We investigated the distribution of serotypes and patterns of drug resistance of 206 strains of salmonella isolated in southern Italy in the years 1998–2000 from raw food of animal origin, faeces of food animals and animal feed. To improve knowledge of mobile genetic elements carrying the resistance genes, some molecular features were also investigated within isolates resistant to three or more antibiotics. A high proportion of isolates, 52.2% and 37.7%, respectively, belonging to both Typhimurium and other serotypes of animal origin, proved to be multidrug resistant. The DT104 complex specific multidrug pattern of resistance was quite infrequent among isolates other than Typhimurium, but resistances to nalidixic acid and kanamycin were more frequent within these last ones (36.9% vs. 11.4% and 56.5% vs. 2.2%, respectively). Class I integrons were detected in isolates of Typhimurium and seven different serotypes. The relevance of food animal environment as a drug resistance reservoir and animal food as a potential resistance gene vehicle between the farm and human ecological niches is confirmed by our findings.

Escherichia coli O157[ratio ]H7 infection of cows and calves in a naturally-infected beef cattle herd in Alberta, Canada, was investigated over 2 years, encompassing two calf production cycles. In both years of the study, E. coli O157[ratio ]H7 was isolated from the faeces of cows shortly after but not before parturition in late winter: 6/38 (16%) in 1996 and 13/50 (26%) in 1997. At <1 week post-partum, 13/52 (25%) calves born in 1997 were shedding the organism. Faecal shedding of E. coli O157[ratio ]H7 by cows and calves continued over the 7 weeks that they were in the calving pens, with the organism being isolated from the faeces of 2–18% of cows and 23–26% of calves during this period. Five weeks after they were moved onto a native grass pasture, all the calves and all but one cow in 1997 had ceased shedding the organism. When the calves were weaned in the fall, E. coli O157[ratio ]H7 was isolated from the faeces of 0–1.5% of the calves 1 week prior to weaning and from 6–14% of the calves within 2 weeks after weaning. Parturition, calving pens and weaning appear to be important factors in maintaining E. coli O157[ratio ]H7 infections in this beef cattle herd. Isolates from cows and calves during the immediate post-partum period were mostly of the same pulsed-field gel electrophoresis (PFGE) type of E. coli O157[ratio ]H7. Similarly, at weaning a common PFGE type of E. coli O157[ratio ]H7, which differed slightly from the post-partum PFGE type, was isolated from the calves. These typing data suggest a common source of infection for the animals as well as demonstrate clonal turnover of resident populations of this pathogen.

The occurrence of Shiga toxin-producing Escherichia coli (STEC) was studied on four cattle farms. STEC were detected in 29–82% of the cattle. STEC with additional EHEC markers were detected on all farms. The occurrence of the complete virulence marker pattern (stx1 and/or stx2, eae, EHEChlyA, katP, espP) was correlated with the presence of known STEC serotypes. STEC O26[ratio ]H11 and O165[ratio ]H25 with the complete pattern of virulence markers were the most prevalent. STEC O157 (H7/H-) STEC O103[ratio ]H2 and STEC O145[ratio ]H- were found sporadically. Five clonal subgroups of the STEC O26[ratio ]H11 isolates were identified by pulsed-field gel electrophoresis. STEC O26[ratio ]H11 were present in three groups of cattle. This serotype was detected in a single group over the entire fattening period. Most STEC O26[ratio ]H11 with the complete pattern of potential virulence markers were found in clinically healthy cattle. These animals may represent a risk factor for farmers and consumers.

In order to determine the prevalence of campylobacter positive broiler flocks in Finland, every flock from all three major slaughterhouses was studied during the period from 1 May to 30 September 1999. Caecal samples were taken in the slaughterhouses from five birds per flock. A total of 1132 broiler flocks were tested and 33 (2.9%) of those were campylobacter positive. Thirty-one isolates were C. jejuni and two isolates were C. coli. Isolates were serotyped for heat-stable antigens (Penner) and genotyped with pulsed-field gel electrophoresis (PFGE). The most common serotypes were serotypes 6, 7, 12 and 4-complex. Together with SmaI and KpnI patterns there were 18 different PFGE genotypes. Simultaneous monitoring of chicken flocks and typing of the isolates produced data which can be used to study the epidemiology of campylobacters in chicken as well as their role in human infections.

One hundred and seven bovine isolates of penicillin and tetracycline resistant Staphylococcus aureus, recovered from 25 different dairy herds in various parts of Norway, were characterized using antimicrobial susceptibility testing, multilocus enzyme electrophoresis, ribotyping, plasmid analysis and serotyping of capsular polysaccharide. Forty-one isolates from one particular herd, 37 isolates from 5 herds that used a common pasture and milking parlour in summer and 21 isolates from 12 herds in 8 different counties belonged to the same strain. The remaining 8 isolates, which originated from herds in 5 different counties, were assigned to 6 different strains. Seven out of these 8 isolates had the same plasmid restriction profile. In conclusion, penicillin and tetracycline resistant S. aureus occurring in dairy herds in Norway mainly seems to represent one particular strain that has achieved widespread distribution or belong to one of several different strains carrying identical plasmids.

Ten transmission trials with Actinobacillus pleuropneumoniae were carried out. The observed transmission was highly variable, which was surprising since the design of the trials was very similar. We investigated whether the variable transmission could be explained by variation in infectivity of A. pleuropneumoniae infected pigs. We looked for measurable characteristics, which could be indicative for infectious pigs or for the level of infectivity. The characteristic that appeared to be most indicative for a pig being infectious was an A. pleuropneumoniae positive tonsil at necropsy. The characteristic that was correlated to the level of infectivity was the number of A. pleuropneumoniae colonies isolated from the nasal swab, i.e. the probability for an infectious pig to infect a susceptible pig was tenfold higher on days where at least ten colonies were isolated. In this study it is shown that it is possible to measure the bacterial transmission of A. pleuropneumoniae under controlled circumstances if variation in infectivity is taken into account.

Demographic and epidemiological field data were used in a deterministic model to describe dog rabies transmission in Machakos District, Kenya and to predict the impact of potential vaccination strategies for its control. The basic reproduction number (R0) was estimated to be 2.44 (1.52–3.36, 95% confidence limits). There were three key model predictions. The first was that a threshold dog density (KT) of 4.5 dogs km−2 (3.8–5.2 dogs km−2, 95% confidence limits) was required to maintain transmission. The second was that the estimated annual vaccination rate of 24% failed to decrease incidence and actually increased the stability of transmission and may be counter-productive. Thirdly, to control rabies, it was predicted that 59% (34%–70%, 95% confidence limits) of dogs should be vaccinated at any one time. This requires approximately 70% coverage for annual but only 60% coverage for semi-annual vaccination campaigns. Community-level vaccination trials are needed to test these predictions.

The street-vended food industry provides employment and cheap ready-to-eat meals to a large proportion of the population in developing countries like Mexico, yet little is known about its role in the transmission of food borne diseases (FBD). Because of its wide consumption, street-vended chili sauces in Mexico are potential vehicles of FBD. An observational study was performed in Mexico City collecting 43 street-vended chili sauces. These sauces were prepared under poor hygienic conditions of handling and selling. Consumers add 4–8 ml of chili sauce per taco, ingest 2–5 tacos per meal and on average, 50 consumers frequent a stall per day. Seventeen (40%) samples were faecally contaminated and 2(5%) sauces harboured sufficient enterotoxigenic Escherichia coli to cause disease. We estimate that the consumption of only one of these chili sauces could result in ETEC disease in at least 21000 consumers per year, making them important potential vehicles of FBD.

To investigate the potential of poultry products as the source of human infections associated with quinolone-resistant campylobacters, 140 human and 75 poultry isolates of nalidixic acid-resistant campylobacters were collected between 1996 and 1998, and analysed by two molecular typing methods. By the analysis of restriction fragment length polymorphism of the flagellin gene, 33 distinct patterns were obtained, with 18 of which shared by both human (89%) and poultry (93%) isolates. By the pulsed-field gel electrophoresis of SmaI-restricted macrofragments, 105 different profiles were obtained, and 11 were found in both human (40%) and poultry (23%) isolates. When the two typing methods were combined, 112 unique genotypes were obtained, 11 of which were shared by both populations, including 53 (38%) human isolates and 14 (19%) poultry isolates. Although domestic poultry products are still important sources of the quinolone-resistant campylobacter infections in humans, there are other factors that might contribute to these increasing infections simultaneously. A more stringent policy in the use of antimicrobial agents in food animals can no longer be ignored.