MIC and Synergy Testing Guide Antimicrobial Treatment of Ventilator-Associated Pneumonia due to Carbapenem-Resistant Acinetobacter baumannii
Sirima Sitaruno PharmD*, Sutep Jaruratanasirikul MD**, Sutthiporn Pattharachayakul PharmD*, Natnicha Ingviya BSc***, Thanaporn Hortiwakul MSc**, Wichai Santimaleeworagun PhD****, Bodin Khwannimit MD**
Affiliation : * Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Songkhla, Thailand ** Department of Medicine, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand *** Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand **** Department of Pharmacy, Faculty of Pharmacy, Silpakorn University, Nakhon Pathom, Thailand
Background : The studies regarding the use of information from in vitro study to guide antimicrobial combination therapy in
clinical settings are limited.
Objective : To determine feasibility and impact of the application of MIC and synergy testing to guide antimicrobial therapy in
clinical setting.
Material and Method: Patients with ventilator-associated pneumonia (VAP) due to carbapenem-resistant A. baumannii
(CRAB) infections were enrolled. Susceptibility information obtained from disk diffusion, MIC determination, and synergy
testing with E-test method was used to select antimicrobial agent to combine with colistin. Treatment outcomes were assessed
following antimicrobial treatment.
Results : Ten VAP-patients with CRAB infections were enrolled. Seven patients received non-active CRAB regimen as empirical
therapy. The results from disk diffusion, MIC determination, and synergy testing enabled the clinicians to choose regimen with
potential to be successful in 70%, 30%, and 20%, respectively. Finally, nine patients received colistin-sulbactam and one
patient received colistin-imipenem. Favorable clinical and microbiological outcomes were observed in nine and six out of 10
patients, respectively.
Conclusion : The information from MIC determination and synergy testing by E-test method enables optimization of treatment
regimens for VAP-patients with CRAB infections. This strategy revealed favorable treatment outcomes and that it is feasible
to perform in clinical setting.
Keywords : Acinetobacter baumannii, CRAB, MIC determination, Synergy testing, Combination therapy, Colistin, Carbapenems, Sulbactam
