Role of Wall Shear Stress in Cryptosporidium parvum Oocyst Attachment to Environmental Biofilms

Abstract

This study investigated oocyst deposition onto biofilms as a function of shear stress under laminar or turbulent flow. Annular rotating bioreactors were used to grow stabilized stream biofilms at shear stresses ranging from 0.038 to 0.46 Pa. These steady-state biofilms were then used to assess the impact of hydrodynamic conditions on oocyst attachment. deposition onto biofilms followed a pseudo-second-order model under both laminar (after a lag phase) and turbulent flows. The total number of oocysts attached to the biofilm at steady state decreased as the hydrodynamic wall shear stress increased. The oocyst deposition rate constant increased with shear stress but decreased at high shear, suggesting that increasing wall shear stress results in faster attachment of due to higher mass transport until the shear forces exceed a critical limit that prevents oocyst attachment. These data show that oocyst attachment in the short and long term are impacted differently by shear: higher shear (to a certain limit) may be associated with faster initial oocyst attachment, but lower shear is associated with greater numbers of oocysts attached at equilibrium. This research provides experimental evidence to demonstrate that shear stress plays a critical role in protozoan-pathogen transport and deposition in environmental waters. The data presented in this work expand scientific understanding of attachment and fate, which will further influence the development of timely and accurate sampling strategies, as well as advanced water treatment technologies, to target protozoan pathogens in surface waters that serve as municipal drinking water sources.

Surveillance of Microsporidia and Protozoan Pathogens in Pensacola Florida: A One‐year Study

“…Pathogens can persist or be released also at a times not normally circulating in the water phase, leading to false assumptions as to their origin. Though not a straightforward relationship, water conditions during periphytometer incubation periods such as low and high flow rates or fluctuating flow rates can influence the survival and growth of microbes in biofilms as well as pathogen deposition (Luo et al 2017). Interrupted, strong, or reversal of water flows, may dislodge and shear biofilms (LeChevallier 1990) that have accumulated in low flow areas.…”

Calcium-Mediated Biophysical Binding of Cryptosporidium parvum Oocysts to Surfaces Is Sensitive to Oocyst Age

“…Nutrient-free water was desirable to limit the impact of phosphates and nitrates on binding strength. To limit variability in our study, we chose to work with water that was prepared in-house, using a chemical composition consistent with water (derived from Hokendauqua Creek) used in a prior work (22). Calcium and magnesium hardnesses were equal to 72 ppm and 32 ppm, respectively, in solutions that contained divalent cations.…”

“…One of the ongoing areas of inquiry involves the nature of C. parvum adhesion to surfaces (7,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). For C. parvum to cause gastrointestinal disease, and thus complete the life cycle, the oocysts must be able to bind to the lumen of the small intestine (23)(24)(25)(26)(27).…”

Biological Fixed Film

“…Stress. Luo et al (2017) . The oligotrophic source water was treated with a pre-cultured biofilm (PCB) on different carriers, and the kinetic and bio properties such as bacterial structures were investigated.…”