T05 Mycobacteria, Fungi and Parasites

Question 1

Mycobacteria are non-motile, non-sporing rods.

What is used to stain them?

Answer 1

Carbol fushin - acid fast bacilli

not readily stained by Gram’s stain

Question 2

Pathogenic mycobacteria requires 2-6 weeks of growth on special media such as?

Answer 2

Lowenstein Jensen medium

**M.leprae fails to grow in vitro.

Question 3

What can be seen on gram’s stain if the organism is Candida albicans?

*It also goes white colonies of 2-3mm diameter, smooth edge and smooth surface on Sabouraud dextrose agar.

Answer 3

G+ with budding yeast and 
pseudohyphae at 20 degrees 
true hyphae (germ tube formation) at 37 degrees 

(dimorphic fungi)

Question 4

Pneumocystis jirovecii shows what in Toluidine O stain?

Answer 4

1. cup shaped/collapsed basketball shaped

2. in clusters

Question 5

Pathogenic effects of Entamoeba histolytica?

Answer 5

Liver abscess;

Amoebic Dysentery

Question 6

Which causative protozoa will cause vaginitis?

Answer 6

Trichomonas vaginalis

Question 7

Which genus of Protozoa stays in RBCs as a habitat?

How to distinguish the 4 different species?

Answer 7

Plasmodium

1. Vivax - Benign tertian malaria (2 days)
2. Falciparum - Malignant tertian malaria (2 days)
3. Ovale - Benign tertian malaria (2 days)
4. Malariae - Quartan malaria (3 days)

Question 8

Pathogenic effects of Toxoplasma gondii? (4)

Answer 8

1. Encephalitis
Congenital toxoplasmosis: 
2. Chorioretinitis
3. Hydrocephalus
4. Intracranial calcifications

Question 9

What can be seen in fresh specimens for Entamoeba histolytica infection?

Answer 9

Trophozoite: Ingestion of red blood cells (only in fresh specimen!)

• Mature cyst has 4 nuclei. (may not be able to see all)

Question 10

Which organism has a characteristic falling leaf movement?

Answer 10

Trichomonas vaginalis (trophozoite)

Question 11

Which organism’s trophozoites have a clown face appearance and move like a falling leaf? (Not Trichomonas vaglinalis)
What disease does it cause?

Answer 11

Giarda lamblia

- causes traveller’s diarrhoea

Question 12

What shape does Toxoplasma gondii trophozoite has?

Answer 12

Crescent shape

Question 13

What is the diagnostic sampling of Plasmodium falciparum?

What specific disease does it cause?

Answer 13

• Blood smear for Giemsa stain > rings inside RBC

- Causes cerebral malaria

Question 14

Trematodes are classified based on their habitats.

Name the organisms that are blood trematodes. (3)

Answer 14

Schistosoma mansoni
Schistosoma japonicum
Schistosoma haematobium

Question 15

Name the lung trematode you know.

Answer 15

Paragonimus westermani

Question 16

Name the hepatic trematode you know.

Answer 16

Chinese liver fluke - Clonorchis sinensis

Question 17

For all trematodes (flukes), common way to diagnose them?

Answer 17

Microscopy: stool OCP for eggs

Question 18

How can we differentiate Schistosoma haematobium from the other 2 species by morphology of the eggs?

Answer 18

S. haematobium has a terminal spine.

S.mansoni: large lateral spine
S. japonicum: small lateral spine

Question 19

What are the characteristic morphological features the eggs of Clonorchis sinensis? (2)

Answer 19

• Pear-shaped

- with an operculum at the narrower end

Question 20

Proglottid is the segment of tapeworms containing both male and female reproductive organs.
Which organisms has proglottids that are passed out in the faecies? (2)

How to differentiate them? (2)

Answer 20

1. Taenia solium - <13 lateral branches on one side of main stem of the uterus
2. Taenia saginata - >15 lateral branches on one side of main stem of the uterus

***Eggs of them are indistinguishable!

Question 21

What causes cysticercus?

Answer 21

Taenia solium

Question 22

Name all the intestinal nematodes that can be found in the small intestines. (5)

Answer 22

1. Ascaris lumbricoides (common roundworm)
2. Ancylostoma duodenale
3. Necator americanus
4. Strongyloides stercoralis
5. Trichenella spiralis

Question 23

Name the 2 intestinal nematodes that can be found at the caecum and appendix.

Answer 23

1. Enterobius vermicularis (pinworm)

2. Trichuris trichiura (whipworm)

Question 24

Name the nematode that infects the lymphatic system.

Answer 24

Wuchereria bancrofti

Question 25

Name the nematodes that infect the subcutaneous tissues. (2)

Answer 25

1. Onchocerca volvulus (river blindness, onchodermatitis)

2. Dracunculus medinensis (chronic cutaneous ulcer from which the worm protrudes)

Question 26

Name the nematode that infects muscles.

Answer 26

Trichinella spiralis

Question 27

Characteristics of eggs of Ascaris lumbricoides?

Answer 27

Fertilized eg has thick shell with lumps

Question 28

Egg is spindle-shaped with a plug at each end. What organism?

Answer 28

Trichuris trichiura (whip worm)

Question 29

Stronglyloides stercoralis

shape of larva and eggs?

Answer 29

Filariform larve

NO EGGS!