Abstract
Staphylococcus aureus is a commensal bacterium in humans and animals able to adapt to multiple environments. The aim of this study was to compare the genetic diversity and virulence profiles of strains of S. aureus isolated from food (29 strains), humans (43 strains), and animals (8 strains). 80 lipase-producing strains belonging to a biobank of 360 isolates, identified phenotypically as S. aureus, were selected. Confirmation of the species was made by amplifying the spA gene and 80% (64/80) of the strains were confirmed within this species. The virulence profile of each of the isolates was determined by PCR. The seA gene coding for enterotoxin A was found in 53.1% of the strains, the saK gene, which codes for Staphylokinase, was amplified in 57.8% of the strains, and, finally, the hlB gene coding for β-Hemolysin was amplified in 17.2%. The profile of antimicrobial resistance was determined by the Kirby Bauer method showing that the strains from food presented greater resistance to erythromycin (40.7%) and ciprofloxacin (18.5%) while in strains isolated from humans were to erythromycin (48.4%) and clindamycin (21.2%). Also, in strains from animals, a high resistance to erythromycin was observed (75%). The frequency of MRSA was 12.5% due to the presence of the mec gene and resistance to cefoxitin. Of the total strains, 68.7% were typed by PCR-RFLP of the coa gene using the AluI enzyme; derived from this restriction, 17 profiles were generated. Profile 4 (490 bp, 300 bp) was the most frequent, containing a higher number of strains with a higher number of virulence factors and antimicrobial resistance, which is associated with greater adaptation to different environments. In this study, a wide genetic diversity of strains of S. aureus from different foods, humans, and animals was found. This demonstrates evolution, genetic versatility, and, therefore, the adaptation of this microorganism in different environments.
Highlights
Staphylococcus aureus is a commensal bacterium that is part of the microbiota of the skin and mucous membranes of humans and some animals
International Journal of Microbiology infections, and healthcare-associated infections (HAI) [1]; in animals, it is associated with infections in mammary glands [2], and, in the case of food, S. aureus produces a great diversity of enterotoxins that generate food poisoning in humans due to the consumption of these [3]; being a microorganism, it affects the quality of foods, such as raw meat products [4] and milk and dairy products [5]
S. aureus has the ability to control the expression of virulence factors according to the environmental conditions in which it is found through a global regulation system known as accessory regulatory gene (Agr) [8] and the sigma factor [9]
Summary
Staphylococcus aureus is a commensal bacterium that is part of the microbiota of the skin and mucous membranes of humans and some animals. In addition to gene regulation, the adaptation of S. aureus in different microenvironments with different environmental, nutritional, and stress conditions could generate the acquisition of genes coding for virulence factors that allow its survival [10]. In the Staphylococcus aureus pathogenicity islands (SaPIs), this phenomenon has been observed, mobilizing two genes of enterotoxins along with the toxin gene of toxic shock syndrome (tsst-1) and the adhesion protein Bap [12]. Another example is the catabolic mobile element of arginine that is transported together with the methicillin resistance cassette (SCCmec) due to its proximity and which has been related to strains that have specific subtypes of SCCmec [1010]. Resistance against methicillin, lincosamides, macrolides, aminoglycosides, and a combination of these antibiotics has been frequently reported in staphylococci [14]
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