A novel luminometer for rapid antimicrobial susceptibility tests on gram-positive cocci by ATP bioluminescence

The susceptibility of 130 clinical isolates of gram-positive cocci to a wide range of antimicrobial agents was assessed by ATP bioluminescence in a 4-h test. ATP assays were performed on a novel luminometer, the Amerlite Analyser, which measures luminescence from microtitration trays. For most organisms tested, there was good correlation (greater than 90%) with conventional MIC values estimated on 18-h cultures. However, a problem was found with detection of penicillin resistance in Staphylococcus aureus by the ATP method, 13% of strains showing major disagreement. Methicillin resistance of S. aureus was shown reliably for most strains (94%) by ATP assay, provided they were incubated at 30 degrees C. The Amerlite Analyser offers the potential for the development of a semi-automated antimicrobial susceptibility test, with a significant reduction in reagent costs when compared with previously described bioluminescence protocols.