Rapid antibiotic susceptibility tests on Enterobacteriaceae by ATP bioluminescence

The susceptibility of 76 clinical isolates of Enterobacteriaceae to ampicillin, piperacillin and gentamicin was assessed by ATP bioluminescence in a 4-h test. For most organisms tested (Escherichia, Klebsiella, Enterobacter and Serratia), there was good correlation with traditional MIC values estimated on 18-h cultures. However strains of Proteus mirabilis showed false resistance to the beta-lactam agents with the ATP method; and concordance was achieved only after manipulation of the growth conditions. Our method is simpler than those described previously, though currently it is still labour-intensive and expensive.