Infections Flashcards
PJP
Outline the characteristics of Pneumocystis Jiroveci (prev. Carinii) infection
Pneumocystis jiroveci. (PCP/PJP)
Clinically - CXR shows widespread pulmonary infiltrates. Another clinical finding is that arterial oxygenation is often strikingly lower than would be expected from symptoms.
Methenamine silver nitrate is used to stain for fungi and Pneumocystis carinii. Pneumocystis is a genus of unicellular fungi.
PCP is identified by staining of cysts with methenamine silver nitrate, or toluidine blue, which stains dark bodies within the cysts.
Pneumocystis pneumonia is a well-recognised major opportunistic infection in HIV-positive individuals. Similar to other opportunistic fungal infections, Pneumocystis pneumonia is most often observed when the CD4+ T helper cell count falls below 200 cells/mm3. CD4+ T cells are absolutely critical for resolution of Pneumocystis, having an essential role in the recruitment and activation of effector cells against the organism.
PERTUSSIS
Define, outline features, epidemiology, clinical signs, treatment
- *Pertussis**
- Gram -ve bacilli
- Spread via droplets
- Incubation 1-3 weeks, 7-10 day course (infectious for up to 21 days)
- Highly infectious- spread 90% to unimmunised contacts (prev. leading cause of death in US children)
- *3 phases:**
1. Catarrhal: 1-2 weeks of coryzal symptoms (congestion, rhinorrhoea. conjunctivitis)
2. Paroxysmal: 2-8 weeks paroxysmal cough + inspiratory whoop, post tussive vomits, gagging/gasping/apnoea in infants Cx pneumonia, encephalopathy
3. Convalescent: (recovery) - Usually absent LRTI features/ fever, myalgia, rash
Diagnosis: predominant cough + >14 days duration/paroxysms with whoop (infants <3mo gagging/gasping/ALTE)
- *Investigations:** respiratory PCR (usually neg >21d or after 5-7d ABx), IgA serology, FBE lymphocytosis, CXR- minimal change
- *Treatment:**
- Azithromycin 5d (neonates), clarithromycin 7d -> bactrim second line
- ABx reduce infectivity but do not alter course of disease
- Indicateed if diagnosed in early phases, cough <14d
- Respiratory isolation
- Prophylaxis if close contact, contact within 14d of illness, child <6/undervaccinated (<3 doses)
- Vaccination (live attenuated) 2,4 & 6 mo routine, 18mo & 10-15yr booster, efficacy 80-85%
MYCOPLASMA PNEUMONIA
Define, outline features, investigations & treatment
- *Mycoplasma Pneumoniae**
- Small bacterium sans cell wall (Mollicutes family)
- Droplet transmission, 1-3week incubation
- Consider in school aged children, rare before 3yrs, in <5s leads to mild URTI +/- D&V
- Presents as headache, malaise, fever & sore throat -> chronic cough(2-4weeks)
- Chest findings not until late disease
- CXR worse than exam -> interstitial bronchopneumonia, LL >UL, ⅓ hilar lymphadenopathy
- Investigations: respiratory PCR most specific, low sensitivity (50-70%) IgM - +ve 6-12mo post infection , culture takes 2-3 weeks
- Treatment: doxycycline, clarithromycin or azithromycin
PBB/Protracted bacterial bronchitis
Define, outline epidemiology, organisms, DDx, investigations & treatment
Protracted bacterial bronchitis (most common 0-2 years)
Chronic suppurative lung disease (CSLD) - umbrella term, includes:
- PBB
- Bronchiolitis
Most common cause of chronic cough <5yrs (40%)
Mean age 1-3yrs
Boys > girls
- *Organisms**
- H.Influenzae
- S. Pneumoniae
- Moraxhella Catarrhalis
Definition
Cough >4weeks
Response to 2/52 ABx
Absence of alternative Dc
- *DDx:**
- Bronchiectasis
- Aspiration events
- CF/PCD
- Retained airway FB
- Interstitial lung disease
- Bronchiolitis obliterans
Pathophysiology
Typically – viral infection 🡪 impaired mucociliary clearance 🡪 secondary bacterial infection 🡪 form into biofilm layers (low grade infection in large airways) 🡪 increased mucous production
CXR: bilateral peribronchial accentution
Rx: 2/52 augmentin (may require longer) -> if still cough, further 2/52 -> if ongoing 4/52, consider CT
Pleural effusions/empeyema
Exudative
Parapneumonic effusion
- Exudative pleural effusion assoc with lung infection
Loculated
- Presence of septations within effusion, interferes with free flow of fluid
Empeyma
- Bacterial organisms, pus, gorssly purulent fluid in pleural space
Complicated parapneumonic effusion
- Loculated effusion or empeyema
- Pneumonia by Strep pneumoniae
- Empeyema –> exudative, fibrinopurulent, organised
Presentation
Sx
- Febrile
- Increased WOB and resp distress
- Appear more unwell
- Shortness of breath
- Chest pain or pleuritic pain - refusing to lie one side
- Pleurisy - pain, worse when lyng flat
Ex
Decreased breath sounds
Dullness to percussion
Tactile fremitus - vibration when speaks, less
Trachea deviation
Investigations
CXR
Supine
- Blunting costphrenic angles
Erect
Along chest wall - layering effect
Meniscus sign - rim of fluid ascending chest wall
USS
- Loculations
CT chest not routinely indicated
Bloods
- CRP useful to measure treatment
- Consider HUS - anemia, thromboycytopenia
Pleural tap/Thoracentesis
Pleural fluid
Relieve symptoms
Also diagnostic
Transudative - clear
Less protein
Exudatie - cloudy (immune cells)
More protein (proteins leak out of inflammed capillaries)
Lymphatic - milk looking
Light Criteria
Exudative
Fluid protein: serum protein > 0.5
More protein
Fluid LDH: serum LDH > 0.6
Fluid LDH > 2/3 upper limit of normal of serum LDH
Cholesterol high
Empyema (exudative)
Protein level > 3.0
LDH > 1000
Pleural fluid protein: serum protein > 0.5
pH < 7.0
Glucose < 40
Management
- AP/PA CXR (no need for routine lateral)
- Chest ultrasound - best technique to differentiate pleural fluid and consolidation, estmate effusion size and grade complexity, presence of fibrinous septations and guide chest drain placement
- Routine pre-op CT should not be performed - reserved for complicated cases where failed to treatment or concern for other pathology
- High dose IV antibiotics (ensure pleural penetration) - coverage for Strep pneumonia and Staph aureus - RCH guidelines fluclox and 3rd gen cephalo
- Large amount of fluid, persistent fever or clinical deterioriation, severe respiratory distress –> drainage
- VATS (required if loculations)
- Percutaneous small bore drainage with urokinase
- PO Abx for 1-6 weeks post discharge
- Follow up CXR 6 weeks
