Protozoans in Stools Unpreserved and Preserved in PVA-Fixative

Abstract

500 normally passed stool specimens were divided into 2 portions immediately after passage; one portion was unpreserved, the other preserved in PVA-fixative. The unpreserved portions were examined by direct wet mounts, Zn sulfate concns., and hematoxylin-stained direct smears. The preserved portions were examined by hematoxylin stains of PVA films. All examinations were performed no sooner than 4 hrs. after the stool was passed. The PVA-fixative portions revealcd more infections with protozoans than did all 3 other techniques combined, mainly as a result of the preservation of trophozoites. Trophozoites were found in 63% of all infections detected and in 59% of the infections found in formed stools. This suggests that it is advisable to preserve both formed and soft stools in PVA-fixative. The combination of the PVA-fixative method (for trophozoites) and the Zn sulfate method (for cysts) demonstrated more infections than did any other combination of 2 techniques used in this study.