[Rapid detection of tolerance of streptococci and enterococci to beta-lactam antibiotics by measurement of bacterial TPA].

The authors developed a rapid method for determination of tolerance of streptococci and enterococci to ampicillin by measuring the bacterial TPA. Of thirty three strains from blood cultures, 11 were tolerant with a MBC/MIC ratio > 32. For these strains, the free TPA/total TPA ratio measuring the bacterial lysis after a 2hrs incubation with 2 MIC of ampicillin, had an average of 38% (SD = 21) versus 88.6% (SD = 17.9) for the non-tolerant strains. There is a good correlation between the values of MBC/MIC ratios and the free TPA/total TPA ratios. The authors concluded that TPA assessment after 2hrs incubation with antibiotic can predict the antibiotic tolerance of streptococci or enterococci.