Blastocystis is the most common enteric parasite found in humans. Blastocystis has a world-wide distribution with higher rates of infection found in developing countries. Due to the sometimes self-limiting nature of Blastocystis infections, there has been some controversy over whether Blastocystis should be considered a pathogen or not. Symptoms that have been related to Blastocystis infection include diarrhoea, abdominal pain, bloating and nausea. Due to these symptoms being similar to those found in patients with irritable bowel syndrome (IBS), an association has been made. It has also been suggested that certain subtypes of Blastocystis may be more pathogenic than others. Therefore, the aim of this study was to determine if there was a relationship between irritable bowel syndrome and Blastocystis infection, and whether symptoms were subtype related.
Eighty-seven patients identified as suffering from IBS and 70 healthy control people were investigated for the presence of Blastocystis by microscopy of a permanent stain and polymerase chain reaction (PCR). Sixteen IBS patients and seven people from the control group were positive for Blastocystis. There were three subtypes identified in the IBS group- 4 subtype (ST) 1, 5 ST3 and 5 ST4 and four subtypes in the control group- 1 ST1, 1 ST2, 4 ST3 and 1 ST6.
From this study we suggest there may be an association between Blastocystis ST4 and IBS as this ST was only found in the IBS group. This study also highlights that a full microbiological and parasitological work-up should be carried out before a diagnosis of IBS is made.