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Biomedical subjects

T V Riley

Publications and source records attributed to T V Riley.

At least 73 records · Page 4Linked to original sources
PubMed1995

Methicillin-resistant Staphylococcus aureus in Western Australia, 1983-1992.

A statewide screening programme has prevented imported strains of methicillin-resistant Staphylococcus aureus (MRSA) from becoming established in any hospital in Western Australia (WA). Recently, notifications of MRSA in WA have increased, prompting a review of surveillance data for the period 1983-1992. Our aims were to determine: (i) the distribution by age and sex of persons with MRSA; (ii) changes in notification rates over time and by location in WA; and (iii) temporal changes in antimicrobial resistance patterns. There were 631 notifications of MRSA for the 10 year period 1983-1992, ranging from a low of 36 in 1988 to a high of 117 in 1992. When the distribution by age and sex was examined, three age group peaks were apparent: 0-9 years, 20-39 years and 60-79 years. There was a predominance of females in the 20-39 years age group, reflecting a greater proportion of hospital nursing staff carrying MRSA. In those aged 50 years or more, there was a marked predominance of males. The highest notification rates overall occurred in the remote Kimberley region of WA, however, rates increased significantly in all regions of the state in 1992. Based on antimicrobial resistance patterns, MRSA was classified into two groups: multiresistant imported strains which often caused outbreaks in hospitals; and a less resistant MRSA (WA MRSA). WA MRSA appears to have originated in the Kimberley region and then spread widely in the community to other regions of the state, and the proportion of WA MRSA has increased significantly since 1989.

Adolescent↗
PubMed1995

Susceptibility of methicillin-resistant Staphylococcus aureus to the essential oil of Melaleuca alternifolia.

All 66 isolates of Staphylococcus aureus tested were susceptible to the essential oil of Melaleuca alternifolia, or tea tree oil, in disc diffusion and modified broth microdilution methods. Of the isolates tested, 64 were methicillin-resistant S. aureus (MRSA) and 33 were mupirocin-resistant. The MIC and MBC for 60 Australian isolates were 0.25% and 0.50%, respectively. Comparable results were obtained by co-workers in Britain using similar methods. These in-vitro results suggest tea tree oil may be useful in the treatment of MRSA carriage.

Methicillin Resistance↗
PubMed1995

Staphylococcus aureus but not Staphylococcus epidermidis can acquire iron from transferrin.

Staphylococci grow and cause infection under the iron-restricted conditions found in vivo. They therefore must possess mechanisms to obtain iron for metabolism from this environment. To determine if staphylococci can extract iron bound to human transferrin, we labelled transferrin with 55Fe and performed uptake assays on cells grown in iron-restricted and iron-plentiful conditions. Growing cultures of Staphylococcus aureus NCTC 8532 could take up radioactive iron during mid- to late-exponential phase of growth. This process was iron-regulated and did not require direct contact between the cell and the labelled transferrin. Siderophore production was detected during this phase, but reductase or protease activity was not. S. epidermidis ATCC 14990 could not access 55Fe bound to transferrin, nor did this isolate produce siderophore, reductase or protease. This difference in the ability to acquire iron bound to transferrin may contribute to the increased virulence of S. aureus when compared to S. epidermidis.

Biological Transport↗
PubMed1995

Antimicrobial activity of the major components of the essential oil of Melaleuca alternifolia.

Tea tree oil, or the essential oil of Melaleuca alternifolia, is becoming increasingly popular as a naturally occurring antimicrobial agent. The antimicrobial activity of eight components of tea tree oil was evaluated using disc diffusion and broth microdilution methods. Attempts were also made to overcome methodological problems encountered with testing compounds which have limited solubility in aqueous media. After assessing media with and without solubilizing agents, the disc diffusion method was used to determine the susceptibility of a range of micro-organisms to 1,8-cineole, 1-terpinen-4-ol, rho-cymene, linalool, alpha-terpinene, gamma-terpinene, alpha-terpineol and terpinolene. While the disc diffusion method lacked reproducibility, it was considered useful as a procedure for screening for antimicrobial activity. Terpinen-4-ol was active against all the test organisms while rho-cymene demonstrated no antimicrobial activity. Linalool and alpha-terpineol were active against all organisms with the exception of Pseudomonas aeruginosa. Minimum inhibitory and minimum cidal concentrations of each component against Candida albicans, Escherichia coli and Staphylococcus aureus were determined using a broth microdilution method. Modifications to this method overcame solubility and turbidity problems associated with the oil components and allowed the antimicrobial activity of each of the components to be quantified reproducibly. There was reasonable agreement between minimum inhibitory concentrations and zones of inhibition. These results may have significant implications for the future development of tea tree oil as an antimicrobial agent.

Anti-Infective Agents, Local↗
PubMed1995

Broth micro-dilution method for determining the susceptibility of Escherichia coli and Staphylococcus aureus to the essential oil of Melaleuca alternifolia (tea tree oil).

A broth micro-dilution method was used to examine the susceptibility of Escherichia coli (n = 110) and Staphylococcus aureus (n = 105) to the essential oil of Melaleuca alternifolia (tea tree oil). The detergent Tween 80 was used successfully to enhance the solubility of tea tree oil in the test medium. The MIC90 of tea tree oil for E. coli was 0.25% while for S. aureus it was 0.50%.

Escherichia coli↗
PubMed1994

Production of siderophore by coagulase-negative staphylococci and its relation to virulence.

The ability to produce siderophore is considered to be a virulence factor for many pathogenic bacteria. To determine if siderophore production by coagulase-negative staphylococci (CNS) was related to virulence, 40 clinical isolates of CNS cultured from peritoneal dialysis fluid were compared with 38 commensal skin isolates. Siderophore activity was detected using the chrome azurol S liquid assay. Using precursor studies, Staphylococcus epidermidis isolates were shown to be more likely to produce the siderophore staphyloferrin A. Production of staphyloferrin B amongst non-Staphylococcus epidermidis species was associated with clinical isolates rather than commensal isolates, and therefore may play a role in pathogenicity.

Citrates↗
PubMed1994

Clostridium difficile-associated diarrhoea: epidemiological data from Western Australia.

The incidence of Clostridium difficile-associated diarrhoea (CDAD) was investigated retrospectively at a 690-bed teaching hospital for the period 1983-92. Our aims were to determine: (i) the distribution by age and sex of patients with CDAD, (ii) the possibility of a seasonal trend and, (iii) the influence of infection control procedures, contamination of the hospital environment and the use of third-generation cephalosporins. The laboratory diagnosis of CDAD was based on demonstration of the organism by stool culture and/or detection of specific cytotoxin in stool filtrates. C. difficile was detected in 917 patients who were being investigated for diarrhoeal illness. Yearly isolations varied from a low of 49 in 1983 to a high of 120 in 1990 (Chi square for linear trend 128.8; P < 0.005). Most patients were elderly, with 63% aged 60 years or more; the majority (59%) were female. The relationship between culture of C. difficile and detection of cytotoxin in faecal extracts was also examined. Sixty percent of a sample of 132 isolates from patients in whom faecal cytotoxin was not detected produced cytotoxin in vitro, suggesting that culture is a more sensitive indicator of infection with C. difficile than cytotoxin detection. When the total number of faecal specimens received in the laboratory was used as a denominator there was an increase in the number of incident cases of CDAD between 1983 and 1990, apart from 1986. When occupied bed days was used as the denominator a similar trend was observed with a peak in 1990.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Evaluation of an enzyme immunoassay kit for the detection of Clostridium difficile enterotoxin.

The Premier Clostridium difficile toxin A enzyme immunoassay (EIA) kit was evaluated for the detection of C. difficile enterotoxin in fecal samples. A total of 314 samples was tested by culture, cytotoxin detection and EIA kit. Compared to a combined culture/cytotoxin result the Premier EIA kit had a sensitivity of 88.3%, a specificity of 100%, a predictive value positive of 100% and a predictive value negative of 87.4%. Test results were available within 3 hrs providing a rapid and reliable means of detecting C. difficile enterotoxin.

Clostridioides difficile↗
PubMed1994

Staphylococcal iron requirements, siderophore production, and iron-regulated protein expression.

Despite the ability of staphylococci to grow in iron-restricted conditions in vivo, their iron requirements and the mechanisms possessed by them for the uptake of iron are poorly understood. Many bacteria are known to produce siderophores. By using the chrome azurol S universal method for the detection of siderophores, all 14 isolates of Staphylococcus aureus tested grew well under conditions of iron restriction and produced iron-regulated siderophore in large quantities, while all 19 isolates of coagulase-negative staphylococci (CoNS) grew poorly under conditions of iron restriction and produced low levels of iron chelator. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of S. aureus isolates revealed altered protein patterns due to iron restriction, while altered profiles were not seen in the CoNS group. The ability to grow in iron-restricted conditions, possibly with the assistance of siderophore-mediated iron uptake, may contribute to the increased pathogenicity of S. aureus when compared with that of the CoNS.

Bacterial Outer Membrane Proteins↗
PubMed1994

Evaluation of three commercial enzyme immunoassay kits for detecting faecal Clostridium difficile toxins.

The detection of faecal cytotoxicity using tissue culture was compared with three commercial Clostridium difficile enzyme immunoassay (EIA) kits; Premier C difficile toxin A (Meridian Diagnostic, Inc.); CD-TOX C difficile toxin A (Porton Cambridge); and Cytoclone A+B EIA (Cambridge Biotech Corporation). Of 160 faecal samples examined by all four methods, 52 (32.5%) were cytotoxic, 44 (27.5%) were positive by Premier, 48 (30%) by CD-TOX EIA, and 50 (31.3%) with Cytoclone. When compared with detection of cytotoxicity by tissue culture assay, the following performance indices were obtained: Premier, sensitivity 84.1%, specificity 99.1%, positive predictive value (PPV) 97.8%, negative predictive value (NPV) 93%; CD-TOX, sensitivity 92.3%, specificity 88.0%, PPV 78.7%, NPV 95.9%; Cytoclone, sensitivity 96.2%, specificity 93.5%, PPV 87.7%, NPV 98.1%. EIA results were available within three hours, whereas the results of the cytotoxin assay were available after 24-48 hours. All three kits provided satisfactory results and, although relatively expensive, all could be used in the laboratory effectively to screen for diarrhoeal disease associated with C difficile.

Clostridioides difficile↗
PubMed1993

Identification of Staphylococcus epidermidis and Staphylococcus hominis from blood cultures by testing susceptibility to desferrioxamine.

Testing susceptibility to desferrioxamine has recently been described as a method for the identification of Staphylococcus epidermidis. This method was compared to a commercial test and the tube coagulase test for the identification of staphylococci from blood cultures and other fluid specimens. A total of 216 isolates was tested over a 13-month period. Sensitivity of the desferrioxamine test in identifying isolates of Staphylococcus epidermidis and Staphylococcus hominis was 97.3%, while specificity was 91.8%. When isolates displaying discrepant desferrioxamine results were characterized using recently described interpretive criteria, sensitivity and specificity of the desferrioxamine test improved to 100%. The desferrioxamine test was reliable, inexpensive and simple to perform, and should prove useful in the diagnostic laboratory.

Bacteremia↗