Detection of novel trimethoprim resistance determinants in the United Kingdom using biotin–labelled DNA probes

Abstract

SUMMARYTwo collections of trimethoprim R plasmids, isolated from strains ofEscherichia coliduring 1978–83 and 1987–8 respectively, were retrospectively screened with specific biotinylated DNA probesfor the presence of genes encoding particular DHFR enzymes. The results confirmed that the type I DHFR gene was the predominant plasmid-encoded gene conferring trimethoprim resistance in strains ofE. colifrom the Nottingham area of the UK, but indicated that genes encoding the more recently recognized types of DHFR enzymes haappeared in the bacterial gene pool and could be recognized with increased frequency in the latter plasmid collection. Thiswasparticularly true of the type IIIa and type VII enzymes which together accounted for 27 % of the trimethoprim R plasmid examined in 1987–8.