1. Community acquired pneumonia Flashcards
what are the 3 common bacterial causes of CAP?
streptococcus pneumoniae
haemophilus influenza
staphylococcus aureus
what are the bacterial atypical causes of CAP?
o Legionella pneumophila
o Mycoplasma pneumoniae
o Chlamydia pneumoniae
o Chlamydia psittaci
what are the viral causes of CAP?
Influenza, Parainfluenza, Respiratory syncytial virus
what is the most common cause of CAP in under 2s?
Respiratory syncytial virus
describe the gram stain of streptococcus pneumoniae
gram positive
diplococci
short chain
virulence factors of strep pneumoniae
- Capsule = Anti-phagocytic and antigenic
* Pili = Attachment of bacteria to the epithelial cells in the respiratory tract
tests for strep pneumoniae?
blood Culture, Nasopharyngeal swab, sputum - green
what are the 2 clinical significance of strep pneumoniae?
- CAP = Bacteria invades RT causing immune response & inflammation
- Bacterial Meningitis = Bacteria enters blood stream –> Crosses BBB –> Colonises CSF –> Infllammatory response
characteristics of strep pneumoniae?
alpha haemolytic
normal flora of nasopharynx
treatment of strep pneumoniae?
- mild: Amoxicillin (doxycycline if allergic to penicillin)
- moderate: Amoxicillin AND doxycycline (only doxycycline if allergic)
- severe: Co-amoxiclav and doxycycline (meropenem and doxycycline if penicillin allergic)
what is the action of drugs for strep pneumoniae?
all cell wall synthesis inhibitors
describe the gram stain of haemophilia influenzae
gram negative
coccobacili
characteristics of haemophilia influenzae?
- Normal flora of URT (Nasopharynx)
- Transmitted via respiratory droplets
- Opportunistic Pathogen in Immunocompromised/Children
virulence factors of haemophilia influenzae?
- LPS Capsule–antiphagocytic and antigenic
* IgA Protease exotoxin–allows it to colonise
clinical significances of haemophilia influenzae?
- Spread from initial site of colonisation of UR – Otitis Media, Sinusitis, Epiglottitis and bronchopneumonia
- Spread into blood and distal sites – Meningitis, Septic arthritis, Cellulitis
investigations for haemophilia influenzae?
Culture & Gram Stain
treatment for haemophilia influenzae?
co-amoxiclav
- contains clavulonic acid = beta lactamase inhibitor
- beta lactamase = enzyme used by bacteria such as H influenzae to break down beta lactam antibiotics so resistant to amoxicillin
- clavulonic acid combined with amoxicillin overcomes this issue
symptoms of CAP?
- fever
- malaise
- tachypnoea
- tachycardia
- cough - productive of sputum
- SOB
- pleuritic chest pain
- vomiting
signs of CAP
- consolidation
- pulmonary oedema
- crackles on auscultation
- dull on percussion
what host defence mechanisms need to be overcome to lead to pneumonia?
- cough reflex
- mucociliary escalator
- IgA, complement, neutrophils and macrophages
- opsonisation by antibody and complements
how is pneumonia transmitted?
via respiratory droplets
what is pneumonia?
Pneumonia is infection of the terminal air sacs (“alveoli”) and tissue of the lung.
3 x-ray categories of CAP and how they appear on x rays?
- bronchopneumonia - patchy areas of consolidation throughout lung - around the larger airways
- lobar pneumonia - consolidation localised to a single lobe
- atypical/interstitial pneumonia - concentrated in the perihilar region -there is usually no sputum production at presentation. It is usually seen in mycoplasma, legionella, and viral pneumonia
investigations of CAP?
- FBC
- blood culture
- naso-pharyngeal swab
- chest x-ray
- auscultaions
- percussion
describe the stages in pneumonia
- congestion - days 1-2
- blood vessels and alveoli fill with excess fluid - red hepatization - days 3-4
- exudate (RBC, neutrophils and fibrin) fill airspaces making them more solid
- liver like appearance - grey hepatization - days 5-7
- colour change - RBCs in exudate break down - resolution - days 8- 3 weeks
- exudate is digested, ingested by enzymes/macrophages or cough up
define CAP?
pneumonia (infection of the lung parenchyma seen on chest X-ray) which develops outside the hospital.
