Screening of auramine-stained smears of all fecal samples is a rapid and inexpensive way to increase the detection of coccidial infections.

Introduction: Coccidia are important causes of diarrhea that is often indistinguishable from other forms of community-acquired diarrhea. However, the detection of oocysts is often only performed when explicitly requested, as part of the ova and parasite (O&P) examination. Reappraisal and understanding of the accurate staining characteristics of auramine O (AuO), which stains nucleic acids, may permit the inexpensive and reliable identification of coccidian oocysts at routine workup of all fecal samples.
Methods: AuO-stained smears were prepared from all stool samples received for stool culture in transport medium (SC) and from concentrated stools received for the ova and parasite (O&P) examination.
Results: A total of 3732 samples for stool cultures and 3132 samples for O&P examinations were included. Ninety-one samples (1.3%) from 52 patients yielded Coccidia (45 Cryptosporidium spp and 7 Isospora belli). In seven cases oocysts were only detected in samples sent for stool culture in transport medium. The oocysts showed a typical staining pattern and were easy to recognize. The observation of one smear took only around 30seconds, and the reagents and glass slide for one smear did not exceed US$ 0.03.
Conclusions: The screening of all fecal samples with AuO-stained smears is a rapid and inexpensive way to increase the detection of coccidial infections, which in most laboratories can be incorporated into the microscopic workup for mycobacteria.