1. What taxonomic or nomenclature update has occurred?
Name change: Klebsiella aerogenes (formerly Enterobacter aerogenes)
2. Does it affect medical microbiology and clinical medicine? (If so, how?)
The name change may confuse medical providers who are accustomed to treatments based on specific antibiogram patterns.
The susceptibility breakpoints and rules are different, according to CLSI M100: Performance Standards for Antimicrobial Susceptibility Testing. Table footnotes indicate significant differences in susceptibility due to derepression of inducible AmpCB-lactamase. Isolates that are initially susceptible to certain cephalosporins may become resistant.41
Unlike the other Klebsiella spp., cefepime should be considered a Tier 1 agent for testing/reporting in this organism.
3. Are the correct antimicrobial susceptibility breakpoints in effect? (If not, what needs to change?)
Must check the breakpoints in use by the microbiology laboratory. Refer to CLSI M100 (table 1A-1.)42
4. Who must be notified? (And how?)
Aside from training the microbiology staff, the pharmacy and infectious disease committees, as well as infectious disease providers would benefit most from immediate communication of this name change.
Carroll et al. reported how best to report pertinent information: "In our laboratory practice, we report both names and add an isolate comment just below the organism identification, as follows: 'Klebsiella aerogenes, formerly Enterobacter aerogenes, may quickly develop resistance during therapy with third-generation cephalosporins (e.g., ceftriaxone, ceftazidime) due to production of AmpC beta-lactamases. This does not apply to cefepime.' "43
