Natural antimicrobial susceptibility patterns of Kluyvera ascorbata and Kluyvera cryocrescens strains and review of the clinical efficacy of antimicrobial agents used for the treatment of Kluyvera infections.

The natural susceptibility of 58 K. ascorbata and 24 K. cryocrescens strains to 71 antimicrobial agents was investigated. MIC values were determined with a microdilution procedure in cation-adjusted Mueller Hinton broth (for all strains) and IsoSensitest broth (for some strains). Both species were naturally sensitive or of intermediate susceptibility to tetracyclines, aminoglycosides, quinolones, antifolates, chloramphenicol, nitrofurantoin, fosfomycin, aminopenicillins plus beta-lactamase inhibitors, acylureidopenicillins, carbapenems, aztreonam and some cephalosporins. Uniform natural resistance was found with several macrolides, lincosamides, streptogramins, glycopeptides, rifampicin, fusidic acid, linezolid, penicillin G, oxacillin, and amoxicillin. To the latter agent, some strains of both species were also of intermediate susceptibility. Species-related differences in natural susceptibility affecting clinical assessment criteria were seen with azithromycin, cethromycin, telithromycin, ticarcillin and some cephalosporins, to which K. ascorbata was less susceptible than K. cryocrescens. Medium-related differences in susceptibility were restricted to a few antibiotics. A data base about the natural susceptibility of the two most common Kluyvera spp. to a wide range of antimicrobial agents is presented. It can be used for the validation of forthcoming susceptibility trials of these microorganisms. Although some susceptibilty patterns might be helpful for the phenotypical separation of K. ascorbata from K. cryocrescens, they do not allow a separation of these species. The literature dealing with the clinical efficacy of antimicrobial agents used for the treatment of Kluyvera infections is discussed.