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Biomedical subjects

W C Noble

Publications and source records attributed to W C Noble.

At least 19 recordsLinked to original sources
PubMed1995

Chloramphenicol resistance in Staphylococcus intermedius from a single veterinary centre: evidence for plasmid and chromosomal location of the resistance genes.

A total of seven Staphylococcus intermedius cultures isolated from cases of canine pyoderma were investigated for the genetic basis of chloramphenicol resistance (Cmr). All of these S. intermedius isolates mediated Cmr via the expression of the Cm-inactivating enzyme chloramphenicol acetyltransferase (CAT); the respective cat genes were found to be located on small multicopy plasmids of 3.1 to 4.1 kb in four of the seven cultures. The four Cmr plasmids, designated pSCS20-23, differed upon restriction endonuclease mapping. Hybridization experiments identified all of them to belong to the pC221-family of staphylococcal Cmr plasmids. The expression of all four plasmid-encoded cat genes was inducible with chloramphenicol. The remaining three S. intermedius isolates also harboured an inducible cat gene of the pC221-type which, however, was found to be located in the chromosomal DNA. These differences in the subcellular localisation and consequently in the number of cat gene copies per S. intermedius cell had no influence on the MIC values of Cm exhibited by the respective S. intermedius isolates.

Animals↗
PubMed1995

Adherence characteristics of coagulase-negative staphylococci isolated from patients with infective endocarditis.

Coagulase-negative staphylococci isolated from patients with endocarditis were divided according to whether the infection was of native or of prosthetic valves and was acquired either in the community or in hospital. Comparisons were made with strains from intravenous line-associated bacteraemias. All strains were examined by direct and indirect adherence tests. Line-associated bacteraemia strains were more likely to produce slime and were more hydrophilic but were less likely to attach HEp2 tissue culture cells than were endocarditis strains, and almost equally likely to adhere to plastic and extracellular matrix proteins. Amongst the endocarditis strains, there was little difference in slime production but hospital-acquired or prosthetic-valve strains were more hydrophobic and more likely to adhere to silicone than were the native-valve or community-acquired strains. Exposure of extracellular matrix proteins on native valves due to a pre-existing non-infective heart condition may account for the selection of strains able to adhere to fibronectin or laminin.

Bacteremia↗
PubMed1995

In vitro indices of tissue adherence in Staphylococcus intermedius.

In vitro indices of adherence showed that strains of Staphylococcus intermedius from lesions of canine pyoderma differed from strains isolated from normal carrier sites in that a significantly greater proportion of pyoderma strains adhered to extracellular matrix proteins whilst fewer adhered to polystyrene. Slime production and a hydrophobicity index did not differ between the groups. This suggests that exposure of extracellular matrix proteins due to underlying disease may result in the selection of a narrower spectrum of strains from amongst those at carrier sites.

Animals↗
PubMed1994

Structure and putative origin of a plasmid from Staphylococcus hyicus that mediates chloramphenicol and streptomycin resistance.

The structure and functional organization of Staphylococcus hyicus plasmid pSCGp3EB that mediates chloramphenicol and streptomycin resistance (CmrSmr) is described and compared with another CmrSmr plasmid, pSCS12, from Staphylococcus sciuri. Both plasmids appeared to be formed by co-integrate formation between plasmids that very closely resemble the chloramphenicol resistance (Cmr) plasmid pC221 and the streptomycin resistance (Smr) plasmid pS194. In addition to the established recombination site B (RSB) in pC221 and pS194, another area suitable for recombination immediately downstream of the cat gene in pC221 and upstream of the str gene in pS194 has been identified. Co-integration at these sites would lead to the structures we have observed in the wild-type CmrSmr plasmids pSCGp3EB and pSCS12.

Amino Acid Sequence↗
PubMed1992

Co-transfer of vancomycin and other resistance genes from Enterococcus faecalis NCTC 12201 to Staphylococcus aureus.

Conjugative transfer, in the apparent absence of plasmid DNA, of high-level vancomycin resistance from Enterococcus faecalis NCTC 12201 to Staphylococcus aureus B111 has been demonstrated in vivo and in vitro. Selection of transconjugants on media containing erythromycin or chloramphenicol may result in the transfer of resistance to erythromycin, chloramphenicol, gentamicin, streptomycin and vancomycin though these are capable of separate transfer. Vancomycin resistance has not been transmitted from staphylococcus to staphylococcus though transfer of erythromycin and of chloramphenicol resistance has been achieved.

Conjugation, Genetic↗
PubMed1992

Staphylococci on the skin of pigs: isolates from two farms with different antibiotic policies.

Staphylococci isolated from pigs on two farms were identified and their antibiotic resistance and plasmid profiles were examined. A highly resistant Staphylococcus hyicus was epidemic on one of the farms which was also that at which antibiotic-containing feedstuffs were used most often. Staphylococci from this farm were more often resistant to two or more antibiotics than were the strains from the other farm. The many plasmids present in these staphylococci prevented the determination of the genetic nature of the antibiotic resistance.

Animals↗
PubMed1992

Antibiotic resistance and plasmids in Staphylococcus aureus from normal populations.

Antibiotic resistance, plasmid profiles and plasmid structures were examined in nasal Staphylococcus aureus collected from a random sample of normal individuals in the mid 1960s and from women at an antenatal clinic in 1989. The results were generally similar except for an increase in the resistance to penicillin in the later sample. The plasmid population had changed little though more uncategorized plasmids were evident in the 1960s samples.

Drug Resistance, Microbial↗
PubMed1992

Characterization of aerobic non-lipophilic coryneforms from human feet.

Aerobic coryneform bacteria from human feet have been studied by analysis of the cell-wall sugars, lipids and diamino acids and by phenotypic tests. Although many isolates studied fall into the established genus Brevibacterium at least two previously unreported taxa of coryneform have been identified bringing the number of aerobic, non-lipophilic taxa known on skin to four. Simple tests can be used to distinguish between these taxa. Studies on the human skin flora continue to reveal the diversity of organisms present.

Actinomycetales↗
PubMed1991

Cloning of the gene conferring resistance to mupirocin in Staphylococcus aureus.

A plasmid known to be associated with mupirocin resistance of Staphylococcus aureus has been isolated and a restriction enzyme map constructed. An EcoRI fragment of 4.05 kb from this plasmid has been cloned into an Escherichia coli-Staphylococcus aureus shuttle vector and shown to carry the gene for resistance to mupirocin. The DNA sequence of a small section of the gene has been determined and the derived amino acid sequence compared with a data bank. The amino acid sequence is identical for eight amino acids with the sequence of isoleucyl tRNA synthetase of E. coli. This finding adds to the evidence that mupirocin resistance is the result of a modified isoleucyl tRNA synthetase.

Amino Acid Sequence↗
PubMed1991

Tn554 inserts in methicillin-resistant Staphylococcus aureus from Australia and England: comparison with an American methicillin-resistant group.

We have compared methicillin-resistant (Mcr) Staphylococcus aureus isolates from Australia, the UK and the USA with regard to chromosomal inserts of the macrolides-lincosamides-streptogramin B (MLS)-resistance transposon Tn554. The American isolates were known to have a distinctive Tn554 insert, designated insert 6, which was closely associated epidemiologically with the methicillin-resistance phenotype. Southern blots of DNA from Australian and London, UK Mcr isolates were hybridized with a range of probes related to Tn554. The isolates had similar or identical Tn554 inserts, and we consider them to be a single group, designated 'Australondon'. Australondon isolates were compared in detail with a deletion mutant, ANS62, that had lost the methicillin-resistance determinant mec, plus other resistance determinants resident in the mec region of the chromosome, and with an American Mcr isolate containing Tn554 insert 6. The Australondon isolates had three Tn554 inserts. Sequence analysis with the polymerase chain reaction showed that all of these inserts differed from classical Tn554 in that the 3'-terminal residues of the transposons were reverse complements of the usual GATGTA. One of the Australondon inserts, designated 6B, closely resembled Tn554 insert 6 in the sequence of its left flanking chromosomal DNA. This insert was found to abut the deletion from the mec region which results in strain ANS62. We infer that Tn554 insert 6B is part of the mec region of the chromosome in Australondon isolates, supporting the idea that insert 6 of the American isolates is also part of this chromosomal region.

Australia↗
PubMed1991

Streptomycin and tetracycline resistance plasmids in Staphylococcus hyicus and other staphylococci.

Plasmids associated with resistance to streptomycin, to streptomycin plus chloramphenicol or to tetracycline in Staphylococcus hyicus isolated from the skin of pigs have been compared, by restriction endonuclease digest patterns, with similar staphylococci from human sources and with published DNA base sequences. Several plasmids from Staph. hyicus have proved to have a very similar structure to those described from Staph. aureus but others appeared very dissimilar. This confirms the opinion that staphylococci from animal skin share a pool of plasmids with those from human skin but may also possess some of quite different structure.

Animals↗
PubMed1991

Nasal, axillary, and perineal carriage of Staphylococcus aureus among women: identification of strains producing epidermolytic toxin.

Following two outbreaks of staphylococcal scalded skin syndrome in a maternity unit, 500 pregnant women attending an antenatal clinic were screened for carriage of epidermolytic toxin producing Staphylococcus aureus. Nasal, axillary, and perineal swabs were collected from women whose gestational ages ranged from 12-40 weeks. Isolates of S aureus were purified, phage typed, and tested for methicillin sensitivity and production of epidermolytic toxin. The results showed that 164 (33%) women carried S aureus; of these, 100 (61%) were from the nose and three (2%) from axillae, but 41 (25%) strains were isolated from the perineum alone. Screening for nasal carriage alone will therefore miss 25% of carriers. More than one strain of S aureus was identified in seven of 20 women with multiple site carriage. Three (2%) methicillin resistant strains were isolated during the survey, and five (3%) isolates produced epidermolytic toxin. Phage typing identified 63 (34%) strains as non-typable, but 50% of isolates typed either groups I, II or III, and a further 10% represented varying combinations of these and other phage groups. These results provide baseline information on S aureus in the community, and identification of methicillin resistant and toxin producing strains shows a reservoir of outbreak potential which could become relevant on hospital admission of such a carrier.

Adolescent↗
PubMed1990

Antigenic cross-reactivity among isolates of group JK corynebacteria.

Using rocket and rocket-line immunoelectrophoresis and immunoblotting it was demonstrated that a group of antibiotic-resistant bacteria, including several authenticated Corynebacterium jeikeium strains, shared many cross-reacting antigens. Only weak cross-reactivity was demonstrated with representatives of three other skin corynebacteria, C. bovis, C. hofmanii and C. minutissimum or with non-coryneforms. Differences within C. jeikeium are sufficient to permit the use of immunoblotting as an epidemiological tool.

Animals↗
PubMed1990

An outbreak of pemphigus neonatorum.

During the summer of 1987, an epidemic of pemphigus neonatorum took place at Guy's Hospital. It involved more than 80 neonates in the maternity unit. Swabs from the umbilical stumps of the babies and from the noses of several attending midwives yielded Staphylococcus aureus of phage-type Group II 3A/3C. Despite an extensive disinfection policy, which included identification and treatment of carriers, the outbreak persisted for 3 months. Final resolution came only after detailed epidemiological research revealed those midwives most likely to be involved. After these had been singled out for further treatment, the outbreak ended. The epidemic strains were later subjected to reverse phage-typing, plasmid profiling and in vivo testing for production of epidermolytic toxin in order to confirm true carriers and cases. Retrospective analysis identified those persons most likely to have been responsible for propagation of the epidemic strain. The exact course of the outbreak was then clarified.

Cross Infection↗
PubMed1990

The value of electrophoretic protein patterns for the study of Microsporum canis.

Whole-cell protein analysis of clinical isolates of Microsporum canis by polyacrylamide gel electrophoresis (PAGE) showed small but inconsistent differences in protein patterns. All clinical isolates closely resembled the (-) mating type of Arthroderma otae. A reference strain of A. otae (+) mating type from Japan gave a PAGE pattern which was distinct from those of the clinical isolates. Mating studies showed that the progeny of these reference (+) and (-) mating types had a variety of distinct protein patterns. Protein patterns can therefore distinguish between genetically different strains of M. canis (A. otae) suggesting that clinical isolates have a common clonal origin.

Animals↗
PubMed1990

Sterols of fungi responsible for superficial skin and nail infection.

Two groups of fungi isolated from human skin and nail are the dermatophytes Epidermophyton, Microsporum and Trichophyton species and the non-dermatophytes Hendersonula toruloidea and Scytalidium hyalinum. Examination of the sterol composition of these fungi by gas chromatography-mass spectrometry (GC-MS) identified five new sterols from dermatophytes, namely cholesterol, campesterol, episterol, fecosterol and sitosterol. These sterols, with ergosterol and brassicasterol, were also identified from extracts of H. toruloidea and S. hyalinum. Sterol patterns produced by GC-MS with selected ion recording of ten ions were analysed by principal components analysis using the SIMCA statistical package. The dermatophyte genera and species were not differentiated using this method, the similarity in sterol content reflecting the close taxonomic relationship of this group. H. toruloidea and S. hyalinum had similar sterol contents to each other, reinforcing the opinion that these fungi are related, although H. toruloidea form 3 was distinguished from forms 1 and 2.

Arthrodermataceae↗