Changing Antimicrobial Susceptibility Patterns among Streptococcus pneumoniae and Haemophilus influenzae from Brazil: Report from the SENTRY Antimicrobial Surveillance Program (1998–2004)

Although antimicrobial resistance rates among Streptococcus pneumoniae and Haemophilus influenzae have increased significantly in most countries in the last years, most studies from Brazil report relatively low resistance rates among these pathogens. In this study, we analyzed the susceptibility patterns of S. pneumoniae and H. influenzae from Brazil during a 7-year period. A total of 829 S. pneumoniae and 718 H. influenzae consecutively collected from 1998 to 2004, mainly from respiratory tract and bloodstream infections, were susceptibility tested by broth microdilution methods against >30 drugs and the results were analyzed by year. Overall, 77.8% of S. pneumoniae strains were considered susceptible (MIC, ≤0.06 µ g/ml) to penicillin. Resistance to penicillin (MIC, ≥2 µg/ml) and ceftriaxone (MIC, ≥4 µg/ml) were detected in 7.5 and 0.5% of strains, respectively. The fluoroquinolones, levofloxacin (MIC_90, 1 µg/ml) and gatifloxacin (MIC_90, 0.5 µ g/ml), were active against 99.8% of the isolates tested. Among the other non-β-lactam drugs tested, the rank order of susceptibility rates was chloramphenicol (98.9%) > clindamycin (96.4%) > erythromycin (90.6%) > tetracycline (69.8%) > trimethoprim/sulfamethoxazole (36.7%). Resistance to penicillin has increased markedly among S. pneumoniae isolates over 7 years (from 2.9 to 11.0%). Additionally, resistance rates against erythromycin, clindamycin, and tetracycline decreased among pneumococcal strains during the same period. S. pneumoniae recovered from pediatric patients (≤5 years) showed increased penicillin and trimethoprim/sulfametroxazole resistance rates compared to older populations. The rate of ampicillin resistance among H. influenzae was 14.0%, which also corresponds with the β -lactamase production rate. All H. influenzae isolates were susceptible to amoxicillin/clavulanate (MIC_90, 1 µg/ml), ceftriaxone (MIC_90, ≤ 0.008 µg/ml), cefepime (MIC_90, 0.12 µg/ml), ciprofloxacin (MIC_90, ≤ 0.12 µg/ml), levofloxacin (MIC_90, ≤ 0.5 µg/ml), and gatifloxacin (MIC_90, ≤ 0.03 µg/ml). Resistance to the antimicrobials tested remained very stable among H. influenzae isolates during the 7-year study period. The continued emerging antimicrobial resistances found in these pathogens (mainly S. pneumoniae) highlight the need for alternative agents for the treatment of infections caused by these species.