摘要:

Oral challenge with a strain ofSalmonella kedougou, resistant to nalidixic acid, gave a time‐course for salmonella survival in the 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>106/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. Pretreatment 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°C but was prevented by addition of the treatment culture, a decline in numbers coinciding withLactobacilluspopulations ofca109/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

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04567.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The incidence of ‘thermophilic’ campylobacters in foods and environmental samples has been studied over a two‐year period. Of 781 environmental samples, 529 (67%) were found to contain campylobacters, and campylobacters were isolated from 835 (39%) of 2116 food samples. Sewage was almost always contaminated with campylobacters (96·6% of samples) and of the food samples both poultry (55·5%) and offal (47·0%) were commonly contaminated. Determination of the heat‐stable serotypes of all strains isolated from these sources and of 921 strains isolated from human faeces showed that there was a wide distribution of serotypes in most types of sample. Serotype Pen 2 was the commonest type found in human faeces (18·9%) and it was also commonest in offal (21·3%), beef (40·0%), sewage (17·7%) and was the third commonest type in poultry. A comparison of culture media and conditions for optimal production of both cytotoxic and cytotonic enterotoxins showed that Brucella Broth incubated under microaerobic conditions for 24 h at 42°C was suitable for both toxins. Detection of cytotoxic activity was most sensitive using HeLa cells. The sensitivities of two ELISA systems and a Chinese Hamster Ovary tissue culture assay for detection of cytotonic enterotoxin were comparable. Not all strains isolated from cases of enteritis in human beings produced toxin; 23·1% produced cytotonic enterotoxin and 17·5% produced cytotoxin. There was no correlation between serotype and toxin production. The wide distribution of campylobacters, indistinguishable from those isolated from cases of enteritis in human beings, leads us to conclude that simplistic statements suggesting that one particular type of food is primarily responsible for cases of human disease s

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04568.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

D‐values of a heterofermentative beer spoilage lactobacillus were measured at 55°C, 60°C and 65°C in beers containing<0·05% to 4·4% v/v ethanol.Z‐values for the different beers varied between 9·17 and 12·13°C. At each temperature an increase in ethanol reduced the measuredD‐value. The maximum, 5·01 min was observed in alcohol‐free beer (<0·05%) at 55°C and the minimum, 0·31 min, at 60°C and 65°C in beer containing 4·4% ethanol.D‐values could be increased by prior growth in the presence of ethanol. They could be reduced by adding ethanol to alcohol‐free beer or by increasing its hop extract content. The implications for the pasteurization of low

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04569.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Three hundred expectorated sputa from patients suffering from chest disorders were examined microscopically and cultured on various media. Among other microorganisms isolated there were four strains ofRhodococcus aurantiacus(Gordona aurantiaca), one each ofRh. erythropolis, Rh. pellegrino, Rh. rubropertinctusandRh. rhodnii.Suspensions in 5% hog gastric mucin were virulent for immuno‐suppressed white mice and the pathology of their lungs was compatible with those produced in experimental nocardial and rhodococcus infections. Thein‐vitroantibiogram was similar to that ofNocardia asteroides.Two of the patients from whomRh. aurantiacusandRh. pellegrinowere isolated responded bacteriologically and clinically to treatment with co‐trimoxazole. The frequency with which these rhodococci were isolated and the clinical conditions of the patients strongly indicated a pathogenic role for someRhodococcusspecies. It is suggested that rhodococci should be sought in chronic pulmonary infections, particularly in those who are immuno‐compromised or debilitated, and their aetiologic role det

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04570.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Strains ofStaphylococcus warneri, Staph. epidermidisandAerococcus viridansisolated from porcine skin were shown to produce substances that inhibited the growth ofStaph. hyicus.Studies of interactions between the inhibitor‐producing bacteria andStaph. hyicuson cellulose acetate membranes demonstrated a significant reduction (P<0.001) of theStaph. hyicuspopulation at various stages of its growth cycle, depending on the inhibitor used. Inhibitor production profiles in batch culture showed a change in production with culture growth. Trypsin and an extracellular substance fromStaph. hyicushad similar effects in reducing inhibitor production.Staphylococcus hyicuswas shown to produce varying amounts of a proteolytic enzyme during growth in batch culture. Suchin vitromodels of bacterial interaction enable potential mechanisms of disease control using inhibitor‐producing organisms to be investigated and provide a basis for studiesin v

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04571.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In a study involving 2760 tests, the BACTEC semi‐automatic radiometric method which measures bacterial metabolic activity and produces a BACTEC growth index, was compared with two conventional methods commonly used for determining growth, absorbance and viable counts. In 92% of radiometry tests the suppression of growth was inversely related to the antibiotic concentration. This compared with 83% for absorbance and 63% for viable counts. The radiometric method was found to be more rapid, easier to use and more reproducible in determining the effect of antibiotics on the activity of bacteria than viable counting or absorbance method

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04572.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Growth rate of salmonellas in Rappaport‐Vassiliadis broth (RV) decreased with higher temperature when incubated at 40, 42 and 43°C. Home‐made RV and RV‐Merck were less inhibitory than RV‐Oxoid and RV‐lab m. At 43°C growth of all strains ofSalmonella dublinwere almost completely inhibited in all types of RV. In home‐made RV and RV‐Merck incubated at 42°C,Salm, dublinwas not inhibited any more than other serotypes tested. Variations in growth rate between different types of RV could be explained by differences in concentration of MgCl2. RV with higher MgCl2‐concentration were most inhibitory. It is proposed that RV should be incubated at 41.5 ± 0.5°C (42.0 ± 0.1°C in a waterbath) and that the amount of MgCl2. 6H2O should be approximately 28.6 g/1 of the ready‐to‐use medium, which corresponds to the formula i

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04573.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The response of luminous bacterial cultures to conditions encountered in the fish gut such as neutral pH, the presence of bile salts, gastric juice and lysozyme was examined. The organisms preferred neutral pH. Bile salts did not inhibit their growth. Neither lysozyme nor gastric juice affected their growth and viability to any extent. In the light of these findings, the adaptability of luminous bacteria to conditions existing in the gut of fish was discussed.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04574.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In continuous‐culture studies chemostat effluents are usually collected into a receiving flask in an ice bath to obtain enough cells for an experiment. It is assumed that the properties of these are not significantly different from those of the culture in the chemostat vessel. This assumption has been tested for the dental pathogenStreptococcus mutansIngbritt. Collected supernatant fluid and cells were compared with supernatant fluid and cells taken directly from the culture vessel, for four major groups of culture properties: viability and biomcss, concentrations of metabolites and nutrients, activities of selected enzymes, and glycolytic rates. The assumption held true except for glycolytic rate during endogenous metabolism. It is suggested that comparison of collected and culture vessel cells is an important control which should be done in all continuous culture studies of microbial physiology and biochemistry, but that the properties ofStrep, mutanscells collected on ice up to 16 h do reflect those of cells actively growing in the chemosta

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04575.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The growth response ofStaphylococcus xylosusstrain CM21/3 to changes in temperature and water activity (glycerol concentration) was similar to that observed when water activity was adjusted by added NaCl. At each water activity level the effect of temperature on bacterial growth rate was described well by the square root model.TMIN(the notional minimum temperature for growth) was found to be constant and was similar to the value obtained for the same organism grown in media containing NaCl. Growth rate was proportional to glycerol concentration/water activity allowing the combined effect of this factor and temperature to be modelled by substitution of the constantbin the basic square root model by a term for water activity. The observed minimum water activity for growth at the optimum temperature was close to that predicted by the model.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb04576.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY