Streptococcus pneumoniae and Haemophilus influenzae are the primary bacterial etiologic pathogens identified in respiratory tract infections, with S pneumoniae causing the greatest morbidity and mortality, especially among the elderly, and having the most significant resistance profile. The ongoing ARM program documents resistance patterns in US inpatient and outpatient isolates and includes data from 251 US institutions on more than 17 million isolates.
Antibiograms and sensitivity reports of S pneumoniae isolates collected in the ARM database from 1995-2002 were reviewed for resistance to penicillin, erythromycin, clindamycin, cefotaxime, and ceftriaxone; H influenzae isolates were reviewed for resistance to cefotaxime and ceftriaxone. Comparisons were conducted using a Web-based analysis tool.
Nationally, S pneumoniae resistance to penicillin was 37.4% (n=37,688); to erythromycin, 29.6%, (n=18,774); and to clindamycin, 9.9% (n=5510). Resistance to cefotaxime was 25.5% (n=10,527) and to ceftriaxone, 16.8% (n=26,594). S pneumoniae isolates in North Central and Northeast remained more susceptible to penicillin and erythromycin than in South Central and Southeast. Across all regions, S pneumoniae was more resistant to cefotaxime than to ceftriaxone, with the difference greatest in the Southeast and least in North Central. For H influenzae, resistance to cefotaxime was 4.3% (n=4927) and to ceftriaxone, 1.0% (n=10,353), a difference seen largely in the Northeast.CONCLUSIONS: Resistance rates from the ARM program showed pneumococcal and H influenzae isolates to be more susceptible to ceftriaxone than cefotaxime, suggesting these third-generation cephalosporins may not be therapeutically equivalent. This disparity is believed to be due to clonal variations. In addition, data through 2001 do not reflect the new NCCLS breakpoints, artificially suppressing sensitivity numbers.CLINICAL IMPLICATIONS: Within each antibiotic class, agents vary significantly with respect to susceptibility to S pneumoniae; use of the more active agent (ie, ceftriaxone) may delay emergence of resistance.
J.G. Gums, Aventis, grant monies; Roche, grant monies; Wyeth, grant monies.