568 Protozoa of the Digestive and Urogenital Tracts 



LABORATORY DIAGNOSIS OF 

 INFECTION 2 



Protozoa of the mouth 



The examination of fresh smears and stained preparations will 

 often demonstrate infections with Entamoeba gingivalis and Tricho- 

 monas tenax, although culture methods seem to be much more reliable. 

 Several satisfactory media have been described for E. gingivalis (54, 78, 

 92, 98) and for T. tenax (13, 72, 73, 76, 109). 



Protozoa of the intestine 



Wet preparations. Material to be examined for active stages should be 

 reasonably fresh, preferably stools passed in the laboratory shortly before 

 examination. Survival of trophozoites of Entamoeba histolytica shows an 

 inverse relationship to temperature — 2-5 hours in stools stored at 37°, 

 6-16 hours at 22-25°, and 48-96 hours at 5°. Cysts can survive for longer 

 periods, while Pentatrichomonas hominis may live as long as two weeks 

 at 22° (162). 



Microscopic examination of fresh material, especially on a warm stage, 

 is useful for detection of amoeboid forms and may serve for complete 

 identification of active flagellates. For encysted flagellates and amoebae, 

 temporary staining techniques are widely used. Lugol's iodin solution, 

 undiluted or in 1:5 dilution (52), Donaldson's iodin-eosin stain (53), and 

 D'Antoni's stabilized iodin stain (7) have given satisfactory results. In 

 addition, a rapid stain which differentiates amoeboid stages in wet 

 preparations has been introduced by Velat, Weinstein, and Otto (164). 



Permanent preparations. Although experienced workers may have no 

 serious difficulty in identifying most intestinal Protozoa by means of 

 fresh smears and the iodin stain or comparable techniques, permanent 

 preparations are useful for purposes of confirmation and for permanent 

 records. In addition, physicians without laboratory facilities, or without 

 experience in identification of Protozoa, may find it convenient to fix 

 smears made directly from stool samples and then ship the smears to a 

 laboratory for staining and diagnosis. One of the various hematoxylin 

 techniques is usually preferred for permanent preparations. 



Concentration methods. Although direct smears are satisfactory for 

 routine examinations, it is advantageous to concentrate the Protozoa 

 when their presence only in small numbers is suspected. A portion of the 

 stool may be mixed with physiological salt solution and then filtered 

 through cheesecloth. The filtrate is centrifuged, the supernatant liquid 

 is discarded, and the sediment is mixed with fresh salt solution and again 



^ Adequate descriptions and evaluations of laboratory techniques will be found in 

 Craig's (42) comprehensive monograph. 



