Microscopy

Question 1

How to gram stain

Answer 1

Fix the smear by:
Either Heat: hot plate, ~1 min, ≤50°C (if 80°C only 30s)
Or 95% methanol: submerse for 2 mins
Flood slide w Crystal violet (pararosaniline violet dye) 30 s flood and rinse w cold water (peptidoglycan walls retain the colour in gram pos, gram neg have complex cell walls that don’t retain this but takes up the counterstain)
Flood slide w Iodine 30 s flood and rinse w cold water
Decolourise w acetone (or ethanol) + wash immediately
Flood w Safranin (or neutral red or carbolfuchsin/basic fuchsin) for 1 min then rinse w cold water
Blotting paper to dry slide

Question 2

Appearance of GC on slide?

Answer 2

gram negative (pink) Intracellular diplococci

Question 3

Appearance of candida on slide?

Answer 3

Yeasts, hyphae, PC
Yeasts no hyphae – might be c.glabrata

Question 4

TV on microscopy

Answer 4

Flagellated organisms with tumbling motility on wet prep

Question 5

What are the Hay-Ison Grades?

Answer 5

Grade 1 (normal): lactobacillus morphotypes predominate
Grade 2 (intermediate): mixed flora with some Lactobacilli present, but Gardnerella or Mobiluncus morphotypes also present
Grade 3 (BV): predominantly Gardnerella and/or Mobiluncus morphotypes. Few or absent lactobacilli
Grade 4: gram-positive bacteria predominate - uncertain significance

Question 6

What do Donovan bodies look like?

Answer 6

Mononuclear cells with intracytoplasmic cysts (Giemsa stain)

Question 7

Microbiological name for chancroid?

Answer 7

Haemophilus ducreyi

Question 8

Microscopic appearance of chancroid?

Answer 8

Gram-negative rods which may show the appearances of railroad lines or schools of fish

Question 9

What is this?

Answer 9

Chancroid

Question 10

What is this?

Answer 10

Donovan bodies

Question 11

What is this?

Answer 11

Histology of donovanosis

Question 12

Preparation of a skin scraping for microscopy in suspected scabies

Answer 12

Scraping of the skin burrows with a scalpel blade
Place specimen on a glass slide
Add 10% potassium hydroxide
( dissolves excess keratin)
OR
Apply a drop of mineral oil to the lesion
Scrape away the entire lesion with the scalpel blade
transfer to slide

Question 13

Common organisms associated with NGU

Answer 13

Chlamydia trachomatis

Mycoplasma genitalium

Ureaplasmas

Trichomonas vaginalis

Adenoviruses

Herpes simplex virus

Question 14

Why is Mycoplasma genitalium not visible with gram stain?

Answer 14

Lacks a cell wall

Question 15

What type of bacteria is Haemophilius ducreyi

Answer 15

Gram-negative facultative anaerobic coccobacillus in the family Pasteurellacae

Question 16

What is the specimen on stool microscopy?

Answer 16

Schistosoma mansoni

Schistosoma mansoni egg measuring ~150 long by 55 μm wide.

Light yellow/brown, elongated oval shape and with a characteristic prominent lateral spine near the posterior end.

Contains a miracidium.

Question 17

What do treps look like on DGM?

Answer 17

8-10 spirals rotation, propulsion, angulation, buckling, undulation, coil compression or looping./ corkscrew and differentiate from commensal trep in mouth - much larger than syph

Question 18

How to distinguish the trypanosomes on microscopy?

Answer 18

Chagas - big kinetoplast
HAT - small neat kinetoplast