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Published on: November 4, 2016

Antimicrobial susceptibility and invasive ability of Staphylococcus aureus isolates from mastitis from dairy backyard

Alejandra Ochoa-Zarzosa1, Pedro D Loeza-Lara, Francisco Torres-Rodríguez

  • 1Centro Multidisciplinario de Estudios en Biotecnología-Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Apdo. Postal 53, Administración Chapultepec, C.P. 58262 Morelia, Michoacán, México.

Antonie Van Leeuwenhoek
|March 6, 2008
PubMed

Insights

Antimicrobial resistance in Staphylococcus aureus from Mexican backyard farms varied. Some isolates showed resistance to common antibiotics and could invade cow cells, highlighting the need for regional monitoring.

Area of Science:

  • Veterinary Microbiology
  • Antimicrobial Resistance
  • Bovine Health

Background:

  • Subclinical mastitis in dairy cows is a significant economic concern.
  • Staphylococcus aureus is a primary pathogen causing bovine mastitis.
  • Understanding antimicrobial susceptibility and virulence factors is crucial for control.

Purpose of the Study:

  • To investigate antimicrobial susceptibility and invasion capabilities of S. aureus from cows with subclinical mastitis in Mexican backyard farms.
  • To identify specific resistance genes and invasion mechanisms.
  • To assess regional variations in S. aureus characteristics.

Main Methods:

  • Sampling of 106 cows from 15 backyard farms in Mexico.
  • Isolation and identification of S. aureus.
  • Antimicrobial susceptibility testing (MIC determination).
  • Detection of resistance genes (erm(B), msr(A), erm(C), lnu(A)).
  • In vitro invasion assays using bovine mammary epithelial cells.

Main Results:

  • 31 S. aureus isolates were recovered, showing resistance to penicillin but susceptibility to gentamicin.
  • Isolates STA9 and STA13 exhibited resistance to erythromycin and lincomycin, carrying specific resistance genes (erm(B), msr(A), erm(C), lnu(A)).
  • Five isolates demonstrated the ability to internalize into bovine mammary epithelial cells.

Conclusions:

  • S. aureus isolates from Mexican backyard farms display diverse antimicrobial susceptibility and invasion abilities.
  • Regional surveillance is essential as resistance patterns and isolate characteristics vary geographically.
  • These findings inform strategies for managing mastitis in smallholder dairy farms.

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