L9 - Gram negative Cocci, mycobacteria

Question 1

What do you call an unexplained fever?

Answer 1

Pyrexia of unknown origin (PUO)

Question 2

What are typical causes of PUO?

Answer 2

Infection (30%)
Tumours (13%)
Autoimmune issues (24%)
None found (18%)

Question 3

What are some zoonotic causes of fever?

Answer 3

Brucella, Q fever and Toxoplasma

Question 4

When do you usually get infected with TB and when does disease normally manifest?

Answer 4

Usually infected in early childhood in a developing country
5% clinical disease within first year
2.5% in the second year
2.5% residual life time risk of re-activation

Question 5

Which populations have high TB progression rates?

Answer 5

Recently infected:
Under 4
Immunosupressed
HIV
Renal Failure
Malnourished
Foreign-born
Homeless
Prison inmates
Elderly

Question 6

Where is the initial site of infection and where does it progress to?

Answer 6

Subpleural midzone
Drains to regional lymph node where it calcifies and forms a Ghon complex
Post-primary disease occurs in the upper lobe

Question 7

What do you do to diagnose TB?

Answer 7

Suspect it
Early morning sputa for three days, takes a long time to grow cultures though
Use mantoux/Quantiferon gold for exposure

Question 8

What do you use to treat TB?

Answer 8

Combination of four drugs for six months if has a sensitive disease: (RIPE) Rifampicin, Isoniazid, Pyrazinamide and Ethambutol
Quinolones, macrolides, streptomycin used for resistant strains

Question 9

What is the relationship between TNF-inhibitors and TB recurrence?

Answer 9

TNF is a major mechanism in killing of TB. inhibitors, used to treat rheumatoid arthritis, impair macrophage killing and so increase the likelihood of TB recurrence

Question 10

How is TB transmitted?

Answer 10

Airbone. Droplet is only 1-5um, so stays in the air for long periods of time.

Question 11

What is the ‘most important’ disease involving fever and a rash?

Answer 11

Meningococcaemia

Question 12

Describe the rash usually seen in patients with meningococcal disease

Answer 12

Puerperic rash, with big blobs of bleeding under the skin. Will also feature perticei, tiny purple spots which are from fragile capillaries bleeding

Question 13

Describe the gram stain appearance of Neisseria meningiditis

Answer 13

Gram negative, diplococci. They are kidney bean shaped

Question 14

Describe meningococcal pathogenesis

Answer 14

Initially colonises the nasopharynx - 5-20% of the population.
In a very small percentage, bacteria cross the mucosal barrier and cause bacteraemia. Once in the blood stream, patients may get septicaemia (20% mortality) or meningitis (5% mortality).
Prevention of intravascular survival of bacteria by complement system.
There is then opsonisation of opsonised organisms in spleen

Question 15

Who is at 800 fold increased risk of Meningococcal?

Answer 15

Household contacts/kissing cousins of someone who is infected

Question 16

Describe Meningococcal onset

Answer 16

Nonspecific: fever, muscle or joint aches, Rubelliform rash - 7-12 hours onset (median)
This progresses to a petechial rash, neck stiffness, photophobia, vomiting and drowsiness - median onset 13-22 hours

Question 17

How do you disprove Meningococcaemia?

Answer 17

Two blood cultures, while providing immediate IV antibiotics. Schedule a clinical review within 4-6 hours if early meningococcal disease cannot be ruled out at the first assessment.