Bacterial biogeographical patterns in a cooking center for hospital foodservice

Microbial contamination in foodservice environments plays a fundamental role in food quality and safety. In such environments the composition of the microbiota is influenced by the characteristics of the specific surfaces and by food handling and processing and a resident microbiota may be present in each site. In this study, the bacterial biogeographical patterns in a hospital cooking center was studied by 16S rRNA-based culture-independent high-throughput amplicon sequencing in order to provide a comprehensive mapping of the surfaces and tools that come in contact with foods during preparation. Across all area, surface swab-samples from work surfaces of different zones were taken: food pre-processing rooms (dedicated to fish, vegetables, and red and white meat), storage room and kitchen. The microbiota of environmental swabs was very complex, including more than 500 operational taxonomic units (OTUs) with extremely variable relative abundances (0.02-99%) depending on the species. A core microbiota was found that was common to more than 70% of the samples analyzed and that included microbial species that were common across all areas such as Acinetobacter, Chryseobacterium, Moraxellaceae, and Alicyclobacillus, although their abundances were below 10% of the microbiota. Some surfaces were contaminated by high levels of either Pseudomonas, Psychrobacter, Paracoccus, or Kocuria. However, beta diversity analysis showed that, based on the composition of the microbiota, the environmental samples grouped according to the sampling time but not according to the specific area of sampling except for the case of samples from the vegetable pre-processing room that showed a higher level of similarity. The cleaning procedures can have a very strong impact on the spatial distribution of the microbial communities, as the use of the same cleaning tools can be even a possible vector of bacterial diffusion. Most of the microbial taxa found are not those commonly found in food as spoilers or hazardous bacteria, which indicates that food and storage conditions can be very selective in the growth of possible contaminants.