The Microbiology of Bloodstream Infection: 20-Year Trends from the SENTRY Antimicrobial Surveillance Program

Abstract

Bloodstream infection (BSI) organisms were consecutively collected from >200 medical centers in 45 nations between 1997 and 2016. Species identification and susceptibility testing followed Clinical and Laboratory Standards Institute broth microdilution methods at a central laboratory. Clinical data and isolates from 264,901 BSI episodes were collected. The most common pathogen overall was <i>Staphylococcus aureus</i> (20.7%), followed by <i>Escherichia coli</i> (20.5%), <i>Klebsiella pneumoniae</i> (7.7%), <i>Pseudomonas aeruginosa</i> (5.3%), and <i>Enterococcus faecalis</i> (5.2%). <i>S. aureus</i> was the most frequently isolated pathogen overall in the 1997-to-2004 period, but <i>E. coli</i> was the most common after 2005. Pathogen frequency varied by geographic region, hospital-onset or community-onset status, and patient age. The prevalence of <i>S. aureus</i> isolates resistant to oxacillin (ORSA) increased until 2005 to 2008 and then declined among hospital-onset and community-acquired BSI in all regions. The prevalence of vancomycin-resistant enterococci (VRE) was stable after 2012 (16.4% overall). Daptomycin resistance among <i>S. aureus</i> and enterococci (DRE) remained rare (<0.1%). In contrast, the prevalence of multidrug-resistant (MDR) <i>Enterobacteriaceae</i> increased from 6.2% in 1997 to 2000 to 15.8% in 2013 to 2016. MDR rates were highest among nonfermentative Gram-negative bacilli (GNB), and colistin was the only agent with predictable activity against <i>Acinetobacter baumannii-Acinetobacter calcoaceticus</i> complex (97% susceptible). In conclusion, <i>S. aureus</i> and <i>E. coli</i> were the predominant causes of BSI worldwide during this 20-year surveillance period. Important resistant phenotypes among Gram-positive pathogens (MRSA, VRE, or DRE) were stable or declining, whereas the prevalence of MDR-GNB increased continuously during the monitored period. MDR-GNB represent the greatest therapeutic challenge among common bacterial BSI pathogens.