A radiometric assay system was developed that uses disposable liquid scintillation vials as incubation chambers, and sensitive liquid scintillation techniques for the detection of evolved 14CO2. The trapping system is constructed of a standard glass liquid scintillation vial a soft rubber stopper bare nickel-chromium, an inner growth chamber made from a glass shell vial cut to halt its length, and a 24-mm diameter filter paper disc. When used to measure antibiotic effects on Histoplasma capsulatum and Mycobacterium bovis (BCG), there was an inverse quantitative relationship between 14CO2 evolved and antibiotic concentration. The technique should prove useful for analyses that require trapping and quantitation of 14CO2, including antimicrobial sensitives of slow-growing organisms.
