Hans P. Riemann

Survival of Salmonella typhimurium and Escherichia coli O157:H7 in poultry manure and manure slurry at sublethal temperatures.

Exponential inactivation was observed for Salmonella typhimurium and Escherichia coli O157:H7 in poultry manure with decimal reduction times ranging from half a day at 37 C to 1-2 wk at 4 C. There was no material difference in inactivation rates between S. typhimurium and E. coli O157:H7. Inactivation was slower in slurries made by mixing two parts of water with one part of manure; decimal reduction times (time required for 90% destruction) ranged from 1-2 days at 37 C to 6-22 wk at 4 C. Escherichia coli O157:H7 consistently exhibited slightly slower inactivation than S. typhimurium. Log decimal reduction time for both strains was a linear function of storage temperature for manure and slurries. Chemical analysis indicated that accumulation of free ammonia in poultry manure was an important factor in inactivation of the pathogens. This finding was experimentally confirmed for S. typhimurium by adding ammonia directly to peptone water or to bovine manure, which was naturally low in ammonia, and adjusting pH to achieve predetermined levels of free ammonia.

Efficacy of disinfection of shell eggs externally contaminated with Salmonella enteritidis: Implications for egg testing

Experimental contamination of the surface of shell eggs by dipping in a culture of Salmonella enteritidis resulted in the presence of Salmonella enteritidis in/on the shells as well as shell membranes but not in the egg content. Disinfection with Lugols solution, chlorhexidine, ethanol, quarternary ammonium solutions or flaming after dipping in ethanol failed to achieve complete decontamination of the shell and membranes with resulting false positives when eggs were broken for culturing of the content. Dipping eggs for three seconds in boiling water resulted in complete destruction of Salmonella enteritidis in shells and membranes but sometimes caused the eggs to crack. A method of aseptically opening eggs without risk of contaminating the content from the shell or membrane was developed. Salmonella enteritidis deposited in/on the shell and membranes did not multiply during storage of the eggs at 20 degrees C for four weeks, the counts seemed to decrease. No Salmonella enteritidis was detected in the contents of any contaminated eggs.

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.

Heat Destruction of Salmonella in Poultry Feed: Effect of Time, Temperature, and Moisture

Salmonella enteriditis in poultry feed declines with increasing time of exposure to heat. The interactions of temperature, time, and moisture and their effect on the thermal death of S. enteriditis were established in a factorial randomized experiment. Two other serotypes were tested, and though there was some variation, the thermal death rate followed the same basic pattern. A number of samples of poultry feed were collected and dried. After drying, the water was added back to give specific percentages of moisture contents. The feed was then inoculated with salmonella and heated at specific temperatures, with samples being removed at certain time intervals. These samples were then cultured, and the surviving salmonella were counted. A linear relationship was obtained when the logarithm of survivors was plotted against the logarithm of exposure time. These results permitted the construction of a graph depicting that the rate of reduction in numbers of S. enteriditis when plotted against increasing temperatures is linear. This linear relationship is apparent for other salmonella serotypes such as S. typhimurium and S. haardt. Our results show that the thermal death rate of salmonella in poultry feed can now be predicted at varying time, temperature, and moisture contents.

Reduction of Escherichia coli O157:H7 and Salmonella Typhimurium in Artificially Contaminated Alfalfa Seeds and Mung Beans by Fumigation with Ammonia

Sprouts eaten raw are increasingly perceived as hazardous foods because they have been vehicles in outbreaks of foodborne disease, often involving Escherichia coli O157:H7 and Salmonella Typhimurium. Although the source of these pathogens has not been established, it is known that the seeds usually are already contaminated at the time sprouting begins. Earlier studies had shown that ammonia was lethal to these same pathogens in manure, so it seemed reasonable to determine whether ammonia was effective against them when associated with seeds to be used for sprouting. Experimentally contaminated (10(8) to 10(9) CFU/g) and dried seeds, intended for sprouting, were sealed in glass jars in which 180 or 300 mg of ammonia/liter of air space was generated by action of ammonium sulfate and sodium hydroxide. Samples were taken after intervals up to 22 h at 20 degrees C. Destruction of approximately 2 to 3 logs was observed with both bacteria associated with alfalfa seeds, versus 5 to 6 logs with mung beans. Greater kills are apparently associated with lower initial bacterial loads. Germination of these seeds was unaffected by the treatment. It appears that this simple treatment could contribute significantly to the safety of sprout production from alfalfa seeds and mung beans.

A Survey for Salmonella by Drag Swabbing Manure Piles in California Egg Ranches

A cross-sectional study was conducted between August 1995 and November 1996. Sixty California egg-producing ranches were chosen at random; 39 ranches agreed to participate in the study. The surface of the manure pile in one house on each ranch was sampled by drag swabbing. The drag swabs were tested for Salmonella using a most probable number procedure that had a detection level of one to five Salmonella per drag swab. In 12 ranches (32.4%), the drag swabs were negative for Salmonella; the remaining had Salmonella counts in the range of 1 to over 1700 per swab. Twenty-two different serotypes were found. Salmonella heidelberg and Salmonella cerro represented the majority of the typed isolates. Salmonella enteritidis (SE) was found on only one ranch. This study found SE to be rare in California egg ranches, which implies that these ranches are not a major source of S. enteritidis.

Destruction of Salmonella enteritidis in poultry feed by combination of heat and propionic acid.

A factorial laboratory experiment was conducted to assess the effects of heating times of 0, 20, 40, and 80 sec at 160 F and propionic acid concentrations of 0, 0.1%, and 0.2% on reduction of Salmonella enteritidis in poultry feed with approximately 15% moisture. The results showed that after 80 sec heating time an approximately 10,000-fold reduction in living salmonella was obtained in the samples with 0.2% propionic acid. Survival in the 0.2% acid group was 2 log10 lower than in the 0.1% and control groups. This difference was statistically significant. Multivariate analysis with repeated measures showed there was no interaction between heating time and propionic acid concentration (P = 0.4113). There were overall significant effects for both acid concentration (P < 0.00001) and heating time (P < 0.0001).

ANTIBODIES TO Clostridium botulinum TOXINS IN FREE-LIVING BIRDS AND MAMMALS

Naturally-occuring antibodies against Clostridium botulinum toxins were found in Cathartes aura (turkey vultures), Canis latrans (coyotes) and Corvus brachyrhynchos (crows) by the passive hemagglutination (PHA) test and verified by the serum neutralization (SN) test. The prevalence of IHA antibodies was 18 of 20 vultures (90%), 5 of 12 crows (42%) and 25 of 110 coyotes (23%). Vultures and coyotes were seropositive by the PHA test against A, B, C, D and F toxins. The highest antibody titer 1:8192 was in vulture serum against type C. In descending order, the highest antibody levels were against type C, D, F, E, A and B toxins.

Removal of Escherichia coli O157:H7 from Surface Tissues of Beef Carcasses Inoculated with Wet and Dry Manure

Beef tissues were contaminated with wet and dry manure. The manure was previously inoculated with Escherichia coli O157:H7 GFP, genetically modified with a plasmid encoding a protein that fluoresces green when exposed to long-wave ultraviolet light. After incubation at 37 degrees C for 5 days, the wet manure was spread on the surface of beef tissues at an average E. coli O157:H7 GFP level of 6.62 log CFU/cm2. Dry manure was obtained by subjecting wet manure to natural drying (simulating dry manure adhering to the hides of cattle) and was also applied to the surfaces of beef tissues. The degree of removal of E. coli O157:H7 GFP by washing was compared to the removal of cells of the same strain that had been inoculated as a suspension. The E. coli O157:H7 mixed into feces of cattle adhered more strongly to meat surfaces than that applied as a suspension, complicating the removal by conventional washing procedures. The fate of the bacterium mixed into wet or dry manure was evaluated. An initial decrease of the inoculated population was observed; this was probably an effect of the changed environment represented by the manure. After adaptation, the inoculated bacteria grew in the wet manure; a maximum population was reached in 5 days at 37 degrees C; levels declined with drying. The use of the GFP marker was of great value, since it allowed enumeration of E. coli O157:H7 in the presence of the natural flora of manure.

Descriptive Study of California Egg Layer Premises and Analysis of Risk Factors for Salmonella enterica serotype enteritidis as Characterized by Manure Drag Swabs

Abstract 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.