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 Str eptococcus pneumoniae-induced rhinosinusitis. Design: We randomized 18 C57B L/6 mice to either treatment with intraperitoneal( trimethoprim-sulfamethox azole (Bactrim, 30 mg/kg) or no treatment (control). After 2 days, we inocu lated all C57BL/6 mice intranasally with a Bactrim-susceptible strain of St reptococcus pneumoniae, ATCC 49619, suspended in Trypticase soy broth. At d ay 5 after bacterial inoculation, we sacrificed the mice and prepared histo pathologic sections of their sinuses after culturing their nasal cavities b y lavage. Setting: Animal care facility at a tertiary, academic institution . Methods: The histopathologic sections of the sinuses were examined in a b lind manner for the percent of sinus cavity area occupied by neutrophil clu sters, and for the number of neutrophils per square millimeter of sinus muc osa. Results: The Bactrim group had a significantly smaller sinus area occu pied by neutrophil clusters (1.58%+/-1.13 vs 4.38%+/-3.41; P<0.05), signifi cantly fewer neutrophils infiltrating the mucosa (58.81+/-29.63/mm(2) vs 10 5.85+/-48.49/mm(2); P<0.05), and significantly, less growth of Streptococcu s pneumoniae colonies in the intranasal cultures (8 few and I moderate vs 3 few: 3 moderate and I many; P=0.05) compared to the control group. Conclus ion In our murine model of acute rhinosinusitis, Bactrim decreased the numb er 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 pathophys iology and treatment of acute rhinosinusitis.