic and genetic examinations. The majority of the CTX-M beta-lactamase-producing bacteria were Escherichia coli (85.1%). The study revealed the wide dissemination of CTX-M beta-lactamase-producing Enterobacteriaceae in the healthy population.