No correlation between clinical symptoms and Blastocystis hominis in immunocompetent individuals

Abstract Background and Aim: Previous reports regarding the clinical significance and pathogenicity of Blastocystis hominis have been contradictory. The aim of this study was to examine the association between Blastocystis and gastrointestinal symptoms in immunocompetent individuals.

METHODS

We monitored over 2800 healthy people for a period of 15 months, and took stool specimens during both asymptomatic periods and during periods of gastrointestinal symptoms.

RESULTS

After exclusion of individuals who had simultaneous identification of other fecal pathogens, we compared the proportions of asymptomatic versus symptomatic individuals positive for Blastocystis and found no significant difference (P = 0.5). Symptom status did not correlate with parasite abundance. We found that some individuals were likely to have Blastocystis detected during both asymptomatic and symptomatic periods, possibly suggesting carriage of the organism.

CONCLUSION

In conclusion, we found no correlation between clinical symptoms and the presence or absence of Blastocystis among this healthy cohort.

Clinical characteristics and endoscopic findings associated with Blastocystis hominis in healthy adults

Ninety-nine individuals with stools positive for Blastocystis hominis but negative for other parasites were identified from medical records of healthy adults who had received a physical examination at Taipei Veterans General Hospital from November 2000 to October 2002. The medical records of these 99 positive cases and 193 randomly selected controls, matched for age, sex, and date of examination, were retrospectively reviewed. The pathogenicity of B. hominis could not be demonstrated due to a lack of association with the development of gastrointestinal symptoms or pathologic findings on endoscopic examination. Multivariate analyses revealed that chronic hepatitis B infection was a predisposing condition to the acquisition of B. hominis (odd ratio = 2.848, 95% confidence interval = 1.299-6.242, P = 0.009), and concentration of urate was significantly lower in B. hominis-positive individuals (mean +/- SD = 361.64 +/- 87.44 versus 392.57 +/- 93.38 micromol/L; P = 0.009). Among the 64 individuals who underwent gastric biopsy, Helicobacter pylori was found more frequently in the individuals harboring B. hominis (19 of 26 versus 15 of 38; P = 0.017).

Epidemiological survey of Blastocystis hominis in Huainan City, Anhui Province, China

AIM: To provide scientific evidence for prevention and controlling of blastocystosis, the infection of Blastocystis homonis and to study its clinical significance in Huainan City, Anhui Province, China.

METHODS: Blastocystis homonis in fresh stools taken from 100 infants, 100 pupils, 100 middle school students and 403 patients with diarrhea was smeared and detected with method of iodine staining and hematoxylin staining. After preliminary direct microscopy, the shape and size of Blastocystis homonis were observed with high power lens. The cellular immune function of the patients with blastocystosis was detected with biotin-streptavidin (BSA).

RESULTS: The positive rates of Blastocystis homonis in fresh stools taken from the infants, pupils, middle school students and the patients with diarrhea, were 1.0% (1/100), 1.0% (1/100), 0% (0/100) and 5.96% (24/403) respectively. Furthermore, the positive rates of Blastocystis homonis in the stool samples taken from the patients with mild diarrhea, intermediate diarrhea, severe diarrhea and obstinate diarrhea were 6.03% (14/232), 2.25% (2/89), 0% (0/17) and 12.31% (8/65) respectively. The positive rates of Blastocystis homonis in fresh stools of male and female patients with diarrhea were 7.52% (17/226) and 3.95% (7/177) respectively, and those of patients in urban and rural areas were 4.56% (11/241) and 8.02% (13/162) respectively. There was no significant difference between them (P > 0.05). The positive rates of CD₃⁺, CD₄⁺, CD₈⁺ in serum of Blastocystis homonis-positive and-negative individuals were 0.64 ± 0.06, 0.44 ± 0.06, 0.28 ± 0.04 and 0.60 ± 0.05, 0.40 ± 0.05 and 0.30 ± 0.05 respectively, and the ratio of CD₄⁺/CD₈⁺ of the two groups were 1.53 ± 0.34 and 1.27 ± 0.22. There was significant difference between the two groups (P < 0.05, P < 0.01).

CONCLUSION: The prevalence of Blastocystis hominis as an enteric pathogen in human seems not to be associated with gender and living environment, and that Blastocystis hominis is more common in stool samples of the patients with diarrhea, especially with chronic diarrhea or obstinate diarrhea. When patients with diarrhea infected by Blastocystis hominis, their cellular immune function decreases, which make it more difficult to be cured.

Prevalence of Blastocystis hominis carriage in Thai army personnel based in Chonburi, Thailand

Blastocystis hominis is one of the most common intestinal parasites found in humans. The prevalence of B. hominis carriage in personnel who worked in the First Army Support Command, Chonburi, Thailand, was determined. Forty-four percent of 616 stool samples were positive for B. hominis using both simple smear and concentration (Formalin/ethyl acetate) techniques. The usefulness of the concentration technique in the diagnosis of B. hominis has been confirmed. Of 272 positive specimens, 75% were detected by simple smear and 25% were additionally identified by the concentration technique. The prevalence of B. hominis carriage was highest among the privates who had lived longest in this command. This finding indicates that they might have acquired B. hominis during their stay at this base. The significantly high prevalence of B. hominis carriage was found in the Ordnance Ammunition Battalion. In this battalion, privates who had education lower than the secondary school level had significantly greater risk of B. hominis carriage.

[50-year-old patient returning from Hawaii with changed stool habits. Blastocystis hominis]

Ein 50-jähriger Künstler kehrt nach sechsjährigem Auslandaufenthalt in Hawaii in die Schweiz zurück. Seit einigen Wochen beklagt er breiigen Stuhlgang und Flatulenz bei normaler Stuhlfrequenz und sonst gutem Allgemeinbefinden. Bei unauffälligem Laborbefund wird in dreimaligen Stuhluntersuchungen jeweils Blastocystis hominis vorgefunden, ein Parasit dessen pathogene Dignität kontrovers diskutiert wird. Bereits nach einigen Dosen Metronidazol (500 mg) bessern sich die Blähungsgefühle und der Stuhl erhält seine normale Konsistenz zurück. Bei einem symtomatischen Patienten bei welchem Blastocystis hominis im Stuhl vorgefunden wird, sollte nur dann behandelt werden, wenn die aktive Suche nach dem Vorliegen eines weiteren Organismus negativ ausgefallen ist und andere Ursachen für das Beschwerdebild ausgeschlossen werden konnten.

Intestinal parasites, including Cryptosporidium species, in Iraqi patients with sickle-cell anaemia

Stool samples were obtained from individuals admitted to three hospitals in Basra during November 1997-May 1998. Of 40 patients with sickle-cell anaemia, 25 (62.5%) had parasitic infections. In the apparently healthy comparison group, 26 of 175 individuals (14.8%) had intestinal parasitic infections, a statistically significant difference. The most common intestinal parasites isolated in the sickle-cell patients were Blastocystis hominis (36%) and Giardia lamblia (28%). The isolation rate of Cryptosporidium species in sickle-cell patients (5%) was not significantly different from that in apparently healthy individuals (1.14%). We report for the first time the isolation of Isospora belli from a sickle-cell patient in Iraq and the Mediterranean region.

[Acute infectious lymphocytosis associated to Giardia lamblia and Blastocystis hominis coinfection]

Acute infectious lymphocytosis is characterized by marked peripheral blood lymphocytosis, often associated with a mild, nonspecific febrile illness. We present a 4-year-old girl with acute infectious lymphocytosis associated with Giardia lamblia and Blastocystis hominis coinfection. Analysis of peripheral lymphocyte markers showed overall proliferation of B and T cells with a reduction in the proportion of T cells, especially in the CD4T cell subpopulation. Hematologic values returned to normal after treatment with metronidazole.

Inhibition of enteric parasites by emulsified oil of oregano in vivo

Oil of Mediterranean oregano Oreganum vulgare was orally administered to 14 adult patients whose stools tested positive for enteric parasites, Blastocystis hominis, Entamoeba hartmanni and Endolimax nana. After 6 weeks of supplementation with 600 mg emulsified oil of oregano daily, there was complete disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis in eight cases. Also, Blastocystis hominis scores declined in three additional cases. Gastrointestinal symptoms improved in seven of the 11 patients who had tested positive for Blastocystis hominis.

Intestinal protozoa in HIV-infected patients: effect of rifaximin in Cryptosporidium parvum and Blastocystis hominis infections

In HIV-1 infected patients severe enteritis and chronic diarrhea are often documented as a consequence of multiple opportunistic infections. We analyzed 48 HIV-1 positive patients for the presence of intestinal pathogenic protozoa. Patients with CD4 > or = 200/mm3 showed a higher prevalence of a single pathogenic protozoa than patients with CD4 < or =200/mm3, who showed the presence of multiple protozoal infections. Patients who proved positive for only a single protozoa, Cryptosporidium or Blastocystis, were also positive, by stool culture, for the presence of Proteus mirabilis (3 samples), Citrobacter freundii (3 samples), Escherichia coli (one sample) or Enterobacter cloacae (one sample). Treatment with rifaximin (600 mg, 3 times a day, for 14 days) was efficacious in resolving the clinical symptoms and clearing protozoan infections in HIV-1 infected patients with CD4 > or = 200/mm3, who presented enteric and systemic symptoms due to Criptosporidium or Blastocystis associated with enteropathogenic bacteria.

Irritable bowel syndrome in patients with Blastocystis hominis infection

The prevalence of Blastocystis hominis in stool specimens of individuals with gastrointestinal symptoms was evaluated to study a possible link between the protozoan and the irritable bowel syndrome. According to the Rome diagnostic criteria, 388 patients were evaluated. Altogether, 81 patients were classified as affected by irritable bowel syndrome. Blastocystis hominis was recovered from the stools of 38 subjects, 15 of whom belonged to the group with irritable bowel syndrome (P = 0.006). In addition, patients with irritable bowel syndrome were significantly more likely to have five or more Blastocystis hominis organisms per field (P = 0.031). In conclusion, there was a set of patients with irritable bowel syndrome in whom the presence of Blastocystis hominis may not be incidental.

Prevalence and clinical relevance of Blastocystis hominis in diverse patient cohorts

The pathogenicity of Blastocystis hominis is extensively debated in the medical literature. Therefore, we did a prevalence study to investigate the association between the presence of several intestinal parasites and gastrointestinal symptoms in diverse patient cohorts. The study population consisted of 1216 adults, including immunocompromised patients, institutionalized psychiatric or elder subjects, immigrants from developing countries, travellers to developing tropical countries and controls. Several variables for each risk group were considered. Stools specimens, collected in triplicate, were processed by the same technicians. Clinical data about each subject were provided by standardized questionnaires. The presence of gastrointestinal symptoms were related to the presence of any parasite. In addition, on the basis of microbiological results, five subgroups of subjects were evaluated. The results showed a high prevalence of parasites in all the risk groups. Immunocompromised status, recent arrival from developing countries and the presence of behavioural aberrations were significantly related to presence of parasites. B. hominis was the parasite most frequently detected in each studied group. B. hominis showed a significant correlation with gastrointestinal symptoms only when detected in the group including subjects with a severe immunodepression. Immunodepression seems to be a factor of primary importance of the pathogenic role of B. hominis.

Cytopathic effect of Blastocystis hominis after intramuscular inoculation into laboratory mice

The present study investigated the pathogenesis of Blastocystis hominis by intramuscular injection of the organism into experimental mice. A total of 27 naïve BALB/c mice aged 6-8 weeks were injected in the leg muscle with axenic culture isolate B of B. hominis. Histological examination at different times revealed that B. hominis could produce a severe inflammatory reaction and myonecrosis. Most changes were observed at 6 h after injection and for up to 2-3 days. By 2 weeks the muscle had regained normal histology. There was infiltration of polymorphonuclear leukocytes (PML) into the injection site, indicating that B. hominis had a strong chemoattractant activity for PML.

The role of Blastocystis hominis as a possible intestinal pathogen in travellers

The role of Blastocystis hominis as a pathogen for man has been controversially discussed, while travel history has been implicated as a risk factor of infection. Few controlled studies of the association between B. hominis and symptomatic diseases have been performed. Therefore, a case-control study among 795 German tourists returning from tropical countries was conducted. The prevalence of the organism among patients with and without symptoms was assessed. Blastocystis hominis was detected in 69 of 469 (14.7%) patients with diarrhoea and in 21 of 326 (5.7%) controls. However, other organisms causing diarrhoea were detected in 18 of the 69 (26.1%) symptomatic patients with B. hominis. Thus, 51 of 469 (10.8%) symptomatic patients had B. hominis in the absence of other pathogens in their stool, significantly more than in the asymptomatic group (5.2%; P = 0.005). Irrespective of the development of symptoms, the organism was most frequently acquired during journeys to the Indian subcontinent. The results of this study suggest that B. hominis is associated with development of diarrhoea in travellers to tropical destinations and that frequently concurrent infections with other organisms occur.

[Prevalence of Blastocystis hominis infection in schoolchildren from Bolivar City, Venezuela]

Blastocystis hominis is found in about 25% of feces in normal asymptomatic people. Its pathogenic role is still discussed. A prospective study was performed to determine the prevalence of B. hominis infection in schoolchildren from Bolivar City. We evaluated 446 children, between five and fourteen years old, both sexes, using direct examination of feces and Willis Method. They were also evaluated clinically. Results showed that B. hominis had a prevalence of 16.8%. We did not find a statistically significant association between sex (P > 0.05) or age and infection with B. hominis (x2 = 1.94 g.l = 4). In 39 schoolchildren (52.0%) we identified other parasites along with B. hominis, the most frequent was Trichuris trichiura as helminth and Giardia lamblia as protozoan. We observed B. hominis alone in 36 cases (48.0%). There was a spectrum of clinical symptoms in 41 (54.7%) of all children evaluated. Diarrhea was the most frequently clinical manifestation observed. Other studies are necessary to determine clinical relevance of B. hominis in school population in Bolivar City.