Infection

Question 1

Give three pathogens causing meningitis

Answer 1

Bact:

S. pneumoniae

N. meningitids

M. tuberculosis

Viral:

HIV

HSV

Question 2

How is meningitis diagnosed?

Answer 2

Lumbar puncture (cauda equina, taken between L4 and L5 to avoid hitting nerves)

Check WBC count and type, gram stain

Question 3

Most abundant WBC in viral and fungal infection?

Answer 3

Lymphocyte

Question 4

Most abundant WBC in bacterial infection?
Exception and what is found?

Answer 4

Neutrophil.
TB - mix of lymphocyte and neutrophil

Question 5

Most abundant WBC in parasitic infections or foreign body breach?

Answer 5

Eosinophils

Question 6

What five patient factors are most important to establish in ED acute sepsis?

Answer 6

Age

Pathological State

Physiological State

Social Factors

Relative Time

Question 7

Give two indicators and their values used to diagnose SIRS (systemic inflammatory response syndrome).

Answer 7

Heart Rate: >90

Temp: <36 OR >38

Respiratory rate: >20

WBC count: <4 x 10^9/L OR >12 x 10^9/L

Question 8

How many indicators of inflammation need to be present for a diagnosis?

Answer 8

Two

Question 9

What is the structure of Adenovirus?

Answer 9

Non-enveloped

Icosahedral

Double Stranded DNA

Question 10

During what times in the year is adenovirus most prevalent?

Answer 10

Endemic: throughout the year

Question 11

Give two common sites of adenovirus infection and the mode of access to the body.

Answer 11

Respiratory tract: droplet inhalation

GI: faecal-oral route

Question 12

What are the two main interactions exhibited by adenovirus to host cells? (Hint: viral phases)

Answer 12

Lytic: replication cycle resultant in cytolysis and dissemination, no host genome integration

Lysogenic (aka latent phase): continuous replication, bypasses cell lysis, insertion of viral DNA into host cell genome.

Question 13

Advice to reduce spread of viral infection?

Answer 13

Cover nose and mouth when sneezing/coughing

Don’t share towels/drink/food with anyone

Wash hands regularly and well with plenty of soap and hot water

Stay home when possible

Question 14

Name a gram positive pathogen and an infection caused by it.

Answer 14

Question 15

Name a gram negative organism and and infection caused by it.

Answer 15

Question 16

Give one physical and one physiological barrier of the innate immune system.

Answer 16

Physical: Skin, Mucous membranes, Ciliated epithelia Physiological: Diarrhoea, vomiting, coughing, sneezing

Question 17

What is meant by ‘biological barrier’ in the innate immune system? Give an example.

Answer 17

The biofilm of commensal bacteria that compete with pathogenic bacteria for growth and nutrients. Commensals also produce bactericidal chemicals preventing the growth of pathogenic microorganisms. Examples: Staph aureus on skin Bacteroides fragilis/ E. coli in colon Strep viridans in mouth

Question 18

Asplenia/Hyposplenia increases risk of infection from what? Give an example.

Answer 18

Polysaccharide encapsulated bacteria/pneumococcus E.g: Strep pneumonia, H. influenzae (type B), N. meningitidis

Question 19

The deficiency of what complement components increases risk of Neisseria infection?

Answer 19

C3 and C5-9 (MAC)

Question 20

The two mechanisms of killing in a macrophage are?

Answer 20

Oxygen-dependent: hydrogen peroxide, oxide radicals Oxygen-independant: proteolytic and hydrolytic enzymes (lysozymes)

Question 21

What is chronic granulomatous disease?

Answer 21

The absence of a respiratory burst and therefore oxygen-dependent killing mechanism in macrophages.

Question 22

What is the function of a dendritic cell? What receptors are found on them?

Answer 22

Tissue-resident immune cells. First line of defence against barrier breach. Called Langerhans cells in the skin. These are primarily antigen presenting cells and therefore bridge the innate and adaptive immunity. TLR’s 2 and 4 responsible for Gram +ve and -ve detection.

Question 23

What vascular changes might there be at the site of inflammation?

Answer 23

Vasodilatation - histamine, prostaglandin Increased vascular permeability - histamine, bradykinin

Question 24

Name an opsonising complement component

Answer 24

C3b, C4b

Question 25

What is the action of IL-8?

Answer 25

Neutrophil chemoattractant. Produced by macrophages.

Question 26

Where is C-reactive protein produced? Give two functions.

Answer 26

Liver Measured to indicate inflammation. Monitored to check progress of inflammation/response to treatment.

Question 27

Mean Arterial Pressure = Total Peripheral Resistance (TPR) x Cardiac Output (CO) Knowing this, how could severe sepsis lead to circulatory shock?

Answer 27

Inflammation due to sepsis leads to mass vasodilatation. Vasodilatation reduces total peripheral resistance. Mean arterial pressure drops. If this continues it could cause circulatory shock.

Question 28

Why is tachycardia a symptom of septic shock? (cross modular: why are both CO and TPR not reduced in simple septic shock?)

Answer 28

Mean Arterial Pressure = Total Peripheral Resistance (TPR) x Cardiac Output (CO) Sympathetic response to a drop in mean arterial pressure due to drop in total peripheral resistance. Pressure drop detection in carotid sinus and aortic arch –> increased vagus stimulation of SAN to increase HR –> tachycardia to restore cardiac output. (Venous and arterial systems work in opposition. If TPR falls, more blood enters venous system so CO should not be affected unless there is a circulatory breach i.e trauma leading to haemhorraging)