A total of 530 strains of Staphylococcus aureus were isolated from the defeathering machinery of a chicken processing plant and from neck skin samples of carcasses at different stages of processing in two visits 4 weeks apart. Eleven different plasmid profiles were detected in the isolates, eight being common to both visits. The plasmid profiles of the strains forming the majority of the population on the freshly slaughtered birds were rarely present in the strains isolated from the pluckers (except at the entry to the first plucker) and were present in only a small proportion of the strains isolated from carcasses after plucking. However, the profiles from the strains isolated from the pluckers on both visits were different from those forming the majority of the population on the incoming birds but formed the major part of the carcass flora after plucking, suggesting that such strains were endemic. These strains were found as a small proportion of the isolates made from the incoming birds, suggesting that this was the route by which the endemic strains were introduced into the plant. Such endemic strains exhibited a clumping growth, even in liquid shake culture, which may have made it easier for them to become established on the pluckers and to resist cleaning and disinfection. This clumping phenotype was correlated with the presence of a 7.5-megadalton plasmid.

Strains of Staphylococcus aureus can become endemic within poultry processing plants and increase the contamination of the poultry carcasses by up to one thousand fold, leading to their rejection for use in further processed products. The main contamination occurs on the rubber fingers of the defeathering machinery, where the endemic strains, which grow in clumps and are eight times more resistant to hypochlorite than nonendemic strains, resist cleaning and disinfection by producing a glucosamine-rich extracellular polymer, which has been characterised by electron microscopy and chemical tests. Use of plasmid profiling has shown that the endemic, polymer-producing strains are present at about 4% of the S. aureus population on the live birds but form the majority of the strains isolated from the exit of the first plucker and, due to their extremely adhesive nature, contaminate the carcasses as they pass through the pluckers so that these strains predominate in the S. áureus flora of the final product.

A rabbit polyclonal antibody-linked probe was developed which detected 76% of 800 food isolates of the spoilage bacterium Brochothrix thermosphacta when cells were bound to nitrocellulose. In slide cross-reaction tests all six environmental isolates tested were stained but the type strain was not. The antibody did not cross-react with Listeria grayi, L. monocytogenes, Lactobacillus plantarum, Lactococcus lactis, Streptococcus mutans, Bacillus cereus or B. subtilis. The antibody-linked probe detected Br. thermosphacta in thin sections of British fresh sausage when the viable count was greater than 10(6) g-1. Cells were detected mainly within 1 or 2 mm of the surface on the loose starchy material. They were not detected within muscle blocks or in the centre of the sausage. Such results suggest that growth of this organism occurs close to the surface of the sausage.