Transmission of viruses through foods

16 Methods for Detecting Microbial Pathogens in Food and Water

Newly developed methods for the detection of bacteria and viruses have provided microbiologists with the means to rapidly identify and monitor specific microorganisms in food and water. Traditional methods of testing involve culture techniques to increase the numbers of the organism to a detectable level, followed by isolation and biochemical identification. This chapter focuses on the methodologies to detect pathogens and indicator organisms; however, the methods described are applicable to most bacteria. As detection and isolation methods have improved, a growing number of pathogens have been identified as important food- and waterborne pathogens. This chapter describes the use of nucleic acid and antibody probes that have the potential to circumvent the need to culture the organism prior to identification. Nucleic acid probes have become a valuable diagnostic reagent in the identification of human and animal pathogens and have made possible the identification of viruses and bacteria that are difficult, if not impossible, to cultivate. DNA probes have also proved to be a useful tool for identifying and monitoring the organisms in food and the environment.

Microbiological safety of irradiated foods

This paper attempts to summarize relevant information on microbiological safety of irradiated foods in the light of previous reports of expert committees and current literature references. After a brief survey of the relative radiation resistance of food-borne microorganisms, the importance of microbial load for dose requirement, and the role of post-irradiation conditions, it addresses the following questions: Could selective changes in the microflora, caused by non-sterilizing radiation doses, make known pathogens more likely to occur, or bring into prominence unfamiliar pathogens? Is it probable that 'mutational' (including adaptive) changes might make pathogens more virulent, more harmful, or more difficult to recognize, and could new pathogens arise in this way? Is it possible that development of radiation-resistant strains might render the antimicrobial irradiation processes ineffective? The present survey of relevant scientific evidence related to these questions reaffirms the basic conclusion of earlier reviews, that microbiological safety of irradiated food is fully comparable with that of foods preserved by other acceptable preservation methods. Similar to other preservation processes, gains in microbiological or keeping quality attained by food irradiation can be and must be safeguarded by proper control in the food irradiation facilities and by proper care of the product before and after processing.

IN VITRO EFFECTS OF MONOLAURIN COMPOUNDS ON ENVELOPED RNA AND DNA VIRUSES

Monolaurin alone and monolaurin with tert-butylhydroxyanisole (BHA), methylparaben, or sorbic acid were tested for in vitro virucidal activity against 14 human RNA and DNA enveloped viruses in cell culture. At concentrations of 1% additive in the reaction mixture for 1 h at 23°C, all viruses were reduced in infectivity by >99.9%. Monolaurin with BHA was the most effective virucidal agent in that it removed all measurable infectivity from all of the viruses tested. The compounds acted similarly on all the viruses and reduced infectivity by disintegrating the virus envelope.

Residual viruses in pork products

Partly cooked canned hams and dried pepperoni and salami sausages were prepared from the carcasses of pigs infected with African swine fever virus and pigs infected with hog cholera virus. Virus was not recovered from the partly cooked canned hams; however, virus was recovered in the hams before heating in both instances. Both African swine fever virus and hog cholera virus were recovered from the dried salami and pepperoni sausages, but not after the required curing period.

Survival of foot-and-mouth disease virus in cheese

Persistence of foot-and-mouth disease virus during the manufacture of Cheddar, Mozzarella, Camembert cheese prepared from milk of cows experimentally infected with the virus was studied. Cheese samples were made on a laboratory scale with commercial lactic acid starter cultures and the microbial protease MARZYME as a coagulant. Milk was heated at different temperatures for different intervals before it was made into cheese. Food-and-mouth disease virus survived the acidic conditions of Cheddar and Camembert cheese processing but not that of Mozzarella. Foot-and-mouth disease virus survived processing but not curing for 30 days in Cheddar cheese preparaed from heated milk. However, the virus survived curing for 60 days but not for 120 days in cheese (pH 5) prepared from unheated milk. Foot-and-mouth disease virus survived in Camembert cheese (pH 5) for 21 days at 2 C but not for 35 days.