Trimethoprim resistance determinants encoding a dihydrofolate reductase in clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci

Tennent, Jan M.; Young, H; Lyon, B. R.; Amyes, Sebastian G. B.; Skurray, Ronald A.

doi:10.1099/00222615-26-1-67

Cited by 26 publications

(14 citation statements)

References 12 publications

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“…A probe developed from a conjugative S. aureus trimethoprim resistance plasmid hybridized with chromosomal DNA of 14 isolates, plasmid DNA from 9 isolates, and both plasmid and chromosomal DNA from 1 isolate, and no hybridization was observed with 5 isolates (92). Similar results were obtained in a comparable study in Australia (339). However, no specific resistance determinant was named.…”

Section: Resistance To Trimethoprimsupporting

confidence: 76%

Molecular Detection of Antimicrobial Resistance

2001

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The determination of antimicrobial susceptibility of a clinical isolate, especially with increasing resistance, is often crucial for the optimal antimicrobial therapy of infected patients. Nucleic acid-based assays for the detection of resistance may offer advantages over phenotypic assays. Examples are the detection of the methicillin resistance-encoding mecA gene in staphylococci, rifampin resistance in Mycobacterium tuberculosis, and the spread of resistance determinants across the globe. However, molecular assays for the detection of resistance have a number of limitations. New resistance mechanisms may be missed, and in some cases the number of different genes makes generating an assay too costly to compete with phenotypic assays. In addition, proper quality control for molecular assays poses a problem for many laboratories, and this results in questionable results at best. The development of new molecular techniques, e.g., PCR using molecular beacons and DNA chips, expands the possibilities for monitoring resistance. Although molecular techniques for the detection of antimicrobial resistance clearly are winning a place in routine diagnostics, phenotypic assays are still the method of choice for most resistance determinations. In this review, we describe the applications of molecular techniques for the detection of antimicrobial resistance and the current state of the art

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Section: Resistance To Trimethoprimsupporting

confidence: 76%

Molecular Detection of Antimicrobial Resistance

2001

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“…21 The plasmid-free S. aureus strain SK98222 was used as a recipient in the plasmid transfer experiments and as a control in the MIC determinations and DNA hybridisation experiments. S. aureus strains SK2355,23 carrying pSK 1 (qacA), SK2725,7 carrying pSK23 (qacB), and SK272 1 ,7 carrying pSK89 (qacC), were also used as controls in the MIC determinations and in the DNA hybridisation experiments.…”

Section: Bacterial Strains and Plasmidsmentioning

confidence: 99%

Multidrug resistance to antiseptics and disinfectants in coagulase-negative staphylococci

Leelaporn

Paulsen

Tennent

et al. 1994

Journal of Medical Microbiology

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148

104

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Summary. The occurrence of resistance to antiseptics and disinfectants in clinical isolates of coagulase-negative staphylococci (CNS) was examined. Of 164 clinical strains of CNS isolated in the early 1980s, 65 were resistant to cationic antimicrobial compounds such as cetyltrimethylammonium bromide. Further characterisation of 40 resistant isolates by DNA-DNA hybridisation analysis and phenotypic resistance studies revealed that this resistance was mediated by the multidrug export genes qacA and qacC, characterised previously in Staphylococcus aureus. Of the resistant CNS isolates, 50 YO contained only qacA, 10% contained only qacC, and the remaining 40% contained both qacA and qacC. Both qacA and qacC genes resided on plasmids in all cases, with qacA located on plasmids of > 10 kb, whereas qacC was located primarily on plasmids of 2-3 kb. Representative qacA and qacC plasmids were characterised by restriction endonuclease mapping, and were found to be similar in some cases, but different in others, to those plasmids on which these genes are found in S. aureus.

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“…methoprim resistance (TprH; MIC, .1,000 jig/ml) (47). The Tpr determinant on pSK1 is located on the 4.7-kb composite transposon-like structure designated Tn4003 (see Fig.…”

mentioning

confidence: 99%

“…This determinant is also flanked by three IS257 elements in an arrangement similar to that in Tn4003 (7). Plasmid-mediated TprH and TprL have also been detected in coagulase-negative staphylococci (16,47), a group of organisms hypothesized to act as a reservoir of antimicrobial resistance genes for S. aureus (14,28,46). Furthermore, DNA-DNA hybridization studies have revealed homology between the dfrA resistance determinant of Tn4003 and the determinants of TprH in coagulase-negative staphylococci (47).…”

mentioning

confidence: 99%

Possible role of insertion sequence IS257 in dissemination and expression of high- and low-level trimethoprim resistance in staphylococci

Leelaporn

Firth

Byrne

et al. 1994

Antimicrob Agents Chemother

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The transposon-like structure Tn4003 and related elements were found to encode high-and low-level trimethoprim resistance (Tpr) in Staphylococcus aureus and coagulase-negative staphylococci. By using transcriptional fusions in Escherichia coli, the variation in resistance levels was found to correlate with the transcriptional activity of the region presumed to carry the promoter for the operon containing the Tpr dihydrofolate reductase gene, dfrA, encoded by these elements. The reduced transcriptional activities exhibited by elements encoding low-level Tpr appear to be a consequence of deletions adjacent to the copy of IS257 which normally encodes the -35 sequences of these promoters. The data obtained not only support the involvement of IS257 in the transcription of the proposed thyE-dfrA-orf-140 operon of Tn4003 but may also implicate this insertion sequence in the mechanisms resulting in the variation in Tpr levels observed in staphylococci.

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Trimethoprim resistance determinants encoding a dihydrofolate reductase in clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci

Cited by 26 publications

References 12 publications

Molecular Detection of Antimicrobial Resistance

Molecular Detection of Antimicrobial Resistance

Multidrug resistance to antiseptics and disinfectants in coagulase-negative staphylococci

Possible role of insertion sequence IS257 in dissemination and expression of high- and low-level trimethoprim resistance in staphylococci

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