Bacterial pathogens isolated from patients with bloodstream infections in Latin America, 1997: Frequency of occurrence and antimicrobial susceptibility patterns from the SENTRY antimicrobial surveillance program

RESUMO

We report the antimicrobial susceptibility of 736 organisms isolated from bloodstream infections in 10 Latin American medical centers during the first six months of 1997. The data presented here is from the SENTRY Antimicrobial Surveillance Program, a comprehensive surveillance study involving 72 medical centers worldwide. The isolates were tested for in vitro susceptibility to 35 antimicrobial agents by the broth microdilution method. The five most frequently isolated species were(n/percent) Staphylococcus aureus (165/22.4 percent), Escherichia coli (118/16.0 percent), coagulase-negative staphylococci (CoNS - 115/15.6 percent), Pseudomonas aeruginosa (51/6.9 percent), Klebsiella ssp. (46/6.3 percent). Susceptibility to oxacillin was 70.9 percent for S.aureus and only 33.9 percent for CoNS. Vancomycin was active against all of staphylococci, while teicoplanin was active against 99.4 percent of S.aureus and only 90.4 percent of CoNS. The new fluoroquinolones sparfloxacin, gatifloxacin, and trovafloxacin, and the streptogramin, quinupristin/dalfopristin, were very active against these species. Only one vancomycin-resistant enterococcus was detected; however, high-level aminoglycoside resistance rates were common (66.7 percent). E.coli and Klebsiella spp. showed low susceptibilities for cefotaxime (90.7 percent and 41.3 percent) and for cefoxitin (85.6 percent and 78.3 percent respectively), indicating a high frequency of isolates that produce ESBL and/or stably derepressed ampC enzymes. These strains, phenotypically consistent with extended-spectrum ß-lactamase (ESBL) production, were typed using ribotyping and pulsed-field gel electrophoresis. The most active compounds (MIC90 in µg/mL/ percent susceptibility) against P. aeruginosa were meropenem (2/94.1 percent), followed by amikacin (>32/86.3 percent), and piperacillin alone or with tazobactam (128/84.3 percent). Ceftazidime and cefepime showed similar activity (70.6 percent susceptibility) and levofloxacin was the most active fluoroquinolone (MIC50 menor do que 0.5; 76.5 percent susceptibility) against this gram-negative species. These results show the unique pattern of bloodstream isolates for Latin America and they demonstrate the present utility of several classes of compounds against emerging antimicrobial-resistant species in this region.