Frequency of occurrence and antimicrobial susceptibility of Gram-negative bacteremia isolates in patients with urinary tract infection: results from United States and European hospitals (2009-2011)

We evaluated the frequency of occurrence and antimicrobial susceptibility patterns of Gram-negative bacteria isolated from bacteremic patients with UTI from European (EU) and United States (USA) hospitals during a 3-year period (2009-2011). Susceptibility testing was performed by the reference broth microdilution method on 2071 Gram-negative bacilli. The most frequently isolated pathogens were Escherichia coli (63.3/71.3% in USA/EU), Klebsiella spp. (16.7/11.2%) and Proteus mirabilis (6.4/5.0%). Escherichia coli susceptibility rates were generally similar in the USA and EU, with extended-spectrum beta-lactamase (ESBL)-phenotype rates at 8.1% in both regions. Among Klebsiella spp., ESBL rates varied from 11.4/17.1% in 2009 to 16.1/40.4% in 2011 in USA/EU, and susceptibility rates were generally lower in EU compared to the USA. Pseudomonas aeruginosa exhibited lower susceptibility rates to ceftazidime, meropenem and piperacillin/tazobactam in EU (78.4, 78.4 and 76.5%, respectively) compared to USA (91.2, 88.2 and 91.2%, respectively). In summary, very few antimicrobials provided satisfactory coverage (>90%) when tested against Klebsiella spp. and P. aeruginosa isolates in EU.