Vancomycin-resistant Staphylococcus aureus endangers Egyptian dairy herds

Area of Science:

• Microbiology
• Veterinary Medicine
• Public Health

Background:

• Bovine mastitis is a significant concern in dairy production, impacting animal welfare and milk safety.
• The emergence of antimicrobial-resistant Staphylococcus aureus, including methicillin-resistant (MRSA) and vancomycin-resistant (VRSA) strains, presents a growing threat.
• These resistant strains can harbor virulence factors and form biofilms, complicating treatment and increasing transmission risk.

Purpose of the Study:

• To investigate the prevalence, antimicrobial resistance profiles, and genetic characteristics of MRSA and VRSA in Egyptian dairy animals.
• To assess the biofilm-forming ability and identify virulence factors in these resistant isolates.
• To determine the spa and staphylococcal cassette chromosome mec (SCCmec) types of the isolated MRSA and VRSA.

Main Methods:

• Collection and analysis of 808 milk samples from 202 dairy animals (31 buffaloes, 171 cattle) with clinical or subclinical mastitis.
• Isolation and identification of Staphylococcus species, including coagulase-positive S. aureus (CoPS) and coagulase-negative staphylococci (CoNS).
• Antimicrobial susceptibility testing, detection of resistance genes (mecA, vanA, vanB), biofilm gene analysis (icaA, icaD), virulence gene profiling (hlb, lukMF, tsst, enterotoxins), and molecular typing (spa, SCCmec).

Main Results:

• Mastitis prevalence was 48.4% in buffaloes and 29.2% in cattle. 65 Staphylococcus isolates were recovered, including 27 CoPS.
• All CoPS isolates were mecA-positive, exhibiting high-level antimicrobial resistance. Three pandrug-resistant (PDR), four extensive drug-resistant (XDR), and 20 multidrug-resistant isolates were identified.
• VRSA was detected in 85.2% of CoPS isolates. All isolates formed biofilms, harbored virulence genes (hlb, lukMF, enterotoxins), and belonged to eight MRSA spa types and three SCCmec types.

Conclusions:

• The study identified a significant presence of PDR/XDR MRSA and VRSA in Egyptian dairy animals, capable of biofilm formation and carrying various virulence genes.
• These findings highlight a serious threat to bovine milk safety, animal welfare, and public health due to the potential for transmission.
• Strict hygiene practices and continuous antimicrobial surveillance are essential to mitigate the risk of MRSA and VRSA colonization and dissemination in dairy herds.