Group A Streptococcus is identified as the causative organism for a surgical site infection, and an infection preventionist recommends culturing asymptomatic surgical team members. What rate best describes the expected finding?

• A. Infection rate
• B. Colonization rate
• C. Carriage rate
• D. Transmission rate

Answer: (B)

The key idea is asymptomatic carriage of a pathogen and how it’s measured. When you culture people who don’t show symptoms, you’re looking for who harbors the organism without illness. The metric that fits that scenario is the colonization rate—it's the proportion of people in the group who carry the organism without symptoms. Infection rate would require illness to be present, and transmission rate describes how the pathogen spreads between people, not how many are carrying it without disease. Carriage rate is a closely related term, but in this context colonization rate is the precise description of the finding.