Testing of methods for detecting Salmonella in the air of poultry processing plants.

The aim of the study is to compare the effectiveness of microbiological and PCR methods for detecting Salmonella in the air at various technological sites in four poultry processing plants and in one poultry farming enterprise. The objects of the study were air samples collected on two nutrient agars: non-selective PCA agar and selective XLD agar. Microbiological and PCR methods were used. Air samples collected on PCA agar were cultured in the BPW (enrichment stage). The culture liquid obtained in this way was used in the isolation of Salmonella by the microbiological and PCR methods. The identification of colonies typical of Salmonella isolated by the microbiological method was carried out by mass spectroscopy. The conducted study demonstrated the indisputable advantages of the PCR method (after enriching air samples in BPW) over the classic microbiological method without enrichment for monitoring Salmonella in the air of poultry processing plants. The PCR method has a higher sensitivity and detection speed, allowing the pathogen to be detected even at low concentrations in a sample. This is especially important for monitoring areas with a potentially low microbial load, such as the final washing of broiler chicken carcasses. The microbiological method without the enrichment stage showed low detection of Salmonella in the study of 66.6 % of air samples (false negative results were obtained) of poultry processing plants and 80 % of air samples taken at the poultry farming enterprise. Increasing its sensitivity to a level comparable to the PCR method is possible only with the introduction of an additional enrichment step in a liquid non-selective nutrient medium, for example, in buffered peptone water. Thus, for prompt and reliable control of Salmonella contamination in the air, it is advisable to use the PCR method as the most rapid and sensitive tool, ensuring high reliability of results even with minimal bacterial contamination, and the microbiological method with sample enrichment as a relatively slow but reliable “golden” standard method.