The properties and classification of the predominant bacteria in rotten eggs

Thermal and biological treatments to control psychrotrophic pathogens

Over the past decade, advances in egg processing technologies have permitted commercial production of ultrapasteurized liquid whole egg (LWE) products with a shelf-life of greater than 10 wk at 4 C. The inactivation and control of psychrotrophic pathogens such as Listeria monocytogenes and Aeromonas hydrophila in extended shelf-life LWE and conventionally pasteurized egg products is an ongoing food safety concern. This manuscript reports on the common features of these two psychrotrophic pathogens, their incidence in egg products, and their survival, growth potential, and heat resistance in liquid egg. Furthermore, this manuscript reports in detail on the results of two specific studies conducted in our laboratory whose objectives were: 1) to determine the heat resistance (D-values) of A. hydrophila in LWE using a low-volume immersed sealed glass capillary tube (ISCT) procedure; 2) to assess the impact of methodology (i.e., ISCT procedure vs a conventional capped test tube procedure) on the apparent thermal resistance of A. hydrophila; and 3) to report on the use of the bacteriocin nisin to restrict the survival of L. monocytogenes in ultrapasteurized LWE stored at refrigeration temperatures.

Growth of Salmonella enteritidis in artificially contaminated hens' shell eggs

The effect of some factors on the growth of Salmonella enteritidis phage type 4 in artificially contaminated shell eggs was investigated. Salmonella enteritidis was found to be resistant to the antimicrobial properties of the albumen. Growth occurred on storage at 25 degrees C but not at 4 or 10 degrees C. The rate and extent of infection was influenced by the size of inoculum, the site of contamination relative to yolk movement, and the presence of iron in the inoculum.

Classification of bacteria from commercial egg washers and washed and unwashed eggs

A total of 432 bacterial isolates from washed and unwashed eggs, egg-washer surfaces, and washwaters from five egg-grading plants in Maryland and southeastern Pennsylvania were classified. Counts on equipment surfaces showed considerable variation from plant to plant, reflecting care used in cleaning. Unwashed eggs had a higher percentage of gram-positive cocci (71%), and isolates included Streptococcus faecalis, Aerococcus, and Escherichia coli, which were not isolated from equipment surfaces and washwaters. Equipment surfaces had a higher proportion of actinomycetes than unwashed eggs, and predominant gram-negative rods were Alcaligenes and Moraxella, which were not found on unwashed eggs. Flavobacterium and Alcaligenes have been implicated in shell egg rots, Staphylococcus aureus has been implicated in food poisoning, and organisms resembling micrococci and actinomycetes have been found in broken-out egg products.