Detection of antibiotic resistant E. coli and Enterococcus spp. in stool of healthy growing children in Portugal

From stool specimens of 118 healthy children's (1-14 years) in Portugal 92 E. coli and 101 Enterococcus spp. strains have been isolated. Almost half (40.2%) of the E. coli isolates were resistant to ampicillin, 25.0% were resistant to tetracycline and 26.1% were resistant to streptomycin. Resistance genes detected by specific PCR included bla(TEM) and/or bla(SHV) and/or bla(CTX-M) (33 of 37 ampicillin and/or cefotaxime resistant isolates), tet(A) and/or tet(B) (16 of 23 tetracycline-resistant isolates), aadA (19 of 24 streptomycin-resistant isolates), cmlA (in the two chloramphenicol-resistant isolates), aac(3)-II with/without aac(3)-IV (in the four gentamicin-resistant isolates), sul1 and/or sul2 and/or sul3 (in all trimethoprim/sulfamethoxazole resistant isolates). The majority of the resistant E. coli isolates (69.1%) belonged to phylogenetic group B2. Of the enterococci isolates E. faecium (n = 53), E. faecalis (n = 41), E. hirae (n = 4) and E. durans (n = 3) more than one-fourth (28.7%) of the isolates were resistant to tetracycline; 21.8% were resistant to erythromycin and 8.9% were resistant to kanamycin. Resistance genes detected by PCR in enterococci included aph(3)'-IIIa (in all kanamycin-resistant isolates), aac(6') (in all gentamicin-resistant isolates), tet(M) and/or ret(L) (26 of 29 tetracycline-resistant isolates), erm(B) (17 of 22 erythromycin-resistant isolates). This survey showed that faecal bacteria such as E. coli and enterococci of healthy growing children's could be a reservoir of antimicrobial resistance genes.