Loss of vtx genes after the first subcultivation step of verocytotoxigenic Escherichia coli O157 and Non-O157 during isolation from naturally contaminated fecal samples.

Verocytotoxins VT1 and VT2,produced by Verocytotoxigenic Escherichia coli (VTEC), are encoded on temperate bacteriophages. Several studies reported the loss of the vtx genes after multiple subcultivation steps or long preservation. The objective of this study was to determine if the loss of the verocytotoxin genes can already occur during the first subcultivation step. Consequently, the stability of the vtx genes were tested in 40 isolates originating from 40 vtx-positive fecal samples after the first subcultivation step following the isolation procedure. The loss occurred in 12 out of 40 strains tested and was rather rare among the O157 strains compared to the non-O157 strains. This is the first study demonstrating that the loss of the verocytotoxin genes can already occur after the first subcultivation step. This may lead to an underestimation of VTEC positive samples.

Effect of administration of organic acids in drinking water on faecal shedding of E. coli, performance parameters and health in nursery pigs.

This study evaluated the effect of altering the pH of drinking water on the excretion of Escherichia coli (haemolytic and total count) by nursery piglets under field conditions as well as their performance parameters and health. The pH of the normal drinking water (pH 8) was lowered by using a mixture of organic acids (lactic, formic, propionic and acetic acid) to obtain a final pH of 6, 5 or 4. Reducing the pH to 4 resulted in the excretion of less faecal E. coli compared to pigs given water of pH 8 (P<0.05), but the fall in pH also significantly decreased water intake. The highest daily weight gain and lowest mortality rate were observed in the group receiving drinking water of pH 5 (P>0.05). No significant differences in the clinical parameters measured were seen between groups. The results of this study suggest that lowering the pH of the drinking water in newly weaned pigs reduces the E. coli load.

Processing practices contributing to Campylobacter contamination in Belgian chicken meat preparations.

The aim of this study was to obtain insight into processing practices in the poultry sector contributing to the variability in Campylobacter contamination in Belgian chicken meat preparations. This was achieved by company profiling of eleven food business operators, in order to evaluate variation of processing management, in addition to statistical modelling of microbiological testing results for Campylobacter spp. contamination in 656 end product samples. Almost half (48%) of chicken meat preparation samples were positive for Campylobacter spp. Results revealed a statistically significant variation in Campylobacter contamination between 11 chicken meat producers across Belgium at both quantitative and qualitative detection levels. All producers provided Campylobacter-positive samples, but prevalence ranged from 9% up to 85% at single producer level. The presence or addition of skin during production of chicken meat preparations resulted in almost 2.2-fold increase in the probability of a sample being positive for Campylobacter, while chicken meat preparations made from frozen meat, or partly containing pre-frozen meat, had a significant (Odds Ratio=0.41; CI 95% 0.18:0.98) lower probability of being positive for Campylobacter. However, the quantitative results indicated that the positive freezing effect on Campylobacter count was compromised by the presence and/or adding of skin.