Determination of the Toxigenic Profile of Staphylococcus aureus Strains Isolated from Clinical and Artisanal Cheese Samples Produced in Costa Rica

Introduction: S. aureus is a pathogen with a wide capacity of producing disease in humans and some animals.  This capacity is linked to the expression of toxins, its invasive capacity and the resistance to antibiotics. Toxins produced by these bacteria include enterotoxins (SEs), toxic shock syndrome (TSST-1) and eritrogenic toxins (eta and etb).  Not all strains possess the genes that codify for these toxins but some might have two or more same time.

Purpose: The aim of this work was to determine which toxigenic genes are present in strains isolated from food and clinical samples.

Methods: Two hundred twenty-nine S. aureus strains coming from fresh cheese samples, and 210 clinical isolates from the same region were analyzed.  Sea, seb, sec, sed, see, eta, etb and tsst genes were detected using PCR methodology described by Mehrotera et al. Extraction was done according to the methodology described by Brizzio et al., with an additional incubation with ampicillin in order to help with wall rupture. 

Results: In fresh cheese samples, enterotoxin B gene was the most frequent (19 positive samples), followed by D gene (6 positive samples). Enterotoxin A gene was not detected in these samples.  For clinical isolates, B enterotoxin was also the most frequent one (42 positive samples) followed by tsst (38 positive samples). Eight samples were positive for enterotoxin A gene.

Significance: Both isolates from cheese and clinical samples present toxigenic genes, being these more frequent in isolates from hospital origin.