Erratum: Ertapenem Susceptibility of Extended Spectrum Beta-lactamase Producing Organisms Rupal Mody, Walter Reed Army Medical Center 18 November 2007 To the editor- An error was made in reporting the ertapenem MIC for the E.coli and K.pneumoniae isolates as posted in our original article published Jun 6, 2007 (ACMA 2007, 6:6). We recorded the mean and range of the MIC, however in reporting the mean we neglected to take into account the fact that the MIC is not linear, but instead exponential in nature. This issue is addressed by reporting the MIC 50/90 (ie the median and 90th percentile for the MICs in which the MICs of organisms are 50% and 90% below these values). The MIC 50/90 for the E.coli isolates (range 0.006-0.5 ug/ml) is 0.032/0.125 ug/ml. The MIC 50/90 for the K.pneumoniae isolates (range 0.006-2 ug/ml) is 0.047/0.19 ug/ml. Since the MIC 90 is below the critical breakpoint, the organisms are still considered susceptible to ertapenem as was asserted in our original article. We thank the astute comments made by Dr.Leonard Mada (CJAS Timis, Romanian National Health Insurance, Timis County) which led to this erratum.Rupal M. Mody, MDDaniel P. ErwinKimberly A. Moran, MD Competing interests There are no competing interests to declare.