Microbiology

Question 1

What are some pyogenic conditions associated with staphylococci?

Answer 1

Wound infections
Abscesses
Osteomyelitis

Question 2

What are toxin mediated conditions associated with staphylococci?

Answer 2

Scaled skin syndrome

Toxic shock syndrome

Question 3

What are conditions linked to coagulase negative staphylococci?

Answer 3

Septicaemia

Endocarditis

Question 4

What is the main virulence factors for staphylococci epidermidis?

Answer 4

Persistent biofilm

Question 5

Virulence factors for S. saprophyticus?

Answer 5

Haemagglutinin for adhesion

Urease - kidney stone

Question 6

Complications of S. pyogenes

Answer 6

Rheumatic fever

Glomerulonephritis

Question 7

Virulence factors of S. pyogenes can be classified into

Answer 7

Surface factors

Secreted factors

Question 8

Secreted virulence factors of S. Pyogenes

Answer 8

Hyaluronidase - spreading
Streptokinase - break down clots
Streptolysin - O and S toxin - binding cholesterol
C5a peptidase - decrease chemotaxis
Erythrogenic toxin - exaggerated response

Question 9

Surface virulence factors of S. Pyogenes

Answer 9

Hyaluronic acid capsule - protect phagocytosis

M protein surface proteins - encourage complement degradation

Question 10

Diseases caused by S. pneumoniae

Answer 10

Sinusitis
Meningitis
Otitis media
Pneumonia

Question 11

Percent of people who carry S. Pneumoniae commensally??

Answer 11

30%

Question 12

Risk factors for s. Pneumoniae infection

Answer 12

Hypogammaglobulinaemia
Asplenia
Impaired mucus trapping

Question 13

What is likely to be if child presents with severe sore throat, fever, malaise, thick greyish membrane tonsils and lymphadenopathy in neck for 2 days?

Answer 13

Corynebacterium diphtheriae

Question 14

Treating C. diphtheriae?

Answer 14

Anti toxin

Erythromycin

Question 15

What are the 5 species of plasmodium?

Answer 15

1. P. vivax
2. P. ovale
3. P.falciparum
4. P. malariae
5. P. knowlesi

Question 16

Vectors for malaria?

Answer 16

Female anopheles mosquito

Question 17

Describe the vector stage of pathophysiology of malaria?

Answer 17

1. Female anopheles mosquito becomes infected after taking a blood meal containing gametocytes - sexual form
2. Developmental cycle in mosquito = 7-21 days depending on temperature –> infective sporozoites –> migrate to salivary glands

Question 18

Describe the host stage of pathophysiology of malaria?

Answer 18

1. Injected into human host –> destroyed by immune system –> taken up by liver
2. Multiple inside hepatocytes as merozoites - pre-erythrocyte sporogeny
3. After few days - rupture of hepatocytes - release of merozoites into blood , taken up by erythrocytes
4. Inside - parasites multiply changing from merozoites to trophozoites to schizont to merozoites (8-24 new)
   7) Erythrocyte rupture - release merozoites

Question 19

What are malaria cycles known as in blood?

Answer 19

Erythrocytic schizogony - 48 hrs in P. falciparum, P. vivax, P. ovale

Question 20

Clinical features of malaria?

Answer 20

1. Fever
2. Chills, sweats
3. Headache
4. Myalgia
5. Fatigue
6. Nausea and vomiting
7. Diarrhoea

Question 21

Specific presentation of P. falciparum

Answer 21

1. Cerebral malaria - marked diminished consciousness, convulsion
2. ARDS - vascular occlusion, anaemia, lactic acidosis, increase vasc permeability –> SOB, hypoxia, pulmonary oedema
3. Shock
4. Bleeding - thrombocytopoenia, activation of coagulation cascade,
5. Renal failure - fatigue, proteinuria, haematuria

Question 22

Time frame of malaria presentation

Answer 22

Falciparum unlikely to be present >3months

Vivax up to 1 year

Question 23

Non-specific features of malaria?

Answer 23

1. Anaemia
2. Low platelets
3. Hyper bilirubinaemia
4. Mildly raised transaminases

Question 24

Diagnosis of malaria?

Answer 24

1. Thick films:
   - indicates malaria presence
2. Thin films:
   - what species and count

Question 25

Treating uncomplicated falciparum malaria?

Answer 25

1. Riamet oral (brand name) | 2. Oral quinine + doxycycline to treat undiscovered malaria

Question 26

What is complicated falciparium malaria?

Answer 26

1. Impaired consciousness/ extreme weakness 2. Parasitic count 3. Spontaneous bleeding, Haemoglobulinuria 5. Shock, pulmonary oedema

Question 27

P. vivax and p.ovale treatment?

Answer 27

Primaquine for hypnozoite clearance

Question 28

Non-falciparum malaria treatment?

Answer 28

Oral chloroquine

Question 29

Specific action pathway of P.falciparum?

Answer 29

1. Cytoadherence - infected RBC display specific membrane proteins on their surface - adhere to microvascular endothelium 2. Rosetting - adhere to other non-infected RBC -rosettes 3. Sequestration - of parasites in major organs - can hide from immune system and mature