AUTHOR=Avila-Novoa María Guadalupe , Solis-Velazquez Oscar Alberto , Guerrero-Medina Pedro Javier , González-Gómez Jean-Pierre , González-Torres Berenice , Velázquez-Suárez Noemí Yolanda , Martínez-Chávez Liliana , Martínez-Gonzáles Nanci Edid , De la Cruz-Color Lucia , Ibarra-Velázquez Luz María , Cardona-López Marco Antonio , Robles-García Miguel Ángel , Gutiérrez-Lomelí Melesio 

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

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1001700

DOI=10.3389/fmicb.2022.1001700

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Staphylococcus aureus</italic> is an important pathogen that can form biofilms on food contact surfaces (FCS) in the dairy industry, posing a serious food safety, and quality concern. Biofilm is a complex system, influenced by nutritional-related factors that regulate the synthesis of the components of the biofilm matrix. This study determines the prevalence of biofilm-associated genes and evaluates the development under different growth conditions and compositions of biofilms produced by <italic>S. aureus</italic>.</p></sec><sec><title>Methods</title><p>Biofilms were developed in TSB, TSBG, TSBNaCl, and TSBGNaCl on stainless-steel (SS), with enumeration at 24 and 192 h visualized by epifluorescence and scanning electron microscopy (SEM). The composition of biofilms was determined using enzymatic and chemical treatments and confocal laser scanning microscopy (CLSM).</p></sec><sec><title>Results and discussion</title><p>A total of 84 <italic>S. aureus</italic> (SA1–SA84) strains were collected from 293 dairy industry FCS (FCS-stainless steel [<italic>n</italic> = 183] and FCS-polypropylene [<italic>n</italic> = 110]) for this study. The isolates harbored the genes <italic>sigB</italic> (66%), <italic>sar</italic> (53%), <italic>agrD</italic> (52%), <italic>clfB/clfA</italic> (38%), <italic>fnbA/fnbB</italic> (20%), and <italic>bap</italic> (9.5%). 99. In particular, the biofilm formed by <italic>bap</italic>-positive <italic>S. aureus</italic> onto SS showed a high cell density in all culture media at 192 h in comparison with the biofilms formed at 24 h (<italic>p</italic> &lt; 0.05). Epifluorescence microscopy and SEM revealed the metabolically active cells and the different stages of biofilm formation. CLSM analysis detected extracellular polymeric of <italic>S. aureus</italic> 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 (<italic>p</italic> &lt; 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 <italic>S. aureus</italic> biofilms present in the dairy industry, which promotes the development of more efficient composition-specific disinfection strategies.</p></sec>