Abstract
BackgroundBlastocystis species are common human enteric parasites. Carriage has been linked to Irritable Bowel Syndrome (IBS). Treatment of Blastocystis spp. with antimicrobials is problematic and insensitive diagnostic methods and re-infection complicate assessment of eradication. We investigated whether triple antibiotic therapy comprising diloxanide furoate, trimethoprim/sulfamethoxazole and secnidazole (TAB) given to diarrhoea-predominant IBS (D-IBS) patients positive for Blastocystis would achieve eradication.MethodsIn a longitudinal, prospective case study 10 D-IBS Blastocystis-positive patients took 14 days of diloxanide furoate 500 mg thrice daily, trimethoprim/sulfamethoxazole 160/80 mg twice daily and secnidazole 400 mg thrice daily. Faecal specimens were collected at baseline, day 15 and 4 weeks after completion of TAB. Specimens were analysed using faecal smear, culture and polymerase chain reaction (PCR) of the 16 SSU rRNA. Patients kept a concurrent clinical diary.ResultsSix (60%) patients cleared Blastocystis spp. after TAB, including three who had failed previous therapy. Subtypes detected were ST3 (60%), ST4 (40%), ST1 (20%) and ST7, 8 (10%); four patients had mixed ST infections. Serum immunoglobulin A (IgA) levels were low in 40% of patients. Higher rates of Blastocystis clearance were observed in patients symptomatic for less than a year (Mann–Whitney, p = 0.032, 95% confidence) with no associations found with age, previous antibiotic therapy, faecal parasite load, ST, IgA level or clinical improvement.ConclusionsClearance of Blastocystis spp. was achieved with TAB in 60% of D-IBS patients, an improvement over conventional monotherapy. Higher clearance rates are needed to facilitate investigation of the relevance of this parasite in clinically heterogenous IBS.
Highlights
Blastocystis species are common human enteric parasites
Patients presenting with chronic diarrhea were clinically assessed and patients who were subsequently diagnosed with diarrhoea-predominant Irritable Bowel Syndrome (IBS) (IBS-D) [4] and were positive for Blastocystis carriage were invited to participate in the study
Successful faecal eradication of Blastocystis spp.occurred in 60% of patients at the end of this study following fourteen days of triple antibiotic therapy using diloxanide furoate, trimethoprim/sulfamethoxazole and secnidazole (TAB)
Summary
Blastocystis species are common human enteric parasites. Carriage has been linked to Irritable Bowel Syndrome (IBS). Blastocystis spp. are the most common parasite found in human faeces and carriage has been reported has focused research on microbial interactions with the luminal gut mucosa [6]. Changes in cytokine secretion are reported with many luminal enteric microbial infections but increased levels of pro-inflammatory cytokines (interleukin (IL)-6, IL-8, and tumour necrosis factor-α (TNF-α)) have been reported in the plasma and peripheral blood mononuclear cells of IBS patients [6]. Many of these cytokines increase epithelial permeability by disrupting the mucosal tight junctions [11]. Blastocystis organisms have been shown to activate IL-8 gene expression in human colonic epithelial cells in vitro [14], increase epithelial permeability [15] and degrade intestinal Immunoglobulin A (IgA) [16], mediated possibly by action of cysteine proteases [17] reported to be present on the cell surface [18]
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