title: Epidemiology of Klebsiella oxytoca-associated diarrhea detected by Simmons citrate agar supplemented with inositol, tryptophan, and bile salts.
abstract: 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.
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, China.
authors.forename: Vincent C C
authors.initials: VC
authors.lastname: Cheng
authors.forename: Wing-Cheong
authors.initials: WC
authors.lastname: Yam
authors.forename: Lee-Lee
authors.initials: LL
authors.lastname: Tsang
authors.forename: Miranda C Y
authors.initials: MC
authors.lastname: Yau
authors.forename: Gilman K H
authors.initials: GK
authors.lastname: Siu
authors.forename: Sally C Y
authors.initials: SC
authors.lastname: Wong
authors.forename: Jasper F W
authors.initials: JF
authors.lastname: Chan
authors.forename: Kelvin K W
authors.initials: KK
authors.lastname: To
authors.forename: Herman
authors.initials: H
authors.lastname: Tse
authors.forename: Ivan F N
authors.initials: IF
authors.lastname: Hung
authors.forename: Josepha W M
authors.initials: JW
authors.lastname: Tai
authors.forename: Pak-Leung
authors.initials: PL
authors.lastname: Ho
authors.forename: Kwok-Yung
authors.initials: KY
authors.lastname: Yuen
mesh_terms: D000293:Adolescent; D000328:Adult; D000362:Agar; D000368:Aged; D000369:Aged, 80 and over; D001431:Bacteriological Techniques / Q000379:methods*; D001647:Bile Acids and Salts / Q000378:metabolism; D002460:Cell Line; D002648:Child; D002675:Child, Preschool; D019343:Citric Acid / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry*; D003967:Diarrhea / Q000453:epidemiology* / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D022781:Hepatocytes / Q000382:microbiology; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007294:Inositol / Q000378:metabolism; D007710:Klebsiella Infections / Q000453:epidemiology* / Q000382:microbiology*; D041121:Klebsiella oxytoca / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D008297:Male; D008875:Middle Aged; D058889:Molecular Typing; D012680:Sensitivity and Specificity; D014364:Tryptophan / Q000378:metabolism; D055815:Young Adult
chemical_list: D001647:Bile Acids and Salts; D003470:Culture Media; D019343:Citric Acid; D007294:Inositol; D014364:Tryptophan; D000362:Agar