title: Surveillance for antimicrobial resistance in Australian isolates of Clostridium difficile, 2013-14.
abstract: OBJECTIVE
  The objective of this study was to determine the activity of fidaxomicin and comparator antimicrobials against Clostridium difficile isolated from patients with C. difficile infection (CDI) in Australian hospitals and in the community.
  
  
  METHODS
  One private and one public laboratory from five states in Australia submitted a total of 474 isolates/PCR-positive stool samples during three collection periods in August-September 2013 (n = 175), February-March 2014 (n = 134) and August-September 2014 (n = 165). Isolate identification was confirmed by selective culture for C. difficile and a proportion of isolates from each state were characterized by PCR for toxin genes and PCR ribotyping. MICs of fidaxomicin and eight comparator antimicrobials were determined for all isolates using agar methodology.
  
  
  RESULTS
  Site collection yielded 440 isolates of C. difficile and PCR revealed a heterogeneous strain population comprising 37 different PCR ribotypes (RTs), 95% of which were positive for tcdA and tcdB (A+B+). The most common RTs were 014 (29.8%) and 002 (15.9%). Epidemic RT 027 was not identified; however, small numbers of virulent RTs 078 and 244 were found. Resistance to vancomycin, metronidazole and fidaxomicin was not detected and resistance to moxifloxacin was very low (3.4%). Fidaxomicin showed potent in vitro activity against all 440 isolates (MIC50/MIC90 0.03/0.12 mg/L) and was superior to metronidazole (MIC50/MIC90 0.25/0.5 mg/L) and vancomycin (MIC50/MIC90 1/2 mg/L).
  
  
  CONCLUSIONS
  These data confirm the potent in vitro activity of fidaxomicin against C. difficile. Moreover, this study provides an important baseline for ongoing long-term surveillance of antimicrobial resistance and prospective tracking of prominent and emerging strain types.
authors.affiliation: Microbiology and Immunology, School of Pathology and Laboratory Medicine, The University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Knight
authors.affiliation: Healthscope Pathology, Microbiology Department, Wayville, South Australia, Australia.
authors.forename: Steven
authors.initials: S
authors.lastname: Giglio
authors.affiliation: Department of Microbiology, Pathology North, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Huntington
authors.affiliation: Monash Infectious Diseases, Monash Health, Monash University, Clayton, Victoria, Australia.
authors.forename: Tony M
authors.initials: TM
authors.lastname: Korman
authors.affiliation: Monash Infectious Diseases, Monash Health, Monash University, Clayton, Victoria, Australia.
authors.forename: Despina
authors.initials: D
authors.lastname: Kotsanas
authors.affiliation: Microbiology and Infectious Diseases Laboratories, SA Pathology, Adelaide, South Australia, Australia.
authors.forename: Casey V
authors.initials: CV
authors.lastname: Moore
authors.affiliation: University of Queensland Centre for Clinical Research, Royal Brisbane and Women's Hospital, Herston, Queensland, Australia.
authors.forename: David L
authors.initials: DL
authors.lastname: Paterson
authors.affiliation: Melbourne Pathology, Collingwood, Victoria, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Prendergast
authors.affiliation: University of Queensland Centre for Clinical Research, Royal Brisbane and Women's Hospital, Herston, Queensland, Australia.
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Huber
authors.affiliation: Sullivan Nicolaides Pathology, Taringa, Queensland, Australia.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Robson
authors.affiliation: Melbourne Pathology, Collingwood, Victoria, Australia.
authors.forename: Lynette
authors.initials: L
authors.lastname: Waring
authors.affiliation: Douglass Hanly Moir Pathology, Macquarie Park, New South Wales, Australia.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Wehrhahn
authors.affiliation: Microbiology and Infectious Diseases Laboratories, SA Pathology, Adelaide, South Australia, Australia.
authors.forename: Gerhard F
authors.initials: GF
authors.lastname: Weldhagen
authors.affiliation: Healthscope Pathology, Microbiology Department, Wayville, South Australia, Australia.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Wilson
authors.affiliation: Microbiology and Immunology, School of Pathology and Laboratory Medicine, The University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia Department of Microbiology, PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia thomas.riley@uwa.edu.au.
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Riley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001315:Australia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016360:Clostridioides difficile / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D003015:Clostridium Infections / Q000382:microbiology*; D017714:Community-Acquired Infections / Q000382:microbiology; D003428:Cross Infection; D024881:Drug Resistance, Bacterial; D062665:Epidemiological Monitoring; D005260:Female; D000077732:Fidaxomicin; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D021521:Ribotyping; D055815:Young Adult
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000077732:Fidaxomicin