FIG 1.

Liquid chromatography-tandem mass spectrometry analysis of ertapenem to determine the rate of degradation after incubation at 37°C. The percentage of ertapenem measured after incubation at 37°C, after 5 (A) and 50 (B) mg/liter initial concentrations, is shown. M. tuberculosis grows slowly compared to the other bacteria (72 times slower than E. coli when in log-phase growth and 720 times slower for semidormant M. tuberculosis) (5). As shown, the longer the incubation period, the greater the degradation of ertapenem. This could eventually lead to falsely high ertapenem MICs.