Factors of extended-spectrum beta-lactamase production and/or minimal inhibitory concentration breakpoint predicting microbiologic outcome in patients with acute pyelonephritis caused by Enterobacteriaceae treated with ceftriaxone.
Abstract:
Background: There is still a controversial issue about treatment of ESBL-producing Enterobacteriaceae whether minimal inhibitory concentration (MIC) susceptibility or resistance mechanism is the most reliable factor to predict the treatment outcome. Objective: To determine the microbiological outcome depending on which factor between MIC breakpoint and extended-spectrum beta-lactamase (ESBL) production. Materials and Methods: This is an observational prospective study carried out in patients with acute pyelonephritis caused by Enterobacteriaceae in 3 hospitals in Thailand from March 2012 to January 2013. The microbiological and clinical outcomes were evaluated at 48-72 hours after ceftriaxone treatment, and MIC breakpoint and ESBL production of each isolate were determined. Results: During the study period, there were 97 patients with the mean age of 73.16+14.62 years. There were 48 (49.5%) patients with MIC breakpoint in the susceptible range. In this susceptibility group, there were 47 (97.9%) patients with microbiologic response. Of 49 patients in the non-susceptibility group, there were 32 (65.3%) patients with microbiological response. Of 97 patients, there were 47 (48.4%) patients with ESBL production. Of these 47 patients, there were 19 (40.4%) patients with microbiologic response. Of 50 patients infected with non-ESBL-producing Enterobacteriaceae, there were 49 (98%) patients with microbiologic response. Multiple logistic regression analysis revealed that the factor determining response in acute pyelonephritis patients was ESBL production (odds ratio=8.594, 95% CI 1.21-61.12, P=0.032). Conclusions: The present study demonstrated that microbiologic response in patients with acute pyelonephritis may be determined by ESBL production of the causative organism.