Escherichia coli strains from Kenyan patients carrying conjugatively transferable broad-spectrum beta-lactamase, qnr, aac(6')-Ib-cr and 16S rRNA methyltransferase genes.

摘要

Strains exhibiting combined resistance to different classes of cephalosporins, aminoglycosides and (fluoro)quinolones present a major challenge, especially in resource-poor settings where alternative treatment agents are not affordable or readily available. We applied a combination of PCR and sequencing strategies to investigate 16 patient-unique, highly resistant Escherichia coli strains from Kenyan patients for plasmid-borne beta-lactamase,1 16S ribosomal methyltransferase (RMT),2 aac(6)-Ib-cr1 and qnrh genes. The ability of the strains to conju-gatively transfer a combination of these resistance markers en bloc was also assessed. Donors and transconjugants were analysed for elements frequently implicated in the dispersal of antibiotic resistance markers such as plasmids, integrons, trans-posons Tn22 and Tn7 and insertion sequences ISCR1 and ISEcpl.5 Strains were assigned to various phylogenetic groups and their genetic relatedness determined using published PCR methods. We also screened for strains belonging to the internationally spreading E. coli ST131 donal complex among these isolates.6 The MICs of all major classes of antibiotics were determined using Etest strips following the manufacturer's recommendations (AB bioMerieux, Solna, Sweden). Mating experiments were carried out using the sodium azide-resistant E. coli J53 strain as recipient.