Prevalence and clinical relevance of Blastocystis hominis in diverse patient cohorts

The pathogenicity of Blastocystis hominis is extensively debated in the med ical literature. Therefore, we did a prevalence study to investigate the as sociation between the presence of several intestinal parasites and gastroin testinal symptoms in diverse patient cohorts. The study population consiste d of 1216 adults, including immunocompromised patients, institutionalized p sychiatric or elder subjects, immigrants from developing countries, travell ers to developing tropical countries and controls. Several variables for ea ch risk group were considered. Stools specimens, collected in triplicate, w ere processed by the same technicians. Clinical data about each subject wer e 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 evaluate d. The results showed a high prevalence of parasites in all the risk groups . Immunocompromised status, recent arrival from developing countries and th e presence of behavioural aberrations were significantly related to presenc e of parasites. B. hominis was the parasite most frequently detected in eac h studied group. B. hominis showed a significant correlation with gastroint estinal symptoms only when detected in the group including subjects with a severe immunodepression. Immunodepression seems to be a factor of primary i mportance of the pathogenic role of B. hominis.