Continuous blood culture systems that detect changes in headspace pressure in bottles are referred to as which methods?

• A. Fluorescence methods
• B. Manometric methods
• C. 14C detection methods
• D. Colorimetry methods

Answer: (B)

Measuring growth by changes in the bottle’s headspace pressure is the manometric approach. In this method, microorganisms in the blood culture bottle metabolize substrates and release gases like CO2, which increases the pressure inside the sealed bottle. A transducer continuously monitors this pressure change and flags growth when it crosses a threshold. Other detection methods rely on optical signals (color or fluorescence changes) or radiolabeled metabolism rather than pressure, so they don’t detect headspace pressure changes.