Finding positive blood cultures from a group of asymptomatic patients with identical susceptibility patterns is most consistent with which type of outbreak?

• A. True outbreak
• B. Pseudo-outbreak
• C. Endemic event
• D. Cluster investigation

Answer: (B)

The situation points to a lab artifact rather than genuine spread of infection. When you find positive blood cultures in asymptomatic patients that all show the same antibiotic susceptibility patterns, it strongly suggests a common contaminant or procedural issue in the laboratory, producing a false cluster of positives. This is what infection-control specialists call a pseudo-outbreak: the numbers look like an outbreak, but there’s no true transmission or clinical illness behind them.

In contrast, a true outbreak would typically involve actual infections with related clinical symptoms and a plausible transmission link, and an endemic event would reflect baseline, expected infection rates rather than a sudden, clustered finding of identical isolates in asymptomatic people. A cluster investigation is the process you’d start to explore any apparent grouping, but the defining scenario here—the uniform culture results in people without symptoms—fits a pseudo-outbreak driven by laboratory contamination.