Evaluation of the value of using bovine kidneys as an additional matrix in a bacteriological examination of carcass fitness for human consumption

In Denmark, the spleen and the muscle act as matrices in a bacteriological examination that may be used as support for judgement of carcass fitness for human consumption when a systemic infection is suspected. We investigated whether use of the kidney as an additional matrix would provide relevant information when kidney petechiae are detected at post-mortem inspection. A total of 66 bovine kidneys, divided into four groups (petechiae +/- and endocarditis +/−), were subjected to bacteriological examination. The bacteria detected were identified with MALDI-TOF-MS analysis. The results were interpreted in accordance with the official guidelines of Denmark. Kidneys that produced bacteria colonies on culture were found in all four groups. The most detected bacteria were staphylococci and micrococci. Several kinds of potentially pathogenic bacteria were detected – most of them only rarely known as causing foodborne disease in humans. The agreement between results of using kidney and the results of the official protocol was low (40%). In conclusion, the kidney is not a suitable matrix due to a non-negligible proportion of kidneys that harboured bacteria in all four bovine groups. Kidney petechiae alone do not render the carcass as unfit for human consumption, whereas carcasses with endocarditis additional to kidney petechiae should be sent to bacteriological examination.