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Biomedical subjects

M Deighton

Publications and source records attributed to M Deighton.

9 recordsLinked to original sources
PubMed2006

Coagulase-negative staphylococci in very-low-birth-weight infants: inability of genetic markers to distinguish invasive strains from blood culture contaminants.

Selected coagulase-negative staphylococci from the blood of very-low-birth-weight infants in the Neonatal Intensive Care Unit at the Royal Women's Hospital, Melbourne, collected over a 5-year period were examined. Isolates were classified as invasive or contaminants, speciated, typed by pulsed-field gel electrophoresis, and examined for biofilm genes (icaA, icaC, and icaD), adhesion genes (atlE, fbe), and the number of copies of IS256. Of the 24 isolates studied, there were 13 contaminants and 11 invasive isolates. The collection included 15 Staphylococcus epidermidis, eight Staphylococcus capitis, and one each of Staphylococcus warneri and Staphylococcus haemolyticus. Two small clusters of S. epidermidis that belonged to the same molecular type were identified. All S. capitis isolates belonged to the same molecular type or subtype, suggesting that a particular clone was circulating in the unit. There was no significant difference in the species found, the presence of icaA, icaC, icaD, atlE, or fbe, or the number of copies of IS256 between invasive isolates and contaminants. A series of nasal isolates from nonhospitalized adults differed from hospital isolates in the absence of IS256 and the low prevalence of icaC. There was no evidence of IS256-mediated insertion into ica genes as a mechanism of phase variation. These findings suggest that contaminants and invasive isolates derived from the same pool of hospital strains capable of causing sepsis in compromised hosts and that other mechanisms of phase variation exist, apart from IS256 insertion into ica genes.

Biofilms↗
PubMed2006

In vivo anthelmintic activity of Dorycnium rectum and grape seed extract against Ostertagia (Teladorsagia) circumcincta and Trichostrongylus colubriformis in sheep.

AIM: To assess the in vivo anthelmintic activity of condensed tannins (CT) in the forage species Dorycnium rectum and Medicago sativa, and in an extract from grape (Vitus vinifera) seeds (GSE), against two species of parasite, Teladorsagia (Ostertagia) circumcincta and Trichostrongylus colubriformis, at different stages of their life cycle, in sheep that were parasite-naïve or previously exposed to nematodes. METHODS: In Trial 1, a factorial treatment structure was used to compare faecal nematode egg counts (FEC) and worm burdens in 40 weaned Romney lambs fed either the CT-containing forage D. rectum (12% dry matter; DM) or M. sativa (lucerne; 0.2% DM). Twenty naïve and 20 previously-exposed lambs were drenched free of parasites then reinfected with known species and numbers of parasites, and housed in pens indoors on a diet of lucerne pellets and chaffed hay. Groups of lambs (n=5 lambs per group) were fed one of the forages over one of two time periods within the parasite's life cycle. Six to nine days after the last feeding of fresh forages, faecal samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. In Trial 2, 12 Suffolk x Romney lambs were surgically implanted with an abomasal cannula and then housed indoors in metabolism crates. After infection with parasites, six lambs were infused continuously over a 14-day period with a commercially available CT GSE (96% DM, made up to 34 g/L in water); the remaining lambs were infused with water. During infusion, samples were collected for egg hatch and larval development assays. After infusion, samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. RESULTS: In Trial 1, there was a significant (p<0.001) difference in burdens of O. circumcincta between naïve lambs and those previously exposed to parasites, but no other differences were recorded. In Trial 2, lambs infused with GSE had significantly (p<0.05) fewer T. colubriformis at slaughter and significantly (p<0.001) fewer eggs hatched in the egg hatch assay (EHA) than for lambs infused with water. Overall, the differences attributable to GSE were small in magnitude, being an 11% drop in egg hatch, and an 18% drop in numbers of adult T. colubriformis after 14 days of continuous infusion. No other differences were recorded. CONCLUSION: The results indicate that the in vivo anthelmintic activity of these CT sources is, at best, modest and is unlikely to be of any practical value. Further, these data emphasise that in vitro activity is an unreliable indicator of in vivo efficacy for CT-containing forages and extracts.

Animals↗
PubMed2001

Phenotypic and genotypic markers of Staphylococcus epidermidis virulence.

OBJECTIVES: To analyze Staphylococcus epidermidis strains, previously tested for their virulence in a mouse model of subcutaneous infection, for various phenotypic traits (biofilm density, extracellular polysaccharide, slime-associated antigen (SAA)) and for the presence of the ica gene cluster, to determine which of these phenotypic and genotypic methods best correlates with virulence in the mouse model. METHODS: The quantitative biofilm assay was performed on 10 strains of S. epidermidis, comprising (1) RP62A (ATCC 35984), (2) the strongest and weakest biofilm producers in our collection, (3) a pair of phenotypic variants, and (4) a strain whose biofilm density was enhanced in iron-limited media. Biofilm density was measured after growth at 37 degrees C and at ambient temperature, in trypticase soy broth (TSB) with and without glucose supplementation and using both chemical and heat fixation. Strains were assayed for SAA using a double immunodiffusion method. Extracellular polysaccharide was detected by transmission electron microscopy (TEM). A 546-base-pair segment of the ica gene cluster was amplified by PCR. RESULTS: Biofilm formation in TSB, glucose-enriched TSB, extracellular polysaccharide (observed by TEM), expression of SAA and presence of the ica gene predicted virulence of nine, nine, nine, eight and eight of 10 strains, respectively. The phenotypic expression of biofilm and related properties was medium and temperature dependent. We encountered one ica-positive strain that failed to express biofilm in standard TSB at 37 degrees C, but was virulent in a mouse model, and another strain that lacked ica, produced biofilm and was virulent in the model. CONCLUSIONS: Mouse virulence in our model can be predicted by any of the phenotypic or genotypic methods examined for > or = 80% of strains. Medium and incubation conditions affect the expression of phenotypic markers by some strains. For the remaining strains, possible reasons for inconsistencies between the presence of the ica gene, phenotypic markers and mouse virulence include (1) dependence of biofilm on genes other than ica, (2) sequence differences in ica, (3) dependence of biofilm expression in vivo on strain characteristics and media used to prepare inocula for in vivo studies.

Animals↗
PubMed1999

Molecular typing of Staphylococcus aureus of bovine origin by polymorphisms of the coagulase gene.

Mastitis caused by Staphylococcus aureus is a disease of major economic importance to the dairy industry. Transmission occurs during milking, with chronically-infected cows acting as the major reservoirs of infection. PCR-coagulase gene typing of 151 S. aureus isolates from seven farms generated only six PCR types, with 110 (73%) isolates assigned to PCR type 1 and 23 (15.2%) isolates assigned to type 2. PCR type 1 was the predominant type on five of the seven farms, including farms in geographically separated regions of Victoria, while type 2 predominated on two farms. With the exception of the 41 isolates from one farm, all isolates were resistant to penicillin, but susceptible to other antibiotics that are routinely used to manage mastitis in dairy cattle. Nine of 11 cows with chronic S. aureus infection showed evidence of persistence of a single PCR type for periods of up to 9 months. Two different PCR types of S. aureus were isolated from the other two cows over the same period.

Animals↗
PubMed1993

Regulation of slime production in Staphylococcus epidermidis by iron limitation.

Slime production by most strains of Staphylococcus epidermidis was enhanced by conditions of iron limitation produced by the addition of ethylenediamine-di-o-hydroxyphenol acetic acid to the growth medium. The density of the biofilm which formed on the base of microtiter plates was dependent on the degree of iron limitation, the stage of the growth cycle, and the nutritional state of the initial inoculum. One repeatedly slime-negative S. epidermidis strain, passaged in tryptic soya broth containing ethylenediamine-di-o-hydroxyphenol acetic acid, expressed high levels of slime after two passages. These observations suggest that iron limitation is one factor that regulates slime production by S. epidermidis. These findings could explain inconsistencies between the in vivo observation that biofilms invariably form on implanted catheters and the in vitro finding that some isolates from catheter-associated infection fail to produce slime.

In Vitro Techniques↗
PubMed1992

Phenotypic variation of Staphylococcus epidermidis isolated from a patient with native valve endocarditis.

Two colonial variants of Staphylococcus epidermidis were isolated from the valvular tissue of a patient with native valve endocarditis. In addition to differing in colonial morphology, the two variants differed in hemolysis on blood-containing media, in adherence capacity, and in the expression of certain enzymes. Under suitable conditions, both variants were themselves capable of phenotypic variation, although they differed in the rate at which variants were generated. The variants yielded identical profiles on restriction endonuclease analysis of plasmid DNA and pulsed-field gel electrophoresis of whole-cell DNA. This report suggests a possible role for phenotypic variation in coagulase-negative staphylococcal virulence. Congo red agar would be an excellent medium for studying the contribution of variation to the virulence of these organisms.

Adult↗
PubMed1992

Lactic acid bacteria in the gut in normal and disordered states.

The human gut flora is a complex and finely balanced ecosystem which plays an important protective role in humans. Although relatively stable, its composition may be altered in various disease states and by the administration of antimicrobial agents. Preparations containing viable lactic acid bacteria of human origin appear to have value in restoring normal microbial function and alleviating symptoms in some patients with gastrointestinal infection and other conditions.

Animals↗
PubMed1977

Toward a comprehensive methodology for resident evaluation.

The development of a useful system of medical resident evaluation over a two year period demonstrated that traditional measures used successfully in undergraduate medical education were less appropriate and acceptable than more complex measures designed to assess actual clinical performance. The greater cost, time involvement and personnel required by the more complex measures were shown to be partially offset by the greater utility and acceptability of the evaluative data provides. The feasibility of using skilled, non-medically trained personnel to minimize faculty-physician time was demonstrated.

Clinical Competence↗