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Biomedical subjects

B A Wylie

Publications and source records attributed to B A Wylie.

10 recordsLinked to original sources
PubMed1993

Trimethoprim resistance in South African isolates of aerobic gram-negative faecal flora.

Aerobic gram-negative commensal faecal flora from 362 healthy volunteers was examined for resistance to trimethoprim. Three hundred fifty-seven trimethoprim-resistant organisms were isolated from 272 of the volunteers (297 Escherichia coli, 46 Klebsiella spp., 9 Enterobacter spp. and 7 other species). Trimethoprim resistance was associated with resistance to other antibiotics at the following frequencies: ampicillin 71.4%, tetracycline 88%, cephalosporins 14% and aminoglycosides 4%. High-level resistance to trimethoprim (MIC > or = 1024 mg/l) occurred in 98.6% of the isolates. Trimethoprim resistance was transferable in 51.2% of the isolates. An X+ factor was required to mobilize resistance in a further 3.4%. Resistance to other antibiotics cotransferred with trimethoprim at the following frequencies: ampicillin 55.4%, tetracycline 30%, cephalosporins 1.5% and aminoglycosides 2.6%. Restriction enzyme analysis of 148 plasmids revealed 79 different profiles. Two restriction profiles represented 10.1 and 8.8% of these plasmids, respectively. The large number of different antibiograms and restriction profiles indicates that there is a large gene pool of trimethoprim-resistant organisms in the faecal flora.

Bacteria, Aerobic↗
PubMed1993

The prevalence of antimicrobial resistance in human faecal flora in South Africa.

Between January and March 1992, 361 faecal specimens were collected from the healthy black population in the Transvaal Province of South Africa. Each specimen was examined for the prevalence of antimicrobial resistance in commensal bacteria. Volunteers, from both rural and urban dwellings, were divided into four age groups. The overall carriage rate of resistance varied from 88.6% for ampicillin, 74.2% for trimethoprim, 52.6% for chloramphenicol, 10.2% for nalidixic acid to 7.5% for gentamicin. The carriage of resistance found to each individual antimicrobial agent was slightly higher in the rural population rather than the urban population but there was no correlation between the prevalence of antimicrobial resistance and the age group.

Adolescent↗
PubMed1991

Nucleotide sequence of dihydrofolate reductase type VI.

The complete sequence of the type VI dihydrofolate reductase (DHFR) gene from plasmid pUK672 was determined. The structural gene coded for a polypeptide of 157 amino acids which had a deduced mol. wt of 17,424. Comparison with amino-acid sequences of the type I, type V and Escherichia coli K12 chromosomal DHFRs showed that there was 63%, 61% and 31% homology respectively. Putative RNA polymerase and ribosomal binding sites were identified proximal to the initiation codon and a feature consistent with transcription termination was present distal to the coding region. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that the enzyme had a subunit mol. wt of 17,500.

Amino Acid Sequence↗
PubMed1989

Trimethoprim resistance in gram-negative bacteria isolated in South Africa.

Resistance to trimethoprim was surveyed in 2914 Gram-negative bacteria isolated in three hospitals in South Africa. Bacteria were collected from November 1986 to January 1987 and the minimum inhibitory concentration (MIC) of trimethoprim for each isolate was determined. The overall resistance rate (MIC greater than 8 mg/l) was 56.2%, and high-level resistance (MIC greater than 1024 mg/l) occurred in 24.0% of the total. The frequency of resistance in isolates of Enterobacteriaceae was 48.5% (MIC greater than 8 mg/l). Of the organisms isolated from urine specimens, 49.1% were resistant to trimethoprim, 71.8% of these being highly resistant. Investigation of 36 isolates for the presence of the type I and/or type II dihydrofolate reductase genes showed that eight isolates reacted with the type I probe but none with the type II probe.

DNA Probes↗
PubMed1988

Identification of a novel plasmid-encoded dihydrofolate reductase mediating high-level resistance to trimethoprim.

A Proteus mirabilis strain, isolated in South Africa, carried a 79kb transferable plasmid (pUK672) which encoded high-level resistance to trimethoprim (minimum inhibitory concentration greater than 2048 mg/l). The trimethoprim resistance was mediated by a dihydrofolate reductase which had completely different properties from any plasmid-encoded dihydrofolate reductase previously described. This enzyme has been designated type VI. The type VI enzyme is small (10,000 daltons) and is unstable in vitro. It is highly resistant to inhibition by both trimethoprim and methotrexate.

Drug Resistance, Microbial↗
PubMed1987

Bacteremia caused by a lactose-fermenting, multiply resistant Salmonella typhi strain in a patient recovering from typhoid fever.

A female patient suffered a typical attack of typhoid fever due to a lactose-negative, fully susceptible Salmonella typhi strain. During convalescence she became febrile, and a lactose-fermenting S. typhi strain resistant to ampicillin, chloramphenicol, tetracycline, and trimethoprim was isolated from blood culture. This isolated was shown to harbor a plasmid which cotransferred lactose fermentation and antibiotic resistance.

Adolescent↗
PubMed1985

Identification of five new variable restriction sites in HSV-1 DNA.

Restriction endonuclease analysis of herpes simplex virus type 1 (HSV-1) DNA has shown that individual strains differ from one another. The differences can be recognized by the presence or absence of cleavage sites due to base changes, small insertions and occasional deletions. In a study in which 13 HSV-1 isolates from South Africa were analysed, a total of 5 new variable restriction sites were identified using the restriction endonucleases Hind III, Eco RI and Bgl II.

Bacterial Proteins↗