Ammonia disinfection of animal feeds --laboratory study.

Animal feeds may be contaminated, accidentally or maliciously, with a number of zoonotic bacteria. Animal infections with these bacterial agents, whether or not they cause animal disease, may lead to human illnesses. Anhydrous ammonia was introduced on farms in developed countries as a high-nitrogen soil amendment, but later found use in enhancing crude protein in low-quality roughage fed to ruminants and in neutralizing mycotoxins in fungus-infested feed grains. Although ammonia has been known to be effective against bacteria in other contexts (e.g., manure, community sewage sludge, seeds for sprouting, and boneless lean beef trimmings), it appears that the antibacterial effect of ammoniating animal feeds had not been tested. In the present study, samples of roughage (wheat straw, corn silage) and concentrates (corn grain, cottonseed) produced as animal feed were contaminated with dried-on zoonotic bacteria (Salmonella Newport in all; Campylobacte jejuni, E. coli O157:H7, Listeria monocytogenes, Yersinia enterocolitica in corn grain only). Disinfection with anhydrous ammonia gas was conducted for 24 h at room temperature ( 25 degrees C). The treatment was least effective in silage because the silage alone showed strong antibacterial activity, which may have been slightly reduced by ammoniation. In the other three feeds, depending on the initial level of contamination, ammonia destruction of >or= 5 log10 cfu/g (99.999%) of the selected contaminant was usually observed.

Pathogen survival in chorizos: ecological factors.

This study addressed health risks from ethnic sausages produced on a small scale, without inspection, in California and elsewhere. Mexican-style chorizo, a raw pork sausage that is not cured, fermented, or smoked, was contaminated experimentally in the batter with Escherichia coli O157:H7, Listeria monocytogenes, or Salmonella serotypes and stuffed into natural casings. Formulations were based on a market survey in California. Physical parameters that were controlled were pH, water activity (a(w)), and storage temperature. The pH was adjusted with vinegar, stabilizing at 5.0 within 24 h. Initial a(w) levels adjusted with salt were 0.97, 0.95, 0.93, 0.90, and 0.85; levels declined with time because of evaporation. Pathogen numbers declined with storage up to 7 days, with few brief exceptions. Main effects and interactions of constant temperature and pH with declining a(w) on survival of the pathogens were determined. Maximum death rates occurred at higher a(w) for E. coli O157:H7 and Salmonella than for L. monocytogenes. Salt used to adjust a(w) affected palatability. Spices (black pepper, chili pepper, chili powder, cumin, garlic, guajillo pepper, oregano, and paprika) comprised another, potentially significant aspect of the sausage formulation. Some (notably black pepper and cumin) carried an indigenous microflora that contributed significantly to the microbial load of the sausage batter. Only undiluted fresh and powdered garlic exhibited a significant antimicrobial effect on the pathogens. Although each of the tested formulations caused death of the inoculated pathogens, none of the death rates was sufficiently rapid to ensure safety within the probable shelf life of the product.

Descriptive study of California egg layer premises and analysis of risk factors for Salmonella enterica serotype enteritidis as characterized by manure drag swabs.

This cross-sectional, double-blind study reports the prevalence of Salmonella enterica serotype enteritidis (SE) on California egg layer premises using single vs. pooled manure drag swabs and presents a description of egg production and management systems in the state and an initial analysis of risk factors for SE. The study included 91% of all known eligible egg premises in California, representing the majority of eggs produced in the state. The overall prevalence of SE on California egg layer premises was 10.5%, while 1.1% of all rows sampled were positive for SE. The percentage of positive rows for SE on any premises never exceeded 25% of the 16 swabs collected per premises. A description of egg production and management on California egg layer premises is presented. Statistically significant associations for SE were not evident and were limited because of sample size and the low prevalence of SE on California egg layer premises. Several biological and management factors, such as flock health, stage of production, manure management, ventilation, and watering systems, show trend associations with premises positive for SE and require further investigation. Manure drag swabs serve as a useful tool to validate the core components of an egg quality assurance program for SE based on process control principles.

The occurrence and distribution of Salmonella enteritidis and other serovars on California egg laying premises: a comparison of two sampling methods and two culturing techniques.

Between the summer of 1998 and the winter of 2000, Salmonella analysis was performed on 2128 single and 532 pooled manure drag swabs obtained from 133 California commercial egg laying farms. The isolation of Salmonella from all rows and from all flocks using single or pooled swabs was 80% and 92%, respectively. Hence, there was no statistical difference between single vs. pooled swabs in terms of identifying Salmonella on a row or flock basis. A total of 14 serogroups comprising 44 serotypes were isolated from 123 of 133 farms. When the top 10 serotypes were considered, there was no significant difference in the range of serotypes isolated by the two culturing methods. The overall S. enteritidis prevalence for California flocks was 10.5% (14/133). The overall row prevalence for S. enteritidis for all the farms was 1.1% (24/2128), and the overall pool prevalence was 2.4% (13/532). Sixty percent (12/20) of the S. enteritidis isolates from the positive farms were phage type 4, and 40% (8/20) represented five other phage types (1, 6B, 7, 8, and 28).

Short-Time Treatment with Alkali and/or Hot Water To Remove Common Pathogenic and Spoilage Bacteria From Chicken Wing Skin.

Dipping in 10% trisodium phosphate (TSP) at 10°C for 15 s and/or hot water (95°C) for 5 s significantly (P < 0,05) reduced the numbers of live Salmonella typhimurium , Listeria monocytogenes , and Staphylococcus aureus inoculated on the surface of chicken wings. Mean reductions after treatment with TSP (after storage at 10°C or 4°C, respectively) were 93.45% and 62.42% for S. typhimurium , 80.33% and 54.45% for S. aureus , and 39.04% and 81.41 % for L. monocytogenes . Similarly treatment with hot water resulted in reductions of 83.5% and 47.44%, 90.19% and 91.49%, and 68.57% and 77.83%, respectively, for the three bacterial species. The combined effects of TSP and hot water were 94.76% and 99.67%, 84.41 % and 96.68%, and 79.49% and 94.88%. After treatment with TSP, there was always a better recovery of L. monocytogenes when the wings were stored at 10°C compared to 4°C. No similar storage temperature effect on recovery of L. monocytogenes was observed in the absence of TSP. Based on the smell and appearance of uninoculated, fresh chicken wings after treatment with 10% solutions of TSP or Na2CO3 (10°C) and hot water, the control group was always preferred after 1 day of storage, but not after 6 days of storage. Combination treatment with TSP and hot water showed that after 7 days of storage the number of spoilage organisms was 3 log units higher on the control samples than on the treated wings. The combined TSP and hot water treatments were more effective in reducing counts of S. typhimurium , S. aureus , and L. monocytogenes than the combined Na2CO3 and hot water treatment (95°C for 5 s). Changes in subcutaneous temperature as a result of treatment with TSP and hot water treatment were minimal.