Characterization of coagulase-positive Staphylococcus spp., antimicrobial resistance profile, and presence of enterotoxin-producing genes in goat milk in Paraná State

Abstract

Goat milk presents interesting characteristics to consumers, but the production of this food faces several challenges that influence its quality. Process failures from milking to processing and commercialization can expose milk to contamination by pathogenic microorganisms, including the coagulase-positive Staphylococcus group. Although Staphylococcus aureus is the most relevant species in mastitis and food poisoning, other species in this group are also important, especially those related to food poisoning. This study aimed to identify the coagulase-positive Staphylococcus species in goat milk using biochemical tests, determine the prevalence of antimicrobial resistance using the disc diffusion test, and investigate enterotoxin-producing genes, sea, seb, sec, sed, see, seg, seh, and sei by multiplex PCR. A total of 384 coagulase-positive Staphylococcus strains obtained from raw goat milk collected from nine farms in Paraná during four seasons of the year were studied. Biochemical tests showed that 85.69% of the 384 strains were S. aureus, followed by 9.38% of S. intermedius, 4.17% of S. hyicus and 0.78% of S. delphini. For the antimicrobial resistance test, up to three strains of each species identified as coagulase-positive Staphylococci were chosen from each farm, with a total of 74 strains. Of these, 27% (20/74) showed resistance to at least one antibiotic, and among all penicillin-resistant strains, 45% (9/20) also presented resistance to tetracycline. In the search for staphylococcal enterotoxin-producing genes, 49 S. aureus strains were studied; among them, 40.81% (20/49) presented enterotoxin-producing genes. The highest prevalence was detected for the sec gene, which was present in 22.44% (11/49) of the strains, followed by the seh gene in 18.36% (9/49), and the see gene was detected in 4.08% (2/49). It was concluded that S. aureus was the predominant species in raw goat milk, with a high prevalence of penicillin- and tetracycline-resistant Staphylococci and a significant number of strains with staphylococcal enterotoxin-producing genes. The strains studied carried enterotoxin-producing genes involved in food poisoning in humans, indicating that goat milk is a possible source of contamination and, therefore, a potential danger to public health.

Keywords

• Antimicrobial susceptibility
• Biochemical tests
• Enterotoxin
• Public health