C28 | Parallel microbiological analysis of muscle samples from emergency slaughter in South Tyrol: preliminary data

Purpose. Ministerial Note DGSAN 0013895/2022 introduced some changes regarding the management of special emergency slaughter (MSU), including the obligation to subject all carcasses to microbiological analysis aimed at detecting specific contamination of deep muscle tissue. In particular, testing for three pathogens using methods accredited according to ISO17025 is required: balancing of sulphite-reducing anaerobes and E. coli ß-glucuronidase positive and testing for Salmonella spp. In addition, at least 10% of carcasses must be tested for substances with antimicrobial activity. Prior to this Note, MSU checks included non-accredited bacteriological culture tests carried out using internal laboratory methods (and an analysis for the detection of inhibitors), also aimed at ensuring compliance with EU Regulation 627/2019, which excludes from human consumption meat obtained from animals affected by a generalised disease, such as septicaemia or pyemia. The aim of this study was to verify the possible correspondence between the positive results detected by the analyses required by the Note and those found using the bacteriological methods commonly used in Official Laboratories. To this end, double sampling was carried out on carcasses of animals slaughtered as a matter of urgency, analysing the samples using both methods. Methods. Over a period of 6 months, 46 muscle samples were taken from animals for which MSU was requested at various slaughterhouses in South Tyrol. For each sample, a double analytical protocol was performed: balance of sulphite-reducing anaerobic bacteria (CSR) and E. coli ß-glucuronidase positive and Salmonella spp. according to accredited methods (MSU method) and a culture test on a plate and/or in enrichment broth for the detection of pathogenic or indicator microorganisms, without predefined targets (internal culture bacteriological method - BCI). Results. Out of 46 samples analysed, the “MSU method” showed 7 positive results (15.2%) for at least one of the target microorganisms (CSR, E. coli). Using the BCI method, 13 samples (28.3%) tested positive for various microorganisms, including coagulase-negative staphylococci, Staphylococcus chromogenes, and Enterococcus faecalis. Only 2 samples (4.3%) tested positive using both methods. Conclusions. From the preliminary analysis, it can be inferred that both methods have pros and cons. Although the MSU method guarantees the use of accredited techniques and provides quantitative data (with a detection limit of 10 CFU/g), it does not seem to be sufficient to identify all pathogens potentially responsible for unsuitability for human consumption, especially those responsible for/involved in septicaemia and paemia. The BCI method, on the other hand, allows for a broader and more sensitive detection of different microbial species, even in the presence of relatively low bacterial loads. Given that the Note clarifies that, in case of doubt, the Official Veterinarian may request the search for other microorganisms, it can be considered that the MSU method is sufficient in cases of timely MSUs performed on animals without complications such as open fractures, visually contaminated wounds and previous pathologies. On the contrary, in cases of MSU in animals at risk, it may be advisable to supplement the investigation with a BCI test in order to identify any causative agents of systemic infections.