Four-year evaluation of frequency of occurrence and antimicrobial susceptibility patterns of bacteria from bloodstream infections in Latin American medical centers

Abstract

As part of the Latin American arm of the SENTRY Antimicrobial Surveillance Program, 7,207 bacterial isolates collected consecutively from bloodstream infections (BSI) during the period of January 1997 through December 2000 were analyzed. Ten Latin American laboratories located in six countries participated in the study during each year. Antimicrobial susceptibility testing was performed using the reference NCCLS broth microdilution method. The most frequently isolated species were (n/%): Staphylococcus aureus (1,532/21.3%), Escherichia coli (1,239/17.2%), coagulase-negative Staphylococcus (1,002/13.9%), Klebsiella pneumoniae (664/9.2%), and Pseudomonas aeruginosa (470/6.5%). The prevalence of S. aureus as a cause of BSI increased from 20.5% in 1997 to 23.3% in 2000 (p = 0.011), but oxacillin-resistance rates remained relatively stable during this period (around 30%). Enterococci (216 isolates) showed low rates of resistance to both vancomycin (2.4%) and ampicillin (7.9%) and 72.7% of 289 Streptococcus pneumoniae isolates evaluated were susceptible to penicillin (MIC </=0.06 microg/mL). Resistance rates among Gram-negative bacilli were much higher than those reported in other regions evaluated in the SENTRY Program. The main antimicrobial resistance problems among these pathogens were the high prevalences of ESBL-producing E. coli (6.7%) and K. pneumoniae (47.3%), and carbapenem-resistance among P. aeruginosa (around 12%) and Acinetobacter spp. (around 10%). P. aeruginosa resistance rates to meropenem, piperacillin/tazobactam, amikacin, and ciprofloxacin showed a significant increase during the 4-year period evaluated. Resistance rates varied according to the country for several pathogen-antimicrobial combinations. In summary, resistance to most antimicrobial agents for a number of species implicated in bacteremia, especially among Gram-negative rods, has reached worrisome levels and continues to increase.