Epidemiology of Klebsiella oxytoca-associated diarrhea detected by Simmons citrate agar supplemented with inositol, tryptophan, and bile salts

J Clin Microbiol. 2012 May;50(5):1571-9. doi: 10.1128/JCM.00163-12. Epub 2012 Feb 22.


We studied the clinical and epidemiological characteristics of Klebsiella oxytoca-associated diarrhea in hospitalized patients in Hong Kong. Between 1 November 2009 and 30 April 2011, all inositol-fermenting colonies found on Simmons citrate agar supplemented with inositol, tryptophan, and bile salts (SCITB agar) used for the culturing of diarrheal stool samples were screened by a spot indole test for K. oxytoca. The overall sensitivity of SCITB agar plus the spot indole test (93.3%) for the detection of K. oxytoca in stool samples was superior to that of MacConkey agar (63.3%), while the specificities were 100% and 60.4%, respectively. The former achieved a 23-fold reduction in the workload and cost of subsequent standard biochemical identifications. Cytotoxin production and the clonality of K. oxytoca were determined by a cell culture cytotoxicity neutralization assay using HEp-2 cells and pulsed-field gel electrophoresis (PFGE), respectively. Of 5,581 stool samples from 3,537 patients, K. oxytoca was cultured from 117/5,581 (2.1%) stool samples from 104/3,537 (2.9%) patients. Seventy-six of 104 (73.1%) patients with K. oxytoca had no copathogens in their diarrheal stool samples. Twenty-four (31.6%) of 76 patients carried cytotoxin-producing strains, which were significantly associated with antibiotic therapy after hospital admission (50% versus 21.2%; P = 0.01). Health care-associated diarrhea was found in 44 (42%) of 104 patients with K. oxytoca, but there was no epidemiological linkage suggestive of a nosocomial outbreak, and PFGE showed a diverse pattern. None of the patients with cytotoxin-producing K. oxytoca developed antibiotic-associated hemorrhagic colitis, suggesting that K. oxytoca can cause a mild disease manifesting as uncomplicated antibiotic-associated diarrhea with winter seasonality.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Agar
  • Aged
  • Aged, 80 and over
  • Bacteriological Techniques / methods*
  • Bile Acids and Salts / metabolism
  • Cell Line
  • Child
  • Child, Preschool
  • Citric Acid / metabolism
  • Culture Media / chemistry*
  • Diarrhea / epidemiology*
  • Diarrhea / microbiology*
  • Electrophoresis, Gel, Pulsed-Field
  • Hepatocytes / microbiology
  • Hong Kong / epidemiology
  • Hospitalization
  • Humans
  • Infant
  • Inositol / metabolism
  • Klebsiella Infections / epidemiology*
  • Klebsiella Infections / microbiology*
  • Klebsiella oxytoca / classification
  • Klebsiella oxytoca / genetics
  • Klebsiella oxytoca / isolation & purification*
  • Klebsiella oxytoca / pathogenicity
  • Male
  • Middle Aged
  • Molecular Typing
  • Sensitivity and Specificity
  • Tryptophan / metabolism
  • Young Adult


  • Bile Acids and Salts
  • Culture Media
  • Citric Acid
  • Inositol
  • Tryptophan
  • Agar