Biomedical subjects

S J Hicks

Publications and source records attributed to S J Hicks.

24 records · Page 2Linked to original sources

PubMed1991

The survival of Listeria monocytogenes in cottage cheese.

Because of the difficulty of ensuring that cottage cheese is produced in conditions that prevent contamination with Listeria monocytogenes, the ability of this bacterium to survive in cottage cheese from three sources was investigated (a) during shelf-life at chill temperature and (b) in conditions of temperature abuse. Three batches of creamed cottage cheese, from three sources, received within 24 h of production, were inoculated with L. monocytogenes strain F6861 and stored at 4, 8 or 12 degrees C for 14 d. The three batches differed in their initial pH, titratable acidity and content of lactic acid and of lactic acid bacteria. No increase in numbers of L. monocytogenes occurred in the cottage cheeses during storage in these conditions. The numbers of listeria decreased; the rate of decrease differed in products from the three sources and was least in the product with the highest pH and lowest content of lactic acid. Acid formation by lactic acid bacteria during storage of the products probably contributed to the inhibition of listeria.

Cheese↗

PubMed1987

Increased incidence of cervical intraepithelial neoplasia grade 3 and human papillomavirus infection at a family planning clinic.

A five-fold increase in the incidence of histologically-proven cervical intraepithelial neoplasia grade 3 (CIN3) was observed for patients attending the Christchurch family planning clinic in 1985 compared with the preceding three years. There were 51 new cases in 1985 and a yearly average of 9.3 between 1982 and 1984. There was an increase also in cervical smears showing evidence of human papillomavirus (HPV) infection. The time interval between the last normal smear and the diagnosis of CIN3 was short, averaging 2.3 years. CIN3 patients were young (average 28.9 years); they had a high average number of sexual partners (10.1). These findings support the theory of a sexually transmitted precursor to the development of CIN3. The 1985 surge in CIN3 may reflect an increased prevalence of this oncogenic agent. The aim of screening is to prevent invasive cervical carcinoma. Annual smears should therefore be considered for young sexually-active women in view of the short time interval between normal smears and the development of CIN3.

Adolescent↗

PubMed1987

Stimulatory effect of phosphate on colicin V synthesis/secretion by strains of Escherichia coli.

Larger inhibitory zones were produced by ColV+ strains on sensitive indicators if the strains were grown on nutrient agar and phosphate rather than nutrient agar. This was due to an effect of phosphate on colicin V synthesis/secretion and not to an effect on the response of the indicator. Phosphate produced an effect at 25 degrees C as well as at 37 degrees C (although zones were larger at 37 degrees C). It seems likely that phosphate stimulation of colicin V synthesis/secretion results from its effect in reducing divalent cation levels in NA because adding EDTA to NA also increased colicin V synthesis/secretion whereas the addition of magnesium or calcium salts had the opposite effect. It is possible that the extent of colicin V synthesis/secretion may depend on the strength of the LPS-LPS bonds in the outer membrane. Phosphate also stimulated synthesis/secretion of colicins E4, G and N but not of the other colicins or microcins tested. Studies with a wild Col+ E. coli isolate suggest that production of some colicins may not be detected on nutrient agar and that addition of phosphate may reveal the synthesis of new colicins.

Calcium↗

PubMed1986

Virulence plasmid-associated adhesion of Escherichia coli and its significance for chlorine resistance.

Introduction of the ColV, I-K94 virulence plasmid into strains of Escherichia coli led (for four out of five strains tested) to a marked increase in the ability of organisms to adhere to glass beads. For strain 1829, the plasmid led to increased attachment to other materials including sand, agar, agarose, chitin and cellulose. The increased adhesion to glass beads was due to the presence of the plasmid and not to its introduction into a variant with altered adhesive properties. The plasmid-encoded VmpA protein did not appear to be necessary for the ColV, I-K94-promoted adhesion but adhesion was absolutely dependent on the presence of derepressed levels of transfer components in the ColV+ strains and partially dependent on the presence of colicin components. The extent of the plasmid-promoted adhesion was greatest for organisms grown at 30 degrees, 37 degrees or 42 decrees C and adhesion was almost abolished by growth at 21 degrees or 25 degrees C; this finding is in accord with transfer and colicin components being involved in adhesion. Of several other plasmids tested for their effects on adhesion, those with derepressed transfer properties showed a marked effect as did the RI resistance plasmid. Because of the ease of handling glass bead-attached organisms, such preparations were used as a model for studying the relevance of attachment to the resistance of E. coli to chlorination in the water purification process. Organisms of 1829 ColV, I-K94, attached to glass beads, were more resistant to damage and killing by chlorine than were unattached organisms. Three findings suggest that such chlorine resistance may be significant for survival during water chlorination. Firstly, ColV, I-K94+ bacteria became attached if incubated in sewage effluent with glass beads at 20 degrees C. Secondly, ColV+ organisms already attached to glass beads maintained their attachment during 24 h incubation in effluent at 20 degrees C and thirdly such effluent incubated organisms remained chlorine resistant provided that they retained their attachment.

Bacterial Adhesion↗

PubMed1969

Preferential synthesis of ferritin and albumin by different populations of liver polysomes.

Free polysomes and a mixture of free and membrane-attached polysomes were isolated separately from rat liver, and each was added to a cell-free, protein-synthesizing system. The free polysomes showed a greater capacity than the mixed polysome population for incorporation of (14)C-leucine into ferritin, whereas the reverse was true for (14)C-leucine incorporation into albumin.

Amino Acids↗

PubMedDate not supplied

Resistance of attached Escherichia coli to acrylic acid and its significance for the survival of plasmid-bearing organisms in water.

As previously reported, free organisms of Escherichia coli are sensitive to damage and killing when exposed to acrylic acid in water. The effect of the agent was greatest in distilled water, but there was a marked effect in effluent and seawater also. The effect was temperature-dependent, with organisms exposed at 4 degrees C being much less affected than those exposed at 20 degrees C. The above sensitivity was for free organisms, but those attached to glass beads were resistant to acrylate. This resistance applied equally to attached plasmid-free and attached plasmid-bearing organisms, but is likely to be more significant for plasmid-bearing strains because some plasmids studied here stimulated bacterial attachment. The likely significance of the acrylate resistance of attached organisms for enterobacterial survival in the aquatic environment, e.g. in the vicinity of shellfish beds, is discussed.

Acrylates↗