Drawbacks of the use of cotrimoxazole in foreign-body infections

Abstract

IntroductionThe anti-staphylococcal efficacy of cotrimoxazole in the setting of difficult-to-treat infections seems to be compromised by large amounts of pus and devitalized tissue, and, therefore, high levels of thymidine. Our objective was to evaluate the activity of cotrimoxazole against a staphylococcal foreign-body infection experimental model, which also yields significant quantities of thymidine. Material and methodsWe used a rat tissue-cage model of infection (with high inherent thymidine levels) caused by a strain of methicillin-susceptible Staphylococcus aureus (MSSA; ATCC 29213). MIC values were determined (microdilution method) and compared in the presence or absence of tissue-cage fluid samples. ResultsThe inefficacy of cotrimoxazole was found to be similar to that of the control group. The MIC of cotrimoxazole was 4–8 fold higher in the presence of rat tissue-cage fluid. ConclusionsThe inefficacy of cotrimoxazole in our foreign-body infection model by MSSA, and the probable negative impact of the presence of thymidine on its efficacy, challenge the use of this drug in acute phases of foreign-body infections. It should be reserved as an alternative treatment when the infection is more controlled.