Micro: Respiratory Tract Infections Flashcards
List some ways in which the body can be compromised, thereby increasing the risk of respiratory tract infection.
- Poor swallow (e.g. CVA, Alcohol)
- Abnormal ciliary function (e.g. smoking, viral)
- Abnormal mucus (e.g. CF)
- Dilated airways (e.g. bronchiectasis)
- Defect in host immunity
Differentiate between URTI and LRTI
URTI = infections above larynx - pharyngitis, sinusitis, tonsilitis
LRTI = lung infection - pneumonia, bronchitis, emphyema, abscess, bronchiectasis
Define pneumonia and its symptoms
= inflammation of lung alveoli
Symptoms
- Fever
- Cough
- dyspnoea
- pleuritic chest pain
Risk factors for pneumonia
- Pre-existing lung condition
- Immunocompromised
- Seasonal organisms (epidemics - e.g mycoplasma)
- Travel history
Classifications of Pneumonia
- Community Acquired vs Hospital Acquired
- Typical vs Atypical (commonly part of CAP)
Differentiate between CAP and HAP (definition and organisms)
Community Acquired Pneumonia
- = acquired outside hospital setting
- Strep pneumonia (commonest)
- Haemophilus influenzae
- Mycoplasma (epidemic)
- Staph A
- often gram pos
Hospital Acquired Pneumonia
- = acquired after >48hr of hospital admission
- Can be ventilator-associated pneumonia
- Enterobacteriaecae (klebsiella, e-coli)
- Staph A (commonly MRSA)
- Pseudomonas
- often gram-ve hence required macrolide
List the most prevalent pathogens causing CAP in the following age groups:
- 0-1 months
- 1-6 months
- 6 months - 5 years
- 16 - 30 years
0 - 1 months:
- Escherichia coli
- Group B Streptococcus
- Listeria monocytogenes
1-6 months:
- Chlamydia trachomatis
- Staphylococcus auerus
- RSV
6 months - 5 years:
- Mycoplasma pnaeumoniae
- Influenza
16-30 years:
- Mycoplasma pneumoniae
- Streptococcus pneumoniae
Outline classic buzzwords for Strep Pneumoniae CAP infection.
- Acute onset of pneumonia symptoms with fevers and rigors
- Rusty coloured sputum
- Lobar consolidation on CXR
- Gram positive diplococci (in pairs or chains) + alpha haemolytic
Outline classic buzzwords for H. Influenzae CAP infection.
- Commonly in elderly with co-existing lung pathology (COPD!!)
- Less severe onset of symptoms
- Gram negative cocco-bacilli
- must check if beta lactamase present to ensure penicillin will be effective tx
Outline classic buzzwords for Moraxella Catarrhalis CAP infection.
- Associated with smoking
- Associated with COPD
- Gram negative diplococci (way to differentiate between H. Influenzae!)
Outline classic buzzwords for Staph. Aureus CAP infection.
- Associated with recent viral infection (post-influenza)
- Cavitation lesion on CXR
- Gram positive cocci (clusters - grape-bunch)
Outline classic buzzwords for Klebsiella Pneumoniae CAP infection.
- Associated in alcoholics, DM, elderly
- CXR: Upper lobe cavitating lesion
- Gram negative rod
Differentiate between typical and atypical pneumonia
Typical
- Classical signs and CXR changes
- Strep pneumoniae, H. influenzae commonly
- Respond to penicillin
Atypical
- No or atypical signs and symptoms
- Common extra-pulmonary features
- Caused by organisms without cell wall THEREFORE does not respond to penicillin
- Treated with protein synthesis inhibitior abx (commonly macrolides)
- behind 20% of CAP hence not that uncommon
Differentiate between the different organisms (3) which cause atypical CAP
*Often atypical CAP has a flu like prodrome phase *
Legionella pneumophilia
- Travel history (commonly hotel with AC)
- Hyponataremia (+ confusion), hepatitis, lymphopaenia, diarrhoea (+ abdo pain)
- Diagnosed with urinary antigen test and culture requires special buffered charcoal yeast extract
Mycoplasma Pneumoniae
- Outbreaks in young people, university
- Dry cough, arthralgia
- AIHA (cold type - IgM)
Chlamydia Psittaci
- Seen in people with birds
- Diagnosis = serology test
Important diagnostic tests for pneumonia
Bloods
- FBC = check for anaemia (potential cause of SOB?)
- U&Es = hyponatraemia in atypical, check baseline creatinine clearance for potential abx use, urea for CURB-65
- CRP = infection
- ABG = check how hypoxic
Chest X-Ray
- Gold standard diagnosis
Sputum Cultures
- identification of pathogen - however many are not cultured as good sputum samples are hard to obtain and empirical abx started early.
May consider atypical screen
- Urine antigen (legionella)
- Serum antibody tests for organisms difficult to culture (chlamydia)
Treatment for CAP
in more severe cases we add macrolides in order to cover atypical pathogens which may be behind the pneumonia
