What are the implications of moderate Blastocystis (Blastocystis species) in stool?

From the Guidelines

Moderate Blastocystis species in stool typically does not require treatment unless you are experiencing symptoms like diarrhea, abdominal pain, bloating, or nausea. If symptomatic, the recommended treatment is metronidazole 500-750 mg three times daily for 5-10 days 1. Alternative medications include trimethoprim-sulfamethoxazole (160/800 mg twice daily for 7 days), nitazoxanide (500 mg twice daily for 3 days), or paromomycin (25-35 mg/kg/day in three divided doses for 7 days) 1. While taking these medications, maintain good hydration and consider probiotics to help restore gut flora. It's essential to complete the full course of medication even if symptoms improve. Blastocystis is a common intestinal parasite with controversial clinical significance - many people carry it without symptoms. Treatment is generally reserved for those with persistent symptoms after other causes have been ruled out. Follow-up stool testing may be recommended 2-4 weeks after treatment to confirm clearance if symptoms persist 1. Some key points to consider:

• The pathogenicity of Blastocystis hominis remains controversial, and treatment is usually only considered when symptoms persist 1.
• Diagnostic algorithms that combine clinical and epidemiologic factors are needed to determine the cause of diarrhea 1.
• Identification of the etiologic agent is important for guiding clinical management and public health control efforts 1.
• Immunocompromised people are more likely to experience severe or prolonged illness, and diarrhea in these patients may involve a broad spectrum of potential causes 1.

From the Research

Moderate Blastocystis Species in Stool

• The presence of Blastocystis species in stool can be associated with gastrointestinal symptoms, although the pathogenicity of this parasite is still controversial 2, 3.
• Studies have shown that metronidazole is the most commonly used treatment for Blastocystis infection, with variable rates of clinical cure and eradication of the parasite from the feces 2, 4, 5, 3, 6.
• Other treatment options that have been suggested include trimethoprim/sulfamethoxazole, nitazoxanide, paromomycin, and Saccharomyces boulardii 2, 4, 5, 6.
• The decision to treat Blastocystis infection should be based on the presence of symptoms and the number of cysts in stool specimens, with asymptomatic individuals with few cysts not requiring treatment 3.
• Some studies suggest that the pathogenicity of Blastocystis may be related to specific subtypes and parasite burden, and that treatment failure and resistance to metronidazole can occur 5, 6.

Treatment Options

• Metronidazole: the most widely accepted treatment for Blastocystis infection, although treatment failure and resistance can occur 2, 4, 5, 3, 6.
• Trimethoprim/sulfamethoxazole: an alternative treatment option, although its effectiveness is variable 2, 6.
• Saccharomyces boulardii: a probiotic that has been shown to have potential beneficial effects in Blastocystis infection 4.
• Paromomycin: a treatment option that has been suggested, although its effectiveness is not well established 6.

Diagnosis and Treatment Considerations

• Stool samples should be microscopically examined after staining with iodine and by culturing in an egg slant medium to diagnose Blastocystis infection 2.
• The presence of symptoms and the number of cysts in stool specimens should be taken into account when deciding whether to treat Blastocystis infection 3.
• Treatment failure and resistance to metronidazole can occur, and alternative treatment options should be considered in these cases 5, 6.