Acute respiratory infection and pneumonia Flashcards
What does the term ‘opportunistic pathogens’ mean?
Opportunistic pathogens are a group of microorganisms that do not usually infect healthy hosts but produce infections in hospitals, to immunosuppressed persons or those patients presenting underlying diseases as cystic fibrosis, which favours infection
What does the term ‘commensal micro-organisms’ mean?
Commensals are those type of microbes that reside on either surface of the body or at mucosa without harming human health.
The microbes living in harmony with human mostly consist of bacteria, also known as commensal bacteria, which are 10 times more than the cells present in our body.
Give some examples of opportunistic pathogens found within the URT? Incl. where they are found
- S.aureus in the nasal cavity
- S.aureus, Strep.pneumoniae, H.influenzae, Neisseria meningitidis in the pharynx
- There is minimal bacterial colonisation in the LRT
What is colonisation?
Presence of organisms not causing infection
Give some infectious causes of pneumonia? (Viral, fungal, mycobacterial and parasitic)
- Viral
- Influenza A, B
- Respiratory syncytial virus (RSV) - Fungal
- Aspergillus sp. - Mycobacterial
- Mycobacterium tuberculosis - Parasitic
- Pneumocystis jirovecii
- Ascaris lumbricoides
Give examples of different URT infections and common symptoms
- Tonsilitis, pharyngitis, laryngitis, sinusitis, common cold, otitis media
- Nasal congestion
- Runny nose
- Sore throat
- Cough
- Sneezing
- Headache
- Facial pain
- Fever
Give examples of different LRT infections
- Bronchitis
- Pneumonia
- Lung abscesses
What are the main aetiological agents for bronchitis?
Viruses such as:
- Influenza
- Adenovirus
- Rhinovirus/coronavirus
What is the most common form of pneumonia?
Bronchopneumonia
Who is most susceptible to bronchopneumonia?
Infants and elderly
Lobar pneumonia is caused by which organisms?
Streptococcus pneumoniae
Klebsiella spp.
Generalised interstitial changes are seen with which pneumonia subtypes?
Viral pneumonia
- Pneumocystic jirovecii pneumonia
Cavitating pneumonia is not very common, which organisms can it be caused by?
S.aureus
Klebsiella spp
Mycobacterial pneumonias
Risk factors for pneumonia
- Mainly due to impairment of host defences
1. Alterations in host consciousness e.g. stroke, seizures (compromise epiglottic closure - aspiration of oropharyngeal flora)
- Cigarette smoking
- Affects immunity and defence mechanisms of mucus production and mucociliary escalator - Alcohol
- General sepsis
- Immunosuppression
- Iatrogenic manipulation e.g. intubation
- Drugs e.g. aspirin, PPI
- Congenital e.g. Kartagener’s syndrome
Main symptoms of pneumonia
- Systemic
- Fever
- Chills - Central
- Headaches
- Loss of appetite
- Mood swings - Skin
- Clamminess
- Cyanosis - Lungs
- Cough with sputum or phlegm
- SoB
- Pleuritic chest pain
- Haemoptysis - Muscular
- Fatigue
- Aches - Vascular
- Low BP - Heart
- High HR - Gastric
- Nausea
- Vomiting - Joints
- Pain
How is pneumonia diagnosed?
- Blood tests: RBC, WCC, CRP
- CXR
- Microbiological tests - cultures, serological tests
- Throat swab or tracheal secretions for virology - PCR or immunofluoresence
- Urine - pneumococcal antigen or legionella antigen detection
What are some differential diagnoses for pneumonia?
- Other causes of consolidation on CXR = bronchiolitis obliterans, eosinophilic pneumonia, chemical pneumonia etc.
- Pulmonary embolism
- Cardiac - Acute heart failure
- Non-infective exacerbation of underlying lung condition e.g. COPD or asthma
- Lung cancer
Management of pneumonia
- Rapid assessment: ABCD (airway, breathing, circulation, disability)
- Supportive management
- Oxygen, fluids, close observation - Specific treatments with antibiotics as per local and national guidelines
How is the severity of pneumonia assessed?
CURB-65 score
- 0-1 = treat as outpatient
- 2-3 = short stay at hospital or monitor closely as OP
- 4-5 = hospitalisation - consider ICU
- This score involves: point for each
1. Confusion of new onset
2. Urea >=7mmol/lt
3. Respiratory rate >=30
4. SBP <= 90mm/Hg or DBP <=60mm/Hg
5. Age >= 65y/o
What is the first line treatment for pneumonia?
Amoxicillin
What are the alternative treatments for pneumonia?
- Doxycycline or clarithromycin in low-moderate severity situations
- Cefotaxime plus clarithromycin in high severity situations
How do we prevent pneumonia?
- Childhood vaccine programme
- HiB
- Pneumococcal vaccine
- Pertussis - Over 65s
- Single dose pneumococcal vaccine
- Yearly seasonal influenza vaccination - At risk adults with chronic conditions
- such as diabetes, COPD, CF, etc
- Yearly seasonal influenza vaccination
- HiB and pneumococcal vaccines
What is consolidation?
Consolidation occurs when the normally air filled lung parenchyma becomes filled with fluid or tissue, most commonly in the setting of pneumonia
What is the pathogenesis of consolidation?
- Inflammatory changes in the region of the lung infected
- Consolidation on CXR
- Increase in polymorphonuclear leukocytes, bacteria, fibrin, and blood
What are non-infective causes of consolidation?
- Fluid - inflammatory, heart failure
- Cells - cancer
- Protein - alveolar proteinosis
- Blood - pulmonary haemorrhage
Which type of organism is the majority of community acquired pneumonia (CAP) caused by? Give examples.
Bacterial infections
- S. pneumoniae (most impt)
- Haemophilus influenzae
- Moraxella catarrali
- Atypical: legionella pneumophilia, mycoplasma pneumoniae, chlamydophila pneumoniae
Give some viral causes of CAP
- Influenza
- RSV
- Human metapneumovirus
- Adenovirus
Acute CAP is most common in which demographic? At which time of year?
Older patients and the elderly
Peak midwinter/spring
What is the classical presentation of acute CAP?
- Sudden onset chills
- Fever
- Cough
- Pleuritic chest pain
- Chest signs
- High WCC, CRP
CAP is a major cause of hospitalisation and morbidity in the elderly, what are the more & less common symptoms of this in elderly people?
- More common
- Tachypnoea
- Non-respiratory symptoms: mental state, abdo pain - Less common: absent in over 50%
- Fever
- Cough
- Dyspnoea
What is the difference between typical and atypical CAP?
Atypical = when the presentation is more subtle, there is cough and dyspnoea but usually no sputum
Causative agents of atypical CAP
- Mycoplasma pneumoniae
- Older children/young adults
- CXR findings more extensive than examination chest findings - Chlamydophila pneumoniae
- Usually mild in adults/self-limiting
- Associated with exacerbations of COPD - Legionella pneumophilia
- Treat with macrolide
Where does Legionella pneumophilia reside?
In stagnant water e.g. air conditioning
What are the syndromes caused by Legionella pneumophilia?
Legionnaire's disease (pneumonia) Pontiac fever (less severe)
What are the syndromes caused by Legionella pneumophilia?
Legionnaire's disease (pneumonia) Pontiac fever (less severe)
What is the definition of hospital acquired pneumonia? HAP
Pneumonia occurring >48 hours after admission or following discharge
If you develop HAP within the first 4-5 days, how does the causative agent change compared to later than 4 days?
Early (within first 4-5 days) = pathogens similar to those of CAP
Later than 4 days - gram negative aerobes e.g. Klebsiella spp/pseudonomas spp and anaerobes
Risk factors for HAP
- > 70y/o
- Severe underlying disease
- Surgical procedures
- Interventional procedures
What is ventilator associated pneumonia (VAP)? Which pathogens are associated with this?
Pneumonia developed after >48hrs mechanical ventilation
- There are particular pathogens associated with VAP, e.g SA, gram neg bacteria
Pathogenesis of HAP
- Inhalation/aspiration
- Direct spread e.g. via ET tube
Presentation of HAP
- New onset of chest symptoms and signs in a hospital patient
- CXR findings are variable
