Special Operations Forces Medical Handbook

8-50

b. Streptococci (general category) colonies are usually small, slightly granular, circular, convex and
translucent. The most important characteristic of streptococci is their hemolytic property. Hemolytic
streptococci will leave clear halos around growing colonies (see Color Plates Pictures 26, 27).
c. Pneumococci (general category) colonies are usually small round colonies surrounded by a zone of
alpha hemolysis.
d. N. gonorrhoeae colonies are grown on Thayer-Martin media. Colonies are smooth, glistening,
translucent and soft. No pigmentation is usually present, however, some strains may show and
iridescent bluish-gray coloration.
e. B. anthracis (anthrax) produces non-hemolytic colonies having a “cut-glass” appearance in transmitted
light with dull, irregular edges (see Color Plates Picture 13).
f. Clostridium perfringens (associated with “gas gangrene”) is strictly anaerobic, and will not grow in the
presence of O 2. They may show hemolysis. They present a characteristic “double zone” or target
appearance
g. E. coli is a facultative anaerobe with 2-3 mm colonies, typically low, convex, smooth, and colorless or
opaque. The colonies tend to bunch together (see Color Plates Picture 28).
h. Shigella (general category) produces colonies that are usually 2 mm, circular, convex and whitish-clear
with a smooth surface.
i. Vibrio cholera colonies are usually 1-2 mm, round, slightly convex, translucent and grayish-yellow in
appearance. On blood agar, they will have a surrounding greenish zone.
j. H. influenzae colonies are usually smooth, raised, slimy, mucoid, confluent and non-hemolytic.

Lab Procedure: Macroscopic Examination of Feces and

Test for Occult Blood

18D Skills and Training Manual

When: To examine a freshly collected fecal specimen for visible parasites, color, consistency, mucus, and
gross or occult blood.

What You Need: An occult blood developer kit with manufacturer’s instructions, disposable transfer pipets,
applicator sticks, a watch that indicates seconds and a laboratory request form.

What To Do:

1. Determine the consistency and color of the specimen and record the results.


2. Examine the specimen for mucus (white patches) on the surface and record the results.


3. Perform a visual inspection for red and/or tarry spots and patches (gross blood) then record the
   results.


4. Perform a survey for visible parasites.


5. Perform the test for occult blood. This is useful in mass screening for colorectal cancer.
   NOTE: Refer to the manufacturer’s instructions for the particular brand of test in the inventory.
   Slight variations in the following procedure are to be found due to different source companies.
   a. Label the test envelope with the patient’s identification.
   b. Collect a small portion of the stool sample on one end of an applicator stick.
   c. Apply a thin smear inside the first box (labeled “A” or “1” depending on the kit).
   d. If indicated, apply a second thin smear inside the second box (labeled “B” or “2”).
   e. Close the cover.
   f. Open the flap on the backside of the kit and apply 2 drops of developer to the paper directly
   over each smear.
   g. Read the results within 60 seconds.
   NOTE: After reading the results, add developer to the positive and negative performance monitors. A
   blue color should appear in the positive monitor within 10 seconds. No blue color will appear in the
   negative monitor. If the positive and negative controls are as expected, the test envelope and reagent