title: Genotypes of Klebsiella oxytoca isolates from patients with nosocomial pneumonia are distinct from those of isolates from patients with antibiotic-associated hemorrhagic colitis.
abstract: Klebsiella oxytoca acts as a pathobiont in the dysbiotic human intestinal microbiota, causing antibiotic-associated hemorrhagic colitis (AAHC), but it also infects other organs, resulting in pneumonia and urinary tract and skin infections. The virulence of K. oxytoca is still poorly understood. The production of a specific cytotoxin has been linked to AAHC pathogenesis. To investigate the clonal relationships of K. oxytoca with regard to clinical origin and virulence attributes, we established a multilocus sequence typing (MLST) method and analyzed 74 clinical K. oxytoca isolates from asymptomatic carriers and patients with AAHC, respiratory infections, and other infections. The isolates were phenotypically characterized, typed, and compared phylogenetically based on the sequences of seven housekeeping genes. MLST analysis yielded 60 sequence types, 12 of which were represented by more than one isolate. The phylogenetic tree distinguished clusters of K. oxytoca isolates between patients with AAHC and those with respiratory infections. Toxin-positive and -negative strains were observed within one sequence type. Our findings indicate that AAHC isolates share a genetic background. Interestingly, K. oxytoca isolates from nosocomial pneumonia showed a different genetic clustering, suggesting that these strains do not originate from the intestines or that they are specialized for respiratory tract colonization. Our results further indicate a polyphyletic origin and possible horizontal transfer of the genes involved in K. oxytoca cytotoxin production. This work provides evidence that K. oxytoca isolates colonizing the two main clinically relevant habitats (lower gastrointestinal [GI] tract and respiratory tract) of the human host are genetically distinct. Applications of this MLST analysis should help clarify the sources of nosocomial infections.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Kathrin A T
authors.initials: KA
authors.lastname: Herzog
authors.forename: Georg
authors.initials: G
authors.lastname: Schneditz
authors.forename: Eva
authors.initials: E
authors.lastname: Leitner
authors.forename: Gebhard
authors.initials: G
authors.lastname: Feierl
authors.forename: Karl Martin
authors.initials: KM
authors.lastname: Hoffmann
authors.forename: Ines
authors.initials: I
authors.lastname: Zollner-Schwetz
authors.forename: Robert
authors.initials: R
authors.lastname: Krause
authors.forename: Gregor
authors.initials: G
authors.lastname: Gorkiewicz
authors.forename: Ellen L
authors.initials: EL
authors.lastname: Zechner
authors.forename: Christoph
authors.initials: C
authors.lastname: Högenauer
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology*; D003603:Cytotoxins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004761:Enterocolitis, Pseudomembranous / Q000188:drug therapy / Q000382:microbiology*; D005838:Genotype; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology*; D041121:Klebsiella oxytoca / Q000145:classification* / Q000187:drug effects / Q000235:genetics*; D005810:Multigene Family / Q000235:genetics; D058885:Multilocus Sequence Typing / Q000379:methods; D010802:Phylogeny; D011014:Pneumonia / Q000188:drug therapy / Q000382:microbiology*; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D003603:Cytotoxins