A Combination of Trimethoprim-sulfamethoxazole and Ceftazidime Showed Good In Vitro Activity against Stenotrophomonas maltophilia

Background: Stenotrophomonas maltophilia has emerged as an important nosocomial pathogen, capable of causing a wide spectrum of infections. Treatment is difficult because it is resistant to many antimicrobial agents, thus reducing the treatment options. The aims of this study were to describe the antimicrobial susceptibility patterns and synergistic effect of selected antimicrobial combinations against S. maltophilia isolates.
Methods: This was a descriptive cross-sectional study undertaken in the Hospital Universiti Sains Malaysia from April 2011 to March 2012. S. maltophilia isolated from various clinical specimens were included in the study. Antimicrobial susceptibility testing was done using the epsilometer test (E-test) and interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. In the synergy test, the isolates were tested against six different antimicrobial combinations.
Results: In total, 84 S. maltophilia isolates were collected and analysed. According to the E-test, the antimicrobial susceptibility of trimethoprim-sulfamethoxazole (TMP-SMX), tigecycline, and ciprofloxacin was 100%, 91.1%, and 88.9% respectively. The antimicrobial combination of TMP-SMX and ceftazidime showed the highest synergistic effect.
Conclusion: TMP-SMX remains the antimicrobial of choice to treat S. maltophilia infection. TMP-SMX and ceftazidime was the most effective combination in vitro.

Keywords
combination; trimethoprim-sulfamethoxazole; ceftazidime; Stenotrophomonas maltophilia