Population deviation of piggery-associated methicillin-resistant Staphylococcus aureus based on mec-associated direct...

Area of Science:

• Veterinary Microbiology
• Zoonotic Diseases
• Molecular Epidemiology

Background:

• Piggery-associated methicillin-resistant Staphylococcus aureus (MRSA) poses a zoonotic risk.
• Understanding the population structure and dynamics of MRSA's staphylococcal chromosome cassette mec (SCCmec) is crucial for tracking transmission.

Purpose of the Study:

• To investigate the population structure and dynamics of SCCmec in MRSA ST9 isolates from Taiwanese piggeries and human clinical cases.
• To identify novel SCCmec types and assess their geographical distribution and potential for cross-species transmission.

Main Methods:

• Analysis of 140 MRSA ST9 isolates (135 piggery, 5 human clinical) from three Taiwanese regions.
• Characterization using mec-associated direct repeat unit (dru) typing.
• Minimum spanning network and Bayesian skyline plot analyses for population structure and temporal dynamics.

Main Results:

• Twenty-eight dru types, including 24 novel ones, and 15 dru-Clonal Complexes (CCs) were identified.
• A predominant novel type, dt12w, was widespread across all sampled populations.
• Genetic differentiation between populations was observed, with at least two ancestral dru types identified.

Conclusions:

• MRSA ST9 in Taiwan exhibits a stable population with a long evolutionary history.
• Shared dru types between piggery and human MRSA ST9 isolates suggest cross-species horizontal transmission of SCCmec.
• The widespread dt12w type may possess enhanced transmissibility among populations.