Natural antibiotic susceptibility of Klebsiella pneumoniae, K-oxytoca, K-planticola, K-ornithinolytica and K-terrigena strains

The natural susceptibility of 221 Klebsiella strains to 71 antibiotics was examined. The strains were isolated from clinical specimens and the environ ment, and belonged to K. pneumoniae subsp. pneumoniae (n=40), K. pneumoniae subsp. ozaenae (37), K pneumoniae subsp. rhinoscleromatis (10), K. oxytoca (44), K. planticola. (40), K. ornithinolytica (25) and K. terrigina(25). M IC values were determined by a microdilution procedure in IsoSensitest brot h according to the German standard (DIN). All Klebsiella spp. were naturall y resistant or intermediate to amoxicillin, ticarcillin and to antibiotics to which other Enterobacteriaceae are also intrinsically resistant. Klebsie lla spp. were naturally sensitive or intermediate to several penicillins, a ll tested cephalosporins, aminoglycosides, quinolones, tetracyclines, trime thoprim, cotrimoxazole, chloramphenicol and nitrofurantoin. K pneumoniae su bsp. ozaenae and subsp. rhinoscleromatis strains were generally more suscep tible to antibiotics than strains of other Klebsiella taxa. K. pneumoniae s ubsp. rhinoscleromatis was the most susceptible taxon, being highly suscept ible to cefuroxime, anti-folates and naturally intermediate to erythromycin and clarithromycin. K. pneumoniae subsp. ozaenae was most susceptible to g lycopeptides. K. oxytoca and K. terrigena strains were least susceptible to cefazoline, cefoperazone and fosfomycin, respectively. The results of the present study describe a database of the natural antimicrobial susceptibili ty of Klebsiella spp., which can be used for the validation of antibiotic s usceptibility results of these bacteria. MIC patterns to beta -lactams indi cate the expression of chromosomally encoded class A beta -lactamases in al l the species, including the subspecies of K. pneumoniae. Similar natural s usceptibility patterns of K. planticola and K. ornithinolytica to all teste d antibiotics support the status of Ii ornithinolytica as a biovar of K. pl anticola.