Frequency of occurrence and antimicrobial susceptibility patterns for pathogens isolated from Latin American patients with a diagnosis of pneumonia: results from the SENTRY antimicrobial surveillance program (1998)

The correct empiric choice of antimicrobial therapy in the treatment of pne umonia in hospitalized patients has established itself as a major therapeut ic challenge to clinicians. Selection of an inappropriate antimicrobial age nt could lead to increased rates of mortality and morbidity. Characteristic s of pathogens responsible for this infection such as species prevalence, o verall antimicrobial resistance rates, and mechanisms of detected resistanc e could serve as an invaluable resource to clinicians in making such therap eutic selections. This report addresses the aforementioned problems/needs b y analysis of 712 strains isolated from the lower respiratory tract of pati ents hospitalized with a diagnosis of pneumonia in 10 Latin American medica l centers in the SENTRY Antimicrobial Surveillance Program (1998). The four most frequently isolated pathogens (no/% of total) were: Pseudomonas aerug inosa (191/26.8%), Staphylococcus aureus (171/24.0%), Klebsiella spp. (86/1 2.1%), and Acinetobacter spp. (75/10.5%); representing nearly 75.0% of all isolates. More than 40 antimicrobial agents (23 reported) were tested again st these isolates by reference broth microdilution methodology, and suscept ibility profiles were established The nonfermentative Gram-negative bacteri a (P. aeruginosa and Acinetobacter spp.) exhibited high levels of resistanc e to the agents tested. Amikacin (77.5% susceptible) was the most active dr ug tested against P. aeruginosa, followed by piperacillin/tazobactam (73.3% susceptible) > meropenem (72.8%) > imipenem (71.7%) as the only antimicrob ials possessing a susceptibility rate of >70.0%. Only the carbapenem class compounds, imipenem (81.3% susceptible) and meropenem (78.3% susceptible) p ossessed susceptibility rates >50.0% against the Acinetobacter spp. isolate s. Based on published interpretive criteria, over 22.0% of the Klebsiella s pp. and 12.5% of the Escherichia coli were classified as extended spectrum beta-lactamase (ESBL) producers. Of the cephalosporin class compounds teste d against the Klebsiella spp. and E. coli isolates, cefepime demonstrated t he highest rates of susceptibility (84.9% and 91.7%, respectively). This co mpound also fared well against the Enterobacter spp. isolates, inhibiting 8 8.2% of the isolates tested, many of which were resistant to ceftazidime an d ceftriaxone. Resistance to oxacillin among the S. aureus isolates was nea rly 50.0%, with vancomycin, teicoplanin, and the streptogramin combination quinupristin/dalfopristin inhibiting all isolates. Several clusters of mult iply resistant organisms were also observed, and further characterization b y ribotyping and pulsed-field gel electrophoresis established possible pati ent-to-patient spread. The results of this study indicate that rates of res istance among respiratory tract pathogens continue td rise in Latin America , with specific concerns for the high prevalence of nonfermentative Gram-ne gative bacteria isolated, oxacillin resistance rates in S. aureus, and the epidemic dissemination of multiply-resistant strains in several medical cen ters. International surveillance programs (SENTRY) should assist in the con trol of escalating antimicrobial resistance in this geographic area. (C) 20 00 Elsevier Science Inc. All rights reserved.