Molecular correlates of host specialization in Staphylococcus aureus

Area of Science:

• Microbiology
• Genomics
• Veterinary Medicine

Background:

• Staphylococcus aureus exhibits host specialization, with distinct clonal groups infecting humans and cattle.
• The genetic underpinnings of this host specialization remain largely unknown.

Purpose of the Study:

• To investigate the molecular basis of host specialization in Staphylococcus aureus.
• To identify genetic features distinguishing bovine-associated S. aureus clones from human-associated ones.

Main Methods:

• Whole-genome sequencing of a bovine mastitis isolate (strain ET3-1).
• Comparative genomic analysis of ET3-1 against human-associated S. aureus strains.
• Whole-genome DNA microarray hybridization to compare gene content among bovine S. aureus clones.

Main Results:

• Strain ET3-1 contains novel genomic elements, including virulence factor homologs.
• ET3-1 exhibits high allelic variation in genes related to host colonization, virulence, and adaptation.
• Key virulence factors like protein A are non-functional pseudogenes in ET3-1.
• Highly successful bovine mastitis clones share similar gene content, unlike less common bovine isolates.

Conclusions:

• Distinct molecular genetic features differentiate successful bovine-adapted S. aureus from human-adapted or less successful bovine strains.
• Bovine specialist clones likely evolved from human-like ancestors via foreign DNA acquisition and gene decay.
• These findings provide insights into the evolution of host-specific pathogens.