Study of the population dynamics of Listeria monocytogenes and Pseudomonas fluorescens in buffalo mozzarella by means of challenge testing

Campania’s buffalo mozzarella is a greatly appreciated cheese in Italy and worldwide. From a microbiological standpoint, it is a highly perishable food and potentially at risk of contamination by pathogens such as Listeria monocytogenes ( L. monocytogenes ). The present paper reports the results of a challenge test carried out to assess the population dynamics of L. monocytogenes , alone and in presence of Pseudomonas fluorescens ( P. fluorescens ), in buffalo mozzarella. For this purpose buffalo mozzarella samples were contaminated with L. monocytogenes alone or combined with P. fluorescens . In samples where L. monocytogenes was inoculated alone, the bacterial load remained unchanged. On the contrary, in samples contaminated with L. monocytogenes and P. fluorescens , the growth of L. monocytogenes increased.