2013 PARASITOLOGY WORKSHOP

LYNNE S. GARCIA, MS, FAAM, CLS, BLM

Diagnostic Medical Parasitology Workshop

2013 UPDATE – QUIZ PART 7 ORGANISM IDENTIFICATIONS, KEY QUESTIONS

SPONSORED BY

MEDICAL CHEMICAL CORPORATIONwww.med-chem.com

ORGANISM # 1 2

Duodenal Fluid, Modified Trichrome StainGeneral name is acceptable.

ORGANISM # 2

3

Stool smear stained with Wheatley’s Trichrome stain.

Give genus, species, stage names

QUESTION 1

4

Is it good laboratory practice to accept 2 (rather than 3) stools for the O&P examination? Why or why not?

ANSWER 1

5

Three stool specimens is more accurate, but many laboratories feel organism recovery with 2 stools is acceptable. Percent recovery varies from ~80% to over 95% with the submission and examination of two stool specimens. A single stool specimen is only about 50% accurate. In one study, they found the following increases examining the third stool: Hiatt, et al. (Am. J. Trop. Med. Hyg. 53:36-9, 1995)

Yield increased 22.7%: Entamoeba histolyticaYield increased 11.3%: Giardia lambliaYield increased 31.1%: Dientamoeba fragilis

ORGANISM # 3

6

Fluorescence immunoassay.What are the two structures?

Use genus, species names

ORGANISM # 47

Blood Stain

Name genus and species

What’s the clue?

QUESTION 2

8

When selecting a single vial stool fixative, what questions should be asked?

What are Universal Fixatives?

ANSWER 2

9

Can one perform a concentration, permanent stained smear, special stains for the coccidia and microsporidia, and/or fecal immunoassay procedures from the specimen received in that vial (Universal Fixative)? What stains work best with that particular fixative?

TOTAL-FIX contains NO mercury, NO formalin, and NO PVA.

ORGANISM # 5

10

Stool smear stained with Wheatley’s Trichrome stain.

Name genus, species, and stage

ORGANISM # 611

Blood Stain;

Name Genus;

What is the structure within the circle called? Is it always seen?O

ORGANISM # 7

12

Blood StainWhat is general term for structures?Name genus and species (bone marrow).

ORGANISM # 8

13

Blood Stain; name genus, species

QUESTION 3

14

What is PVA (stool adhesive)?

Does it work like albumin?

Does every fixative require one or the other?

ANSWER 3

15

PVA stands for polyvinyl alcohol, a plastic powder/resin that is incorporated into the liquid fixative (Schaudinn’s or other fixatives) and serves as an adhesive to “glue” the stool material onto the slide. PVA itself has no preservation capability and is inert in terms of fixation, just like albumin.

TOTAL-FIX requires no adhesive (PVA or albumin).

ORGANISM # 9

16

Blood Stain

Name genus, species and common name of disease

What’s a clue?

ORGANISM # 10

17

Blood StainGenus, species

ORGANISM # 11

18

Stool smear stained with Wheatley’s Trichrome stain.Genus, species

ORGANISM # 12

19

Modified Trichrome StainGeneral term for organisms

QUESTION 4

20

What are some of the immunoassay options available for stool protozoa?

How do they rank in terms of sensitivity and specificity?

RESPONSE 4

21

All of the fecal immunoassay test formats (FA, EIA, Rapids) are comparable in terms of sensitivity and specificity. Selection of a particular method depends on work flow and the number of test requests and personal preference of that particular laboratory.

ORGANISM # 13

22

Stool smear stained with Wheatley’s Trichrome stain.

Name genus, species, and stages

ORGANISM # 14

23

Blood Stain; genus, species

QUESTION 5

24

If Plasmodium falciparum parasites are in the capillaries, why not do a finger stick, rather than a venipuncture?

What is the best anticoagulant to use for blood specimens?

When should blood specimens be drawn for a suspect malaria diagnosis?

ANSWER 5

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The capillaries tend to be in the deep tissues (spleen, liver, bone marrow), so a finger stick sample is no more likely to be positive than a venipuncture blood.

EDTA is recommended as providing better organism morphology, particularly for Plasmodium spp.

Most patients we see in the US have never been exposed to malaria before, thus they have no antibody. These immunologically naïve patients may present with nonspecific symptoms that can mimic many other diseases. The rule of thumb is to draw immediately.

ORGANISM # 15

26

Modified Acid-Fast Stain: What are the 3 structures shown in the slide (from largest to smallest)? The range is 10 µm to 2 µm.

ORGANISM # 16

27

Iodine wet mount; seen on high dry power, X400What are morphologic characteristics that help you to identify this structure?

ORGANISM # 17

28

India Ink stain: What and how do you count and how does this help to identify the structure?Name genus, species.

ORGANISM # 18

29

Iodine wet mount: Seen on high dry power, X400. What are structures at each end called?Name genus, species

ORGANISM # 19

30

Iodine wet mount: Identify genus and species – what is structure called in the circle?

O

ORGANISM # 20

31

Iodine wet mount: What are the structures within the large object that help you to identify the genus and species?

QUESTION 6

32

What are some of the key report comments associated with malaria reports?

What are the pros and cons of the thick and thin blood films?

PLASMODIUM SPP. Report Comments

¨ Plasmodium spp. seen: Unable to “rule out” Plasmodium falciparum.

¨ Plasmodium spp. not seen: One negative set of blood films will NOT “rule out” malaria; submit additional blood specimens every 4-6 hours.

¨ Plasmodium spp. seen, possible mixed infection: Unable to “rule out” Plasmodium falciparum.

¨ NOTE: It is mandatory that the parasitemia be calculated and reported for every initial and subsequent positive set of malarial films – the same method for determining parasitemia must be used for all blood film sets on that particular patient.

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THIN BLOOD FILMS

¨ Advantages– RBC morphology can be seen; RBCs preserved

– Compare size of infected RBCs to uninfected RBCs

– Much easier to identify to species level

– Easier to calculate parasitemia (%/100 RBCs)

¨ Disadvantages– Much lower sensitivity than thick blood film

– Infections with low parasitemia may be missed

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THICK BLOOD FILMS

¨ Advantages– Examining greater volume of blood– May be able to see malaria pigment within WBCs– May be able to see Schüffner's dots

¨ Disadvantages– Can’t compare sizes of infected and uninfected

RBCS– Organism distortion is difficult to recognize– Identification to species level is more difficult

GARCIA 35

ORGANISM # 21

36

Cellophane tape: What are these structures and what is the collection method of choice?Name the genus and species

ORGANISM # 22

37

Tissue biopsy, routine H/E stain: What is the cause of this infection? Why might bears, walrus, or pigs be involved?

THANKS – QUESTIONS?

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