Feed deprivation affects crop environment and modulates Salmonella enteritidis colonization and invasion of leghorn hens.
Leghorn hens over 50 weeks of age were assigned to two treatment groups designated as either unmolted controls or molted. A forced molt was induced by a 9-day feed withdrawal, and each hen was challenged orally with 10(5) Salmonella enteritidis organisms on day 4 of feed withdrawal. On days 4 and 9 of molt, the numbers of lactobacilli and the concentrations of lactate, acetate, propionate, and butyrate, and total volatile fatty acids in the crops decreased while crop pH increased significantly (P < 0.05) in the molted hens compared to the controls. S. enteritidis crop and cecal colonization, in addition to spleen and liver invasion, increased significantly (P < 0.05) in the molted hens compared to the controls. The invasive phenotype of Salmonella spp. is complex and requires several virulence genes which are regulated by the transcriptional activator HilA. Samples of the crop contents from the molted and unmolted birds were pooled separately, centrifuged, and filter sterilized. The sterile crop contents were then used to measure the expression of hilA. By using a lacZY transcriptional fusion to the hilA gene in S. enteritidis, we found that hilA expression was 1.6- to 2.1-fold higher in the crop contents from molted birds than in those from control birds in vitro. The results of the study suggest that the changes in the microenvironment of the crop caused by feed deprivation are important regulators of S. enteritidis survival and influence the susceptibility of molted hens to S. enteritidis infections. Furthermore, our in vitro results on the expression of hilA suggest that the change in crop environment during feed withdrawal has the potential to significantly affect virulence by increasing the expression of genes necessary for intestinal invasion. (+info)
Combinations of intervention treatments resulting in 5-log10-unit reductions in numbers of Escherichia coli O157:H7 and Salmonella typhimurium DT104 organisms in apple cider.
The U.S. Food and Drug Administration (FDA) recently mandated a warning statement on packaged fruit juices not treated to reduce target pathogen populations by 5 log10 units. This study describes combinations of intervention treatments that reduced concentrations of mixtures of Escherichia coli O157:H7 (strains ATCC 43895, C7927, and USDA-FSIS-380-94) or Salmonella typhimurium DT104 (DT104b, U302, and DT104) by 5 log10 units in apple cider with a pH of 3.3, 3.7, and 4.1. Treatments used were short-term storage at 4, 25, or 35 degrees C and/or freeze-thawing (48 h at -20 degrees C; 4 h at 4 degrees C) of cider with or without added organic acids (0.1% lactic acid, sorbic acid [SA], or propionic acid). Treatments more severe than those for S. typhimurium DT104 were always required to destroy E. coli O157:H7. In pH 3.3 apple cider, a 5-log10-unit reduction in E. coli O157:H7 cell numbers was achieved by freeze-thawing or 6-h 35 degrees C treatments. In pH 3.7 cider the 5-log10-unit reduction followed freeze-thawing combined with either 6 h at 4 degrees C, 2 h at 25 degrees C, or 1 h at 35 degrees C or 6 h at 35 degrees C alone. A 5-log10-unit reduction occurred in pH 4.1 cider after the following treatments: 6 h at 35 degrees C plus freeze-thawing, SA plus 12 h at 25 degrees C plus freeze-thawing, SA plus 6 h at 35 degrees C, and SA plus 4 h at 35 degrees C plus freeze-thawing. Yeast and mold counts did not increase significantly (P < 0.05) during the 6-h storage at 35 degrees C. Cider with no added organic acids treated with either 6 h at 35 degrees C, freeze-thawing or their combination was always preferred by consumers over pasteurized cider (P < 0.05). The simple, inexpensive intervention treatments described in the present work could produce safe apple cider without pasteurization and would not require the FDA-mandated warning statement. (+info)
Clinical and veterinary isolates of Salmonella enterica serovar enteritidis defective in lipopolysaccharide O-chain polymerization.
Twelve human and chicken isolates of Salmonella enterica serovar Enteritidis belonging to phage types 4, 8, 13a, and 23 were characterized for variability in lipopolysaccharide (LPS) composition. Isolates were differentiated into two groups, i.e., those that lacked immunoreactive O-chain, termed rough isolates, and those that had immunoreactive O-chain, termed smooth isolates. Isolates within these groups could be further differentiated by LPS compositional differences as detected by gel electrophoresis and gas liquid chromatography of samples extracted with water, which yielded significantly more LPS in comparison to phenol-chloroform extraction. The rough isolates were of two types, the O-antigen synthesis mutants and the O-antigen polymerization (wzy) mutants. Smooth isolates were also of two types, one producing low-molecular-weight (LMW) LPS and the other producing high-molecular-weight (HMW) LPS. To determine the genetic basis for the O-chain variability of the smooth isolates, we analyzed the effects of a null mutation in the O-chain length determinant gene, wzz (cld) of serovar Typhimurium. This mutation results in a loss of HMW LPS; however, the LMW LPS of this mutant was longer and more glucosylated than that from clinical isolates of serovar Enteritidis. Cluster analysis of these data and of those from two previously characterized isogenic strains of serovar Enteritidis that had different virulence attributes indicated that glucosylation of HMW LPS (via oafR function) is variable and results in two types of HMW structures, one that is highly glucosylated and one that is minimally glucosylated. These results strongly indicate that naturally occurring variability in wzy, wzz, and oafR function can be used to subtype isolates of serovar Enteritidis during epidemiological investigations. (+info)
Outbreak of Salmonella serotype Muenchen infections associated with unpasteurized orange juice--United States and Canada, June 1999.
During June 1999, Public Health-Seattle and King County (PHSKC) and the Washington state health department and the Oregon Health Division independently investigated clusters of diarrheal illness attributed to Salmonella serotype Muenchen infections in each state. Both clusters were associated with a commercially distributed unpasteurized orange juice traced to a single processor, which distributes widely in the United States. As of July 13, 207 confirmed cases associated with this outbreak have been reported by 15 states and two Canadian provinces; an additional 91 cases of S. Muenchen infection reported since June 1 are under investigation. This report summarizes the two state-based investigations and presents preliminary information about the outbreak in the other states and Canada. (+info)
An outbreak of Salmonella typhimurium DT170 associated with kebab meat and yogurt relish.
During July 1995, an outbreak of Salmonella typhimurium definitive type (DT) 170, an unusual strain, occurred in South Wales. A case-control study found that illness was associated with eating kebabs (odds ratio undefined, P = 0.002), doner kebabs (odds ratio 7.9, 95 % confidence interval 1.5-20.5, P = 0.02) and kebabs with yoghurt based relish (odds ratio undefined, P = 0.009) but not with eating kebabs with mayonnaise-based relish (odds ratio 2.4, 95 % confidence interval 0.4-13.9, P = 0.53). Environmental investigations discovered a complex web of producers and wholesale suppliers. Kebab meat and yoghurt had been supplied to the two main implicated outlets by a single wholesaler. Samples of raw minced lamb and several environmental swabs taken at the wholesaler were positive for S. typhimurium DT170. Blood-stained, unsealed yoghurt pots were observed to be stored under a rack of raw lamb. Investigators of food poisoning outbreaks linked to takeaway food should consider cross-contaminated relishes and dressings as well as undercooked meat as potential vehicles of infection. (+info)
Outbreaks of salmonellosis associated with eating uncooked tomatoes: implications for public health. The Investigation Team.
Laboratory-based surveillance of salmonella isolates serotyped at four state health departments (Illinois, Michigan, Minnesota and Wisconsin) led to the identification of multistate outbreaks of salmonella infections during 1990 (176 cases of S. javiana) and 1993 (100 cases of S. montevideo). Community-based case-control studies and product traceback implicated consumption of tomatoes from a single South Carolina tomato packer (Packer A) MOR 16.0; 95% CI2.1, 120.6; P < 0.0001 in 1990 and again in 1993 (MOR 5.7; 95 % CI 1.5, 21.9; P = 0.01) as the likely vehicle. Contamination likely occurred at the packing shed, where field grown tomatoes were dumped into a common water bath. These outbreaks represent part of a growing trend of large geographically dispersed outbreaks caused by sporadic or low-level contamination of widely distributed food items. Controlling contamination of agricultural commodities that are also ready-to-eat foods, particularly fruits and vegetables, presents a major challenge to industry, regulators and public health officials. (+info)
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. (+info)
An international outbreak of Salmonella enteritidis associated with lasagne; lessons on the need for cross-national co-operation in investigating food-borne outbreaks.
We investigated an outbreak of Salmonella enteritidis involving at least 19 British tourists returning from one hotel in another European country. A retrospective cohort study of 47 hotel guests identified lasagne as the most likely vehicle of transmission (RR 11.5; 95% CI 3.0-44.1; P < 0.0001). However, difficulties in information exchange and lack of formal mechanisms to agree on the aims of the cross-national investigation hampered efficient management of the outbreak. The factors leading to contamination of the food vehicle were not identified and therefore specific action to prevent reoccurrence could not be taken. There is need to develop protocols for cross-national investigations of outbreaks in Europe which should include specifying objectives, roles and responsibilities of investigators and control agencies, with formal reporting of the outcome of the investigation. (+info)