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Biomedical subjects

G C Mead

Publications and source records attributed to G C Mead.

At least 37 records · Page 2Linked to original sources
PubMed1994

Use of a marker organism in poultry processing to identify sites of cross-contamination and evaluate possible control measures.

1. Nine different sites at a poultry processing plant were selected in the course of a hazard analysis to investigate the degree of microbial cross-contamination that could occur during processing and the effectiveness of possible control measures. 2. At each site, carcases, equipment or working surfaces were inoculated with a non-pathogenic strain of nalidixic acid-resistant Escherichia coli K12; transmission of the organism among carcases being processed was followed qualitatively and, where appropriate, quantitatively. 3. The degree of cross-contamination and the extent to which it could be controlled by the proposed measures varied from one site to another.

Animals↗
PubMed1993

Microbiological survey of five poultry processing plants in the UK.

1. Neck skin samples were taken from chickens and turkeys at all the main stages of processing to monitor changes in total viable count (TVC) and counts of coliforms and pseudomonads. 2. Processing reduced TVC by up to 100-fold. Geometric mean counts after packaging were log10 4.4 to 5.3 CFU/g whilst corresponding counts of coliforms were 2.7 to 3.8 CFU/g. 3. Increases in mean TVC or coliforms as a result of either defeathering or evisceration did not exceed 0.6 log. 4. Pseudomonads represented only a minor fraction of the initial microflora of the bird and were often reduced by scalding to a figure which could not be detected by direct plating of samples; however, subsequent contamination resulted in means between log10 2.9 and 4.0 CFU/g for packaged carcases. 5. Although Staphylococcus aureus was readily isolated from defeathering equipment, mean counts from defeathered carcases were always below log10 3.0 CFU/g.

Animals↗
PubMed1993

An in vitro model for studies on bacterial interactions in the avian caecum.

An in vitro intermittent-flow model was developed for studying bacterial interactions in the avian caecum. The model provides a closer simulation of caecal conditions than others described previously but does not require elaborate instrumentation. In preliminary trials, growth of caecal bacteria from an adult chicken was shown to be inhibitory to both Salmonella infantis and entero-haemorrhagic Escherichia coli.

Animals↗
PubMed1992

Principles involved in the detection and enumeration of clostridia in foods.

The clostridia are a group of anaerobic bacteria that vary considerably in their biochemical and physiological properties. Not surprisingly, attempts to develop a single isolation medium for all species that occur in foods have not been entirely successful, and the problem is compounded by the need to recover both vegetative cells and spores, some of the latter being unable to germinate without heat activation. Most available isolation media, except some of those used in the dairy industry, include sulphite and an appropriate iron salt, so that blackening due to sulphite reduction can serve as a differential test for clostridia. The limitations of this test in solid agar media are discussed and some advantages described in relation to its use in liquid media for Most Probable Number determinations. A medium favoured for the purpose is the Differential Reinforced Clostridial Medium of Gibbs and Freame (1965). An unresolved issue is whether or not special precautions are needed to exclude oxygen during food sample preparation and dilution, preparation of media, and in conditions used for anaerobic incubation. Although such stringency may be required for maximum recovery of sub-lethally damaged cells or spores, practical constraints in food control laboratories necessitate use of relatively simple procedures for detecting clostridia routinely.

Anaerobiosis↗
PubMed1991

Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat.

Portions of skinless chicken breast meat (pH 5.8) were inoculated with a strain of Listeria monocytogenes and stored at 1, 6 or 15 degrees C in (1) aerobic conditions; (2) 30% CO2 + air; (3) 30% CO2 + N2; and (4) 100% CO2. When samples were held at 1 degree C the organism failed to grow under any of the test conditions, despite marked differences between treatments in spoilage rate and ultimate microflora. At 6 degrees C counts of L. monocytogenes increased ca 10-fold in aerobic conditions before spoilage of the meat, but only when the inoculum culture was incubated at 1 degree C rather than 37 degrees C. In CO2 atmospheres growth of L. monocytogenes was inhibited on meat held at 6 degrees C, especially under 100% CO2. By contrast, storage at 15 degrees C led to spoilage of the meat within 2 d, in all gaseous environments, and listeria levels increased up to 100-fold. Differences in the behaviour of L. monocytogenes on poultry and red meats are discussed.

Aerobiosis↗
PubMed1989

Microbes of the avian cecum: types present and substrates utilized.

This paper discusses the types and properties of microorganisms found in avian ceca, with special reference to the chicken. Microbial activity in the cecum is primarily fermentative, but there has been little evidence of cellulose fermentation, and the predominant bacterial types are relatively inactive against other high-molecular-weight compounds of dietary origin. In all avian species examined, the consistent presence of large populations of uric acid-degrading bacteria supports the view that microbial populations in the ceca permit reabsorption of water and possibly nonprotein nitrogen from the backflow of urine. These capabilities may be of particular importance to wild birds under conditions of water and food deprivation.

Aging↗
PubMed1989

Differentiation of Staphylococcus aureus from freshly slaughtered poultry and strains 'endemic' to processing plants by biochemical and physiological tests.

A comparison was made of 27 'endemic' strains of Staphylococcus aureus and 35 strains from freshly slaughtered birds, isolated at five commercial slaughterhouses processing chickens or turkeys. Of 112 biochemical and physiological tests used, 74 gave results which differed among the strains. Cluster analysis revealed several distinct groupings which were influenced by strain type, processing plant and bird origin; these included a single group at the 72% level of similarity containing most of the 'endemic' strains. In comparison with strains from freshly slaughtered birds, a higher proportion of 'endemic' strains produced fibrinolysin, alpha-glucosidase and urease and were beta-haemolytic on sheep-blood agar. The 'endemic' type also showed a greater tendency to coagulate human but not bovine plasma, and to produce mucoid growth and clumping. The last two properties, relevant to colonization of processing equipment, were less evident in heart infusion broth than in richer media or process water collected during defeathering of the birds.

Animals↗
PubMed1989

Fate of salmonellas in the alimentary tract of chicks pre-treated with a mature caecal microflora to increase colonization resistance.

Oral challenge with a strain of Salmonella kedougou, resistant to nalidixic acid, gave a time-course for salmonella survival in the alimentary tract of chicks pre-treated with a caecal culture from an eight-week-old bird to increase colonization resistance. In untreated, control chicks, salmonella colonization of the caeca resulted in counts of greater than 10(6)/g within 48 h and a mean generation time of 1.6 h. With treated birds, however, the salmonellas failed to multiply in the caeca and decreased to a low level over a 48-h period, thus suggesting a mainly bacteriostatic effect. Pre-treatment of chicks with the caecal culture also reduced the proportion of salmonella-positive crop samples. Growth of the salmonella in a feed-slurry system resembling moistened crop contents occurred rapidly at 37 degrees C but was prevented by addition of the treatment culture, a decline in numbers coinciding with Lactobacillus populations of ca 10(9)/g and a pH value of 5.5. Incorporation of a feed decontaminant, 1% formic acid (pH 4.0), rapidly eliminated both salmonellas and organisms added from the treatment culture.

Animals↗