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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Retrospectively registered

Titles & IDs
Public title
Blastocystis subtypes in symptomatic and asymptomatic family members and pets and response to therapy.
Scientific title
In people positive for Blastocystis carriage in their stools is their any difference in the specific Blastocystis subtypes found between patients with gastrointestinal symptoms and their asymptomatic human and animal household members and do their gastrointestinal symptoms change after therapy with metronidazole or sulfamethoxazole/trimethoprim.
Secondary ID [1] 253225 0
University of Queensland, School of Veterinary Science, Gatton
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Irritable bowel like gastrointestinal symptoms in patients positive for Blastocystis carriage in their stool. 258726 0
Response of symptomatic patients positive for Blastocystis to 14 days of therapy with metronidazole 400 mg three times daily or sulfamethoxazole/trimethoprim 160mg/800mg twice daily. 258727 0
Specific subtypes of Blastocystis found in symptomatic patients compared to asymptomatic human and animal household members. 258728 0
Condition category
Condition code
Oral and Gastrointestinal 258879 258879 0 0
Other diseases of the mouth, teeth, oesophagus, digestive system including liver and colon

Study type
Description of intervention(s) / exposure
Patients with gastrointestinal symptoms positive for Blastocystis carriage in their stool were treated with 14 days of either oral metronidazole 400 mg three times daily or oral sulfamethoxazole/trimethoprim (Bactrim) 160/800 mg twice daily.
Intervention code [1] 257676 0
Treatment: Drugs
Comparator / control treatment
Faecal samples were collected from symptomatic patients before and within 48 hours of cessation of antibiotic therapy and again at Day 28 and 56 after therapy. The patient pre-treatment is acting as his/her own control.
Control group

Primary outcome [1] 259738 0
Presence or absence of Blastocystis in stool samples before and after antibiotic therapy as assessed by fresh faecal smears, faecal culture and PCR analysis of both faecal specimens and faecal cultures.
Timepoint [1] 259738 0
Sample time points were baseline (0-2 weeks before therapy), Day 15, 28 and 56.
Secondary outcome [1] 266474 0
To assess how many asymptomatic human and animal household contacts of symptomatic patients were also positive for Blastocystis in their stool and to assess if there was any difference in Blastocystis subtypes between symptomatic and asymptomatic carriers.
Timepoint [1] 266474 0
Faecal samples were assessed at Day 15 in these groups with fresh faecal smears, faecal cultures and PCR analysis of both faeces and faecal cultures.

Key inclusion criteria
Chronic gastrointestinal symptoms
Minimum age
16 Years
Maximum age
80 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Other documented cause of gastrointestinal symptoms other than Blastocystis carriage

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 258150 0
Name [1] 258150 0
University of Queensland
Address [1] 258150 0
School of Veterinary Science,
University of Queensland,
Building 8114
Gatton Campus,
Queensland 4343
Country [1] 258150 0
Primary sponsor type
Dr Rebecca Traub
School of Veterinary Science,
University of Queensland,
Building 8114
Gatton Campus,
Queensland, 4343
Secondary sponsor category [1] 257315 0
Name [1] 257315 0
Address [1] 257315 0
Country [1] 257315 0

Ethics approval
Ethics application status
Ethics committee name [1] 260127 0
University of Queensland Medical Research Ethics Committee
Ethics committee address [1] 260127 0
Chancellor Place
St Lucia
Ethics committee country [1] 260127 0
Date submitted for ethics approval [1] 260127 0
Approval date [1] 260127 0
Ethics approval number [1] 260127 0

Brief summary
Blastocystis is a common enteric parasite but it is not known if it pathogenic. Many reports suggest that Blastocystis causes Irritable Bowel-like symptoms. In this study we treated 11 patients with gastrointestinal symptoms who were positive for Blastocystis in their stool in order to determine if this therapy made any difference to their symptoms. We also compared Blastocystis subtypes between symptomatic patients and their asymptomatic household contacts (human and animal). We used PCR subtyping tools to assess faecal carriage of Blastocystis which is a more accurate tool than simple smears or culture.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 31962 0
Address 31962 0
Country 31962 0
Phone 31962 0
Fax 31962 0
Email 31962 0
Contact person for public queries
Name 15209 0
Robyn Nagel
Address 15209 0
Unit 105, Medici Medical Centre
11 Scott St
Country 15209 0
Phone 15209 0
+61 7 46394124
Fax 15209 0
+61 7 46394070
Email 15209 0
Contact person for scientific queries
Name 6137 0
Robyn Nagel
Address 6137 0
Unit 105, Medici Medical Centre
11 Scott St
Queensland, 4350
Country 6137 0
Phone 6137 0
+61 7 46394124
Fax 6137 0
+61 7 46394070
Email 6137 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary