A family outbreak of Escherichia coli O157 haemorrhagic colitis caused by pork meat salami.

A family outbreak of Escherichia coli O157 infection was microbiologically associated with consumption of dry-fermented salami made with pork meat only and produced in a local plant. E. coli O157 strains isolated from a wife and husband, both hospitalized with bloody diarrhoea, and from the salami carried vt1, vt2 and eae genes and shared the same PFGE pattern. The food vehicle implicated in this outbreak is unusual because of both the animal species from which it originates and the fermentation and drying steps of the manufacturing process. This could be the first report of an outbreak associated with a product containing pork meat only. Even though sources of contamination other than pork meat could not be excluded, pork products should not be neglected in E. coli O157 outbreak investigations.

Verocytotoxin-producing Escherichia coli O157 in minced beef and dairy products in Italy.

A total of 3879 samples of foodstuffs were examined for the presence of Verocytotoxin-producing Escherichia coli O157 (VTEC O157). The survey was conducted by 9 of the 10 Italian Veterinary Public Health Laboratories. Samples were collected between May 2000 and September 2001 in 14 regions and comprised 931 minced beef specimens and 2948 dairy products (DP) with less than 60 days of ripening. The DP included 657 pasteurised and 811 unpasteurised bovine DP, 477 pasteurised and 502 unpasteurised ovine DP, and 501 water-buffalo's milk mozzarella cheese. Samples were collected at retail level, from plants processing minced beef and dairy plants and from farms directly manufacturing cheeses. All the samples were tested using a sensitive procedure based on ISO/DIS 16654:1999 (later ISO 16654:2001), which includes an immunomagnetic separation step. A preliminary inter-laboratory trial was organised with artificially contaminated samples to assess the ability of all the participating laboratories to isolate E. coli O157 by the established procedure. VTEC O157 was isolated from four (0.43%) of the minced beef samples, collected in four different regions and during different months, but was not detected in any of the dairy products. E. coli O157 VT-eae+ was isolated from one raw cow's milk cheese. This survey provided national data on the presence of VTEC O157 in foodstuffs, demonstrating a low prevalence of the organism. The survey also encouraged updating of knowledge and procedures on VTEC O157 in laboratories with official responsibility for microbiological testing of foods of animal origin.

A field survey of Escherichia coli O157 ecology on a cattle farm in Italy.

A field survey was performed in a heifer raising operation in Northern Italy to study the introduction, maintenance and dissemination of Escherichia coli O157 in the herd and to identify possible control measures at the farm level. Rectal swabs from two different groups of animals (surveys 1 and 2) were tested for E. coli O157 by an immunomagnetic separation technique. In survey 1, a group of female calves (341 animals initially) introduced from 30 dairy herds during April 1996 to March 1997 were tested for E. coli O157 on arrival from the original herd when housed in individual hutches, 2-3 days after completion of weaning (which was associated with grouping) and 2 months after weaning. No statistically significant difference between excretion rates (3.8%, 4.2%, 4.4%, respectively) was found. Calves from which E. coli O157 was isolated on arrival came from 6 of the 30 dairy herds. Strains isolated during survey 1 belonged to seven different pulsed field gel electrophoresis (PFGE) profiles. In survey 2, a group of young animals aged, at the beginning of the study, between 2 1/2 and 7 1/2 months (median = 124 days) was tested monthly for E. coli O157 for 11-15 months from May 1996 to July 1997. The group included 92 animals for 11 months and then gradually decreased to 59 animals. Overall, E. coli O157, belonging to six different PFGE profiles, were isolated from 138 (10.7%) of 1293 rectal swabs. Monthly excretion rates ranged from 2.7% to 23.7%, with summer peaks in both years. Fifty-nine (64.1%) of the 92 heifers were positive at least once: of these 59 animals, 22 (37.3%) were positive on only one occasion, 23 (39%) were positive on two occasions and 14 (23.7%) were positive on three or more occasions. From two heifers positive on 9 out of the 15 sampling visits, strains with the same PFGE profile were isolated, respectively, on seven and eight occasions while strains with only one band difference were isolated on the remaining occasions. E. coli O157 was also isolated from 6 of 16 samples of bedding, two of two samples of slurry and one of five samples from water troughs collected during survey 2.

Atypical strains of verocytotoxin-producing Escherichia coli O157 in beef cattle at slaughter in Veneto region, Italy.

Cattle arriving for slaughter at abattoirs in the Veneto region of N. Italy were examined for intestinal carriage of Escherichia coli O157. Rectal swabs were cultured in modified buffered peptone water and E. coli O157 was concentrated by an immunomagnetic separation technique; the magnetic beads were cultured onto cefixime tellurite sorbitol MacConkey agar. Sorbitol non-fermenting E. coli O157 was isolated from 15 (3.6%) of 419 feedlot cattle but not from 437 veal calves or 65 culled cows. All strains of E. coli O157 hybridized with DNA probes specific for the VT1 or VT2 genes, but two strains did not produce toxin detectable by Vero cell assay. Six different plasmid profiles were observed with all strains harbouring the large 93 kb plasmid characteristic of VTEC. Six strains produced urease but otherwise strains were biochemically typical of E. coli O157. One strain was resistant to streptomycin, tetracycline and sulphonamides but the remainder were sensitive to all antimicrobials tested. This is the first description of the isolation of verocytotoxin-producing E. coli O157 from cattle in Italy. As the contamination of bovine carcasses with E. coli O157 during slaughter and processing has been demonstrated, the risk of transmission of this organism from beef cattle to the human population in the Veneto region, through foods of bovine origin or by other routes, should not be overlooked.