Evidence and Molecular Characterization of Multidrug Resistant Staphylococcus aureus Isolated From Equines in Pakistan.

The research study investigates the presence and drug resistance of Staphylococcus aureus, including versions resistant to methicillin and vancomycin, in equines in Pakistan.

Objective of the study

• To observe the nasal colonization and resistance of Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and vancomycin-resistant S. aureus (VRSA) in donkeys, mules and horses.
• To verify the presence of MRSA and VRSA using phenotypic and molecular methods, followed by a phylogenetic analysis to study the evolutionary relationship among the isolates.
• To evaluate the risk factors linked with the development of S. aureus colonization in the studied animals.

Methods used and findings

• The researchers identified an overall prevalence of 42.86% of S. aureus in equines by targeting the nuc gene on polymerase chain reaction.
• They found that 26.44% of the tested isolates were resistant to vancomycin using the Kirby-Bauer disc diffusion test.
• The mecA and vanB genes, associated with methicillin and vancomycin resistance, showed a prevalence of 14.94% and 13.79% respectively.

Phylogenetic analysis and risk factor evaluation

• The researchers used phylogenetic analysis to study the evolutionary variations of the isolated strains. They found significant variations among the study isolates and previously reported sequences of the mecA and vanB genes.
• Risk factor analysis showed significant results related to the purpose of raising the animals, work intensity, stocking density, presence of other livestock animals in the surroundings and usage of common drinking water source.

Antimicrobial susceptibility testing

• The MRSA and VRSA isolates were tested through antimicrobial susceptibility testing and found to have high resistance to various commonly used antibiotics.
• Any isolate found to be resistant to three or more antibiotics was considered as multidrug-resistant.

Conclusion and implications of the study

• The study provides molecular evidence of MRSA and VRSA isolated from equines in Pakistan, shedding light on the emerging issue of multidrug resistance in S. aureus in equines.
• The results highlight the need for urgent measures to tackle this issue and to prevent spread of resistant bacteria.