Incidence of Staphylococcus aureus and analysis of associated bacterial communities on food industry surfaces

Abstract

Biofilms are a common cause of food contamination with undesirable bacteria, such as pathogenic bacteria. Staphylococcus aureus is one of the major bacteria causing food-borne diseases in humans. A study designed to determine the presence of S. aureus on food contact surfaces in dairy, meat, and seafood environments and to identify coexisting microbiota has therefore been carried out. A total of 442 samples were collected, and the presence of S. aureus was confirmed in 6.1% of samples. Sixty-three S. aureus isolates were recovered and typed by random amplification of polymorphic DNA (RAPD). Profiles were clustered into four groups which were related to specific food environments. All isolates harbored some potential virulence factors such as enterotoxin production genes, biofilm formation-associated genes, antibiotic resistance, or lysogeny. PCR-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprints of bacterial communities coexisting with S. aureus revealed the presence of bacteria either involved in food spoilage or of concern for food safety in all food environments. Food industry surfaces could thus be a reservoir for S. aureus forming complex communities with undesirable bacteria in multispecies biofilms. Uneven microbiological conditions were found in each food sector, which indicates the need to improve hygienic conditions in food processing facilities, particularly the removal of bacterial biofilms, to enhance the safety of food products.

Fig 1

DGGE profiles of microbial populations coexisting with Staphylococcus aureus on food industry surfaces using amplicons of the V3 variable region of the bacterial 16S rRNA gene. Bands are identified in the table at right. Mk: DGGE identification marker. Lc, Leuconostoc; Lb, Lactobacillus; Str, Streptococcus.

Fig 2

Dendrogram obtained by cluster analysis of RAPD-PCR profiles of Staphylococcus aureus isolates from food industry surfaces, using the UPGMA method and the Pearson product moment correlation coefficient. The dashed line represents the threshold similarity value of 95% set for discriminating strains.