Investigation of Salmonella contamination and disinfection in farm egg-packing plants

Abstract

Aims: As part of a field‐based study of the distribution and persistence of Salmonella infection on commercial egg‐laying farms, sampling was carried out on one or more occasions in egg‐packing areas of 12 farms infected with Salm. Enteritidis. Methods and Results: Salmonellas were isolated by cultural methods. Contamination was common, with Salmonella being found in 23·1% of floor swab samples, 30·8% of grading tables, 23·1% of conveyor belts or rollers and 23·8% of candlers. Four farms were sampled after cleaning and disinfection of packing plants had been carried out on the previous day, and residual contamination was found on 6·9% of samples from grading tables, 16·0% holding/sorting tables, 12·6% of conveyors or rollers, 16·7% of vacuum egg lifters, 21·4% of floor surfaces and 5·0% of egg store floor surfaces. Sterilized eggs passed through five farm packing plants showed a contamination rate of at least 16/5948 (0·3%) egg passages. Conclusions: It is apparent that contamination in egg‐packing plants may be a significant contributory factor to external contamination of shell eggs, and improved methods of cleaning and disinfecting egg‐handling equipment are required. Significance and Impact of the Study: The presence of Salmonella contamination in egg‐packing plants presents a contamination hazard for eggs from Salmonella‐free flocks. Samples from equipment in the packing plant could also be used for screening for detection of Salmonella in the throughout of the plant.