L9 - Gram negative Cocci, mycobacteria Flashcards Preview

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Flashcards in L9 - Gram negative Cocci, mycobacteria Deck (17)
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What do you call an unexplained fever?

Pyrexia of unknown origin (PUO)


What are typical causes of PUO?

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


What are some zoonotic causes of fever?

Brucella, Q fever and Toxoplasma


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

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


Which populations have high TB progression rates?

Recently infected:
Under 4
Renal Failure
Prison inmates


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

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


What do you do to diagnose TB?

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


What do you use to treat TB?

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


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

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


How is TB transmitted?

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


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



Describe the rash usually seen in patients with meningococcal disease

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


Describe the gram stain appearance of Neisseria meningiditis

Gram negative, diplococci. They are kidney bean shaped


Describe meningococcal pathogenesis

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


Who is at 800 fold increased risk of Meningococcal?

Household contacts/kissing cousins of someone who is infected


Describe Meningococcal onset

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


How do you disprove Meningococcaemia?

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.

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