From the Guidelines
Blastocystis hominis infection typically does not require treatment unless it is the only identifiable cause of persistent gastrointestinal symptoms, in which case metronidazole is often considered the first-line treatment. Blastocystis hominis is a microscopic parasite that can inhabit the human digestive tract, and its pathogenicity remains controversial among researchers, as many people carry it without symptoms 1. The diagnosis of Blastocystis hominis is typically made through ova and parasite examination, including permanent stained smear, or nucleic acid amplification test (NAAT) on stool samples 1.
Key Considerations
- The presence of Blastocystis hominis in the absence of other pathogens may be clinically relevant if symptoms persist 1.
- Reporting semi-quantitative results (rare, few, many) may help determine the significance of Blastocystis hominis and is a College of American Pathologists accreditation requirement for participating laboratories 1.
- Treatment with metronidazole, typically at a dose of 500-750 mg three times daily for 5-10 days, may be considered for patients with persistent symptoms attributed to Blastocystis hominis.
- Alternative treatments, such as trimethoprim-sulfamethoxazole or nitazoxanide, may also be effective, but the choice of treatment should be individualized based on patient factors and susceptibility patterns.
- Prevention of Blastocystis hominis infection involves good hygiene practices, including thorough handwashing, drinking clean water, and proper food handling.
Management Approach
- Complete the full course of medication even if symptoms improve to ensure eradication of the parasite.
- Maintain good hydration and consider probiotics to help restore gut flora during and after treatment.
- Regular follow-up with a healthcare provider is essential to monitor the effectiveness of treatment and address any potential side effects or complications.
From the Research
Overview of Blastocystis Hominis
- Blastocystis hominis is a unicellular organism found in the intestinal tract of humans and many other animals 2.
- The pathogenicity of Blastocystis hominis is controversial, and it is not clear whether it is a commensal or a pathogen 3.
Symptoms and Treatment
- Symptoms attributed to B. hominis infection are nonspecific and include abdominal pain, diarrhea, nausea, and vomiting 4, 5.
- Treatment is warranted in patients with persistent symptoms, and metronidazole is often suggested as the drug of choice 4, 5, 3, 2.
- However, treatment failure has been reported, and recent studies have suggested the occurrence of metronidazole-resistant strains 6.
Efficacy of Different Treatments
- A study comparing the efficacy of Saccharomyces boulardii and metronidazole in symptomatic children with B. hominis infection found that both treatments had potential beneficial effects 4.
- Another study found that metronidazole and trimethoprim/sulfamethoxazole were effective in some individuals with severe B. hominis infections, but not all 5.
- In vitro studies have suggested that other potential drug treatments, including trimethoprim-sulfamethoxazole and ivermectin, may be effective against B. hominis 6.
Diagnosis and Life Cycle
- Infection is diagnosed by light microscopic examination of stained smears or wet mounts of fecal material 2.
- The life cycle of B. hominis is not well understood, and several life cycles have been proposed but not experimentally validated 2.
- The form used for transmission has not been defined, and the biochemistry of the organism has not been studied to any extent 2.