Assessment of the excess risk of Salmonella dublin infection associated with the use of certified raw milk

The risk of serious illness attributable to infection with Salmonella dublin associated with the consumption of certified raw milk in California was evaluated. Data were derived from case reports of S. dublin isolations from persons in the State of California during the period 1980-83 and from production figures for raw milk from the major supplier. It is estimated that more than one-third of reported S. dublin infections in California in the first 4 years of this decade were attributable to raw milk consumption. Among raw milk consumers, it is estimated that more than 95 percent of reported S. dublin infections were acquired from raw milk; this proportion corresponds to a rate of reported S. dublin infections acquired from raw milk in the range of 8 to 35 cases per 100,000 users per year. It appears that immunocompromised persons are at exceptionally high risk of becoming seriously ill or dying from S. dublin exposure, and therefore raw milk is a particular health hazard for such persons.     

The diagnosis of salmonella abortion in cattle with particular reference to Salmonella dublin. A review.

The diagnosis of abortion in cattle caused by Salmonella dublin depends upon the isolation of the organism from either the products of conception, uterine discharges, vaginal mucus or milk together with serological evidence of active infection. S. dublin may be isolated when an active or a latent carrier cow abourts but in these cases an active infection will not be demonstrable. The retrospective identification of a case of S. dublin abortion may prove difficult as excretion of the organism is usually transient and the serum agglutinating antibodies frequently fall to low titres soon after the abortion.     

A milk-borne outbreak due to Salmonella dublin.

Salmonella dublin is primarily adapted to bovines and is a relatively rare cause of human illness. An outbreak is described in which it was estimated that at least 700 persons were infected from milk which had not been subjected to heat treatment. Although the organism was isolated from retail samples of milk, investigations at the dairy farm were inconclusive and a number of questions are posed. Attention is drawn to the value of inter-disciplinary cooperation in the investigation of the outbreak.     

Salmonellosis in two dairy herds associated with a sewage farm and water reclamation plant.

Two dairy herds, situated on a sewage farm, were monitored for the presence of salmonellas following outbreaks of Salmonella dublin infection. In addition an S. dublin control scheme, which involved examination of adult animals and calf vaccination, was instigated. During the period 1975-84, 12 salmonella serotypes and 10 phage types of S. typhimurium were isolated from the cattle and their environment although their presence was seldom associated with disease. Two adult S. dublin excreters were detected but it was concluded that none of the tests employed to examine the adult animals was sensitive enough. The prevalence of disease in the calves was low and although vaccination may have been beneficial it did not eradicate S. dublin infection. Thus S. dublin persisted in adults and calves during the 8-year period but its presence was seldom associated with disease. The results are discussed with regards the disease risk to animals from the agricultural use of sewage sludge and the public health aspects.     

Salmonellosis in two dairy herds associated with a sewage farm and water reclamation plant

Two dairy herds, situated on a sewage farm, were monitored for the presence of salmonellas following outbreaks of Salmonella dublin infection. In addition an S. dublin control scheme, which involved examination of adult animals and calf vaccination, was instigated. During the period 1975-84, 12 salmonella serotypes and 10 phage types of S. typhimurium were isolated from the cattle and their environment although their presence was seldom associated with disease. Two adult S. dublin excreters were detected but it was concluded that none of the tests employed to examine the adult animals was sensitive enough. The prevalence of disease in the calves was low and although vaccination may have been beneficial it did not eradicate S. dublin infection. Thus S. dublin persisted in adults and calves during the 8-year period but its presence was seldom associated with disease. The results are discussed with regards the disease risk to animals from the agricultural use of sewage sludge and the public health aspects.     

Salmonellosis in wild mammals.

One thousand two hundred and sixty-nine freeliving, wild mammals, representative of 16 species from estates in Berkshire, Oxfordshire and Surrey, were examined for the presence of salmonellas. Salmonella typhimurium was isolated from 1 and S. dublin from 7 house mice (Mus musculus). There were no isolations from the other species examined. It was concluded that the house-mice infected with S. dublin acquired the organism from experimentally infected cattle. The wild mammal population does not at present appear to constitute a reservior for infection of domestic animals.     

A men with a Salmonella dublin-infected aneurysm of the abdominal aorta

A 71-year-old male was diagnosed with a Salmonella dublin infection. He presented with abdominal pain with no diarrhoea, and sepsis, and was found to have an infected aneurysm of the infrarenal abdominal aorta. He was treated surgically with resection of the aneurysm and implantation of an extra-anatomic axillobifemoral bypass, followed by long-term antibiotic treatment. Nine months after the primary treatment, the patient died as a result of rupture of the aortic stump. S. dublin-infected aneurysm of the abdominal aorta is a rare condition with high mortality. Human S. dublin infections are associated with the consumption of unpasteurised dairy products from infected animals.     

Salmonella dublin infection of calves: use of small doses to simulate natural infection on the farm.

Small numbers of Salmonella dublin were used to infect calves in an attempt to simulate natural infection on the farm. Twenty calves were exposed to S. dublin by one or more of the following methods: Sucking cows which were excreting S. dublin in their faeces (less than 10(2)-10(5) organisms/g). Housing on S. dublin contaminated bedding. Drinking S. dublin contaminated water (10(2)-10(4) organisms/ml). During this experiment some calves were given therapeutic does of oxytetracycline. After exposure the calves were examined for faecal excretion of S. dublin (in some instances mouth swabs and blood samples were also examined) and for clinical signs of illness. Most of the calves became infected with S. dublin but excretion was usually sporadic and the numbers of salmonellas excreted were small. No clinical signs of salmonellosis were observed by S. dublin was isolated from one calf at post-mortem. Another six calves, dosed orally with either 10(6) or 10(8) S. dublin, showed signs of mild illness and although three calves had diarrhoea excretion of salmonellas was intermittent. S. dublin was isolated from one of these calves at post-mortem.     

Synthetic recombinant vaccine expressing influenza haemagglutinin epitope in Salmonella flagellin leads to partial protection in mice.

The influenza virus haemagglutinin epitope 91-108, which is a conserved amino acid sequence in all type A H3 strains, was expressed in Salmonella flagellin, to evaluate its potential as a vaccine. For that purpose, a synthetic oligonucleotide comprising 54 bases coding for the corresponding sequence was inserted into the plasmid pLS408 and transformed into Escherichia coli JM101. Colonies containing the recombinant plasmid were used to transform Salmonella typhimurium LB5000 and were then transduced to a flagellin negative 'live vaccine' aroA mutant of Salmonella dublin. Rabbits immunized either with the live recombinant S. dublin or with the flagellin isolated from it, showed significant levels of IgG response against the synthetic peptide 91-108 as well as against the intact A/Texas/77 influenza virus. Mice immunized with the same preparations developed influenza-specific IgG antibodies in the blood and secreted IgA antibodies in their lungs. Furthermore, these mice showed about 50% protection against challenge infection with the virus. The most successful results were achieved by intranasal immunization with the isolated recombinant flagellin, when employed without the aid of adjuvant.     

Packed with Salmonella--investigation of an international outbreak of Salmonella Senftenberg infection linked to contamination of prepacked basil in 2007

Salmonella Senftenberg is uncommon in the United Kingdom. In January-June 2007, the Health Protection Agency reported on 55 primary human cases of Salmonella Senftenberg in England and Wales. In May 2007, fresh basil sold in the United Kingdom was found to be contaminated with Salmonella Senftenberg. We launched an investigation to elucidate the cause of this outbreak. Isolates were examined using plasmid profiling and pulsed-field gel electrophoresis, and the outbreak strain (SSFTXB.0014) was identified. We enquired via Enter-net whether other countries had isolated the outbreak strain, analyzed samples of fresh herbs from U.K. retailers, and interviewed patients on food history. Thirty-two patient-cases were referred to this outbreak in England and Wales. Onsets of illness occurred between 5 March and 6 June 2007. Fifty-six percent of patient-cases were females and 90% adults (>20 years old); three were admitted to hospital as a result of Salmonella infection. Scotland, Denmark, the Netherlands, and the United States reported on 19 cases of Salmonella Senftenberg infection presenting with the outbreak strain since January 2007. Eight samples of prepacked fresh basil imported from Israel tested positive with the same strain. A minority of patients could recall the consumption of basil before illness, and some reported consumption of products where basil was a likely ingredient. Environmental investigations in Israel did not identify the contamination source. Microbiological evidence suggested an association between contamination of fresh basil and the cases of Salmonella Senftenberg infection, leading to withdrawal of basil from all potentially affected batches from the U.K. market.     

The Abuela Project: safe cheese workshops to reduce the incidence of Salmonella typhimurium from consumption of raw-milk fresh cheese.

OBJECTIVES: A multiagency intervention was implemented in Yakima County, Wash, to reduce the incidence of Salmonella serotype Typhimurium infections resulting from eating queso fresco (fresh cheese) made from raw milk, a traditional food in the Hispanic diet. METHODS: A pasteurized-milk queso fresco recipe with taste and texture acceptable to the Hispanic community was developed. Trained Hispanic volunteers conducted safe cheese workshops, which were attended by more than 225 persons. RESULTS: Workshop participants' acceptance of the new recipe was excellent and positive behavior changes were maintained over 6 months. CONCLUSIONS: Educational interventions in Hispanic communities can reduce the incidence of Salmonella Typhimurium associated with eating queso fresco.     

Genotype analysis of faecal and blood isolates of Salmonella dublin from humans in England and Wales.

An analysis of genotype was made for representative strains of Salmonella dublin. The collection consisted primarily of strains isolated from humans in England and Wales, and were of both intestinal and extra-intestinal origin. Three genetic elements were characterized by DNA hybridization. They were the spvBC genes, extrachromosomal virulence determinants, the salmonella-specific insertion sequence IS200, and the 16S ribosomal RNA genes, a phylogenetic marker. Two clones of S. dublin (SdRI and SdRII) which shared an identical IS200 profile, were identified on the basis of restriction fragment length polymorphism at the 16S rRNA locus. With one exception, all strains harboured a 52 MDa plasmid which contained a conserved 3.7 kbp Hind III fragment homologous to the spvBC mouse-virulence genes of S. typhimurium. However, a single plasmid-free strain of SdRI, isolated from a patient with septicaemia exhibited no spc homology. In SdRI there was no observable genotype distinction between strains causing gastroenteritis or bacteraemia. In contrast, none of the strains of SdRII were from cases of bacteraemia, and all human isolates of this clone were from cases of gastroenteritis.     

The effect of storage in slurry on the virulence of Salmonella dublin.

The mouse was used as a model to determine whether storage of Salmonella dublin in slurry and in broth reduces the virulence of the organism. No reduction in virulence of S. dublin stored in slurry for 36 days or in maintenance broth for 70 days was observed. The disease hazard involved in pasture-spreading of slurry contaminated with salmonellas is related to factors other than virulence.     

The in vitro drug resistance of Salmonella dublin isolated from cattle.

The resistance of Salmonella dublin to eight antibacterial drugs was assessed under diagnostic laboratory conditions. Two techniques were used consecutively and the differences in the results are described. Strains of S. dublin isolated from either calves, adult cattle or abortion material showed no differences in resistance for either of the techniques, though differences between the two techniques were found.     

An outbreak of E. coli O157:H7 hemorrhagic colitis associated with unpasteurized gouda cheese

BACKGROUND: A cluster of E. coli O157:H7 hemorrhagic colitis was identified in metro Edmonton, Alberta through notifiable disease surveillance in late 2002. METHODS: Environmental health officers collected food histories and clinical information from cases in the cluster. The provincial public health laboratory conducted pulsed field gel electrophoresis (PFGE) analysis on E. coli O157:H7 isolates from cluster cases. Public health and food regulatory agencies conducted an investigation when a food source (unpasteurized gouda cheese) was implicated. RESULTS: PFGE analysis revealed an "outbreak" profile in 13 cases. Onset dates for the outbreak cases ranged between October 2002 and February 2003. Two cases, aged 22 months and 4 years, developed hemolytic uremic syndrome as a result of their infection. Consumption of unpasteurized gouda cheese produced at a local dairy farm was reported by 12 of 13 outbreak cases in the 2 to 8 days prior to illness. E. coli O157:H7 was isolated from 2 of 26 cheese samples manufactured by the implicated producer. The cheese isolates had indistinguishable PFGE profiles as compared with outbreak case isolates. Implicated cheese was found to be contaminated with E. coli O157:H7 104 days after production, despite having met regulated microbiological and aging requirements. CONCLUSION: To our knowledge, this is the first confirmed outbreak of E. coli O157:H7 infection in Canada associated with raw milk hard cheese. A review of federal legislation vis-à-vis raw milk hard cheese may be in order.     

Human milk mucin 1 and mucin 4 inhibit Salmonella enterica serovar Typhimurium invasion of human intestinal epithelial cells in vitro

Many human milk glycans inhibit pathogen binding to host receptors and their consumption by infants is associated with reduced risk of disease. Salmonella infection is more frequent among infants than among the general population, but the incidence is lower in breast-fed babies, suggesting that human milk could contain components that inhibit Salmonella. This study aimed to test whether human milk per se inhibits Salmonella invasion of human intestinal epithelial cells in vitro and, if so, to identify the milk components responsible for inhibition. Salmonella enterica serovar Typhimurium SL1344 (SL1344) invasion of FHs 74 Int and Caco-2 cells were the models of human intestinal epithelium infection. Internalization of fluorescein-5-isothiocyanate-labeled SL1344 into intestinal cells was measured by flow cytometry to quantify infection. Human milk and its fractions inhibited infection; the inhibitory activity localized to the high molecular weight glycans. Mucin 1 and mucin 4 were isolated to homogeneity. At 150 μg/L, a typical concentration in milk, human milk mucin 1 and mucin 4 inhibited SL1344 invasion of both target cell types. These mucins inhibited SL1344 invasion of epithelial cells in a dose-dependent manner. Thus, mucins may prove useful as a basis for developing novel oral prophylactic and therapeutic agents that inhibit infant diseases caused by Salmonella and related pathogens.     

Molecular relationship among Salmonella dublin isolates identified at the Center for Enterobacteriaceae of Palermo during the years 1971-85

A molecular epidemiological study was carried out on 60 Salmonella dublin isolates identified at the Southern Italy Enterobacteriaceae Center between 1971 and 1985. These included 23 isolates from children with diarrhoea in Palermo obtained during 1984. All isolates from the outbreak of gastroenteritis in children were resistant to chloramphenicol and streptomycin and harboured two plasmids of 50 MDa and 3 MDa molecular weight, whereas the majority of the isolates identified before 1984 were susceptible to these antibiotics and carried only a 50 MDa molecular weight plasmid. Four S. dublin strains successively identified from cattle (Palermo, Foggia, Portici) and from a child (Palermo) were shown to possess similar antibiotic resistance patterns and plasmid profiles to S. dublin isolates from the outbreak of gastroenteritis in children. The 50 MDa plasmid was shown to be associated with virulence in mice, while it was not possible to assign any genetic function to the 3 MDa plasmid.     

Salmonella dublin infection in adult cattle: a slaughter house and knackery survey in South West Wales.

A survey was carried out between June 1970 and December 1971 in which gall bladders from cattle either slaughtered for food consumption or disposed of through knackeries were cultured for salmonellas. Salmonella dublin was isolated from 28 of 1917 gall-bladders of adult cattle killed in the slaughterhouse at Carmarthen, and from 23 of 197 gall-bladders obtained from adult cattle sent to a knackery at Abergwili, near Carmarthen. The results are compared with a similar survey carried out in 1947 and 1948. Between June and November 1971 gall-bladders and uteri were also obtained from a slaughterhouse in Newcastle Emlyn, North Carmarthenshire, and a knackery in Tanygroes, South Cardiganshire. S. dublin was cultured from two gall-bladders but from none of the uteri of the 161 slaughterhouse cases. Seven of the 46 cows from the knackery yielded S. dublin on culture: 2 in the gall-bladder only, 3 in the uterus only and 2 in both gall bladder and uterus.     

Evaluation of two enrichment broths, three plating media and ELISA technique for the isolation of salmonella from dairy products

Salmonella is one of the most important food-borne pathogens that can be transmitted through the consumption of contaminated milk and milk products. Early detection of Salmonella in food is important for food safety. Two selective media, brilliant green agar (BGA) and xylose lysine desoxycholate (XLD) agar are commonly used in diagnostic laboratories for the isolation of Salmonella, often after enrichment of the samples in a broth before plating on the solid medium. Recently, a new medium called CHROmagar Salmonella (CAS) has become available for the rapid detection of Salmonella. In the present study, we compared this new medium with BGA and XLD for the isolation of Salmonella from 160 dairy products samples (80 ice cream and 80 kariesh cheese samples) with enrichment in Rappaport- Vassiliadis (RV) and tetrathionate (TT) broth. TECRA Unique Salmonella ELISA test was used. Only one sample was positive for Salmonella, which appeared on each of CAS and XLD agars, after enrichment using RV but not TT. This was associated with a sensitivity and specificity of (100 %, 92.45%), (100%, 93.71%) and (0 %, 100%) for each of CHROmagar Salmonella, XLD and BGA respectively. TECRA Unique Salmonella test yielded the highest sensitivity and specificity among all used methods; it had 100% sensitivity with 100% specificity.