Salmonella and Staphylococcus aureus Contamination in Liquid Whole Eggs

Abstract

One hundred and ninety-six samples of unpasteurized and pasteurized whole eggs from 4 egg processing plants in the Kanto (C and D plants), Kansai (B plant), and Chubu (A plant) districts were bacterioligically examined to investigate Salmonella and Staphylococcus aureus contamination and to observe the relationship between these bacteria and total bacteria or fecal indicators. The Following results were obtained.1) The degree of contamination of eggs with Salmonella and Staphyl. aureus varied from plant to plant. In the unpasteurized eggs of A plant, the occurrence ratio of Salmonella was 11.7% (max. 24/g), and that of Staphyl. aureus was 50.0% (max. 600/g). In B plant the former was 84.1% (max. 540/g) and the latter was 72.2% (max. 400/g), and in C plant the occurrence ratios were 15.8% (max. 24/g) and 31.6% (max. 140/g), respectively. In the unpasteurized eggs of D plant, neither Salmonella nor Staphyl. aureus was detected.2) The high occurrence ratio (84.1%) of Salmonella in the unpasteurized eggs from B plant seemed to be caused by prolonged storage of eggs, dirty eggs, and broken or cracked eggs, which were used without washing or disinfecting. In addition, complex contamination due to secondary contamination from the egg-breaking process and extension of contamination in the mixing tank was suspected.3) The bacteriological status of unpasteurized eggs was greatly improved by pasteurization.4) Total bacterial count and coliform count were related to the Salmonella occurrence ratio to some extent, and a high occurrence ratio was observed in the samples with total bacteria of more than 104/g or with a coliform count of more than 103/g. This relationship was observed for the total samples, but it did not seem to hold in the individual results for each plant. In the case of Staphyl. aureus, the relationship was less marked than in the case of Salmonella.5) Coagulase types of Staphyl. aureus from unpasteurized eggs were II (56.4%), III (12.8%), VII (19.2%), and VIII (6.4%).6) Salmonella detected in unpasteurized eggs were classified into K group (71.4%), C1 (26.4%), C2 (1.4%), and E4 (0.7%) with commercial 0 sera. These Salmonella were identified as S. braenderup, S. senftenberg, S. thompson, S. infantis, S. mbandaka, and S. cerro, S. cerro was detected most frequently among the above Salmonella.