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

Abstract

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.