Enteric protozoan parasites, which are spread by the fecal-oral route, are important causes of diarrhea (Giardia duodenalis) and amebic dysentery (Entamoeba histolytica). Cyst walls of Giardia and Entamoeba have a single layer composed of fibrils of -1,3-linked GalNAc and -1,4-linked GlcNAc (chitin), respectively. The goal here was to determine whether hand sanitizers that contain ethanol or isopropanol as the active microbicide might reduce transmission of these parasites. We found that treatment with these alcohols with or without drying in a rotary evaporator (to model rapid evaporation of sanitizers on hands) kills 85 to 100% of cysts of G. duodenalis and 90 to 100% of cysts of Entamoeba invadens (a nonpathogenic model for E. histolytica), as shown by nuclear labeling with propidium iodide and failure to excyst in vitro. Alcohols with or without drying collapsed the cyst walls of Giardia but did not collapse the cyst walls of Entamoeba. To validate the in vitro results, we showed that treatment with alcohols eliminated oral infection of gerbils by 1,000 G. duodenalis cysts, while a commercial hand sanitizer (Purell) killed E. invadens cysts that were directly applied to the hands. These results suggest that expanded use of alcohol-based hand sanitizers might reduce the transmission of Giardia and Entamoeba.
G iardia duodenalis (also known as Giardia lamblia)is an important cause of human diarrhea in both the developing and developed world and is an important zoonosis of companion and production animals (1-8). Entamoeba histolytica may cause amebic dysentery and liver abscess, primarily in the developing world (9-11). Because these parasites may cause severe infections and are readily transmitted by asymptomatic carriers, the National Institute of Allergy and Infectious Diseases (NIAID) has designated Giardia and Entamoeba category B priority pathogens.Our laboratory has extensively characterized the cyst walls of Giardia and Entamoeba, each of which contains a prominent sugar polymer and a small set of proteins (12, 13). In contrast, the Saccharomyces cerevisiae cell wall contains two sugar polymers (chitin and -1,3-linked glucan) and ϳ100 glycoproteins (14). The Giardia cyst wall contains curled fibrils of -1,3-linked N-acetylgalactosamine (GalNAc) and cyst wall proteins (CWPs) that bind the GalNAc homopolymer (15, 16). Cyst wall proteins have very short Asn-linked glycans composed of two GlcNAc residues (17). While cytosolic proteins of Giardia may contain GlcNAc linked to Ser or Thr residues, no O-linked glycans have been identified in its secreted or cyst wall proteins (18).The Entamoeba cyst wall is modeled by Entamoeba invadens, which infects reptiles but not humans, because E. histolytica does not encyst in axenic culture or in the mouse model. The Entamoeba cyst wall is composed of fibrils of -1,4-linked N-acetylglucosamine (GlcNAc) (chitin), which are labeled by wheat germ agglutinin (WGA) (19,20). Entamoeba cyst walls contain three abundant chitin-binding glycoproteins (lectins) that cross-lin...