Trends in Susceptibility Rates and Extended-Spectrum β-Lactamase Production of Klebsiella pneumoniae in Bloodstream Infections Across the United States Veterans Affairs Healthcare System.

Klebsiella pneumoniae is an important pathogen, increasingly notorious for its ability to become resistant to antimicrobial agents. This study sought to characterize trends in antimicrobial susceptibility rates for K. pneumoniae causing bacteremias across the United States (U.S.) Veterans Healthcare Administration (VHA) from 2007 through 2013 utilizing a national clinical database. K. pneumoniae grew in 9,235 blood cultures from 8,414 patients. Nationally, ampicillin-sulbactam, ceftazidime, cefepime, ertapenem, fluoroquinolones, and amikacin demonstrated statistically significant susceptibility rate increases against K. pneumoniae in the 2010-2013 period versus the 2007-2009 period. No antimicrobial agent had a statistically significant nationwide susceptibility rate decrease. Of the 126 antibiotic-organism pairs tested among 9 U.S. regions, 18 demonstrated statistically significant susceptibility rate increases while 6 demonstrated statistically significant susceptibility rate decreases. The East North Central (eight agents), Mid-Atlantic (five agents), and South Atlantic (four agents) regions demonstrated statistically significant susceptibility rate increases for multiple antimicrobial agents. Of the 70 antibiotic-organism pairs tested among 5 different medical center complexity levels, 11 antibiotics demonstrated statistically significant susceptibility rate increases and 1 demonstrated a statistically significant rate decrease. Extended-spectrum β-lactamase production did not significantly change over the study period across an available nationwide representation of 31 facilities (10.6% in 2007-2009 vs. 9.21% in 2010-2013, p=0.17). The South Atlantic and Mid-Atlantic regions had the highest prevalence of extended-spectrum ß-lactamase production in the two periods, respectively. The recent trend of generally increasing susceptibility rates for K. pneumoniae bloodstream isolates in this nationwide U.S. VHA study contrasts from other U.S. health system reports demonstrating increasing trends of antimicrobial resistance.