Sampling and identification of the dominant microbial population of presumptive biofilms in the food processing industry

Detection and characterisation of biofilms in the food industry is fundamental. The aim of this study was to evaluate different surface sampling methods to assess the presence of biofilms in different food processing companies and to identify the microbial population of these presumptive biofilms.
In 8 companies surfaces were sampled after cleaning and disinfection using 2 methods. The first method was scraping with a cell scraper followed by swabbing with a floqswab, the second method swabbing using a spongestick. Different microbiological and chemical analyses were performed on both types of samples. The dominant bacteria were identified using (GTG)5 clustering followed by 16S rRNA gene sequencing.
For total aerobic plate count (TAC) and Pseudomonas spp. slightly more points were found to be contaminated using the spongestick. Beside, average count for TAC on contaminated areas was 2.04 and 2.53 log CFU/100cm² for scraper and spongestick respectively. The same trend is observed for Pseudomonas spp.. On the other hand, research showed that spongestick gives interference in the chemical analysis of the extracellular polymeric substance of the biofilm, making this method less suitable for chemical analysis of biofilms.
In a meat processing company the microbial population in presumptive biofilms was dominated by Gram-negative bacteria mainly Pseudomonas spp. Also Psychrobacter spp., Rahnella spp., Klebsiella spp. and Stenotrophomonas spp. were identified. In a sauce producing company again Gram-negative bacteria dominated: mostly Pseudomonas spp. but also Acinetobacter spp., Shewanella spp., Enterobacter spp., Lelliottia spp., Stenotrophomonas spp and Citrobacter spp..