Summary: Wooden boards were obtained from 3 cheese-processing facilities and assessed for bacterial diversity. Samples were obtained from the surface and at depths of 0.2 and 0.9 cm. DNA was extracted and amplified by PCR and 16S rRNA analysis was performed to identify bacterial communities present on the surface and within the boards. Although there was board-to-board variation in both diversity and richness, all boards contained bacteria in the phyla Actinobacteria, Firmicutes, and Proteobacteria. In general, the boards selected for saltand cold-tolerant bacteria, with 7 operational taxonomic units (Staphylococcus, Brevibacterium, Psychrobacter, Brachybacterium, Jeotgalicoccus, Nocardiopsaceae, and Yaniella) forming a core microbiota found on all boards.

Listeria monocytogenes is a significant concern in cheese production. It has been assumed by some that wood surfaces pose a greater risk for pathogen contamination during cheese production. The goal of this study was to evaluate the effect of the microbiota obtained from wooden boards used in cheese ripening on the growth of Listeria monocytogenes. Bacterial communities from the surface of wooden boards obtained from cheese-ripening facilities were inoculated into tryptic soy broth (TSB) and incubated at 11 °C for 48 h. These communities (10⁸ CFU/mL stationary phase cells) were co-incubated with 10⁴–10⁵ CFU/mL L. monocytogenes 2203 at 11 °C for up to eight days. At various times, samples were removed, diluted in sterile saline and plated on modified Oxford agar. Bacterial communities from each of the five boards from three different facilities significantly inhibited growth of L. monocytogenes in vitro, compared to growth of L. monocytogenes 2203 alone. Using 16S rRNA analysis, we identified sequences belonging to the genera Carnobacterium, Leuconostoc and Staphylococcus as the most abundant in the communities grown in TSB. Leuconostoc mesenteroides and Staphylococcus equorum isolated from the most inhibitory community significantly inhibited growth of L. monocytogenes in TSB at 11 °C, compared to growth of L. monocytogenes 2203 alone. These findings suggest that some members of the complex microbial communities on wooden boards in cheese aging facilities might inhibit the growth of L. monocytogenes.

The goal of this study was to evaluate the effect of the microbiota obtained from wooden boards used for cheese ripening on the growth of Listeria monocytogenes. Bacterial communities on the surface of wooden boards obtained from cheese ripening facilities were inoculated into Tryptic soy broth (TSB) and incubated at 11°C for 48 h. These communities (108 CFU/ml stationary phase cells) were co-incubated with 104- 105 CFU/ml L. monocytogenes 2203 at 11°C for up to 8 days. At various times, samples were removed, diluted in sterile saline and plated on Modified Oxford agar (MOX). Bacterial communities from each of 5 boards from 3 different facilities significantly inhibited growth of L. monocytogenes in vitro. Using 16S rRNA analysis, we identified sequences belonging to the genera Carnobacterium, Leuconostoc and Staphylococcus as the most abundant in the communities grown in TSB. Leuconostoc mesenteroides and Staphylococcus equorum were isolated from the most inhibitory of these communities. Pure cultures of L. mesenteroides significantly inhibited growth of L. monocytogenes in TSB at 11°C; S. equorum had a modest inhibitory effect. These findings suggest that some of the complex microbial communities on wooden boards in cheese aging facilities might inhibit growth of L. monocytogenes.