Spa type distribution in Staphylococcus aureus originating from pigs, cattle and poultry

Area of Science:

• Veterinary Microbiology
• Bacterial Genomics
• Public Health

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) CC398 is a growing global concern in livestock and humans.
• Limited data exists on the prevalence and clonal distribution of methicillin-sensitive Staphylococcus aureus (MSSA) in animal reservoirs.

Purpose of the Study:

• To investigate the prevalence of S. aureus clonal complexes, including CC398, in pigs, cattle, and poultry.
• To compare the clonal distribution of S. aureus from these animal reservoirs with human isolates.

Main Methods:

• Analysis of 296 S. aureus isolates from pigs, cattle, and poultry using spa typing and multi-locus sequence typing (MLST).
• Comparison of animal isolate spa types with common spa types from Danish human blood isolates.
• Pulsed-field gel electrophoresis (PFGE) for genetic comparison of selected poultry and human isolates.

Main Results:

• Significant differences in spa types were observed among S. aureus isolates from pigs, cattle, and poultry, with little overlap between reservoirs or with human isolates.
• Porcine isolates were dominated by CC398 (spa type t034), CC30, and CC9.
• Bovine isolates were mainly CC50, CC97, and CC151.
• Poultry isolates were predominantly CC5 (spa types t002, t306), a common human type, with PFGE confirming genetic similarity between a poultry isolate and human isolates.
• MSSA CC398 was prevalent in pigs but not detected in cattle or poultry.

Conclusions:

• S. aureus clonal distribution varies significantly across different animal reservoirs (pigs, cattle, poultry).
• Poultry harbors S. aureus CC5, a type frequently found in humans, suggesting potential transmission pathways.
• MSSA CC398 is a significant component of the pig S. aureus population but not found in the other tested animal reservoirs.