Methods and results of testing "low acid" glycol methacrylate (GMA) for light microscopic cytochemistry.

Four samples of "low acid" and one sample of "technical grade" glycol methacrylate from three commercial sources were compared for their suitability in light microscopic cytochemistry. The "technical grade" was found unacceptable, but the four "low acid" products were found to be essentially the same in terms of water and ethanol miscibility, pH, polymerization time, sectioning qualities, and lack of background staining with methylene blue.

An example of the stages in the development of a predictive mathematical model for microbial growth: the effects of NaCl, pH and temperature on the growth of Aeromonas hydrophila.

The stages involved in developing a predictive model are illustrated using data describing the effects of temperature (3-20 degrees C), NaCl concentration (0.5-4.5% w/v) and pH (4.6-7.0) on the aerobic growth of Aeromonas hydrophila (cocktail of 6 strains). Optical density measurements using micro-titre plates were used as an initial screen, to determine the appropriate sampling times for viable counts to be made and to determine the approximate boundaries for growth. Growth curves were generated from viable counts and fitted using a modified Gompertz equation. Quadratic response surface equations were fitted to the log of lag and generation times, in response to the variables of temperature, NaCl and pH (in terms of hydrogen ion concentration). The effects of various combinations of these controlling factors are described. Comparisons between predicted growth rates and lag times from our response surface equations and other models for growth of A. hydrophila, developed with viable count data and optical density measurements, are made, together with comparisons with data from the literature on the growth of this bacterium in foods.

Modelling the thermal inactivation of Salmonella typhimurium using bioluminescence data.

Inactivation of micro-organisms by heat is a traditional food processing technique used to reduce or eliminate the microbial load in foods thus preventing bacterial associated disease and food spoilage. Models of thermal death kinetics are routinely used to predict the amount of heat required but such models are limited by the acquisition of accurate thermal death data for bacteria in situ and in complex microflora. In vivo bioluminescence from lux recombinant bacteria is an important alternative to traditional plate counts for examining bacterial injury and stress but the thermal instability of luciferase has appeared to preclude its application in heating studies. We have developed a procedure which overcomes the thermal instability of luciferase and demonstrate that computer generated models of the thermal injury of Salmonella typhimurium show equivalence between bioluminescence and viable count data.

Application of a log-logistic model to describe the survival of Yersinia enterocolitica at sub-optimal pH and temperature.

A log-logistic model previously used to describe the thermal inactivation of microorganisms has been applied to predict accurately the survival of Yersinia enterocolitica under conditions of sub-optimal temperatures (0-23 degrees C) and growth inhibitory pH values for a number of different acidulants. Predictions from the model were also compared to observed survival times of Y. enterocolitica in mayonnaise and were found to be in excellent agreement. However in yoghurt the model overestimated survival of this organism at both 20 and 4 degrees C but would 'fail safe' if used for predictive purposes. The discrepancy in yoghurt is discussed.

Modelling the growth, survival and death of microorganisms in foods: the UK food micromodel approach.

Techniques for the development of mathematical models in the area of predictive microbiology have greatly improved recently, allowing better and more accurate descriptions of microbial responses to particular environmental conditions, thus enabling predictions of those responses to be made with greater confidence. Recognising the potential value of applying these techniques in the food industry, the Ministry of Agriculture, Fisheries and Food (MAFF) initiated a nationally coordinated five-year programme of research into the growth and survival of microorganisms in foods, with the aim of developing a computerised Predictive Microbiology Database in the UK. This initiative has resulted in the systematic generation of data, through protocols which ensure consistency of methodology, so that data in the database are truly comparable and compatible, and lead to reliable predictive models. The approaches taken by scientists involved in this programme are described and the various stages in the development of mathematical models summarized. It is hoped that this initiative and others being developed in the USA, Australia, Canada and other countries, will encourage a more integrated approach to food safety which will influence all stages of food production and, eventually, result in the development of an International Predictive Microbiology Database.

Physiological and behavioral responses of stonefly nymphs to enhanced limestone treatment of acid mine drainage.

A new acid mine drainage (AMD) treatment system uses pulsed, fluidized beds of limestone, and carbon dioxide pretreatment of influent AMD, to enhance limestone neutralization of AMD. We conducted laboratory studies to evaluate the behavior and physiology of larval stoneflies (Pteronarcys proteus, Plecoptera) exposed to effluents produced by the treatment system. Survival, sodium balance, drift, and feeding responses by P. proteus to treated and untreated AMD were examined. P. proteus nymphs exhibited significant losses of whole body sodium in exposures to untreated AMD. Nymphs exposed to treated effluents experienced no loss of whole-body sodium. Nymphs exposed to untreated AMD showed elevated drift rates and depressed feeding rates relative to those of nymphs exposed to treated AMD, and to AMD-free controls. No significant differences in feeding or drift behavior occurred between nymphs exposed to treated effluents and those exposed to AMD-free controls. The treatment system, with and without CO2 pretreatment, provided water that was not toxic to the test animals, and that allowed normal behavioral and physiological function.

Estimating the survival of Clostridium botulinum spores during heat treatments.

A recently published study of the inactivation of Clostridium botulinum spores at various temperatures in the range of 101 to 121 degrees C and neutral pH revealed that their semilogarithmic survival curves all had considerable upward concavity. This finding indicated that heat inactivation of the spores under these conditions did not follow a first-order kinetics and that meaningful D values could not be calculated. The individual survival curves could be described by the cumulative form of the Weibull distribution, i.e., by log S = -b(T)t(n(T)), where S is the survival ratio and b(T) and n(T) are temperature-dependent coefficients. The fact that at all temperatures in the above range n(T) was smaller than 1 suggested that as time increases sensitive members of the population parish and survivors with increasing resistance remain. If damage accumulation is not a main factor, and the inactivation is path independent, then survival curves under monotonously increasing temperature can be constructed using a relatively simple model, which can be used to calculate the spores' survival in a limiting case. This is demonstrated with computer-simulated heating curves and the experimental constants of the C. botulinum spores, setting the number of decades reduction to 8, 10, and 12 (the current criterion for commercial sterility).

Assessment of control measures to achieve a food safety objective of less than 100 CFU of Listeria monocytogenes per gram at the point of consumption for fresh precut iceberg lettuce.

The important new concept of the food safety objective (FSO) offers a strategy to translate public health risk into a definable goal such as a specified maximum frequency or concentration of a hazardous agent in a food at the time of consumption that is deemed to provide an appropriate level of health protection. For the foodborne pathogen Listeria monocytogenes, there is a proposed FSO of < 100 CFU/g in ready-to-eat (RTE) products at the time of consumption. Fresh precut iceberg lettuce is one of these RTE products. In this study, we worked with a commercial manufacturer to evaluate the effectiveness of two antimicrobial washing agents (sodium hypochlorite and a mixture of hydrogen peroxide and peroxyacetic acid) against L. monocytogenes under simulated fresh precut washing conditions and evaluated the growth potential of this pathogen on lettuce packaged in a gas-permeable film and stored at 4 or 8 degrees C for 14 days. We used the results of this experiment to demonstrate how the commercial manufacturer could meet the FSO for L. monocytogenes in fresh precut lettuce through the application of performance, process, and microbiological criteria.

The boundary for growth of Zygosaccharomyces bailii in acidified products described by models for time to growth and probability of growth.

Models to predict days to growth and probability of growth of Zygosaccharomyces bailii in high-acid foods were developed, and the equations are presented here. The models were constructed from measurements of growth of Z. bailii using automated turbidimetry over a 29-day period at various pH, NaCl, fructose, and acetic acid levels. Statistical analyses were carried out using Statistical Analysis Systems LIFEREG procedures, and the data were fitted to log-logistic models. Model 1 predicts days to growth based on two factors, combined molar concentration of salt plus sugar and undissociated acetic acid. This model allows a growth/no-growth boundary to be visualized. The boundary is comparable with that established by G. Tuynenburg Muys (Process Biochem. 6:25-28, 1971), which still forms the basis of industry assumptions about the stability of acidic foods. Model 2 predicts days to growth based on the four independent factors of salt, sugar, acetic acid, and pH levels and is, therefore, much more useful for product development. Validation data derived from challenge studies in retail products from the U.S. market are presented for Model 2, showing that the model gives reliable, fail-safe predictions and is suitable for use in predicting growth responses of Z. bailii in high-acid foods. Model 3 predicts probability of growth of Z. bailii in 29 days. This model is most useful for spoilage risk assessment. All three models showed good agreement between predictions and observed values for the underlying data.

Modeling the growth boundary of Staphylococcus aureus for risk assessment purposes.

Knowing the precise boundary for growth of Staphylococcus aureus is critical for food safety risk assessment, especially in the formulation of safe, shelf-stable foods with intermediate relative humidity (RH) values. To date, most studies and resulting models have led to the presumption that S. aureus is osmotolerant. However, most studies and resulting models have focused on growth kinetics using NaCl as the humectant. In this study, glycerol was used to investigate the effects of a glass-forming nonionic humectant to avoid specific metabolic aspects of membrane ion transport. The experiments were designed to produce a growth boundary model as a tool for risk assessment. The statistical effects and interactions of RH (84 to 95% adjusted by glycerol), initial pH (4.5 to 7.0 adjusted by HC1), and potassium sorbate (0, 500, or 1,000 ppm) or calcium propionate (0, 500, or 1,000 ppm) on the aerobic growth of a five-strain S. aureus cocktail in brain heart infusion broth were explored. Inoculated broths were distributed into microtiter plates and incubated at 37 degrees C over appropriate saturated salt slurries to maintain RH. Growth was monitored by turbidity during a 24-week period. Toxin production was explored by enterotoxin assay. The 1,280 generated data points were analyzed by SAS LIFEREG procedures, which showed all studied parameters significantly affected the growth responses of S. aureus with interactions between RH and pH. The resulting growth/no growth boundary is presented.

Starting a level I fieldwork program.

In response to the occupational therapy students' need for meaningful early experiences in the clinical setting, an educational strategy was devised for marketing and implementing an occupational therapy clinical program for hospitalized psychiatric patients, which involves students in all aspects of its implementation. The pilot program was started at the Veterans Administration Medical Center in West Haven, CT, on a long-term psychiatric unit. This unit's previously limited occupational therapy services were expanded by the student program. The program has also extended into an acute psychiatric unit and a psychiatric day treatment program (which previously had not provided occupational therapy services). Sixteen to thirty Quinnipiac College junior occupational therapy students (per semester) were involved in assessment, treatment planning, program planning, administration, and documentation and evaluation under the close supervision of the occupational therapy educator. Students, patients, and administrators were surveyed, and the results were reported. For the first class of participants, the two significant learning outcomes were an improvement in attitude toward patients and an increased level of comfort in working with them.

Time mastery in business and occupational therapy.

This article compares the results of an occupational therapy focused ethnographic study of time management with current concepts of time management in the business field. Researchers conducted in-depth interviews with six married working mothers to explore issues of time management. Qualitative analysis was used to identify four essential components, which are re-labeled Time Mastery: (1) Routines, (2) Instrumental and Social strategies, (3) Motivation, and (4) Cognitive Components. This occupational therapy model, is discussed within the context of Stephen Covey's 'four generations' of time management in the world of business: (1) Notes and checklists, (2) Calendars and appointment books, (3) Prioritization and goal-setting and (4) Enhancing relationships and accomplishing results. Possible applications of the Time Mastery Model in work rehabilitation are suggested.

Level and form of psychopathology and the structure of group therapy.

Drawing upon concepts derived from ego psychological and object relations psychoanalytic theories of individual development and from a depth group psychology, the present empirical study, a naturalistic field investigation, explored hypothesized relationships between aspects of patients' psychological boundaries and structural features of inpatient therapy groups. More specifically, patients were assessed in terms of their level (i.e., psychotic vs. borderline organization) and form (i.e., anaclitic vs. introjective) of psychopathology. Their perceptions of themselves and of their therapy groups were measured following participation in two kinds of small group treatment designed to differ in terms of degree of internal structuring. Findings, generally supporting the hypotheses, showed the anaclitic borderline patients, in particular, to be most sensitive to structural variations and most adversely affected by an impersonal and highly structured treatment climate. Theoretical and practical implications of these findings were discussed.

Food safety objective approach for controlling Clostridium botulinum growth and toxin production in commercially sterile foods.

As existing technologies are refined and novel microbial inactivation technologies are developed, there is a growing need for a metric that can be used to judge equivalent levels of hazard control stringency to ensure food safety of commercially sterile foods. A food safety objective (FSO) is an output-oriented metric that designates the maximum level of a hazard (e.g., the pathogenic microorganism or toxin) tolerated in a food at the end of the food supply chain at the moment of consumption without specifying by which measures the hazard level is controlled. Using a risk-based approach, when the total outcome of controlling initial levels (H(0)), reducing levels (ΣR), and preventing an increase in levels (ΣI) is less than or equal to the target FSO, the product is considered safe. A cross-disciplinary international consortium of specialists from industry, academia, and government was organized with the objective of developing a document to illustrate the FSO approach for controlling Clostridium botulinum toxin in commercially sterile foods. This article outlines the general principles of an FSO risk management framework for controlling C. botulinum growth and toxin production in commercially sterile foods. Topics include historical approaches to establishing commercial sterility; a perspective on the establishment of an appropriate target FSO; a discussion of control of initial levels, reduction of levels, and prevention of an increase in levels of the hazard; and deterministic and stochastic examples that illustrate the impact that various control measure combinations have on the safety of well-established commercially sterile products and the ways in which variability all levels of control can heavily influence estimates in the FSO risk management framework. This risk-based framework should encourage development of innovative technologies that result in microbial safety levels equivalent to those achieved with traditional processing methods.

Trends in technology, trade and consumption likely to impact on microbial food safety.

Current and potential future trends in technology, consumption and trade of food that may impact on food-borne disease are analysed and the key driving factors identified focusing on the European Union and, to a lesser extent, accounting for the United States and global issues. Understanding of factors is developed using system-based methods and their impact is discussed in relation to current events and predictions of future trends. These factors come from a wide range of spheres relevant to food and include political, economic, social, technological, regulatory and environmental drivers. The degree of certainty in assessing the impact of important driving factors is considered in relation to food-borne disease. The most important factors driving an increase in the burden of food-borne disease in the next few decades were found to be the anticipated doubling of the global demand for food and of the international trade in food next to a significantly increased consumption of certain high-value food commodities such as meat and poultry and fresh produce. A less important factor potentially increasing the food-borne disease burden would be the increased demand for convenience foods. Factors that may contribute to a reduction in the food-borne disease burden were identified as the ability of governments around the world to take effective regulatory measures as well as the development and use of new food safety technologies and detection methods. The most important factor in reducing the burden of food-borne disease was identified as our ability to first detect and investigate a food safety issue and then to develop effective control measures. Given the global scale of impact on food safety that current and potentially future trends have, either by potentially increasing or decreasing the food-borne disease burden, it is concluded that a key role is fulfilled by intergovernmental organisations and by international standard setting bodies in coordinating the establishment and rolling-out of effective measures that, on balance, help ensure long-term consumer protection and fair international trade.

Solute-specific effects of osmotic stress on Staphylococcus aureus.

AIM: To determine if cell death from osmotic stress is because of lack of sufficient energy to maintain cell metabolism. Additionally, the solute-specific effect of five humectants on bacterial osmoregulation and cell survival was examined. METHODS AND RESULTS: Staphylococcus aureus was placed into 84% relative humidity (RH) broth (five humectants used individually). ATP, ADP and cell viability measurements were determined over time. The results indicate that ATP is not the limiting factor for cell survival under excessive osmotic stress. Although the same RH was achieved with various humectants, the rates of cell death varied greatly as did the sensitivities of the cell populations to osmotic stress. CONCLUSIONS: The results from this study provide strong evidence that mechanisms of osmotic inactivation depend on the solute. The molecular mobility of the system may be an important means to explain these differences. SIGNIFICANCE AND IMPACT OF THE STUDY: By bringing together an understanding of solute-specific effects, microbial physiology and genetics, the mechanisms of inactivation of micro-organisms by solute-specific osmotic stress may be elucidated, and this knowledge may then be exploited to ensure the production of high quality, safe foods.