Multiple-strain colonization in nasal carriers of Staphylococcus aureus

Area of Science:

• Microbiology
• Epidemiology
• Genetics

Background:

• Staphylococcus aureus is a common bacterium that can cause serious infections.
• Nasal cocolonization with multiple S. aureus strains is thought to be rare due to the high cost of genetic analysis.
• Understanding S. aureus colonization dynamics is crucial for public health.

Purpose of the Study:

• To develop a resource-efficient protocol for detecting mixed-strain Staphylococcus aureus (S. aureus) nasal cocolonization.
• To investigate the prevalence and dynamics of S. aureus cocolonization in a healthy population over 24 months.

Main Methods:

• A staged protocol was developed to maximize detection of mixed spa-type S. aureus colonization.
• 3,197 S. aureus-positive samples from a longitudinal study in Oxfordshire, UK, were analyzed.
• Pooled DNA was initially typed, followed by single-colony typing for ambiguous results.

Main Results:

• The protocol successfully identified one or more spa types in all samples.
• Point prevalence of S. aureus cocolonization ranged from 3.4% to 5.8%, with 18% experiencing it at least once, often transiently.
• In long-term carriers, 61% continuously carried S. aureus, but only 39% carried a single spa type without cocolonization.

Conclusions:

• Staphylococcus aureus nasal colonization is highly dynamic, even in long-term carriers.
• Transient cocolonization with unrelated S. aureus strains is more common than previously reported.
• Increased detection of cocolonization may reveal new insights into invasive disease risk and bacterial evolution.