Genetic heterogeneity and predominance of bla CTX-M -15 in cefotaxime-resistant Enterobacteriaceae isolates colonizing hospitalized children in Tunisia.

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have emerged as important nosocomial pathogens. Community infections by these organisms have been also reported and were associated with previous intestinal colonization. We aimed to characterize cefotaxime-resistant Enterobacteriaceae (CTX-R-En) isolated from hospitalized children in a Tunisian paediatric ward. Seventy CTX-R-En isolates were collected from 227 rectal swabs from hospitalized children in a paediatric ward. Antimicrobial susceptibility testing was determined according to the EUCAST guidelines. Isolates were characterized by polymerase chain reaction (PCR, genes encoding: ESBLs, pAmpC, carbapenemases, plasmid-mediated quinolone resistance, virulence factors in Escherichia coli and Klebsiella pneumoniae isolates, occurrence of classes 1 and 2 integrons, phylogenetic groups of E. coli isolates, ERIC-PCR and PCR-based replicon typing) and conjugal transfer experiments. In total, 65 out of 227 (28·6%) hospitalized children were colonized with CTX-M-R-En, and 70 isolates were identified. Isolates were 59 ESBL-, 7 plasmidic-AmpC (pAmpC)-, 3 ESBL+pAmpC-, and one ESBL+carbapenemase producers. The following bla genes were identified: bla CTX-M-15 (n = 54), bla CTX-M-1 (n = 5), bla CTX-M-9 (n = 2), bla CTX-M-13 (n = 1) and bla CTX-M-14 (n = 1), bla CMY-2 (n = 5), bla CMY-4 (n = 4), bla ACC-1 (n = 1) and bla OXA-48 (n = 1). Our results showed that hospitalized children were colonized with various CTX-R-En-producing several beta-lactamase enzymes.