Resistance among problem respiratory pathogens in pediatrics.

During the past two decades, the prevalence of beta-lactamase production with nontypable strains of Haemophilus influenzae has increased to about 35%. Fortunately, rates of resistance to other oral antimicrobials have not developed at a comparable pace. Amoxicillin/clavulanate, cefuroxime and cefpodoxime remain nearly uniformly active whereas rates of resistance to tetracycline, trimethoprim/sulfamethoxazole, chloramphenicol, cefaclor, loracarbef, cefprozil, azithromycin and clarithromycin remain low (1 to 5%). Virtually all clinical isolates of Moraxella catarrhalis produce beta-lactamase and are probably resistant to ampicillin and amoxicillin. However, alternative oral antimicrobials are almost always active. A compelling problem facing pediatricians today is the emergence of penicillin resistance with clinical isolates of Streptococcus pneumoniae. Currently, 15 to 25% of pneumococcal isolates in the United States have either intermediate (10 to 20%) or complete (3 to 5%) penicillin resistance caused by alterations in penicillin-binding proteins. Loss of activity of other beta-lactams is observed with penicillin-resistant S. pneumoniae. Third generation cephalosporins retain sufficient activity to warrant use in selected pneumococcal infections, even those caused by completely penicillin-resistant strains. Unfortunately, strains of S. pneumoniae with further alterations in penicillin-binding proteins have emerged such that even extended spectrum third generation cephalosporins lack activity. Rates of resistance to non-beta-lactam agents are also changing. The consequence of these changing patterns of resistance is that therapeutic options for pneumococcal infections in some patients are becoming increasingly limited.