Bactrim reduces the inflammatory response in a murine model of acute rhinosinusitis.

OBJECTIVE

To determine whether treatment with an antibiotic (trimethoprim-sulfamethoxazole) reduced the inflammatory response in a murine form of Streptococcus pneumoniae-induced rhinosinusitis.

DESIGN

We randomized 18 C57BL/6 mice to either treatment with intraperitoneal trimethoprim-sulfamethoxazole (Bactrim, 30 mg/kg) or no treatment (control). After 2 days, we inoculated all C57BL/6 mice intranasally with a Bactrim-susceptible strain of Streptococcus pneumoniae, ATCC 49619, suspended in Trypticase soy broth. At day 5 after bacterial inoculation, we sacrificed the mice and prepared histopathologic sections of their sinuses after culturing their nasal cavities by lavage.

SETTING

Animal care facility at a tertiary, academic institution.

METHODS

The histopathologic sections of the sinuses were examined in a blind manner for the percent of sinus cavity area occupied by neutrophil clusters, and for the number of neutrophils per square millimeter of sinus mucosa.

RESULTS

The Bactrim group had a significantly smaller sinus area occupied by neutrophil clusters (1.58% +/- 1.13 vs 4.38% +/- 3.41; P < 0.05), significantly fewer neutrophils infiltrating the mucosa (58.81 +/- 29.63/mm2 vs 105.85 +/- 48.49/mm2; P < 0.05), and significantly less growth of Streptococcus pneumoniae colonies in the intranasal cultures (8 few and 1 moderate vs 3 few, 3 moderate, and 1 many; P = 0.05) compared to the control group.

CONCLUSION

In our murine model of acute rhinosinusitis, Bactrim decreased the number of neutrophil clusters in the sinus cavities, the number of neutrophils infiltrating the sinus mucosa, and the growth of Streptococcus pneumoniae. We propose that our murine model can be used for the study of the pathophysiology and treatment of acute rhinosinusitis.