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)
Outline the CURB-65 screening test
Confusion
Urea >7
RR > 30
BP < 90/60
Age > 65yo
Treatment for CAP
in more severe cases we add macrolides in order to cover atypical pathogens which may be behind the pneumonia
Treatment for HAP
1st line = Ciprofloxacin + Vancomycin
If severe = Tazocin + Vancomycin
compared to CAP treatment we see a stronger coverage of gram -ve organsims as most HAP are caused by gram -ve organisms. Vancomycin allows cover for MRSA - an important gram +ve organism to cover in HAP
Important differentials to consider if patient not responsive to antibiotic treatment
- Empyema, Abscess (confirm with CT)
- Proximal obstruction (e.g. tumour)
- Resistant organism (TB will resist standard abx tx)
- Immunosuppressed patients
List common respiratory tract infections seen in immunosuppressed patients with:
- HIV
- Splenectomy
- Cystic fibrosis
- Neutropenia
- Bone marrow transplant
HIV pts = Pneumocystits jiroveci (PCP)
Splenectomy = encapsulated organisms (e.g. H influenzae, S. pneumoniae)
Cystic Fibrosis = Pseudomonas aeruginosa
Neutropenia = Invasive Aspergillus
Bone Marrow Transplant = CMV
Outline the presentation of a patient with PCP and treatment
- Desaturation upon low-effort exertion
- Bat’s wing apperance on CXR
- Diffuse ground glass opacity in CXR
- Dx = PCR on BAL + positive fungal markers (Beta d glucan)
- Rx = Co-trimoxazole
Define bronchiolitis
Inflammation of medium sized airways commonly by viruses
Can also be caused by S. pneumoniae, H. influenzae, Morazella Catarrhalis
Treatment regiment for Bronchitis
Physiotherapy +/- antibiotic depending on causative organsism
