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 of Escherichia coli during 1978-83 and 1987-8 respectively, were retrospectively screened with specific biotinylated DNA probes for 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 of E. coli from the Nottingham area of the UK, but indicated that genes encoding the more recently recognized types of DHFR enzymes had appeared in the bacterial gene pool and could be recognized with increased frequency in the latter plasmid collection. This was particularly true of the type Illa and type VII enzymes which together accounted for 27 % of the trimethoprim R plasmids examined in 1987-8.

In34, a Complex In5 Family Class 1 Integron Containing orf513 and dfrA10

“…The identification of two closely related integrons on different plasmids from E. coli and K. pneumoniae strains, isolated almost 20 years apart in 1978 and 1997 at the same hospital, respectively, illustrates how complex structures containing antibiotic resistance genes can persist in a local environment. The fact that the dfrA10 gene has not been seen in surveys of dfr genes conducted in the United Kingdom (40) and South Africa (1) indicates that it is not a widely distributed gene, adding weight to the argument for persistence. It has, however, recently been found in isolates of S. enterica serovar Agona from poultry in Belgium (GenBank accession no.…”

Trimethoprim resistant dihydrofolate reductases in normal faecal flora isolated in India

“…In this survey, however, the type V DHFR was marginally the most frequently isolated of the plasmid-mediated DHFRs, accounting for a third of the transferable resistance. The type Ia DHFR is usually found to be the most commonly isolated DHFR [27,4]. In this case, only 11 of the transconjugants were shown to harbour the dhfrla gene.…”

“…(Table 2). However, on restriction endonuclease digest analysis of the plasmids prepared from the transconjugants, 27 quite distinct patterns could be identified. Thus it appears that 27 different plasmids are responsible for trimethoprim resistance, and a number of other resistance mechanisms, in this population of Gram-negative rods from normal faecal samples.…”

“…The DHFR type Ia is found associated with the transposon Tn7, which integrates at a high frequency into the Escherichia coli chromosome, at a specific site attTn7 [26]. As a result, the type Ia is the most widespread and frequently isolated of the trimethoprim resistant DHFRs [4,27] and has been increasingly identified in the chromosomes of trimethoprim resistant E. coli [28]. The type Ia has also been found, infrequently, in association with Tn2l-like transposons [28,29].…”

Επιδημιολογική Διερεύνηση Της Αντοχής Στα Αντιβιοτικά Φυσιολογικής Εντερικής Χλωρίδας Της Παιδικής Ηλικίας

“…Οι β-λακτάμες είναι αντιβιοτικά που χρησιμοποιούνται ευρύ τατα στην κλινική πράξη και στα οποία έχει αναπτυχθεί αντοχή χρωμοσωμιακού και εξωχρωμοσωμιακού τύπου (29,31), όπως συμ βαίνει και με άλλες ομάδες αντιβιοτικών (32).…”