Abstract
Blastocsytis sp. is a protozoan parasite that has been linked to common gastrointestinal illnesses. Metronidazole, the first line therapy, was reported to show frequent inefficacy. Previously, Blastocystis sp. isolated from different population showed varying metronidazole resistance. However, the effect of metronidazole treatment on pathogenic potentials of Blastocystis sp. isolated from different populations, which is known to have different gut environment, is unclear. This study investigates the in vitro effect of metronidazole on the pathogenic potentials of Blastocystis sp. isolated from urban and orang asli individuals. Blastocystis sp. ST 3 isolated from symptomatic and asymptomatic individuals were treated with a range of metronidazole concentration. The parasites’ growth characteristics, apoptotic rate, specific protease activity and the ability to proliferate cancer cells were analyzed upon treatment with 0.001 mg/l metronidazole. The study demonstrates that Blastocystis sp. isolates showed increase in the parasite numbers especially the amoebic forms (only in urban isolates) after treating with metronidazole at the concentration of 0.001 mg/ml. High number of cells in post-treated isolates coincided with increase of apoptosis. There was a significant increase in cysteine protease of Blastocystis sp. isolates upon treatment despite the initial predominance of serine protease in asymptomatic isolates. Metronidazole resistant Blastocystis sp. also showed significant increase in cancer cell proliferation. Resistance to metronidazole did not show significant different influence on the pathogenicity between Blastocystis sp. isolated from urban and orang asli individual. However, an increase in parasite numbers, higher amoebic forms, cysteine protease and ability to proliferate cancer cells implicates a pathogenic role. The study provides evidence for the first time, the effect of metronidazole towards enhancing pathogenic potentials in Blastocystis sp. when isolated from different gut environment. This necessitates the need for reassessment of metronidazole treatment modalities.
Highlights
Blastocystis sp. is a protozoan parasite with a worldwide distribution where more than a billion individuals are estimated to harbor this organism[1]
Blastocystis sp. isolated from symptomatic urban and orang asli individuals showed greater increase in cell number compared to asymptomatic isolates (Figs 1 and 2)
Amoebic forms of Blastocystis sp. were observed only in isolates obtained from symptomatic urban individuals
Summary
Blastocystis sp. is a protozoan parasite with a worldwide distribution where more than a billion individuals are estimated to harbor this organism[1]. Up to 17 subtypes (ST) have been isolated where ST 1–9 are found in human infections. ST3 have been shown to have higher prevalence followed by ST1 and this ST has been commonly incriminated to possess pathogenic potentials. Previous studies investigating on subtype diversity reported that ST 3 is predominantly isolated from patients with gastrointestinal symptoms such as IBS [6] and the solubilized antigens from ST3 was reported to trigger increased proliferation in colon cancer cells[7]. Sporadic studies on pathogenic potential on other STs, namely ST2 and ST4 have surfaced but at a lower consistency [8, 9]
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