Antimicrobial resistance, integrons and plasmid replicon typing in multiresistant clinical Escherichia coli strains from Enugu State, Nigeria

Eleven multiresistant Escherichia coli strains of animal and human origin were assayed for the presence of antimicrobial resistance genes, integrons and associated gene cassettes, as well as plasmid content. Ciprofloxacin-resistant strains were screened for amino acid changes in GyrA and ParC proteins. The E. coli strains were found to harbor a variety of genes including cmlA, aac(3)-II, aac(3)-IV, aadA, strA-strB, tet(A), tet(B), bla(TEM), sul1, sul2 and sul3. Four of the eight intI1-positive strains were also positive for qacE Delta 1-sul1 region and the following gene cassettes were detected: dfrA7, dfrA12 + orfF + aadA2 and bla(OXA1) + aadA1. Five strains contained class 1 integrons lacking the qacE Delta 1-sul1 region and they showed a single type of gene cassette arrangement (estX + psp + aadA2 + cmlA + aadA1 + qacH + IS440 + sul3). The two intI2-positive strains carried the same type of gene cassette arrangement (dfrA1 + sat + aadA1). The seven ciprofloxacin-resistant E. coli strains exhibited a Ser-83-Leu substitution in GyrA protein and a Ser-80-Ile substitution in ParC protein; six of these strains presented an additional substitution in GyrA (Asp-87-Gly or Asp-87-Asn) and one strain in ParC (Glu-84-Gly). Eight different plasmid-replicon-types were detected among the 11 E. coli strains, IncF being the most frequent one detected, found in nine strains; other plasmid replicon types detected were IncX, IncI1, IncY, IncW, IncFIC, IncB/O, and IncK. Antimicrobial resistance in the E. coli strains studied was mediated by a variety of genes, some of them included in integrons, as well as by mutations gyrA and parC genes.