title: Isolation and Identification of Clostridium difficile Using ChromID C. difficile Medium Combined With Gram Staining and PRO Disc Testing: A Proposal for a Simple Culture Process.
abstract: BACKGROUND
  ChromID C. difficile agar (CDIF; bioMérieux, France), a chromogenic medium, allows for the isolation and identification of Clostridium difficile strains within 24 hr regardless of pretreatment of stool specimens with heat or alcohol shock. In the present study, we designed and evaluated a simple procedure for the implementation C. difficile cultures using CDIF medium in a tertiary hospital setting.
  
  
  METHODS
  We designed a simple protocol for untreated stool specimens using CDIF medium followed by Gram staining and PRO disc (PRO disc K1532B, Key Scientific Products, USA) testing for the identification of C. difficile in colonies produced on CDIF agar. A total of 1,402 prospectively collected stool specimens from patients with suspected C. difficile infection were tested. The protocol was evaluated by phenotypic or molecular identification of C. difficile using Vitek 2 ANC card (bioMérieux) or 16S rDNA/tpi gene sequencing, respectively.
  
  
  RESULTS
  Of 1,402 stool specimens, 650 isolates were cultured in CDIF. Overall, 235 (36.2%, 235/650) strains could be presumptively identified as C. difficile by using Gram staining and PRO disc testing. Of those, 231 (98.3%, 231/235) isolates were confirmed as true C. difficile by molecular assays.
  
  
  CONCLUSIONS
  The use of CDIF combined with Gram staining and PRO disc testing of untreated stool specimens would allow for isolation and accurate identification of C. difficile strains and would be advantageous in reducing the multistep process for C. difficile culture.
authors.affiliation: Department of Laboratory Medicine and Genetics, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Kyung Sun
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Laboratory Medicine and Genetics, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Chang-Seok
authors.initials: CS
authors.lastname: Ki
authors.affiliation: Department of Laboratory Medicine and Genetics, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Nam Yong
authors.initials: NY
authors.lastname: Lee
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D001427:Bacterial Toxins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D001431:Bacteriological Techniques / Q000379:methods*; D016360:Clostridioides difficile / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D003470:Culture Media / Q000737:chemistry*; D004768:Enterotoxins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D005243:Feces / Q000382:microbiology; D005840:Gentian Violet / Q000737:chemistry; D006801:Humans; D007118:Immunoassay; D010619:Phenazines / Q000737:chemistry; D010641:Phenotype; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003470:Culture Media; D004768:Enterotoxins; C035863:Gram's stain; D010619:Phenazines; D012336:RNA, Ribosomal, 16S; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D005840:Gentian Violet
keywords: Clostridium difficile; Culture; Isolation