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T V Riley

Publications and source records attributed to T V Riley.

At least 109 records · Page 6Linked to original sources
PubMed1988

Laboratory diagnosis of Clostridium difficile-associated diarrhoea.

This paper reviews the various laboratory procedures available for the isolation and identification of Clostridium difficile and the detection of toxins produced by this organism. Laboratories should be selective in determining which patients require investigation for Clostridium difficile-associated diarrhoea. Transport and storage of stool specimens at 4 degrees C is recommended when delays in processing may occur. Tissue culture techniques are still the best method for detection of cytotoxin and a variety of cell lines can be used. Other methods for detecting cytotoxin, and methods for detecting other toxins are not sufficiently developed yet to warrant introduction into diagnostic laboratories. Culture techniques remain the most sensitive for diagnosis, particularly since the development of a variety of enrichment techniques. Cycloserine cefoxitin fructose agar is still adequate, although reduced concentrations of antimicrobial agents are necessary, and improvements, such as the addition of sodium taurocholate, increase the recovery of spores. Enrichment cultures have markedly increased isolation rates for Clostridium difficile but the significance of these isolates needs to be carefully evaluated. Until simpler and more reliable tests are available in clinical laboratories for the detection of toxins, the isolation of Clostridium difficile from patients with diarrhoeal disease should be considered paramount.

Bacterial Toxins↗
PubMed1988

UV red fluorescence of Veillonella spp.

A total of 34 clinical isolates and 7 type strains of Veillonella spp. were tested for their ability to fluoresce on various culture media. Fluorescence was medium dependent and varied among the species. Scanning absorption spectrophotometry of culture extracts showed that the absorption spectrum of the fluorescent pigment is typical of a metal-free porphyrin.

Culture Media↗
PubMed1987

Comparison of alcohol shock enrichment and selective enrichment for the isolation of Clostridium difficile.

Two enrichment methods were compared for their ability to recover Clostridium difficile from stool samples. One method used selective enrichment in an antibiotic-containing broth followed by detection with a latex particle agglutination (LPA) reagent. The other used enrichment in a non-selective broth following treatment of the specimen with alcohol. With clinical specimens enrichment culture was significantly more successful at detecting C. difficile than direct plating. Alcohol shock enrichment was twice as effective as direct culture, while selective broth enrichment was three times more effective. The use of LPA for screening selective enrichment broths for C. difficile should prove a cost-effective measure as only positive broths (about 20%) require subculture for confirmation.

Bacteriological Techniques↗
PubMed1987

Respiratory tract infections due to Branhamella catarrhalis: epidemiological data from Western Australia.

During a 3-year period Branhamella catarrhalis was isolated in significant numbers from 239 (1.3%) of 19,488 specimens of sputum sent for routine microbiological examination at a 700-bed general hospital. The majority of patients (83%) were over 60 years of age and 65% were male. There was a distinct seasonal variation in isolations with a peak incidence during the winter and early spring, a pattern not found with other pathogens. Susceptibility to amoxycillin decreased by approximately 50% over the 3 years, corresponding to an increased incidence of beta-lactamase-producing strains. There were minimal changes in susceptibility to other antimicrobial agents. Underlying pulmonary disease was the major factor predisposing to B. catarrhalis infection, and 71% of patients were smokers or ex-smokers.

Adult↗
PubMed1987

Susceptibility of Branhamella catarrhalis to sulphamethoxazole and trimethoprim.

Fifty strains of Branhamella catarrhalis were examined for susceptibility to sulphamethoxazole, trimethoprim and a combination of the two by determinating minimum inhibitory concentrations (MICs) and fractional inhibitory concentrations (FICs). All strains were susceptible to sulphamethoxazole and resistant to trimethoprim. On the basis of the MIC results it was predicted that greater synergy between sulphamethoxazole and trimethoprim would be observed with approximately equal proportions of each component. The lowest FIC values were obtained with a ratio of 1:1 and the greatest synergy was observed at this ratio with 39 strains (78%). Only seven strains were most synergistically inhibited at the ratio of 20:1 (sulphamethoxazole: trimethoprim) although this ratio was still synergic for most strains. Overall the 1:20 ratio was not synergic.

Drug Combinations↗
PubMed1987

A note on hydrolysis of tributyrin by Branhamella and Neisseria.

Sixty-three strains of Branhamella and Neisseria were tested by two methods for their ability to hydrolyse glycerol tributyrate. After the conventional plate test, gas liquid chromatographical (GLC) analysis of the agar medium was carried out to detect the hydrolysis product, butyric acid, and other volatile fatty acids. All strains of Branhamella catarrhalis, Neisseria caviae, N. cuniculi and N. ovis but no other Neisseria spp. gave positive results with the conventional test. With GLC, however, most strains of Branhamella and Neisseria were shown to liberate butyric acid. In addition, some strains liberated acetic and isovaleric acids. Greater amounts of butyric acid were produced by clinical strains, in particular B. catarrhalis, compared with reference strains. It was concluded that the conventional plate test for tributyrin hydrolysis differentiates B. catarrhalis, N. caviae, N. cuniculi and N. ovis from other Neisseria.

Butyrates↗
PubMed1987

Heparinase production by anaerobic bacteria.

The production of heparinase by a wide range of anaerobic bacteria isolated from clinical specimens was investigated. None of the 29 strains of Bacteroides fragilis produced heparinase. Of 62 other Bacteroides tested, only two of four strains of B ovatus, two of three strains of B thetaiotaomicron, and two of four strains of B uniformis were heparinase producers. None of the 48 strains of fusobacteria or seven strains of Veillonella produced heparinase. The anaerobic cocci (19 peptococci and seven peptostreptococci) were also negative for heparinase production as were 46 Clostridium spp tested. It was concluded that heparinase production by anaerobic bacteria was unlikely to play a part in the regional thrombophlebitis that sometimes occurs in anaerobic infections.

Bacteria, Anaerobic↗
PubMed1986

Clostridium difficile in general practice and community health.

The isolation rate for Clostridium difficile in diarrhoeal stools was investigated in patients from general practice and community health centres over a 14-month period. C. difficile or its cytotoxin was detected in specimens from 89 (4.7%) of 1882 patients studied and accounted for 30.3% of all enteropathogenic micro-organisms isolated. Overall C. difficile was second only to Giardia lamblia in frequency. Recovery rates in the different groups of patients surveyed varied from 3.6 to 27.5%. The relationship between stool culture results and stool cytotoxin assay also varied considerably between groups of patients studied. Coincident infections with a variety of enteropathogenic bacteria and intestinal parasites were diagnosed in 14 of the 89 patients. It was concluded that laboratories servicing this type of practice should be aware that C. difficile may be a cause of diarrhoea. An adequate clinical history should facilitate proper processing of the specimen.

Australia↗
PubMed1986

Latex particle agglutination for detecting and identifying Clostridium difficile.

A total of 329 selective enrichment broth cultures were tested for detection of Clostridium difficile by latex particle agglutination (LPA), gas-liquid chromatography, and bacterial culture. Of 53 broths positive by LPA, 36 were positive by gas-liquid chromatography, and 42 were positive by bacterial culture. The sensitivity and specificity of LPA relative to bacterial culture was 95.6% and 96.3%, respectively, while the sensitivity and specificity of gas-liquid chromatography relative to bacterial culture was 84.6% and 100%, respectively. The high predictive value of a negative test (99%) should make LPA on broth cultures a good screening test for detecting C difficile. Of several other Clostridium spp tested in pure culture, strains of C sordellii and C bifermentans also gave a positive result by LPA. These results, together with the low cost and simple facilities required, suggest that the LPA test will be a useful procedure for the presumptive identification of C difficile in selective enrichment broths and for the identification of pure cultures.

Caproates↗
PubMed1985

Lactic acid levels in pleural fluid from patients with bacterial pleuritis.

Pleural fluid lactic acid estimations were carried out on 60 samples by gas-liquid chromatography. Lactic acid levels in 12 patients with bacterial pleural infection were statistically significantly higher (mean, 287 mg/dl; range, 135 to 482 mg/dl) than in 18 patients with malignancy (mean, 71 mg/dl; range, 24 to 157 mg/dl) and 30 other patients with pleural effusions (mean, 19 mg/dl; range, 10 to 57 mg/dl). The determination of pleural fluid lactic acid may help in differentiating between empyema and nonbacterial pleural effusions in most cases. It is of particular value when antibiotic therapy has commenced before specimen collection and may be useful for monitoring therapy.

Bacterial Infections↗
PubMed1985

A comparative study of three bacteriocins of Bacteroides fragilis.

Three different bacteriocins produced by strains of Bacteroides fragilis were compared in terms of their production kinetics, physico-chemical nature, and action on macromolecular synthesis in a common indicator strain. Bacteriocin 78/438 was produced during the logarithmic growth phase, was thermolabile and stable between pH 5 and 9. It was susceptible to trypsin and pepsin, and affected DNA, RNA and protein syntheses in susceptible cells. Bacteriocin A49 was produced during the stationary growth phase, was thermolabile and stable between pH 7 and 9. This bacteriocin was also susceptible to trypsin and pepsin, but only RNA synthesis was affected in the indicator strain. Bacteriocin A55 differed markedly from both 78/438 and A49, and was found to be predominantly cell-bound, resistant to inactivation by high temperatures and stable over a wide pH range of 2 to 12. It was susceptible to trypsin but resistant to pepsin. A55 had a delayed effect on macromolecular synthesis with DNA synthesis being inhibited after 60 min. With all three bacteriocins, killing of the indicator strain followed single hit kinetics with the interaction of bacteriocin and target cell occurring in two stages. Killing by bacteriocin A55 was much slower than the other two and this may be related to its effect on macromolecular synthesis. The killing action of all three bacteriocins was dependent on the growth phase of the susceptible cells.

2,4-Dinitrophenol↗
PubMed1984

Physiological properties and plasmid content of Bacteroides spp.

A collection of 50 clinical isolates of Bacteroides was examined for plasmid deoxyribonucleic acid content. An attempt was then made to correlate the presence of plasmids with a specific phenotypic property. Of the 20 Bacteroides which contained plasmids, 18 were found to harbour plasmids of less than or equal to 9.8 megadaltons. The most common plasmid had a molecular weight of 4.8 megadaltons and was found in 9 strains. Most strains had multiple plasmid bands. All strains were examined for resistance to penicillin, cefoxitin, erythromycin, tetracycline, sulphamethoxazole, clindamycin, chloramphenicol, arsenate, silver, cadmium, mercury, chromium, lead, nickel and cobalt, and for the production of beta-lactamase, heparinase, deoxyribonuclease, haemolysins and bacteriocins. Using a Chi-squared analysis, there was no statistically significant correlation between any of these phenotypic traits and the presence of plasmids, except bacteriocin production. A total of 15 out of 20 (75%) of plasmid-containing strains produced bacteriocins while only 10 out of 30 (33%) of plasmid-free strains were capable of bacteriocin production (chi 2, p less than 0.005). Attempts to transfer or cure resistance to antibiotics and heavy metals or bacteriocin production were not successful.

Bacteriocins↗