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Biomedical subjects

P R Hunter

Publications and source records attributed to P R Hunter.

At least 19 recordsLinked to original sources
PubMed1995

Outbreak of cryptosporidiosis associated with a disinfected groundwater supply.

In an outbreak of cryptosporidiosis in Warrington, a town in North-West England, 47 cases were recorded between November 1992 and February 1993, most within the first month. There was a strong statistical association between cases and residence in an area supplied from two groundwater sources. In a case-control study, a strong association between having drunk unboiled tap water from these sources, and a dose-response relationship were found. Oocysts were not detected in the water supply. During very heavy rainfall one source of water was found to drain surface water directly from a field containing livestock faeces, thereby bypassing natural sandstone filtration. Exceptionally heavy rainfall occurred at the probable time of infection. After withdrawal of the original water supply, the outbreak rapidly subsided. It was concluded that there was very strong evidence that this outbreak was waterborne. This, the second documented outbreak of cryptosporidiosis attributable to a groundwater supply, demonstrates that infection can be transmitted from a disinfected groundwater source despite apparently satisfactory treated water quality. We recommended that guidelines for protection of groundwater are implemented, raw groundwater should be routinely monitored for microbiological contamination, and the structure of all sources and waterworks should be assessed in risk surveys of water catchment areas.

Adult↗
PubMed1995

Physiological traits associated with success of Candida albicans strains as commensal colonizers and pathogens.

DNA fingerprinting with the moderately repetitive sequence Ca3 has repeatedly identified groups of genetically similar strains of Candida albicans that are more frequently isolated than other groups of strains from human hosts in a geographical locale. Members of these groups are found in approximately 30% of healthy individuals and in up to 70% of patients suffering from candidiasis. The high prevalence of these strains implies that they are more successful in colonizing human hosts and in causing disease than other strains (J. Schmid, Clin. Adv. Treatment Fungal Infect. 4(6):12-16, 1993). In the present study, we have compared one such group of highly prevalent strains with other strains from the same locale to identify physiological traits a larger number of chemicals than other strains in a resistogram assay. When resistance to individual chemicals used in the resistogram assay was analyzed, strains from the group of highly prevalent strains were significantly more often resistant to boric acid, cetrimide, chlorhexidine, 5-fluorocytosine, and high sodium chloride concentrations than other strains. Strains from the group of highly prevalent strains also adhered significantly (1.5 times) better to saliva-coated surfaces than did other strains. Because members of highly prevalent groups of strains are the most common infectious agents in candidiasis, these physiological traits may be involved in determining not only the success of C. albicans in colonizing human hosts in general but also its ability to cause disease. Sodium chloride resistance and increased adherence were also associated with infectious isolates outside the group of highly prevalent strains, indicating that they may be of particular importance in pathogenesis.

Anti-Infective Agents↗
PubMed1993

A numerical method for allocating microbial isolates to strain types when characterized by typing methods that are not 100% reproducible.

Many methods for typing microbial strains are not 100% reproducible. This can create problems when deciding whether different groups of isolates are really distinct or represent typing errors or variation of a single strain. Neither hierarchical clustering nor iterative partitioning methods are suited for analysing such data. A novel iterative partitioning method is described which allows for the uncertainty of the typing method in use. Before grouping strains, the maximum dimension of the groups is set based on a previous knowledge of the typing method's reproducibility. Isolates are only allocated to a group if they differ from that group's typical strain type by less than the number of reaction differences required to distinguish between two strains. In a series of Monte Carlo studies the accuracy of strain allocation was found to be very good, even when the two groups were situated close to each other.

Bacteria↗
PubMed1993

A latitudinal diversity gradient in virus infections in humans in England and Wales.

This paper reports the presence of a latitudinal diversity gradient in reports of human viral infections in the various health regions of England and Wales. The data used in this study are reports of the laboratory diagnosis of virus infections made to the Public Health Laboratory Service Communicable Disease Surveillance Centre. Two indices of diversity were calculated from the data--Fisher's and Simpson's. Both indices were shown to correlate with latitude but not longitude. Possible mechanisms for this diversity gradient are discussed. It is suggested that such a gradient in the class of human viruses is more likely to be due to increasing environmental stress in colder climates, than to the after-effects of major climatic change.

Analysis of Variance↗
PubMed1992

Epizootics of Salmonella infection in poultry may be the result of modern selective breeding practices.

This paper discusses the hypothesis that a major factor in the epizootics of Salmonella infection in poultry is a declining host genetic diversity. A computer model is described which is based on models that have been previously used to investigate host-pathogen coevolution in cereal crops. It is shown that, as host genetic diversity declines, parasite diversity also declines to a lower equilibrium level. With a highly diverse host, parasite numbers decline to zero. With a homogeneous host population, after an initial decline, there is a rapid increase in parasite numbers, due to the selection of a particularly well adapted parasite strain. This simple computer simulation is used as the basis for a discussion of the literature supporting the suggestion that a major factor in the epizootic of Salmonella in poultry is related to the low genetic diversity of commercial poultry flocks.

Animals↗
PubMed1992

Laboratory evaluation of a filter for the control of cross-infection during pulmonary function testing.

Nosocomial transmission of respiratory pathogens is a possible complication of lung function testing. The use of a filter, placed between the patient and the spirometer equipment may be one way of preventing such nosocomial spread. This paper reports the laboratory evaluation of the efficiency of such a filter at removing bacteria from exhaled breath. Volunteers exhaled 100 normal breaths or four forced exhalations through a filter on to a blood agar plate. Bacterial counts on the agar plate were compared with recoverable bacterial counts from the filter. Total challenge from the forced exhalations ranged from 161-84,200 colony forming units. The calculated efficiency of 10 volunteers was 99.9%. For the normal breaths the challenge ranged from 0-262,000 colony forming units. There was no growth on any of the blood-agar plates. These filters appear to be highly efficient at removing exhaled bacteria.

Bacteria↗
PubMed1991

Application of Hazard Analysis Critical Control Point (HACCP) to the handling of expressed breast milk on a neonatal unit.

Hazard Analysis Critical Control Point (HACCP) is a powerful procedure for ensuring quality and safety and has gained widespread use in industry. This paper describes the basic method which is a four-stage process including process analysis, hazard identification, identification of critical control points and devising effective control options. Suggestions as to how the method can be adapted to the control of hospital infection are made. A HACCP analysis, on the supply of expressed human breast milk to babies on a Special Care Baby Unit, is presented. Although only the mother's own milk was given to babies on the unit, several potential hazards were identified and suggestions have been made for their control.

Cross Infection↗
PubMed1991

The isolation of Listeria species from fresh-water sites in Cheshire and North Wales.

We report a study to determine the presence of Listeria species in surface waters. One hundred ml volumes of 30 water samples taken from 21 different sites were analysed. Most of the samples examined were from ponds and lakes. Listeria species were isolated on eight (27%) occasions, six of these isolates were L. seeligeri, one was L. innocua and one L. welshimeri. Although not statistically significant, coliform and Escherichia coli counts were higher in waters that were positive than were negative for Listeria spp. It is suggested that the low isolation rate of listeria in this study reflects the fact that most waters examined did not receive sewage outfalls. Water sports activities are unlikely to be a risk factor for listeriosis.

Colony Count, Microbial↗
PubMed1991

A critical review of typing methods for Candida albicans and their applications.

During the 1980s, a large number of typing methods for the strain differentiation of Candida albicans were described in the literature. Although these methods have been based on a variety of physiological and genetic markers, none is ideal. This review discusses the characteristics of an ideal typing method in terms of its typability, reproducibility, and discriminatory power. Ways of determining these characteristics are presented so that the available typing methods for Candida albicans can be objectively compared. Available typing methods for C. albicans include serotyping, morphotyping, resistotyping, biotyping, and killer yeast typing. Electrophoretic methods include immunoblotting, isoenzyme analysis, analysis of DNA restriction fragment length polymorphism, karyotyping, and the use of DNA probes. The application of these methods to epidemiological research, the investigation of outbreaks of disease, and the study of virulence is described. The potential impact of the phenomenon of phenotypic switching on the reproducibility of these typing methods is discussed. It is concluded that many of the available typing methods have not been adequately assessed by their developers and that several have only poor discriminatory power or reproducibility.

Candida albicans↗
PubMed1991

The sub-specific numerical analysis of Candida albicans.

This paper reports the numerical analysis of 100 strains of Candida albicans using 96 physiochemical characters. Principal co-ordinate analysis and the modified multidimensional group analysis (MGA) method were used for the numerical analysis. MGA detected optimal solutions for five, 11, 15 and 17 groups. A single large swarm represented the majority of strains for the five- and 11-group solutions. Of the remaining two solutions only the 17-group solution was analysed further as the 15-group solution was close to the 17-group solution and contained less information. Of the 17 groups within the data, 10 "groups" contained only a single member, whilst the other groups contained 32, 24, 14, 13, three, two and two members each. Characters that tended to distinguish between the four larger groups included colonial fringe state, valerate assimilation, and resistance to borate, cetrimide, benzalkonium chloride, chlorhexidine, arsenate and salt. These larger groups appeared to form reasonably distinct clusters when tested by Sneath's overlap statistics. However, as the squared Euclidean distances between these group centroids were small, it would appear that most strains of C. albicans form a single swarm. It is suggested that these groups may represent "preferred phenotypes" for C. albicans, between which individual strains may switch.

Bacterial Typing Techniques↗
PubMed1990

Infection of staff during an outbreak of viral gastroenteritis in an elderly persons' home.

An outbreak of viral gastroenteritis in an elderly persons' residence is reported. Seventeen of 37 (47%) residents and 22 of 50 (44%) staff developed illness. Adenovirus was seen by direct electron microscopy in two vomitus and two faeces specimens. It is suggested that the most likely mode of transmission was environmental contamination by vomitus.

Adenoviridae Infections↗