Adhesion of Cryptosporidium parvum and Giardia lamblia to solid surfaces: the role of surface charge and hydrophobicity.

Adhesion of Cryptosporidium parvum and Giardia lamblia to four materials of different surface charge and hydrophobicity was investigated. Glass beads were used with and without three polymer coatings: aminosilines (A0750), fluorosilines (T2494), an amino cationic polymer. Surface charge density and hydrophobicity of the beads were characterized by measuring the zeta potential (ZP) and the contact angle, respectively. Adhesion was derived from batch experiments where negatively charged (oo)cysts were mixed with the beads and recovery was determined by counting (oo)cysts remaining in suspension using a flow cytometer. Experimental results clearly show that adhesion to solid surfaces of C. parvum is different from G. lamblia. Adhesion of C. parvum to positively charged, hydrophilic beads (82% recovery relative to control) indicated that surface charge was the more important factor for C. parvum, dominating any hydrophobic effects. Adhesion of G. lamblia cysts to negatively charged, hydrophobic beads (0% recovery relative to control) indicated that although hydrophobicity and surface charge both played a role in the adhesion of G. lamblia to solid surfaces, hydrophobicity was more important than surface charge.