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Biomedical subjects

H A Foster

Publications and source records attributed to H A Foster.

14 recordsLinked to original sources
PubMed2003

Evaluation of Chromocult coliform agar for the detection and enumeration of Enterobacteriaceae from faecal samples from healthy subjects.

The purpose of this study was to examine the use of Chromocult agar medium for isolation and enumeration of Enterobacteriaceae from human faecal samples, to compare it to MacConkey agar and to evaluate its usefulness as a possible alternative selective medium in human faecal studies. The medium was shown to be effective in identifying Escherichia coli and coliforms in faeces without the need for extensive accompanying biochemical tests for confirmation of identity. A positive correlation (r=0.86) was found between the recovery of Enterobacteriaceae on the two media, and no significant difference (P>0.05) between overall mean bacterial counts for the whole study group or at different intervals of faecal collection were observed. Chromocult agar is an effective replacement for MacConkey agar in human faecal studies and has the advantage of differentiating E. coli from other coliforms.

Agar↗
PubMed2003

Comparison of adhesion of wound isolates of Staphylococcus aureus to immobilized proteins.

AIMS: To determine the ability of 149 clinical isolates of Staphylococcus aureus from burns, other wounds and environmental isolates to adhere to immobilized proteins. METHODS AND RESULTS: The ability to bind to immobilized fibrinogen, fibronectin, laminin, collagen, IgG and lysozyme was studied using a microtitre plate assay. The strains were very diverse. Binding to fibrinogen was most frequent, followed by fibronectin, collagen and laminin. Binding to IgG and lysozyme was weak and few strains showed strong binding. Numerical analysis showed that 65% of the strains infecting burns had similar properties and bound to fibrinogen, fibronectin, collagen and IgG. The strains infecting other wounds had more variable characteristics. CONCLUSIONS: The ability to adhere to proteins is important in wound infection, but clinical isolates were diverse in their ability to bind to the proteins tested. Burn wounds were more likely to be infected with strains showing multiple binding characteristics. SIGNIFICANCE AND IMPACT OF THE STUDY: The study confirms the importance of adhesins in clinical infection.

Bacterial Adhesion↗
PubMed2003

Detection of antibodies to Staphylococcus aureus Toxic Shock Syndrome Toxin-1 using a competitive agglutination inhibition assay.

AIMS: To develop a competitive agglutination inhibition assay (CAIA) for the detection of anti-Toxic Shock Syndrome Toxin-1 (TSST-1) antibody in serum samples using a commercially available reverse passive agglutination assay (RPLA) kit. METHODS AND RESULTS: TSST-1 toxin and sera were incubated together, so that anti-toxin IgG would complex with the toxin. Latex particles sensitized with rabbit IgG anti-TSST-1 were added to test for un-complexed toxin. The sensitivity and specificity of the CAIA assay was determined relative to positive and negative ELISA results. The sensitivity (proportion of positive ELISA sera which tested positive by CAIA) was 66% whilst the specificity (proportion of ELISA negative sera which tested negative by CAIA) was 75%. Seven sera (14%) were negative by ELISA but positive for CAIA and 12 (18.8%) were positive for ELISA but negative for CAIA, suggesting some interference with the assays. Statistical analysis showed no significant difference between the methods in terms of the numbers of individuals testing positive (chi2, P = 0.04). CONCLUSIONS: The CAIA assay allowed detection of anti-TSST-1 within 18 h and was simple to read visually. SIGNIFICANCE AND IMPACT OF THE STUDY: The method is a useful test for individual serum samples and a preliminary investigation for medical screening of suspected toxic shock syndrome and is applicable in situations where antibody assays are not routinely used for anti-TSST-1 and also where sophisticated equipment (e.g. microtitre plate reader) is not available.

Animals↗
PubMed2002

Effects of silver sulphadiazine on the production of exoproteins by Staphylococcus aureus.

The effects of subinhibitory concentrations of silver sulphadiazine (AgSD) on exoprotein production in Staphylococcus aureus strains T1, T4, RN4282 and RN 4282agr were studied. AgSD markedly increased levels of toxic shock syndrome toxin (TSST)-1 in strains T4 and RN4282. This effect was independent of agr and AgSD restored TSST-1 production to the wild-type level in RN 4282agr. AgSD had no effect on enterotoxin A or coagulase activity in strains T1 or T4. Strain T4 produced enterotoxin C at high levels and no effect was observed with AgSD. AgSD repressed metalloprotease production in strain T4 but the overall protease activity remained the same. No change in proteolytic activities was seen in strainT1 with AgSD. Molecular mechanisms for these observations are discussed.

Anti-Infective Agents, Local↗
PubMed2001

Field survey and literature review on traditional fermented milk products of Ethiopia.

The wide variety and the socio-economic and dietary importance of traditional fermented milk products of Ethiopia are discussed in this paper. Information on the microbiology of these products is sparse and has relevance to those organisms associated with spoilage and to those considered desirable for fermentation. There is a clear need to improve the production of African foods and beverages [Int. J. Food Microbiol. 18 (1993) 85]. The objective of this review was to document traditional technology used and information on the microbiology of the products, and to identify various constraints to the development and commercialisation of fermented milk products. Thereby the major problems and potential areas for improvement are pointed out. Ergo, the most important traditional product resembles yoghurt and, as the other traditional products, is prepared by "spontaneous" fermentation, commonly initiated by either "back slopping" or by repeated use of the same utensil. Other products include traditional fermented curd or ititu, traditional butter or kibe, neter kibe or traditional ghee, ayib resembling cottage cheese, arrera or defatted buttermilk and augat or traditional whey.

Animals↗
PubMed1999

Thermostable Newcastle disease vaccines in Tanzania.

The V4 thermostable Newcastle disease vaccine was tested under village conditions in Central Tanzania. The vaccination regimes were four vaccinations by eye drop (eye drop group), one vaccination by eye drop followed by three vaccinations by drinking water (drinking water group), one vaccination by eye drop followed by three vaccinations with vaccine supplied on boiled sorghum (food vaccine group) and no vaccine (control group). Antibody responses in the eye drop and drinking water groups suggested that at least 70% of the chickens would be protected against challenge with virulent virus. In both groups, eight of the 11 chickens survived laboratory challenge. Only three of the 11 chickens in the food vaccine group resisted challenge, and none of the 10 control chickens.

Administration, Oral↗
PubMed1998

Speciation of presumptive viridans streptococci from early onset neonatal sepsis.

Twenty isolates resembling viridans streptococci, 16 from blood and four from gastric aspirates, from 17 cases of early onset neonatal sepsis were identified by the API20 Strep, Rapid ID 32 Strep and conventional tests plus hydrolysis of methylumbelliferyl glycoside substrates. Nineteen of the isolates were identified as species of viridans streptococci and one as a Leuconostoc sp. Ten of the isolates were Streptococcus oralis, three S. mitis biotype 1, two S. mitis biotype 2 and one each of S. sanguis, S. vestibularis, S. salivarius and S. intermedius. The Rapid ID 32 Strep and conventional plus methylumbelliferyl tests gave the same species identity for 17 of the isolates. S. intermedius was identified by the Rapid ID 32 Strep as S. constellatus and S. salivarius as S. equinus, with S. salivarius at lower probability. The API20 Strep failed to identify S. vestibularis and identified S. salivarius as S. defectivus. The absence of certain critical tests, including urea hydrolysis, does not allow the API20 Strep to identify all the currently recognised species of viridans steptococci. The species distribution was unexpected and the incidence of S. oralis and other viridans streptococci in vaginal swabs from prenatal patients is being investigated further.

Bacteremia↗
PubMed1996

A comparison of phenotypic properties of Staphylococcus aureus isolated from burned children and other patient groups.

This study aimed to determine whether strains of Staph. aureus isolated from children on our paediatric burns unit were different from strains isolated from other patient groups. Of particular interest was the incidence of toxin production amongst the different patient groups and the potential association with toxic shock syndrome (TSS). Wound isolates of Staph. aureus were collected from three patient groups: (1) hospital inpatients, (2) community patients and (3) patients from a regional burns unit. One hundred isolates were collected from each group (n = 300). Each isolate was tested for enterotoxin and TSST-1 production, phage type, antibiogram and tryptophan dependence. The results were compared, to determine whether there were any differences between the isolates from each of these patient groups. There were some variations in antibiotic sensitivity patterns and phage type of the isolates between the different patient groups but there was no significant difference in the incidence of toxin production, which was an important observation. The 100 isolates collected from this burns unit were derived from 58 patients. The colonization patterns of the Staph. aureus showed that 12 patients were colonized by more than one isolate and that these were a mixture of toxin-positive and toxin-negative strains. The medical records were examined for evidence of TSS; there was a higher incidence of toxic episodes in the patients colonized with strains which produced TSST-1 toxin.

Anti-Bacterial Agents↗
PubMed1996

Comparison of five methods for the determination of arginine hydrolysis by viridans streptococci.

Seventy-eight clinical isolates and four control strains of viridans streptococci were tested in parallel for arginine hydrolysis by five different methods. These comprised two commercial systems, the API20 STREP and Vitek GPI card, two published methods, one based on ammonia production and one on alkalisation of Møeller's decarboxylase medium, and a method based on alkalisation of a phenol-red broth medium dispensed into microtitration plates. The clinical isolates were speciated by their biochemical reactions in the API20 STREP and API20 ZYM systems. One strain produced only a weak reaction for arginine hydrolysis in the medium by ammonia production, but otherwise the results with this medium, the API20 STREP and the microtitration plate method were identical. Tests with the Møeller decarboxylase medium and Vitek GPI card gave negative results with isolates that were positive by other methods. Inoculum size was shown to influence arginine hydrolysis obtained with Streptococcus sanguis NCTC 7863 and S. milleri 10713.

Adult↗
PubMed1994

The effect of topical antimicrobial agents on the production of toxic shock syndrome toxin-1.

Three hundred isolates of Staphylococcus aureus from wound swabs were examined for the production of toxic shock syndrome toxin 1 (TSST-1). The isolates were collected from community patients, surgical inpatients and from patients in the Regional Burns Unit, Booth Hall Children's Hospital, Manchester. The overall incidence of toxin production was 17% and there was no significant variation between the sources of the strains. All 55 TSST-1-producing strains were grown in sublethal concentrations of five topical antimicrobial compounds and the level of toxin produced was determined and compared with the amount produced in a control broth after incubation for 24 h. The effects of sublethal concentrations of the compounds on TSST-1 production were strain dependent; some compounds tended to increase production (at least four-fold) and some tended to decrease production (at least four-fold). Some of the strains showed an increase in toxin production in the presence of chlorhexidine gluconate/cetrimide solution and silver sulphadiazine cream whereas 18%, 42% and 47% of the strains showed a decrease in toxin production in the presence of povidone iodine solution, stabilised hydrogen peroxide cream and mupirocin ointment, respectively. Preliminary results suggest that silver sulphadiazine cream induces toxin formation earlier in the growth cycle.

Anti-Infective Agents, Local↗
PubMed1993

Antifungal activity of Myxococcus species 1 production, physicochemical and biological properties of antibiotics from Myxococcus fulvus S110 (Myxobacterales).

Chloroform extracts of the culture supernatant of a strain of Myxococcus fulvus isolated from soil were fungistatic and prevented germination of spores of Botrytis cinerea. The antibiotics were produced during the exponential phase of growth and the effects of altering medium composition are described. The activity was fractionated into neutral, acidic and basic fractions. The neutral fraction had a molecular weight of 244 and was tentatively identified as 11-phenyl-undecadiene-2-ol. The acidic fraction was primarily n-hexadecanoic acid. The basic fraction contained components [N-(2-phenylethyl)-acetamide, and compounds tentatively identified as 1-isoquinoline carbonitrile and substituted quinolines] which have not previously been described in the myxobacteria.

Antifungal Agents↗
PubMed1991

Evaluation of a rapid fluorogenic method for the detection of Escherichia coli in dairy products.

A rapid fluorogenic medium was evaluated for the detection of Escherichia coli in dairy products. The medium was capable of detecting Esch. coli after 7.5 h incubation at 41.5 degrees C. Samples of pasteurized milk (136), raw milk (63), soft cheese (60) and pasteurized cream (39) were examined with media based on 4-methylumbelliferyl-beta-D-glucuronide (MUG-7) and Violet red bile agar and there were no significant differences between the numbers of Esch. coli detected on the two media. MUG-7 medium had a specificity of 98.6% and the small number of organisms giving a false positive reaction were identified as Klebsiella pneumoniae. The incidence of false negative results was approximately 2%. MUG-7 medium was suitable for pour plate, spread plate and membrane filtration methods. Possible applications of the method are discussed.

Animals↗
PubMed1991

A rapid fluorogenic method for the detection of Escherichia coli by the production of beta-glucuronidase.

A medium containing the fluorogenic substrate 4-methylumbelliferyl-beta-D-glucuronide was developed for the isolation and identification of Escherichia coli within 7.5 h and was based on the detection of beta-glucuronidase. Optimum conditions for the rapid development of fluorescent colonies were determined. The optimum temperature was 41.5 degrees C. Development of fluorescence was delayed when carbohydrates were incorporated into the medium. Water samples were used to evaluate the medium by surface plating and membrane filtration. The frequency of false-negative results was 6.1% and false-positives were 3.7% for freshwater samples. The false-positive organisms were identified as Klebsiella spp. and Shigella sonnei. The potential applications of the medium are discussed.

Carbohydrate Metabolism↗