Marie-Louise Danielsson-Tham

Campylobacter incidence on a chicken farm and the spread of Campylobacter during the slaughter process

To get a better understanding of the epidemiology of Campylobacter, a chicken farm was studied for 16 weeks with samplings in each flock weekly from input until the flock became colonized with Campylobacter or slaughtered. Samples were taken from fresh droppings and from drinkers during the rearing period, as well as from the environment in empty houses. The spread of Campylobacter during the slaughter process was also surveyed. No Campylobacter was found in samples from newly-hatched or one-week-old chickens or their drinkers. All flocks but one were colonized at two to five weeks of age. All Campylobacter isolates belonged to the same sero- and biotype; C. jejuni Penner 2. The spread of Campylobacter in the flock was rapid and usually all samples were positive once colonization had been proven. C. jejuni was isolated from flies in ante-rooms as well as from air in chicken units in houses with positive chicken flocks. Samples were taken at slaughter when some of the Campylobacter positive flocks from the farm were slaughtered. Campylobacter were isolated from all sampled equipment along the processing line, from the chicken transport crates to the chillers, as well as from the air.

A 1-year epidemiological study of campylobacters in 18 Swedish chicken farms

Broiler chickens are often intestinal carriers of Campylobacter. During processing, Campylobacter may be spread over the carcass. Thus, undercooked chicken meat, or other foods contaminated by raw ...

Campylobacter jejuni in Black-Headed Gulls (Larus ridibundus): Prevalence, Genotypes, and Influence on C. jejuni Epidemiology

ABSTRACT Campylobacteriosis is a zoonotic disease in which birds have been suggested to play an important role as a reservoir. We investigated the prevalence of Campylobacter jejuni subsp. jejuni in black-headed gulls (Larus ridibundus) in southern Sweden with the aim of examining the nature of C. jejuni infection in this bird species. Birds were sampled in four sampling series each year during 1999 (n = 419) and 2000 (n = 365). Longitudinally sampled C. jejuni isolates from individual gulls were subjected to macrorestriction profiling (MRP) by pulsed-field gel electrophoresis to investigate the genotypical stability during the natural course of infection. Furthermore, a subset (n = 76) of black-headed gull isolates was compared to isolates from broiler chickens (n = 38) and humans (n = 56) originating from the same geographic area. We found a pronounced seasonal variation in C. jejuni carriage, with the highest rates found in late autumn. MRP similarities were higher between isolates of human and broiler chicken origin, than between those of wild bird origin and either of the other two hosts. However, identical MRPs were found in two gull isolates and one human isolate after digestion with two restriction enzymes, strongly indicating that they may have been colonized by the same clone of C. jejuni. The MRPs most prevalent in gull isolates did not occur among isolates from humans and broiler chickens, suggesting the existence of a subpopulation of C. jejuni adapted to species-specific colonization or environmental survival.

Bovine subclinical mastitis caused by different types of coagulase-negative staphylococci

Subclinical mastitis caused by intramammary infections (IMI) with coagulase-negative staphylococci (CNS) is common in dairy cows and may cause herd problems. Control of CNS mastitis is complicated by the fact that CNS contain a large number of different species. The aim of the study was to investigate the epidemiology of different CNS species in dairy herds with problems caused by subclinical CNS mastitis. In 11 herds, udder quarter samples were taken twice 1 mo apart, and CNS isolates were identified to the species level by biochemical methods. The ability of different CNS species to induce a persistent infection, and their associations with milk production, cow milk somatic cell count, lactation number, and month of lactation in cows with subclinical mastitis were studied. Persistent IMI were common in quarters infected with Staphylococcus chromogenes, Staphylococcus epidermidis, and Staphylococcus simulans. The results did not indicate differences between these CNS species in their association with daily milk production, cow milk somatic cell count, and month of lactation in cows with subclinical mastitis. In cows with subclinical mastitis, S. epidermidis IMI were mainly found in multiparous cows, whereas S. chromogenes IMI were mainly found in primiparous cows.

Prevalence and fingerprinting of Listeria monocytogenes strains isolated from raw whole milk in farm bulk tanks and in dairy plant receiving tanks

ABSTRACT The incidence of Listeria species in raw whole milk from farm bulk tanks and from raw milk in storage at a Swedish dairy plant was studied. Listeria monocytogenes was found in 1.0% and Listeria innocua was found in 2.3% of the 294 farm bulk tank (farm tank) milk specimens. One farm tank specimen contained 60 CFU of L. monocytogenes ml−1. L. monocytogenes was detected in 19.6% and L. innocua was detected in 8.5% of the milk specimens from the silo receiving tanks at the dairy (dairy silos). More dairy silo specimens were positive for both Listeria species during winter than during summer. Restriction enzyme analysis and pulsed-field gel electrophoresis were applied to 65 isolates of L. monocytogenes, resulting in 16 different clonal types. Two clonal types were shared by the farm tank milk and the dairy silo milk. All except one clonal type belonged to serovar 1/2a. In the dairy silo milk five clonal types were found more frequently and for a longer period than the others. No Listeria species were found in any other samples from the plant.

Occurrence of Listeria monocytogenes in soft and semi-soft cheeses in retail outlets in Sweden.

Samples of 333 retail cheeses produced in or imported into Sweden were examined for the presence of Listeria monocytogenes. Listeria monocytogenes was isolated from 6% of the cheese samples. Cheeses made from raw milk were more frequently contaminated with L. monocytogenes (42%) than cheeses made from heat-treated milk (2%). The incidence of the organism in whole cheeses and pre-cut wedges was similar (6%). L. monocytogenes was only found in imported cheeses (18 from France, and one from Germany and Italy, respectively). The numbers of L. monocytogenes varied from < 1 x 10(2) to 1 x 10(5) cfu/g. All L. monocytogenes strains belonged to serogroup 1/2, except isolates from two samples that belonged to serogroup 4.

Febrile gastroenteritis after eating on-farm manufactured fresh cheese : an outbreak of listeriosis?

An outbreak of febrile gastroenteritis affected consumers of on-farm manufactured dairy products from a summer farm in Sweden. Symptoms included diarrhoea, fever, stomach cramps and vomiting in 88, 60, 54 and 21% of cases identified. The median incubation period was 31 h. A cohort study with 33 consumers showed an attack rate of 52% and an association between the total amount of product eaten and illness (P=0.07). Twenty-seven of 32 (84%) stool samples cultured for Listeria monocytogenes tested positive, although there was no association between clinical disease and the isolation of L. monocytogenes. In addition, gene sequences for VTEC and ETEC were detected in 6 and 1 subjects, respectively. Bacteriological analysis of cheese samples revealed heavy contamination with L. monocytogenes and coagulase positive staphylococci in all of them and gene markers for VTEC in one of them. Molecular profiles for L. monocytogenes isolated from dairy products, stool samples and an abscess from 1 patient who developed septic arthritis were identical. Results of both microbiological and epidemiological analyses point to L. monocytogenes as the most likely cause of this outbreak. The finding of markers for VTEC in some humans and cheese samples means that a mixed aetiology at least in some cases cannot be conclusively ruled out.

A laboratory study of survival of selected microorganisms after heat treatment of biowaste used in biogas plants

The aim of the study was to assess the effect of pasteurisation, as set by the European regulation EC 1774/2002, on selected pathogens and indicator organisms. Unpasteurised substrate (biowaste), including animal by-products from a full-scale biogas plant was heat treated under laboratory conditions at 70 degrees C and 55 degrees C for 30 min and 60 min. Heat treatment at 55 degrees C for 60 min was not sufficient to achieve a hygienically acceptable product. Heat treatment at 70 degrees C for 30 min and 60 min was effective in reducing pathogenic bacteria, Ascaris suum eggs, Swine vesicular disease virus and indicator organisms. However, this level of pasteurisation will still not reduce the quantity of Clostridia spores, or completely inactivate heat-resistant viruses such as Porcine parvovirus or Salmonella phage 28B. The results still give cause for some concern regarding the use of digested residue from biogasplants in agriculture.

Lessons from an outbreak of listeriosis related to vacuum-packed gravad and cold-smoked fish.

The first lesson learned from this outbreak was that vacuum-packed rainbow trout is not only an excellent medium for the growth of Listeria monocytogenes, but may also cause human listeriosis. Another lesson is that one single fish processing plant may spread multiple clonal types of L. monocytogenes by selling contaminated products to consumers. Thus, when investigating fish-borne outbreaks of listeriosis one should identify and type several isolates of L. monocytogenes from each food and environmental sample, since multiple clonal types might be present. The outbreak described in this paper involved at least eight human cases, three clonal types of L. monocytogenes, and lasted for 11 months. During the outbreak investigation, L. monocytogenes was also isolated from another brand of rainbow trout found in the refrigerator of one of the patients. These latter isolates belonged to a clonal type not associated with the outbreak. However, this clonal type is of considerable interest since it has been associated with foodborne outbreaks of listeriosis in several countries, and is also the second most common clonal type among human clinical isolates of L. monocytogenes in Sweden. Besides the described outbreak, it is likely that vacuum-packed, cold-smoked and gravad rainbow trout have been involved in additional cases of foodborne listeriosis in Sweden.

A combined culture and PCR method for detection of pathogenic Yersinia enterocolitica in food

A combined method based on traditional culturing, buoyant density centrifugation, (BDC), and polymerase chain reaction (PCR) techniques for detection and identification of pathogenic Y. enterocolitica in food was developed and evaluated. An internal control, which was added in each PCR-tube and co-amplified by the same primer pair as the pathogen, monitored false-negative PCR results. The sample preparation step, BDC, was used to remove PCR inhibiting food substances and to concentrate the Y. enterocolitica cells. Single PCR with a chromosomal gene (ail) as target was chosen for screening the samples. The method was tested on naturally and artificially contaminated food samples. In three different food samples, processed meat (brawn), unprocessed beef and minced pork, inoculated with 10 cfu pathogenic Y. enterocolitica per gram, Y. enterocolitica was detected and cultural bacteria indicated within 18 h of enrichment.