Infectious lung disease- Aspergillosis, pneumonia Flashcards
Define Aspergillus Lung Disease and its 5 potential pulmonary manifestations depending on patient status
The clinical presentation of Aspergillus lung disease is determined by the interaction between fungus and host.
-
Allergic bronchopulmonary aspergillosis
- Hypersensitivity reaction to Aspergillus antigens
- Typically seen in patients with asthma/C
-
Aspergilloma (fungal ball)
- Occurs in pre-existing lung cavities
- commonly 2/2 tuberculosis/sarcoidosis
-
Invasive aspergillosis
- Invasion of hyphae to pulmonary parenchyma + spread to multiple organ sites
- in severly immunocompromised individuals
-
Chronic necrotising aspergillosis
- indolent destructive process in patients without obvious immune compromise
- With lung disease (COPD, pneumoconiosis, CF)
Define aspergilloma
Growth of an A. fumigates mycetoma ball in a pre-existing lung cavity (e.g. post-TB/sarcoidosis, old infarct or abscess)
Explain the pathogenesis of allergic bronchopulmonary aspergillosis (ABPA)
- Colonisation of the airways by Aspergillus fumigatus → IgE and IgG-mediated immune responses
- Asthmatics and CF patients
- The release of proteolytic enzymes, mycotoxins and antibodies → airway damage
- Causes bronchoconstriction + permanent damage (bronchiectasis)
Explain the pathogenesis of invasive aspergillosis
Inhalation of conidia in immunocompromised patients leads to colonisation in lung tissue
- can disseminate to multiple organ sites via the haematogenous route
- commonly occurs into the brain and skin, leading to tissue infarction at those sites.
Summarise the epidemiology of the 4 aspergillus lung diseases
uncommon
Allergic bronchopulmonary aspergillosis
⇒ asthmatics
⇒ CF
Invasive aspergillosis
⇒ immunocompromised- neutropaenic, steroids, AIDS
Chronic (necrotising) aspergillosis
⇒ COPD, pneumoconiosis, CF
⇒ no significant immunocompromise
Aspergilloma
⇒ TB, sarcoidosis
Recognise the presenting symptoms of Aspergillus lung disease
INVASIVE ASPERGILLOSIS
- pleuritic chest pain due to peripheral lesions in lung
- pleural rub
- nasal ulcer, skin rash(es)- erythematous, slightly tender, raised lesion, with a necrotic, often ulcerated, centre (ecthyma gangrenosum)
- dry cough
- headache/seizure - intercranial disease
- haemoptysis- can be severe
ASPERGILLOMA
- haemoptysis- erosion of lesion into bronchial vessels
- fever/malaise/weight loss
- may be asymptomatic
ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS
- Difficult to control asthma
- Recurrent episodes of pneumonia with wheeze, cough, sputum, dyspnoea, fever and malaise
Identify appropriate investigations for Aspergillus lung disease
Chest X-ray
- Allergic Bronchopulmonary aspergillosis- consolidation, distended, mucus-filled bronchi
- Invasive aspergillosis- nodules, consolidation, non-specific infiltrates, ground glass opacities, pleural effusion
- Aspergilloma- round mass with crescent of air + adjacent pleural thickening
CT chest
- as for CXR, just more sensitive
- may need brain + sinuses in IA to check for spread
Cytology/histology
- Sputum culture- may be negative in aspergilloma as no communication with bronchial tree
- Bronchoalveolar lavage
- Tissue culture- biopsy = DIAGNOSTIC
Serology
- EIA- aspergillus GM antigen (lavage or serum)
- IgG antibodies to Aspergillus
- FBC- eosinophilia
Describe + explain the appearance of invasive aspergillosis on CT
- Nodules surrounded by a ground-glass appearance (halo sign)
- This is caused by haemorrhage into the tissue surrounding the fungal invasion
Define pneumonia
Infection + inflammation of the distal lung parenchyma with consolidation or interstitial lung infiltrates
Categorised according to causative organism
note- consolidation = refers to build up of denser material in alveoli + terminal bronchioles
Explain some of the different categories of penumonia
- Community acquired pneumonia (CAP)
- Hospital acquired pneumonia (HAP)
- Viral pneumonia
- Aspiration pneumonia
- Pneumonia in the immunocompromised
- Atypical (Mycoplasma, Chlamydia, Legionella)
State the most common typical + atypical causative organisms for CAP
TYPICAL (80%)
- Streptococcus pneumoniae = most common
- Haemophilus influenzae = 2nd most, adults
- Staphylococcus aureus (including MRSA)
- Group A streptococci
- Moxarella catarrhalis = COPD patients
ATYPICAL (20%)
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Legionella pneumophila
Most common causative organims for viral CAP?
- Influenza A/B
- Respiratory syncytial virus
- Adenovirus
- Rhinovirus
- Coronavirus
Which pneumonia can be caused by air conditioning?
Legionella
Which pneumonia causes Q fever?
Coxiella burnetii
What are the requirements for a pneumonia to be hospital acquired?
Acquired after at least 48 hours of admission to hospital and is not incubating at the time of admission
What are the most common causative organisms for HAP?
Early onset HAP (<5days) most likely Streptococcus pneumoniae (commonest also in CAP)
Late onset HAP >5 days = caused by microorganisms acquired in hospital:
- MRSA
- Pseudomonas aeruginosa
- E. coli
- Klebsiella pneumoniae
GRAM NEGATIVE
State some patient groups that may suffer from aspiration pneumonia
Commonly occurs in patients with altered mental status who have an impaired gag or swallowing reflex.
Inhalation into lower airways → lung injury → bacterial infection
- stroke
- myasthenia
- bulbar palsies
- oesophageal disease
- poor dental hygiene
Which pathogens may be responsible for penumonia in the immunocompromised?
- Strep pneumoniae aka pneumococcus
- Fungal + parasitic infections may occur
- H. Influenza
- RSV
Most common CAP causative organisms?
- Haemophilus influenzae
- Staphylococcus aureus (including MRSA)
- group A streptococci
- Moxarella catarrhalis
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Legionella pneumophila
State some risk factors for CAP
- age >65 years
- residence in a healthcare setting
- COPD + other pre-existing lung disease
- smoking
- intubation + mechanical ventilation
- alcohol abuse
-
poor oral hygiene
- Bacteria in dental plaques are shed into the saliva and aspirated into the LRT causing infection.
- immunodeficiency, chronic disease
- contact with children + patients with pneumonia
Summarise the epidemiology of pneumonia
Globally LRTIs are the most deadly disease- 3 million deaths p/a
Incidence of CAP appears to be significantly higher in men than in women.
HAP is more common in ICU patients + those who have recently had major surgery, and those who have been in hospital for a long time
What are the presenting symptoms of pneumonia?
-
Cough with increasing sputum production
- usually thick yellow/green
- Dyspnoea
- Pleuritic chest pain
- Fever/rigors
- Confusion
- Malaise/anorexia
- Haemoptysis
What are the signs of pneumonia on examination?
- Tachypnoea
- Tachycardia
- Cyanosis
- Asymmetrical chest expansion
- Diminished resonance on percussion
- On auscultation:
- Crackles/rhonci
- Increased vocal resonance (99)
- Increased tactile vocal fremitus
- Confusion and may be hypothermic – elderly
Identify appropriate investigations for pneumonia
Bloods:
- LFTs
-
U+Es
- CKD = poor prognostic factor
-
CRP
- >100 mg/L makes pneumonia likely
- <20 mg/L makes penumonia highly unlikely
-
FBC
- Leukocytosis
- WBC count > 15 x109/L indicates a bacterial aetiology
- ABG
Cultures:
- Sputum/pleural fluid MC+S
- Urine MC+S- pneumococcal + legionella urine antigen tests
- Blood cultures
- Bronchoalveolar lavage
- PCR/viral serology - if unresponsive to Abx
Imaging:
-
CXR- 1st line
- shows consolidation
- CT if CXR unclear/diagnostic uncertainty
What is the name of the scoring system for assessment of the severity of penumonia?
CURB-65
1 point for each:
- Confusion – abbreviated mental test <8
- Urea >7mmol/l
- RR > 30
- BP < 90 systolic and/or 60 diastolic
- Age >65
0 – 1: home treatment if possible
2: hospital therapy
3 or more: severe pneumonia – consider ICU
How is pneumonia treated?
1: Supportive:
- O2 if SaO2 = <94% (COPD<88%)
- CPAP, BiPAP or ITU care for ARDS
- IV fluid resuscitation
- Vasopressors- if in shock/hypotension
- Analgesia (IV paracetamol)
2: Start broad spectrum empirical antibiotics
- If clinical diagnosis, whilst waiting for blood cultures
- Mild: oral amoxicillin
- Moderate: IV/oral amoxicillin + clarithromycin
- Severe: IV co-amoxiclav + clarithromycin
3: Immediately order CXR
- Confirm diagnosis
4: Switch from empirical antibiotics to pathogen-targeted antibiotics as soon as specific pathogens are identified
Which Abx do you do to treat aspiration pneumonia?
cephalosporin IV + metronidazole IV
State some indicators of clinical instability that prevent discharge
Fever in past 48hrs or >1 of:
- SBP <90 mmHg
- HR >100/minute
- RR >24/minute
- Arterial SaO2 <90% or PaO2 <60 mmHg in room air.
State some preventative measures for pneumonia. What groups are eligable for these measures?
- Pneumococcal vaccine
- Haemophilus influenzae type B vaccine
These are only usually given to high risk groups (e.g. elderly, splenectomy)
Identify the possible complications of pneumonia
RESP
- Pleural effusion
- Pneumothorax
- Empyema (pyothorax)
- Necrotising pneumonia
- Localised suppuration (e.g. abscess)
- Symptoms of abscesses:
- Swinging fever
- Persistent pneumonia
- Copious/foul-smelling sputum
- Symptoms of abscesses:
- ARDS
SYSTEMIC
- Septic shock
- Acute renal failure
CARDIAC
- Pericarditis
- Arrhythmias
- ACS
- HF
Summarise the prognosis for patients with pneumonia
Most resolve within treatment within 1-3 weeks
For patients admitted to hospital, mortality = 5-15%
Risk factors associated with increased 30-day mortality:
- bacteraemia
- admission to the ICU (20-50% mortality)
- comorbidities (cardiovascular, pulmonary, or neurological disease)
- infection with multidrug-resistant pathogen (S. aureus, P. aeruginosa, Enterobacteriaceae)
Which bacterial pneumonia is the most common? Patients at risk?
Common in elderly, alcoholics, post-splenectomy, immune-suppressed, patients with HF/lung
Which pneumonia can complicate influenza? How is it treated?
Staphylococcal
- Bilateral cavitating bronchopneumonia
- Tx: flucloxacillin +/- rifampicin
