Isolation and identification of tetracycline resistant lactic acid bacteria from pre-packed sliced meat products

In recent years, the food chain has been recognised as one of the main rout es for transmission of antibiotic resistant bacteria between the animal and human population. In this regard, the current study aimed to investigate i f tetracycline resistant (tet(R)) lactic acid bacteria (LAB) are present in ready-to-eat modified atmosphere packed (MAP) sliced meat products includi ng fermented dry sausage, cooked chicken breast meat and cooked ham. From p opulation graphs based on doubling tetracycline concentrations between 0 an d 256 mu g ml(-1), only fermented dry sausage was shown to contain a high-l evel tet(R) LAB population (5.10(1)-2,23.10(4) CFU/g), and this in four out of ten examined sausages. From these four positive sausages, a total of 10 0 strains were isolated on de Man, Rogosa and Sharpe-sorbic acid (MRS-S) ag ar without tetracycline (n = 45) and on MRS-S agar supplemented with a tetr acycline breakpoint concentration of 64 mu g ml(-1) (n = 55). Using resista nce histograms derived from the disc diffusion method, all these strains we re grouped as sensitive to rifampicin, erythromycin and ampicillin. All str ains from the tetracycline-containing MRS-S plates were resistant to tetrac ycline. Identification with whole-cell protein profiling revealed that the total strain set represented four different species: Pediococcus pentosaceu s, Lactobacillus plantarum, Lactobacillus sakei subsp. carnosus and Lactoba cillus curvatus. All species are commonly associated with fermented dry sau sage, either as starter culture or as natural contaminants. The latter thre e species were found to comprise all tetracycline resistant strains. To our knowledge, this is the first report providing evidence for the presence of tet(R) LAB in final ready-to-eat pre-packed fermented dry sausages.