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Updated: Sep 5, 2025
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
Outbreak of methicillin-resistant Staphylococcus aureus sequence type 1, spa type t1784, in an equine hospital in
Eri Uchida-Fujii1, Hidekazu Niwa1, Kota Kanai2
1Equine Research Institute, Japan Racing Association, Shiba 1400-4, Shinotsuke, Tochigi 329-0412, Japan.
Abstract:
Methicillin-resistant Staphylococcus aureus (MRSA) has often been isolated from livestock and companion animals, including horses. Seven cases of MRSA infection in Thoroughbred racehorses were observed in an equine hospital in Japan in 2020. In this study, MRSA isolates from these seven horses and nine veterinarians in the equine hospital were studied to examine their genetic relatedness and evaluate the possibility of MRSA transmission. The MRSA isolates were subjected to whole-genome sequencing for multi-locus sequence typing, S. aureus protein A (spa) typing, staphylococcal cassette chromosome typing, and antimicrobial resistance gene detection. Minimum inhibitory concentrations of antibiotics were assessed to determine the antimicrobial susceptibility phenotype of the isolates. Phylogenetic trees based on single nucleotide polymorphisms were constructed to identify genetically close isolates. All isolates from horses and veterinarians belonged to sequence type (ST) 1, spa type t1784, with a point mutation in gyrA and double point mutations in grlA, which is known to cause fluoroquinolone resistance. All ST1-t1784 isolates were genetically closely related based on the phylogenetic tree. Our results suggested an outbreak and horse-veterinarian transmission of ST1-t1784 strains in an equine hospital.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) infected seven horses and nine veterinarians in a Japanese equine hospital. Genetic analysis revealed close relatedness, suggesting an outbreak and horse-to-veterinarian transmission of the ST1-t1784 strain.
Area of Science:
- Veterinary Medicine
- Infectious Diseases
- Genomics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in both human and animal health.
- MRSA has been frequently detected in various animal populations, including horses, raising concerns about zoonotic potential.
- Equine MRSA infections pose a risk to both horses and veterinary professionals.
Purpose of the Study:
- To investigate the genetic relatedness of MRSA isolates from infected Thoroughbred racehorses and veterinarians in an equine hospital.
- To evaluate the potential for MRSA transmission between horses and veterinary staff within the hospital environment.
- To characterize the antimicrobial resistance profiles and genomic features of the circulating MRSA strains.
Main Methods:
- Whole-genome sequencing was performed on MRSA isolates from seven horses and nine veterinarians.
- Multi-locus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome (SCC) typing were conducted.
- Antimicrobial susceptibility testing and phylogenetic analysis using single nucleotide polymorphisms (SNPs) were employed.
Main Results:
- All MRSA isolates from horses and veterinarians belonged to sequence type (ST) 1 and spa type t1784.
- Isolates shared fluoroquinolone resistance-associated mutations in gyrA and grlA genes.
- Phylogenetic analysis indicated close genetic relatedness among all ST1-t1784 isolates, suggesting a common source or transmission event.
Conclusions:
- The study suggests an outbreak of ST1-t1784 MRSA in the equine hospital.
- Evidence points towards transmission of MRSA between infected horses and veterinarians.
- Genomic analysis is crucial for understanding MRSA epidemiology and transmission dynamics in veterinary settings.
