Respiratory tract pathogens isolated from patients hospitalized with suspected pneumonia in Latin America: frequency of occurrence and antimicrobial susceptibility profile: results from the SENTRY Antimicrobial Surveillance Program (1997-2000)

Abstract

In spite of the recent medical advances, lower respiratory tract infections are still the most frequent infectious causes of mortality worldwide. The objective of this study was to determine the frequency of occurrence and antimicrobial susceptibility of bacterial isolates collected from hospitalized patients with pneumonia in Latin American medical centers during the first four years of the SENTRY Program. The five most frequently isolated species were (n/%): Pseudomonas aeruginosa (659/26.3%), Staphylococcus aureus (582/23.3%), Klebsiella pneumoniae (255/10.2%), Acinetobacter spp. (239/9.6%), and Enterobacter spp. (134/5.4%). P. aeruginosa demonstrated high rates of resistance to most of the antimicrobials tested. Against P. aeruginosa, the most active agents were meropenem (MIC 50, 1 μg/ml; 71.6% susceptible), amikacin (MIC 50, 4 μg/ml; 71.0% susceptible), and piperacillin/tazobactam (MIC 50, 16 μg/ml; 70.4% susceptible). Imipenem (MIC 50, 1 μg/ml; 84.1% susceptible) and meropenem (MIC 50, 2 μg/ml; 84.9% susceptible) were the most active agents against Acinetobacter spp. followed by tetracycline (MIC 50, ≤4 μg/ml; 52.3% susceptible). Although the broad-spectrum cephalosporins had demonstrated excellent in vitro activity against Klebsiella pneumoniae isolates (MIC 50s range, ≤ 0.12 to 0.25 μg/ml), elevated rates of resistance (46.3%-58.5%) were observed. Approximately 44.0% and 29.0% of K. pneumoniae and E. coli isolates were considered ESBL producers based on NCCLS criteria, respectively. Overall, the prevalence of methicillin-resistant S. aureus was 46.2%. The most active drugs against this pathogen were vancomycin, teicoplanin, linezolid and quinupristin/dalfopristin. In summary, the SENTRY Antimicrobial Surveillance Program has detected a high prevalence of methicillin-resistant S. aureus and multidrug resistant non-fermentative Gram-negative bacilli isolated from respiratory tract specimens of hospitalized patients with pneumonia in Latin America. Our results emphasize the importance of local surveillance programs in correctly guiding empiric therapy and local intervention programs in attempt to reduce antimicrobial resistance.