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.

Smoking rates among Rhode Island physicians: achieving a smoke-free society.

Over a 25-year period, regular surveys of physicians licensed in Rhode Island have recorded their smoking behavior. The six surveys show a decrease in the rate of cigarette smoking from 33% in 1963 to 4.6% in 1988. In the most recent survey, 65% of respondents reported never having smoked, and 87% of those who had ever smoked reported having quit. However, the statistic for the maximum number of cigarettes smoked regularly was higher for current smokers than for former smokers. Among physicians in the 1988 survey, most former smokers (85%) reported using only unassisted personal effort in quitting, whereas nearly half (48%) of current smokers tried methods involving assistance, such as self-help programs, group programs, or nicotine gum. Among former smokers who quit after 1983, the percentage trying assisted methods (34%) was closer to the percentage among current smokers. Apparently, remaining smokers include many heavy smokers who require more potent interventions in order to quit. Physicians in Rhode Island have almost become a smoke-free group. Their experience, coupled with their involvement in smoking prevention and cessation for their patients, can lead the rest of society on its path to becoming smoke-free.

Multilaboratory evaluation of methods for detecting enteric viruses in soils.

Two candidate methods for the recovery and detection of viruses in soil were subjected to round robin comparative testing by members of the American Society for Testing and Materials D19:24:04:04 Subcommittee Task Group. Selection of the methods, designated "Berg" and "Goyal," was based on results of an initial screening which indicated that both met basic criteria considered essential by the task group. Both methods utilized beef extract solutions to achieve desorption and recovery of viruses from representative soils: a fine sand soil, an organic muck soil, a sandy loam soil, and a clay loam soil. One of the two methods, Goyal, also used a secondary concentration of resulting soil eluants via low-pH organic flocculation to achieve a smaller final assay volume. Evaluation of the two methods was simultaneously performed in replicate by nine different laboratories. Each of the produced samples was divided into portions, and these were respectively subjected to quantitative viral plaque assay by both the individual, termed independent, laboratory which had done the soil processing and a single common reference laboratory, using a single cell line and passage level. The Berg method seemed to produce slightly higher virus recovery values; however, the differences in virus assay titers for samples produced by the two methods were not statistically significant (P less than or equal to 0.05) for any one of the four soils. Despite this lack of a method effect, there was a statistically significant laboratory effect exhibited by assay titers from the independent versus reference laboratories for two of the soils, sandy loam and clay loam.

Heat resistance of Listeria monocytogenes in naturally infected and inoculated cow's milk.

A two phase slug flow tubular heat exchanger was used for the thermal inactivation of Listeria monocytogenes in natural infected milk from seven cows. L. monocytogenes serotype 4b inoculated UHT sterilized milk was monitored in a parallel study. The two milks were heated at 71.1 degrees C for holding times of 2, 4, 10, 15, 20 and 30 s. Milk was assayed for survivors immediately after heat treatment and weekly thereafter for 4 weeks during storage at 4 degrees C. No survivors were detected in the naturally infected milk at any of the holding times. Survivors were found at 2 and 4 s in the inoculated UHT milk with initial titres of 8 x 10(2) to 7.1 x 10(3) c.f.u./ml, only after storage at 4 degrees C for 28 days. No survivors were detected for 10 through 30 s holding times.

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.

The future of public health: a survey of the states.

A survey of state health agencies was conducted to determine agreement and disagreement of state health officers with the recommendations contained in The Future of Public Health issued by the Institute of Medicine in 1988. The survey also measured the extent to which the IOM recommendations were judged currently in place or in the process of being implemented in the states. The survey showed almost unanimous consensus among the nation's state health officers for the vast majority of the recommendations. There was less consensus concerning the appropriateness of locating substance abuse, Medicaid, mental health, and regulation of health professions within state departments of health. However, a significant proportion of health officers favored a health agency location for these responsibilities (72%, 52%, 48%, and 38% respectively).

Thermal inactivation of Listeria monocytogenes within bovine milk phagocytes.

Thermal resistance of intracellular and freely suspended Listeria monocytogenes that was associated with a milkborne outbreak of listeriosis was studied by using the sealed tube and slug flow heat exchanger methods. Test temperatures for the former method were 57.8, 62.8, 66.1, and 68.9 degrees C (136, 145, 151, and 156 degrees F, respectively); whereas those for the latter method were 66.1, 68.9, 71.7, and 74.4 degrees C (151, 156, 161, and 166 degrees F, respectively). The heating menstruum was sterile, whole milk. The intracellular inoculum was generated from an in vitro phagocytosis reaction by using endotoxin-induced bovine milk phagocytes. The phagocyte population consisted of 88% neutrophils, 8% macrophages, and 4% lymphocytes. Neutrophils harbored the majority of intracellular L. monocytogenes. The mean level of infectivity in the phagocyte population was 43%, and there were 26.1 +/- 19.3 bacteria per cell (10(4) viable cells per ml of test milk). Initial bacterial counts for the freely suspended and intracellular experiments (the latter was based on a sonically disrupted sample) were 10(6) L. monocytogenes cells per ml. Heat-stressed bacteria were recovered by direct plating in parallel with recovery from an enrichment broth; both methods gave comparable results. The predicted D62.8 degrees C (145 degrees F) value for intracellular sealed tube studies was 53.8 s (ZD = 5.6 degrees C [10.0 degrees F]), indicating a safe 33.4 D margin of inactivation for vat pasteurization (62.8 degrees C for 30 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal resistance of intracellular Listeria monocytogenes cells suspended in raw bovine milk.

The thermal resistance of Listeria monocytogenes associated with a milk-borne outbreak of listeriosis was determined in parallel experiments by using freely suspended bacteria and bacteria internalized by phagocytes. The latter inoculum was generated by an in vitro phagocytosis reaction with immune-antigen-elicited murine peritoneal phagocytes. The heat suspension medium was raw whole bovine milk. Both suspensions were heated at temperatures ranging from 52.2 to 71.7 degrees C for various periods of time. Mean D values for each temperature and condition of heated suspension revealed no significant differences. The extrapolated D71.7 degrees C (161 degrees F) value for bacteria internalized by phagocytes was 1.9 s. Combined tube and slug-flow heat exchanger results yielded an estimated D71.7 degrees C value of 1.6 s for freely suspended bacteria. The intracellular position did not protect L. monocytogenes from thermal inactivation.

Cigarette smoking behavior among Rhode Island physicians, 1963-83.

A survey of practicing physicians in Rhode Island revealed a cigarette smoking rate of only 8.3 per cent in 1983. This represents a continuation of the consistent decrease seen in the percentage of physician smokers in each such survey since 1963. Under age 30, the rate was only 4.5 per cent. An exponential model suggests that the overall rate for Rhode Island physicians will be below 3 per cent by the year 2000.