Epithelial cells are generally more or less disintegrated. In the mucus of bacillary dysenteric stools, however, large intact phagocytic cells are frequent, which may be mistaken for encysted amoebae, and the polynuclear cell count averages 90% as contrasted with the average polynuclear count of 7.5% in amoebic dysentery.
When a smear preparation is desired, we may smear out a fragment of mucus and stain by Romanowsky’s or Gram’s method. Beautiful preparations may be made by mixing the faeces with water, then centrifuging for one minute. This throws down vegetable débris and crystals. Now decant the supernatant fluid, which holds the bacteria in suspension, and add an equal amount of alcohol. Again centrifuge, decant, and smear out and examine the bacterial sediment.
Simply taking a small mass of faeces and emulsifying it with a wooden toothpick on a concave slide in 70% alcohol—then, after the sediment settles, taking up a loopful with platinum loop from the surface and smearing out, gives a very satisfactory smear. Gram’s method, with dilute carbol fuchsin counterstaining, gives the best picture.
To culture for typhoid, dysentery, cholera, or other bacteria, take up the material in a tube of sterile bouillon and smear it out with a swab over a lactose litmus agar plate or an Endo or Conradi-Drigalski plate. Before streaking the plates they should be very dry on the surface. This can be best done by pouring the melted agar into a plate with a circular piece of filter-paper in the lid and placing in the incubator for one-half hour to dry. The filter-paper absorbs the moisture. Then inoculate the surface of the plate with the faecal material.
Teague Medium.—We have formerly preferred the Endo plate for typhoid work and the lactose litmus agar when culturing for dysentery bacilli. More recently we have obtained most satisfactory results with the Teague medium. The colon colonies, after eighteen hours, are deep black and opaque while the typhoid-dysentery group show colorless, transparent colonies.
The medium is prepared as follows: Nutrient agar is made in the usual way, containing 1.5% agar, 1% Witte’s peptone, 0.5% sodium chloride, and 0.5% Liebig’s meat extract, to the liter of distilled water. It is cleared with egg-white, placed in flasks, and sterilized in the Arnold sterilizer on three successive days. The reaction is brought to plus 0.8. The agar is melted and saccharose 0.5% and lactose 0.5% are added. The medium is then heated for ten minutes in the Arnold. To every 50 cc. of the medium are added 1 cc. of 2% yellowish eosin and 1 cc. of 0.5% methylene blue. The mixture is shaken and plates poured. Eosin solution should be added first.
Occult Blood.—In performing the test for occult blood, one should exclude the possibility of blood reaching the bowels from an extraneous source, such as ingested foods, mouth, nose, lungs and vagina, and the absence of interfering substances should be ensured. An absolute milk diet, or, at least, a diet containing neither meat nor green vegetables, is indicated for two or three days prior to the test, and all medication should be suspended. The technique noted on [page 524] should be followed scrupulously when dealing with faeces.
It has been suggested that the absence of occult blood from the faeces may be accepted as an indication of cure in ancylostomiasis.
