Louis R. Fina

Contact and demand‐release disinfectants

A new class of solid‐phase disinfectants has emerged in recent years. Certain types of these disinfectants, the iodinated strong base resins, release iodine upon demand to microorganisms in water. These triiodide and pentaiodide resins have proven effective against a large number of bacterial genera, viruses, and representative parasites such as Giardia lamblia. Although federal regulatory policies have prevented their use for large scale water purification, they have been selectively applied in the U.S. Space Program and in situations for short‐term water disinfection. They appear to hold promise as components of hybrid devices utilizing filtration and halogen scavenging to produce high quality, potable water.

Efficacy of a pentaiodide resin disinfectant on Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae) oocysts in vitro

The resin-I5 column developed at Kansas State University was tested for efficacy against oocysts of Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae). Cesium chloride gradient-purified oocysts were passed through 1.0-cm-diameter columns with lengths of 2.5, 5.0, and 10.0 cm at 23 C. Following column passage, oocyst viability was determined both in vitro by excystation and in vivo by the ability to establish infections in suckling mice. Oocysts were found to be retained by the pentaiodide resin in a linear fashion, probably by electrostatic interactions. Linear regression analysis revealed 100% of the oocysts should be removed in such a manner using a column length of greater than or equal to 25.7 cm. When compared to untreated control oocysts, less than 12% of the oocysts that passed through the columns appeared to be affected by the resin, as assessed by excystation. Inoculation of suckling mice with these column-treated oocysts supported the excystation data and revealed the coccidian to be viable. These results indicate that oocysts of C. parvum are retained on the pentaiodide column in a 1-hit manner and that, although killing of parasites may occur within the column, the greatest effect that the column may have on the parasite is as an electrostatic retention device.