The progressive intercontinental spread of methicillin-resistant Staphylococcus aureus

Area of Science:

• Microbiology
• Epidemiology
• Infectious Diseases

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) emerged shortly after methicillin's introduction in the 1960s.
• Naturally resistant strains existed prior to widespread antibiotic use, suggesting pre-existing genetic factors.
• MRSA strains have evolved, with new epidemic strains emerging globally since the 1970s.

Purpose of the Study:

• To trace the historical emergence and spread of MRSA.
• To understand the genetic and epidemiological factors driving MRSA evolution and transmission.
• To review current control strategies and their effectiveness.

Main Methods:

• Historical data analysis of MRSA isolation and spread.
• Genetic analysis of MRSA strains to identify ancestral clones and evolutionary pathways.
• Review of epidemiological studies on MRSA transmission dynamics.

Main Results:

• MRSA initially emerged from naturally resistant strains, spreading via horizontal gene transfer.
• Hospital environments and antibiotic selection significantly amplified MRSA strains.
• New epidemic MRSA strains have emerged and spread globally, often showing high-level antibiotic resistance.

Conclusions:

• MRSA spread is driven by a combination of genetic factors, antibiotic selection, and human transmission.
• Person-to-person transmission within healthcare settings is the primary mode of spread.
• Effective infection control, early detection, and rational antibiotic use are crucial but insufficient to halt increasing global MRSA transmission.