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Escherichia coli colonizing healthy children in Tunisia: High prevalence of extra-intestinal pathovar and occurrence of non-extended-spectrum-β-lactamase-producing ST131 clone

Ferjani, Sana, Saidani, Mabrouka, Maamar, Elaa, Harbaoui, Sarra, Hamzaoui, Zeineb, Hosni, Houda, Amine, Faouzi Slim, Boubaker, Ilhem Boutiba Ben
International journal of antimicrobial agents 2018 v.52 no.6 pp. 878-885
Escherichia coli, aminoglycosides, ampicillin, antibiotic resistance, carbapenems, cephalosporins, children, colistin, hygiene, intestinal microorganisms, mutation, pandemic, pathogenicity islands, pathogens, pathovars, phylogeny, plasmids, quinolones, replicon, resistance genes, sulfamethoxazole, ticarcillin, virulence, Tunisia
This study was performed to investigate the distribution of antimicrobial resistance genes and extra-intestinal virulence determinants in a collection of 98 Escherichia coli strains isolated from rectal swabs of healthy children. Forty-six isolated strains were resistant to at least one of the tested antibiotics (usually active against enterobacteria). They were mainly resistant to ampicillin and ticarcillin (42.97%), tetracyclin (26.5%), and trimethoprim/sulfamethoxazole (18.4%). No resistance to the third generation of cephalosporins, carbapenems, aminoglycosides and colistin was found. Resistance to penicillins was encoded by blaTEM-1 (n=34) and blaSHV-1 genes (n=4). Tetracyclin resistance was encoded by tetB (n=12), tetA (n= 5), and tetC (n=1) genes. Amongst resistant quinolones isolated (n=5), chromosomal mutations in gyrA and parC genes were detected in four isolates and qnrS1 gene in two strains. Nine plasmid replicon types were detected; IncFIB (n=36) and IncI1 (n=7) were the most frequent ones. Isolates frequently belonged to phylogenetic groups A (51.1%) and D (27.5%). Extra-intestinal pathovar (n=38) occurred mainly in B2 phylogroup (P=0.0002). Amongst them, two isolates (non-extended-spectrum-β-lactamase (ESBL)-producers) belonged to the pandemic clone ST131. A significant distribution of virulence determinants and pathogenicity island marker was observed within strains belonging to B2 and D phylogroups. Interestingly, our results showed that ExPEC strains, including ST131 pandemic clone, are present within fecal isolates in healthy children. These findings highlight the importance of intestinal microbiota as a reservoir for virulent and resistant strains. Thus, reinforcing hand hygiene and antibiotic rational use is imperative to avoid the diffusion of these pathogens in the community.