Resistance of Blastocystis to chlorine and hydrogen peroxide

Abstract

Blastocystis is a ubiquitous, widely distributed protist inhabiting the gastrointestinal tract of humans and other animals. The organism is genetically diverse, and so far, at least 28 subtypes (STs) have been identified with ST1–ST9 being the most common in humans. The pathogenicity of Blastocystis is controversial. Several routes of transmission have been proposed including fecal–oral (e.g., zoonotic, anthroponotic) and waterborne. Research on the latter has gained traction in the last few years with the organism having been identified in various bodies of water, tap water, and rainwater collection containers including water that has been previously filtered and/or chlorinated. Herein, we assessed the resistance of 11 strains maintained in culture, spanning ST1–ST9 to various chlorine and hydrogen peroxide concentrations for 24 h, and performed recovery assays along with re-exposure. Following the treatment with both compounds, all subtypes showed increased resistance, and viability could be visualized at the cellular level. These results are hinting at the presence of mechanism of resistance to both chlorine and hydrogen peroxide. As such, this pilot study can be the platform for developing guidelines for water treatment processes.

Circulation and colonisation of Blastocystis subtypes in schoolchildren of various ethnicities in rural northern Thailand

“…This hints at the waterborne transmission of these STs. A possible explanation for their environmental persistence is a higher resistance to a water environment [ 93 , 94 ]. Future studies focusing on Blastocystis circulation should consider the sequences beyond the ST level.…”

Identification and validation of novel Blastocystis subtype ST41 in a Colombian patient undergoing colorectal cancer screening

“…As the patient sampled in this study declared no regular contact with domestic or wild animals, the origin of this colonization/infection remains unclear. Cultured Blastocystis cells have been demonstrated to be resistant to drinking water disinfectants including chlorine and hydrogen peroxide (Martín‐Escolano et al, 2023). Drinking of either untreated or chlorinated water contaminated with fecal material from rodents is, therefore, a potential source of Blastocystis ST41.…”

Protozoan Infections Acquired from Food or Drinking Water: An Update

“…All isolates were also resistant to hydrogen peroxide, with ST8 and ST9 showing the highest resistance, and concentrations ranging from 103 ppm to 3,338 ppm were necessary to impede recovery after 24 without exposure. Therefore, hydrogen peroxide at concentrations used for disinfection, 5 -30 ppm, is adequate to eliminate the organism from surfaces and objects [12].…”

“…The oocysts and cysts of protozoa are the infectious stage of these organisms released with feces by infected hosts in the environment. These are very resistant to disinfectants and other external agents, which explains their wide distribution and long term persistence [4][5][6][7][8][9][10][11][12][13]. Despite cysts generally do not multiply outside the host, they may survive in moist foods for months at refrigeration temperatures, enhancing their ability to cause infection [14].…”