Stenotrophomonas maltophilia susceptibility to ceftazidime-avibactam combination versus ceftazidime alone

To compare the minimum inhibitory concentrations (MIC) of the ceftazidime-avibactam (CZA) combination versus ceftazidime alone (TZ) for Stenotrophomonas maltophilia.

MIC comparison was performed by E-tests. We assumed that CZA was more effective in vitro than TZ alone when CZA led to a category change from "Resistant" with TZ alone to "Susceptible" or "Intermediate" with CZA, or if the MIC of CZA was at least 4-fold lower than the MIC of TZ for TZ-susceptible isolates.

For the 54 clinical isolates included in the study, CZA showed better results in terms of the proportion of susceptible isolates (66.7% vs. 38.9%, P<0.01), MIC₅₀ (2μg/mL vs. 12μg/mL, P<0.05), and MIC distribution. According to our definition, CZA was also more effective in vitro than TZ alone for 50% of the isolates.

Using CZA for empirical treatments in severe or polymicrobial infections with S. maltophilia seems appropriate.