Genetic and compositional analysis of biofilm formed by Staphylococcus aureus isolated from food contact surfaces

Abstract

A total of 84 <i>S. aureus</i> (SA1-SA84) strains were collected from 293 dairy industry FCS (FCS-stainless steel [<i>n</i> = 183] and FCS-polypropylene [<i>n</i> = 110]) for this study. The isolates harbored the genes <i>sigB</i> (66%), <i>sar</i> (53%), <i>agrD</i> (52%), <i>clfB/clfA</i> (38%), <i>fnbA/fnbB</i> (20%), and <i>bap</i> (9.5%). 99. In particular, the biofilm formed by <i>bap</i>-positive <i>S. aureus</i> onto SS showed a high cell density in all culture media at 192 h in comparison with the biofilms formed at 24 h (<i>p</i> < 0.05). Epifluorescence microscopy and SEM revealed the metabolically active cells and the different stages of biofilm formation. CLSM analysis detected extracellular polymeric of <i>S. aureus</i> biofilms on SS, such as eDNA, proteins, and polysaccharides. Finally, the level of detachment on being treated with DNase I (44.7%) and NaIO 4(42.4%) was greater in the biofilms developed in TSB compared to culture medium supplemented with NaCl at 24 h; however, there was no significant difference when the culture medium was supplemented with glucose. In addition, after treatment with proteinase K, there was a lower level of biomass detachment (17.7%) of the biofilm developed in TSBNaCl (<i>p</i> < 0.05 at 24 h) compared to that in TSB, TSBG, and TSBGNaCl (33.6, 36.9, and 37.8%, respectively). These results represent a deep insight into the composition of <i>S. aureus</i> biofilms present in the dairy industry, which promotes the development of more efficient composition-specific disinfection strategies.