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Characterization of borderline oxacillin-resistant Staphylococcus aureus isolated from food of animal origin

Jarosław Bystroń1, Magdalena Podkowik, Kamila Korzekwa

  • 1Department of Food Hygiene and Consumer Health Protection, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.

Journal of Food Protection
|July 10, 2010
PubMed

Insights

Molecular analysis of foodborne oxacillin-resistant Staphylococcus aureus revealed that human handling may contaminate minced pork. Borderline-resistant strains found in milk also appear in human populations, suggesting complex origins for these resistant bacteria.

Area of Science:

  • Food microbiology
  • Antimicrobial resistance
  • Molecular epidemiology

Background:

  • Oxacillin resistance in Staphylococcus aureus (ORSA) is a significant public health concern.
  • Understanding the molecular basis and sources of ORSA in the food chain is crucial for risk assessment.
  • Previous studies have highlighted the presence of antibiotic-resistant bacteria in food products.

Purpose of the Study:

  • To determine the molecular characteristics of oxacillin-resistant Staphylococcus aureus isolated from food sources.
  • To investigate the genetic relatedness of these foodborne strains to those found in human infections.
  • To explore potential sources of contamination for ORSA in the food supply.

Main Methods:

  • Isolation and identification of Staphylococcus aureus from food samples.
  • Determination of oxacillin resistance by Minimum Inhibitory Concentration (MIC) testing.
  • Molecular characterization including detection of the methicillin-resistant determinant (mecA) gene, sequencing typing (ST), staphylococcal protein A (spa) typing, and detection of enterotoxin genes.

Main Results:

  • Eight borderline oxacillin-resistant Staphylococcus aureus strains (MICs 2-4 µg/ml) were identified from 132 food isolates.
  • One strain was mecA-positive (ST228, spa t041), while six were mecA-negative.
  • Enterotoxin genes (selp, egc1, sed-sej-selr) were detected in the mecA-positive strain and four borderline strains. Isolates from minced pork showed genetic links to human strains, suggesting human contamination. Milk isolates had genotypes found in both humans and animals.

Conclusions:

  • Human handling appears to be a significant source of oxacillin-resistant Staphylococcus aureus contamination in certain food products like minced pork.
  • The presence of similar ORSA genotypes in both food and human/animal populations indicates complex transmission routes.
  • Further research is necessary to fully elucidate the origins of antibiotic-resistant Staphylococcus aureus strains within the food ecosystem.

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