Comparison of in vitro and in situ antagonism assays as tools for the selection of bio-preservative lactic acid bacteria (LAB) in poultry meat

Abstract

The study compared 3 antagonism assays, In vitro in broth culture (TSBYE) and In situ in sterile and raw chicken meat, as tools for LABs selection to bio-preserve poultry against Pseudomonas spoilage. To do this, 4 LABs (approximate to 8 log CFU/mL or cm(2)) were inoculated with one P. fragi (approximate to 3 log CFU/mL or cm(2)) on TSBYE or irradiated poultry, or alone on raw chicken meat (Pseudomonas spp. approximate to 3 log CFU/cm(2)). Treatments were incubated at 8 degrees C along time (4-6 days). Bacterial counts were performed on selective agar. In vitro assay was technically easy to perform, but antagonistic LABs abilities observed, were not always consistent with those evidenced In situ. Assay on irradiated meat demonstrated a good predictive potential for LABs selection, but not to discharge them. The main disadvantage of both assays was that sensitivity of P. fragi not necessarily represented the sensitivity shown by Pseudomonas spp. within poultry microbiota. In contrast, trials on raw poultry showed the real bio-preservative capacity of LAB against Pseudomonas spp., but variability within replicates was high. In conclusion, assay on fresh poultry must always be performed to select bio-preservative LABS, while other experiments are useful for reducing the number of LABs to be assayed.