A cloud adult: the Staphylococcus aureus-virus interaction revisited

Area of Science:

• Infectious Diseases
• Epidemiology
• Microbiology

Background:

• Nasal carriage of Staphylococcus aureus (S. aureus) is common in healthcare workers, yet outbreaks are infrequent.
• Previous work linked S. aureus skin infection outbreaks in newborns to nasal carriers with concurrent upper respiratory infections (URIs).

Purpose of the Study:

• To investigate the role of a nasal methicillin-resistant S. aureus (MRSA) carrier (physician 4) with a URI in an MRSA outbreak.
• To quantify airborne S. aureus dispersal by the carrier during a URI.

Main Methods:

• Conducted an epidemiologic study of an MRSA outbreak in a surgical intensive care unit.
• Quantitatively assessed airborne S. aureus dispersal by a physician before and after experimentally induced rhinovirus URI, with and without a surgical mask.
• Utilized molecular typing to confirm strain identity and logistic regression to identify risk factors.

Main Results:

• Identified physician 4 as the sole MRSA nasal carrier; molecular typing confirmed identical strains between the physician and infected patients.
• Exposure to physician 4 and duration of ventilation were independent risk factors for MRSA colonization.
• Airborne S. aureus dispersal by physician 4 increased 40-fold during a URI without a mask, significantly reduced when masked.

Conclusions:

• Physician 4 acted as a "cloud adult," disseminating S. aureus during a URI, similar to "cloud babies."
• Airborne S. aureus dispersal associated with viral URIs represents a significant transmission mechanism.