Report from the 45th Interscience Conference on Antimicrobial Agents and Chemotherapy.

The ketolide telithromycin (Ketek, Sanofi Aventis) has been found to be more effective than the macrolide azithromycin (Zithromax, Pfizer) in eradicating Streptococcus pneumoniae from the nasopharynges of patients with acute maxillary sinusitis. Furthermore, the emergence of antimicrobial resistance following therapy occurs only with azithromycin. The growing resistance of S. pneumoniae to penicillin and macrolides has resulted in the development of a new class of antibiotics—the ketolides. A study designed to compare the efficacy of telithromycin with that of azithromycin enrolled 105 patients with acute maxillary sinusitis. Fifty-nine patients received azithromycin 500 mg once daily for three days, and 46 patients received telithromycin 800 mg once daily for five days. Nasopharyngeal cultures were obtained before therapy and at a follow-up visit 10 to 12 days after antibiotic therapy was initiated. Prior to therapy, 67 potential pathogens had been recovered in 57 patients; 32 of these patients received telithromycin, and 25 received azithromycin. Overall, there were 31 isolates of S. pneumoniae: 14 in the azithromycin patients and 17 in the telithromycin patients. There were also 13 Haemophilus influenzae non-type b pathogens, eight of Staphylococcus aureus, and seven of Moraxella catarrhalis. A single pathogen was recovered in 46 patients, two pathogens were found in six patients, and three different pathogens were found in three patients. No pathogens were found in 48 patients. Of the 14 S. pneumoniae isolates found before therapy in the azithromycin patients, seven were resistant to penicillin, four were resistant to macrolides, and none were resistant to telithromycin. Of the 17 S. pneumoniae isolates in the telithromycin group, nine were resistant to penicillin, six were resistant to macrolides, and none were resistant to telithromycin. Following treatment, the number of S. pneumoniae isolates in the azithromycin patients was reduced from 14 to eight. Five of these isolates were resistant to azithromycin prior to therapy. By contrast, the number of S. pneumoniae isolates in the telithromycin patients was reduced from 17 to one after treatment. No differences were noted in the bacterial eradication rate of all other groups of isolates, all of which were susceptible to both azithromycin and telithromycin. The development of resistance to the antimicrobial agents used was reported in only five isolates (four of S. pneumoniae and one of H. influenzae). These resistant isolates were recovered only from patients who had received azithromycin.