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Biomedical subjects

J T Peeler

Publications and source records attributed to J T Peeler.

17 recordsLinked to original sources
PubMed1992

Thermotolerance of heat-shocked Listeria monocytogenes in milk exposed to high-temperature, short-time pasteurization.

The effect of prior heat shock (48 degrees C for 15 min) on the thermotolerance of Listeria monocytogenes at the minimal high-temperature, short-time (71.7 degrees C for 15 s) parameters required by the Pasteurized Milk Ordinance was examined. The mean D71.7 degrees C value for heat-shocked L. monocytogenes was 4.6 +/- 0.5 s (control D = 3.0 +/- 1.0 s); the ratio of D to control D was 1.5. The increased thermotolerance of heat-shocked Listeria cells was not significant and appeared unlikely to have practical implications, in terms of risk assessment, for the safety of pasteurized milk.

Animals↗
PubMed1992

Virulence characteristics of clinical and environmental isolates of Vibrio vulnificus.

Twenty-four randomly selected clinical and environmental Vibrio vulnificus isolates were tested for virulence in iron-overloaded mice (250 mg of iron dextran per kg of body weight). The log10 50% lethal doses of 17 isolates were lower by greater than or equal to 3.5 log10 units in iron-overloaded mice than in control mice. These isolates were classified as virulent. The 50% lethal doses of these virulent isolates were also lower in mice that were immunosuppressed by treatment with cyclophosphamide (150 mg/kg). Four of the seven isolates initially classified as avirulent were virulent in mice that were simultaneously iron overloaded and immunosuppressed. These isolates were classified as moderately virulent. The remaining three isolates were avirulent under all conditions. The incidence of virulent strains among clinical and environmental isolates did not differ. The virulent isolates produced high titers of hemolysin, were resistant to inactivation by serum complement, produced phenolate siderophore, and utilized transferrin-bound iron. The moderately virulent isolates differed from the virulent isolates only in their increased sensitivity to inactivation by serum complement. The avirulent isolates differed from those of the other two classes in their inability to either produce significant amounts of phenolate siderophore or utilize transferrin-bound iron. A modified agar plate diffusion method for transferrin-bound iron utilization was developed to differentiate the two classes of virulent isolates from the avirulent isolates in vitro.

Animals↗
PubMed1990

Thermotolerance of Listeria monocytogenes and Salmonella typhimurium after sublethal heat shock.

The effect of prior heat shock on thermotolerance of Listeria monocytogenes and Salmonella typhimurium in broth culture was determined. Bacteria were grown at the permissive temperature of 35 degrees C, sublethally heated at 35 (control), 42, 48, and 52 degrees C (nonpermissive control) for various times, and inactivated at either 57.8 or 52 degrees C. The induction of increased thermotolerance by heat shock, although consistent within each experiment, was generally not significant for L. monocytogenes; the increase was significant for S. typhimurium. Temperature shift experiments with L. monocytogenes suggested that induced thermotolerance was not long lived unless the shock temperature was maintained.

Hot Temperature↗
PubMed1990

Incidence of Vibrio parahaemolyticus in U.S. coastal waters and oysters.

Oyster and seawater samples were collected seasonally from May 1984 through April 1985 from shellfish-growing areas in Washington, California, Texas, Louisiana, Alabama, Florida, South Carolina, Virginia, and Rhode Island which had been designated as approved or prohibited by the National Shellfish Sanitation Program. Fecal coliforms counts, aerobic plate counts, and Vibrio parahaemolyticus densities were determined for the samples. Mean V. parahaemolyticus density was more than 100 times greater in oysters than in water, whereas density of fecal coliforms was approximately 10 times higher in oysters. Seasonal and geographical distributions of V. parahaemolyticus were related to water temperature, with highest densities in samples collected in the spring and the summer along the Gulf coast. The synthetic DNA probe for thermostable direct hemolysin hybridized with 2 of 50 isolates, 1 of which was positive by the Kanagawa test.

Animals↗
PubMed1989

Comparative recovery of uninjured and heat-injured Listeria monocytogenes cells from bovine milk.

The standard selective enrichment protocols of the Food and Drug Administration (FDA) and U.S. Department of Agriculture (USDA) were compared with an experimental nonselective broth enrichment (NSB) protocol and variations of the standard cold-enrichment (CE) protocol for the recovery of heat-injured Listeria monocytogenes. Bacterial cells (10(7)/ml) were suspended in sterile milk and heated at 71.7 degrees C in a slug-flow heat exchanger for holding times ranging from 1 to 30 s. Surviving cells were determined (50% endpoint) by the given protocols, and the following D values were obtained: NSB, D = 2.0 +/- 0.5 s; FDA, D = 1.4 +/- 0.3 s; USDA, D = 0.6 +/- 0.2 s; CE, D less than or equal to 1.2 s. The respective direct-plating media used in these enrichments were also analyzed for recovery, and the following D values were calculated from the enumeration of surviving cells; NSB, D = 2.7 +/- 0.8 s; FDA, D = 1.3 +/- 0.4 s; USDA, D = 0.7 +/- 0.2 s. The low levels of heat-injured L. monocytogenes cells which were detected at inactivation endpoints on the optimal nonselective media (25 degrees C for 7 days) failed to recover and multiply during experimental CEs (4 degrees C for 28 days). Initial inactivation experiments in which raw whole milk was used as the heating menstruum gave much lower recoveries with all protocols. The detectable limits for uninjured cells that were suspended in raw milk were similar (0.35 to 3.2 cells per ml) for the standard CE, FDA, and USDA protocols.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Listeria spp. found on fresh market produce.

From October 1987 to August 1988, 1,000 tests were conducted on 10 types of fresh produce from two Minneapolis area supermarkets to detect Listeria spp. The produce included broccoli, cabbage, carrots, cauliflower, cucumbers, lettuce, mushrooms, potatoes, radishes, and tomatoes. The vegetables were tested by the Food and Drug Administration method for isolation of Listeria spp., with the addition of LiCl-phenylethanol-moxalactam agar in the last 280 tests; 8.6 and 11.4% of these tests were positive by modified McBride and LiCl-phenylethanol-moxalactam agars, respectively. Listeria monocytogenes was isolated from cabbage, cucumbers, potatoes, and radishes; L. innocua was isolated from cucumbers, lettuce, mushrooms, potatoes, and radishes; L. seeligeri was isolated from cabbage and radishes; and L. welshimeri was isolated from cucumbers, potatoes, and radishes. The isolates were of various serotypes; however, the L. monocytogenes isolates were predominantly serotype 1 (82%). Only potatoes (25.8% positive) and radishes (30.3% positive) showed significant amounts of L. monocytogenes contamination.

Food Microbiology↗
PubMed1979

Rapid methods for differentiating reactivated from residual phosphatase in milk and cream: collaborative study.

Three methods for differentiating reactivated from residual phosphatase in milk and cream were collaboratively tested using both magnesium acetate and magnesium chloride for reactivating phosphatase. The methods evaluated were the modified Scharer rapid test, the rapid colorimetric test, and the Rutgers method. Nine collaborators tested 6 unknown milk samples containing reactivated and/or residual phosphatase, and 16 collaborators tested 6 unknown cream samples containing reactivated and/or residual phosphatase. Results indicated that use of magnesium acetate in place of magnesium chloride for reactivating phosphatase improved test results. Visual tests (modified Scharer rapid and Rutgers) predicted correct results when the samples contained high levels of reactivated or residual phosphatase. In borderline cases where the reactivated phosphatase contents of the undiluted control sample and the diluted sample containing Mg were very close, the test results of the visual methods were significantly different from 100% correct results at the alpha=0.05 level. Use of a photoelectric colorimeter or its equivalent for measuring the absorbance in conjunction with the modified Scharer rapid test improved results considerably. The modified Scharer rapid test was adopted official first action.

Acetates↗
PubMed1978

Thermal resistance of naturally occurring airborne bacterial spores.

Simulation of a heat process used in the terminal dry-heat decontamination of the Viking spacecraft is reported. Naturally occurring airborne bacterial spores were collected on Teflon ribbons in selected spacecraft assembly areas and subsequently subjected to dry heat. Thermal inactivation experiments were conducted at 105, 111.7, 120, 125, 130, and 135 degrees C with a moisture level of 1.2 mg of water per liter. Heat survivors were recovered at temperatures of 135 degrees C when a 30-h heating cycle was employed. Survivors were recovered from all cycles studied and randomly selected for identification. The naturally occurring spore population was reduced an average of 2.2 to 4.4 log cycles from 105 to 135 degrees C. Heating cycles of 5 and 15 h at temperature were compared with the standard 30-h cycle at 111.7, 120, and 125 degrees C. No significant differences in inactivation (alpha = 0.05) were observed between 111.7 and 120 degrees C. The 30-h cycle differs from the 5-and 15-h cycles at 125 degrees C. Thus, the heating cycle can be reduced if a small fraction (about 10-3 to 10-4) of very resistant spores can be tolerated.

Air Microbiology↗
PubMed1977

Thermal resistance of Bacillus subtilis var. niger in a closed system.

The heat resistance of Bacillus subtilis var. niger has been measured from 85 to 125 degrees C using moisture levels of percent relative humidity (%RH) less than or equal to 0.001 to 100 in a closed system. Five curves have been presented to characterize the thermal destruction, using thermal death times defined as F values at a given combination of three moisture and temperature conditions. Reductions of 99.99% (4-log10 cycles) of the initial population were estimated for the three moisture conditions. At 110 degrees C, the expected time for a 4-log10 reduction was 1.1 h at %RH = 100, 3.1 h at %RH less than or equal to 0.1 and 54 h at %RH = 10.7. Goodness-of-fit tests to examine the adequacy of three polynomial models failed to indicate a trend. The linear model (from which estimates of D are obtained) was satisfactory for estimating the thermal death times (%RH less than or equal to 0.1) in the plate count range. The estimates based on observed thermal death times and D values for the %RH = 100 diverged so that D values generally gave a more conservative estimate over the temperature range 90 to 125 degrees C. Estimates of ZF and ZL ranged from 32.1 to 58.3 degrees C for the %RH less than or equal to 0.1 and 100. A ZD value of 30.0 was obtained for data observed at %RH less than or equal to 0.1. The ZF results were obtained from plotting observed log times to achieve a 99.99% reduction in the initial population versus temperature. Estimates of ZL and ZD were obtained by using linear estimates of L100 approximately equal to 4D and D values in a similar plot.

Bacillus subtilis↗
PubMed1977

Thermal inactivation of ileal loop-reactive Clostridium perfringens type A strains in phosphate buffer and beef gravy.

The thermal resistance of spore crops produced from each of two ileal loop-reactive strains of Clostridium perfringens type A was determined in two suspending vehicles consisting of 0.067 M (pH 7.0) phosphate buffer and a commercial beef gravy. D115.6 values obtained in buffer and enumerated after pretreatment with sodium ethylenediaminetetraacetate and recovery in plating medium containing lysozyme were two- to threefold greater than those obtained without this treatment. D115.6 values obtained with beef gravy were less than those obtained in buffer with or without lysozyme; however, the D98.9 and D104.4 values were 1.3 to 2 times greater than those obtained in buffer with lysozyme. The z values were within the ranges reported by previous investigators.

Animals↗
PubMed1977

Collaborative study comparing the spiral plate and aerobic plate count methods.

The spiral plate count method is a semiautomated plating technique that greatly reduces manpower and material costs normally associated with the pour plating technique. In this collaborative study, 8 laboratories compared the spiral and pour plating techniques, using 4 samples each of 3 products: frozen pumpkin pie, frozen chicken pot pie, and shampoo. The results show that 10 of the 12 comparisons of means of the pour and spiral methods were not significantly different; 2 values were significant at alpha = 0.01. Overall, the components of variance were less than that of the current milk standard, and the replicate per cent coefficient of variation was satisfactory. This study indicates that the spiral plate method is an acceptable alternative to the pour plate method; the spiral plate method has been adopted as official first action.

Aerobiosis↗
PubMed1976

Spiral plate count method for the examination of raw and pasteurized milk.

The spiral plate count method (SPLPC) was compared with the standard plate count (SPC) method by examining 201 samples of raw and pasteurized milk. Although the means of the two methods differed significantly at alpha = 0.01,the difference was less than 10% and was not considered to be of any practical importance. The pooled replicate variances of both methods were less than 0.003, indicating good agreement between duplicate plates, with the variance of the SPLPC slightly less than that of the SPC. We believe this study indicates that the SPLPC could be substituted for the SPC in the bacteriological examination of milk.

Animals↗
PubMed1975

Comparative inhibitory effects of antigen and antibody in the staphylococcal enterotoxin solid-phase radioimmunoassay system.

A solid-phase radioimmunoassay employing 125I-labeled enterotoxins and polystyrene tubes coated with specific antibody has been developed for assaying the relative concentrations of antibodies to staphylococcal enterotoxins A and B. Competitive binding occurs between tube-bound antibody and free antibody for binding sites on 125I-labeled enterotoxin. The sensitivity of the system is affected by the amount of antibody on the walls of the tubes, the concentration of 125I-labeled enterotoxin added to the system, and probably by the relative binding affinities of the bound and unbound antibodies. Antibody, 0.01 to 0.07 mug/ml, inhibited the uptake of 125I-labeled enterotoxin by 20%. Both the antibody and antigen solid-phase radioimmunoassay inhibition systems can be appropriately represented by either of the following two models: Loge (Y/1 - Y) = alpha0 + alpha1 LogeX and LogeY = beta0 + beta1 LogeX, where Y is bound activity, X is antigen or antibody concentration for inhibition, and alpha0, alpha1, beta0, and beta1 are regression coefficients. Estimates from the first model were slightly more precise for the antibody system, whereas the reverse was true for the antigen system.

Animals↗
PubMed1975

Heat resistance of ileal loop reactive Bacillus cereus strains isolated from commercially canned food.

Sporeformers isolated from a commercially canned food were identified as Bacillus cereus, lactose-positive variants. The thermal resistance of spore crops produced from each of two representative cultures was determined in 0.067 M phosphate buffer at pH 7.0. The D121.1 values for one isolate were approximately 0.03 min (z = 9.9C), whereas the D121.1 values for the other isolate were 2.35 min (z = 7.9 C). Thermal inactivation results for heat-stressed isolates from each strain showed no significant alteration in heat resistance from that of the two parent spore crops. Both isolates were reactive when injected into the ligated rabbit ileum.

Animals↗
PubMed1975

Collaborative study of the glass wool filtration method for the recovery of virus inoculated into ground beef.

A method for estimating viral population levels in ground beef was studied collaboratively in 7 laboratories. The collaborators recovered virus from 6 inoculated samples. Three samples were replicates of the high virus concentration 050 plaque-forming units (pfu)/g) and 3 replicates represented the low concentration (10 pfu/g). Six of the 7 collaborators recovered acceptable levels of virus from the samples. The per cent of variation was 30.6 for the high concentration and 18.5 for the low concentration. Collaborators did not differ from one another significantly in the results obtained for the 10 pfu/g samples, but results from one collaborator were significantly low for the recovery of virus from the 50 pfu/g samples. The results indicate that the glass wool filtration method is adequate for the detection of a number of viruses that may be found in foods. The method has been adopted as official first action.

Animals↗
PubMed1975

Direct plating method for enumeration of Staphylococcus aureus: collaborative study.

Considerable evidence has been published regarding the adverse effect of sodium chloride on physiologically impaired cells of Staphylococcus aureus, such as are to be expected in processed foods. A direct plating method for enumeration of S. aureus eliminating the use of sodium chloride was devised and subjected to collaborative study by 16 analysts. Results obtained by the direct plating method were compared to those obtained by the AOAC official first action method (46.036--46.040). Participating analysts examined duplicate samples at population levels of 91, 34, and 20 S. aureus/g. Coefficients of variation among analysts were considerably lower for the direct plating method (31, 81, and 48%, respectively) than for method 46.040 (59, 156, and 150%, respectively) at all 3 population levels. High coefficients of variation for the direct plating method at 2 of the 3 levels were due principally to low populations of S. aureus. The direct plating method has been adopted as official first action for general purpose use and use of method 46.036--46.040 has been restricted to raw food ingredients and nonprocessed foods.

Culture Media↗