Transmission of methicillin-resistant Staphylococcus aureus isolates on broiler farms

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Molecular Epidemiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant zoonotic pathogen.
• MRSA CC398 is frequently found in livestock, particularly pigs and poultry.
• Understanding MRSA transmission dynamics in broiler farms is crucial for public health.

Purpose of the Study:

• To investigate the resistance profiles and molecular characteristics of MRSA CC398 isolates from broiler farms.
• To explore the transmission pathways of MRSA between broilers, farm environments, and humans.
• To evaluate the utility of various molecular typing methods for epidemiological investigations.

Main Methods:

• Phenotypic and genotypic resistance profiling using broth microdilution and DNA microarray.
• Molecular typing including spa, dru, SCCmec typing, pulsed-field gel electrophoresis, and DNA microarray.
• Whole genome mapping for detailed analysis of selected isolates from broilers and humans.

Main Results:

• MRSA isolates from broilers, housing, residences, and humans on the same farm were often closely related, indicating within-farm transmission.
• However, distinct MRSA strains were identified on three of the four farms, suggesting introduction from external sources or diversification.
• Different typing methods provided varying levels of discriminatory power for epidemiological links.

Conclusions:

• Evidence supports MRSA transmission between broilers, humans, and their farm environment.
• The presence of diverse MRSA strains on some farms highlights the need to consider multiple sources or evolution.
• A combination of molecular typing techniques, including whole genome mapping, is recommended for comprehensive epidemiological investigations of MRSA.