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

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

Answer: (D)

Manometric detection relies on measuring gas pressure changes in the bottle’s headspace as microorganisms metabolize and produce CO2 and other gases. In a sealed blood culture bottle, this gas buildup increases the internal pressure, and a pressure sensor or manometer continuously monitors this change. When the pressure rises beyond a set threshold, the system signals a positive culture, allowing rapid notification and handling. This approach differs from radiometric methods that track CO2 via radioactivity, or colorimetric/fluorescence methods that infer growth from changes in sensor optics or pH indicators; those do not directly measure headspace pressure.