How soon is now? The urgent need for randomized, controlled trials evaluating treatment of multidrug-resistant bacterial infection.

Antibiotic resistance among gram-negative bacilli shows no signs of abatement. Resistance of Pseudomonas aeruginosa, Acinetobacter baumannii, and the Enterobacteriaceae to multiple antibiotic classes is a growing clinical problem worldwide [1]. Two trends are particularly noteworthy. First, there has been increased recognition of successful antibiotic-resistant clones appearing in multiple geographic regions. Multilocus sequence typing analyses of contemporary collections of multidrug-resistant strains have shown that carbapenem-resistant A. baumannii ST92 [2], K. pneumoniae carbapenemase–producing K. pneumoniae ST258 [3], and extended-spectrum b-lactamase–producing Escherichia coli ST131 [4] are global problems. Second, new mechanisms of multidrug resistance are becoming evident. These include aminoglycoside 16S ribosomal RNA methylation [5] and production of the New Delhi metallo-b-lactamase [6].