S5: principles of diagnosis + management

Question 1

Write an infection model for cellulitis (pathogens, virulence factors, patient, aetiology, symptoms, complications, treatment)

Answer 1

Pathogens – staph aureus (gram positive cocci in clusters), strep pyogenes (gram positive cocci in chains)
Virulence factors – staph aureus: capsule, protein A, exotoxins; strep pyogenes: hyaluronic acid capsule, M - protein (hijacks respiratory burst mechanism of neutrophils), streptokinase (breaks down blood clots)
Patient – prior episodes of cellulitis, diabetic, immunocompromised, pre-existing lymphoedema
Aetiology - cellulitis develops when micro-organisms gain entry to the dermal and subcutaneous tissues via disruptions in the cutaneous barrier (i.e. cutaneous trauma, surgery)
Symptoms – red, painful, hot, swollen, most commonly on leg
Complications – lymphangitis
Treatment – flucloxacillin; if allergy to penicillin: doxycycline

Question 2

Write an infection model for UTI (pathogens, virulence factors, patient, aetiology, symptoms, complications, treatment)

Answer 2

Pathogens – E coli (gram negative bacilli)
Virulence factors – K capsule, adhesins
Patient – pregnant women, elderly women, previous UTIs
Aetiology – bacteria displaced from the intestine into the urinary tract
Symptoms – dysuria, frequency
Complications – recurrent infections, permanent kidney damage
Treatment – trimethoprim, if resistant: nitrofurantoin

Question 3

Write an infection model for CAP (pathogens, virulence factors, patient, aetiology, symptoms, complications, treatment)

Answer 3

Pathogens – strep pneumoniae, haemophilus influenza (gram negative coccobacilli)
Virulence factors – HI: capsule, adhesion proteins
Patient – children, immunocompromised (opportunistic infection)
Aetiology – direct spread by aerosols and droplets
Symptoms – cough, breathlessness, fever
Complications – pleural effusion, lung abscess
Treatment – amoxicillin

Question 4

Define healthcare infections and hospital-acquired infections

Answer 4

Healthcare infections = occur in healthcare settings

Hospital-acquired infections = infections acquired in hospitals 48 hours after admission

Question 5

Define endemic disease, outbreak, epidemic & pandemic

Answer 5

Endemic disease: usual background rate
Outbreak: two or more cases linked in time and place
Epidemic: a rate of infection greater than the usual background rate
Pandemic: very high rate of infection spreading across many regions, countries, and continents

Question 6

This session was very waffly (most common sense) – important thing is the infection models

Answer 6

Cool