Joainig et al.: Cytotoxic Effects of Klebsiella oxytoca Strains isolated from cases of Antibiotic Associated Hemorrhagic Colitis or other Infections and from Healthy Subjects

Joainig, MM; Gorkiewicz, G; Leitner, E; Weberhofer, P; Zollner-Schwetz, I; Lippe, I; Feierl, G; Krause, R; Hinterleitner, T; Zechner, EL; Hoegenauer, C.
Cytotoxic Effects of Klebsiella oxytoca Strains isolated from cases of Antibiotic Associated Hemorrhagic Colitis or other Infections and from Healthy Subjects.
J Clin Microbiol. 2010; [Fulltext] [PubMed]

Abstract:
Antibiotic associated hemorrhagic colitis (AAHC) is associated with Klebsiella oxytoca. This study analyzed whether cytotoxic properties are linked to specific subtypes of K. oxytoca. Klebsiella isolates from stools of AAHC patients, healthy carriers and diarrhea patients, as well as from infections of other organs were investigated. Cytotoxic effects on human epithelial cells were limited to the species K. oxytoca and not detectable in any other Klebsiella species. Isolates of AAHC patients and from stools showed the highest proportion of cytotoxic strains. Urinary or respiratory tract isolates exhibited no cytotoxicity. Macro-restriction profiling of strains revealed no genetic relationships of AAHC isolates or the cytotoxic phenotype, but identified that different K. oxytoca strains with different cytotoxic behaviour may be prevalent in the same AAHC patient. Under laboratory conditions cytotoxicity was maximally effective after exponential bacterial growth, then declined, despite continued viability of K. oxytoca in culture. Given its capacity to induce AAHC and that a high proportion of stool isolates tested cytotoxin-positive, we argue that K. oxytoca should be considered as opportunistic pathogen, if detected in stools. The ability to induce disease after antibiotic treatment most likely represents overgrowth of the toxin-producing bacterium due to alteration of the normal colonic microflora.


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