Micro - Specimen Processing, Microscopy

Question 1

Why are deep tissue specimen preferred over pus or swab?

Answer 1

Fastidious organisms including anaerobes would be more exposed to atmospheric oxygen on a swab compared to inside a tissue

Question 2

Ideally, specimen should be transported to the lab within ___ of collection

Answer 2

30 mins

Question 3

Transport containers should be marked with a sticker that says ___

Answer 3

Biohazard

Question 4

The preservative, ___, is used in urine samples. Why?

Answer 4

Boric acid

Prevents overgrowth of organisms by converting urine into a bacteriostatic agent
In case of urine, number of cfu/ml is critical in interpreting results for true infection or mere contamination

Question 5

Polyvinyl alcohol (PVA) and buffered formalin are used in samples taken from… They help maintain the integrity of these organisms

Answer 5

Stool

Cysts and trophozoites

Question 6

Inhibitory fatty acids that can kill fastidious organisms can be neutralized by adding

Answer 6

Charcoal

Question 7

Why should we never place anaerobic specimens in the refrigerator?

Answer 7

Anaerobes are sensitive to cold temperature. Medically significant anaerobes grow at human body temperature

Question 8

What temperature should CSF samples be stored at? Why?

Answer 8

37C

Organisms causing central nervous system infections are fastidious and rapidly die at room or cooler temperatures

Question 9

Why is microscopy usually not performed for throat, nasopharyngeal and stool specimens?

Answer 9

All these anatomical sites have abundance of resident flora and it would be almost impossible to distinguish between pathogens and normal flora based on their microscopic morphology

Question 10

Urine, stool, viral specimens, sputum, swabs and catheters should be stored at

Answer 10

4C (fridge)

Question 11

Blood agar and chocolate agar are examples of this type of media

Answer 11

Nutritive agar

Question 12

Blood agar differentiates organisms based on their ability to…

Answer 12

Hemolyse RBCs

Question 13

Darkfield microscopy is generally used to detect this organism

Answer 13

Treponema pallidum

-syphilis

Question 14

The quality of a specimen can be assessed by the gram stain revealing a high number of ___ and a low number of ___

Answer 14

Leukocytes

Epithelial cells

Question 15

A fluorescent acid fast stain uses this dye as the primary stain

Answer 15

Auramine-rhodamine, or auramine alone

Question 16

Phase contrast microscopy - what type of staining does it use?

Answer 16

None, uses wet mount

-common in urinalysis