Bacteriology of chronic sinusitis after ampicillin therapy.

The bacteriologies of the maxillary and ethmoid sinuses were studied in 74 chronic sinusitis patients who took ampicillin (500 mg every 6 hours) for 2 weeks preoperatively. The specimens from one ipsilateral maxillary and ethmoid sinuses were obtained when undergoing functional endoscopic sinus surgery. In 74 specimens of the maxillary sinus, 38 bacterial isolates were recovered. The culture rate was 46.0%. On the other hand, 34 bacterial isolates were taken from the ethmoid sinus specimens. The culture rate was 41.9%. As compared with a previous group who did not take any antibiotic preoperatively, the culture rate significantly decreased in the maxillary as well as the ethmoid sinus specimens. Not surprisingly, a significantly decreased sensitivity to ampicillin was also found in the recovered bacteria from both the maxillary sinus (23.7%) and ethmoid sinus (5.9%) specimens. These results demonstrate that antibiotic therapy with ampicillin could eradicate most sensitive bacteria in chronic sinusitis. However, persistence of resistant bacteria was demonstrated.