Formation of multi-species biofilms by Enterococcus faecium, Enterococcus faecalis, and Bacillus cereus isolated from ricotta processing and effectiveness of chemical sanitation procedures

The formation of multi-species biofilms by Enterococcus faecalis, Enterococcus faecium, and Bacillus cereus and the effectiveness of sanitation procedures in their removal were evaluated. Biofilms were grown on stainless steel at 7, 25, and 39 °C for 8 days. At 7 °C the microorganisms did not form biofilm. After 8 days at 25 and 39 °C the counts of Enterococcus sp. were above 8 log cfu cm−2, while the counts of B. cereus vegetative cells were <0.4 log cfu cm−2. However, there was an increase in the counts of B. cereus spores (above 4 log cfu cm−2). Anionic-tensioactive cleaning complemented with another procedure (acid-cleaning, disinfection or acid-cleaning + disinfection) eliminated the multi-species biofilms formed after 1 and 8 days of contact at 25 and 39 °C. Peracetic acid was the most effective disinfectant and sodium hypochlorite disinfectant the least when only applying the disinfection step directly to the biofilm.