Doctors and the control of major releases of chemicals.
Explore the source record for details and available documents.
Disaster Planning↗
Biomedical subjects
P R Hunter
Publications and source records attributed to P R Hunter.
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↗
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↗
Cyanobacteria and human health.
Explore the source record for details and available documents.
Animals↗
Dual infection from cooked meats?
Explore the source record for details and available documents.
Animals↗
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↗
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↗
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↗
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↗
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↗
Diversity studies of Salmonella incidents in some domestic livestock and their potential relevance as indicators of niche width.
This study attempts to determine whether or not livestock are becoming more susceptible to epidemics of salmonella infections by the analysis of published data on the annual number of reported infections in various animals. The number of incidents reported each year may be subject to a variety of biases due to temporal and geographical differences in reporting practices. This study analysed these reports by the calculation of diversity indices which are not subject to some of these potential biases. The relationship between the ecological concept of niche width and the diversity of species or types occupying that niche is discussed. The diversity of salmonella types reported in fowl has shown a highly significant decline over the 13-year period 1976-88. It is suggested that this declining diversity may be related to the declining niche width of the biotope available to this pathogen. Although speculative, this reduction in niche width could be related to a declining genetic diversity in the host animals or to an increasing intensification of animal husbandry.
Animals↗
A character separation index suitable for binary data containing equivocal responses.
Character separation indices are useful for determining which binary characters best discriminate between two populations. To date these indices are unable to cope sufficiently with binary data that contain equivocal responses. A character separation index is described which can be applied to data containing equivocal responses. Furthermore, for larger numbers of group members this index can be used to derive the significance that a given character would have given a particular separation value by change. The BASIC implementation of a program to calculate character separation indices is presented.
Biometry↗
Mathematical modeling of antimicrobial susceptibility data of Staphylococcus haemolyticus for 11 antimicrobial agents, including three experimental glycopeptides and an experimental lipoglycopeptide.
Antimicrobial MIC data were obtained for 96 strains of Staphylococcus haemolyticus and the following 11 antimicrobial agents: methicillin, gentamicin, rifampin, fusidic acid, ciprofloxacin, vancomycin, teicoplanin; three experimental glycopeptides, MDL 62,873, MDL 62,208, and MDL 62,224; and an experimental lipoglycopeptide, ramoplanin. Resistance to methicillin and gentamicin was present in over 50% of the strains, although resistance to the other agents was present in less than 10%. It is shown how application of mathematical modeling techniques can add to the understanding of such MIC data. MICs of methicillin and gentamicin were highly correlated, suggesting that evolutionary pressures for development of resistance to these agents were similar. The structural relationships among the glycopeptides were accurately reflected in their spatial relationships within the model. MICs of ramoplanin were negatively correlated with MICs of some other antimicrobial agents, particularly gentamicin, suggesting that this agent is more active against gentamicin-resistant strains. Methicillin-resistant strains were more tightly clustered than were methicillin-susceptible strains, suggesting that methicillin-resistant strains were more closely related to each other than were methicillin-susceptible strains. Mathematical modeling techniques enable more detailed analysis of MIC data.
Anti-Bacterial Agents↗
Application of the theory of adaptive polymorphism to the ecology and epidemiology of pathogenic yeasts.
The theory of adaptive polymorphism predicts that species occupying broad ecological niches will be phenotypically and genotypically more varied than those occupying narrow niches. It is suggested that this theory has direct relevance to the epidemiology of microbial pathogens in that environmental pathogens inhabit a broader niche and should be expected to exhibit greater variation than pathogens that are obligate commensals. This proved to be the case when one obligate commensal, the pathogenic yeast Candida albicans, was compared with other Candida spp. and an environmental pathogen, Cryptococcus neoformans. Further evidence of this relationship is derived from the literature. This observation adds further support to the theory of adaptive polymorphism, although the mechanisms of maintenance of polymorphism is asexually reproducing populations must be different from those in sexually reproducing populations. This observation may give important clues to the epidemiology of those infections for which it is not already known.
Adaptation, Biological↗
Reproducibility and indices of discriminatory power of microbial typing methods.
When microbial strain-typing methods are compared, the most important characteristics are typeability, reproducibility, and discriminatory power. While typeability and reproducibility can be presented as numerical values, indices of discriminatory power have only recently been described. This paper examines the relationship between reproducibility and indices of discriminatory power. In an individual typing method, an inverse relationship between reproducibility and discriminatory power appears as the number of test differences required in order to distinguish between strains is increased. A method of standardizing the discriminatory power of a typing method to a predetermined reproducibility is presented. In this way the discriminatory powers of different typing methods can be compared while being standardized for the effect of reproducibility.
Bacterial Typing Techniques↗
Cross-infection and diversity of Candida albicans strain carriage in patients and nursing staff on an intensive care unit.
Colonization of patients and nursing staff on an intensive care unit by Candida albicans was studied over a 4-month period. Multiple swabs and samples were taken from patients and their nurses on 12 occasions during the study period. During this study there were no obvious clinically relevant candidal infections. Patients yielded C. albicans from at least one body site on 68%, and nurses on 57% of occasions. All isolates of C. albicans were further characterized by both morphotyping and resistotyping. All patients but one were colonized by a single strain throughout their stay on the unit, whereas nurses were often colonized by more than one strain type. Strains isolated from nurses' hands were all indistinguishable from strains colonizing the patient under their care, whilst strains isolated from nurses' mouths were usually distinct from their patients'. The probability that a C. albicans culture positive nurse carried an indistinguishable strain from that of her positive patient was p = 0.632, compared with p = 0.325 that a randomly chosen positive nurse would carry a strain indistinguishable from that of a randomly chosen positive patient. Diversity in patients' strains was low (D = 0.667) compared with nurses' strains (D = 0.778). These results suggest that cross-infection by C. albicans is a common occurrence on intensive care units. The reason outbreaks of candidal disease are not more common may be related to differences in virulence of the strains.
Candida albicans↗
Morphotype markers of virulence in human candidal infections.
A study of the morphotypes of 446 strains of Candida albicans, isolated from a variety of clinical specimens, is reported. The method was based on a morphotyping scheme that has recently been described, but not all of the potential characters were used in this analysis. By this limited code, 50 different morphotypes were distinguished, the largest group comprising 23% of the population. The simplicity and good discrimination of the method make it a useful typing scheme for C. albicans. Discontinuous colonial fringes were associated with strains from oral sites and deep infections. Significantly, 67% of strains from fatal infections were of the discontinuous fringe type, compared to only 11% of strains from other infections. Further associations between morphotype and anatomical source included narrow-coarse fringes in genitourinary isolates.
Candida albicans↗
Application of a numerical index of discriminatory power to a comparison of four physiochemical typing methods for Candida albicans.
Four typing methods for the strain differentiation of Candida albicans (morphotyping, resistotyping, extracellular enzyme production, and carbon source assimilation reactions) were compared on a single population of 100 strains. An index of discriminatory power was used to facilitate this comparison. Extracellular enzyme production had poor discriminatory power, and carbon source assimilation reactions were poorly reproducible. Morphotyping and resistotyping had acceptable reproducibility and discrimination. The use of resistotyping and morphotyping in parallel enhanced discrimination without an unacceptable decrease in reproducibility, although other combinations did not enhance discrimination because reproductibility was impaired.
Candida albicans↗