Drawbacks of the use of cotrimoxazole in foreign-body infections

Abstract

Introduction: The 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 methods: We 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.

Results: The 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.

Conclusions: The 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.

Keywords: Cotrimoxazol; Cotrimoxazole; Foreign-body infection; Infección por cuerpo extraño; S. aureus; Thymidine; Timidina.