Session 7 (Pneumonia and Lung Cancer Flashcards
Outline the distribution and composition of the normal flora of the upper respiratory tract
[*] Common (normally non-pathogenic)
- Viridans streptococci
- Neisseria spp
- Anaerobes
- Candida spp
[*] Less common (transient colonisers – tend to come and go, tend to pathogenic leading to invasion of the lower respiratory tract, sinuses and ear causing inflection)
- Streptococcus pneumonia
- Streptococcus pyogenes
- Haemophillus influenzae
[*] Other (usually found in patients on long term antibiotics or in hospital for a long time, can be pathogenic)
- Psuedomonas
- E. coli
Outline the natural defences of the respiratory tract against infection
[*] Cough and Sneezing Reflex
[*] Muco-ciliary clearance mechanisms
- Ciliated columnar epithelium
- Nasal hairs
[*] Respiratory mucosal immune system:
- Lymphoid follicles of the pharynx and tonsils in the submucosa
- Alveolar macrophages
- Secretary IgA and IgG
List the main infectious diseases of the upper respiratory tract and state the organisms commonly causing these infections
[*] Worldwide, lower respiratory tract infections in the elderly. Pneumonias due to Influenza and Streptococcus pneumoniae are x3 more common in the elderly (>75 years) compared to young adults.
[*] Upper Respiratory Tract Infections
- Rhinitis (common cold)
- Pharyngitis
- Epiglottis
- Laryngitis
- Tracheitis
- Sinusitis
- Otitis media (inflammation of middle/inner ear)
[*] URT infections are most commonly caused by Viruses:
- Rhinovirus
- Coronavirus
- Influenza/parainfluenza
- Respiratory Syncytial Virus (RSV)
[*] May also be caused by Bacterial Super-Infection (secondary infection often develops after viral infection)
Common with sinusitis and otitis media
Can lead to
- Mastoiditis
- Meningitis
- Brain abscess
What is the difference between Acute Bronchitis and Chronic Bronchitis?
[*] Acute bronchitis is caused predominantly by viruses and rarely by bacteria. It may lead to pneumonia due to further spread of the organisms into the lung parenchyma
[*] Chronic bronchitis is not primarily infective. Exacerbations have been associated with many organisms, but the role of infection remains controversial (non-infective cause).
What is the difference between Pneumonia and Pneumonitis? What is the pathology behind Pneumonia?
[*] Pneumonia is a general term denoting inflammation of the gas exchanging region of the lung usually due to infection; pneumonia is therefore an infection of the lung parenchyma with consolidation.
[*] Inflammation due to other causes such as physical or chemical damage, is often called ‘pneumonitis’ (non-infective inflammatory disease).
[*] The common feature of pneumonias is a cellular exudate in the alveolar spaces.
- An exudate occurs when there is an inflammatory process causing increased capillary permeability hence there will be a higher protein content in an exudate (but not in a transudate)
- This results in fluid filled air spaces and consolidation (heavy and stiff lungs)
- Gas exchange is impaired as fluid replaces air, resulting in local and systemic manifestations.
What is the difference between Lobar pneumonia and Bronchopneumonia?
- Localised to a particular lobe/s of the lungs – “lobar pneumonia”. Most often due to Streptococcus pneumoniae. Confluent consolidation involving a complete lung lobe. Usually seen in community-acquired pneumonia.
- A typical acute inflammatory response => exudation of fibrin-rich fluid with neutrophil and macrophage infiltration.
- Resolution: immune system plays a part as antibodies lead to opsonisation, phagocytosis of bacteria
- May be diffuse or more patchy “bronchopneumonia”. Infection starts in the airways and spreads to adjacent alveoli and lung tissue. Can infect multiple places in the lobes, normally gets into both lungs. Streptococcus pneumonia, Haemophilus influenza, Staphylococcus aureus, anaerobes, coliforms. More often seen in the context of pre-existing disease. Clinical context
Complication of viral infection (influenza).
Aspiration of gastric contents
Cardiac failure
COPD
Pathology: the consolidation is patchy and not confined by lobar architecture
Patchy infiltrates on X ray
Describe Aspiration pneumonia
[*] Aspiration Pneumonia: aspiration of food, drink, saliva or vomitus can lead to pneumonia.
- This is more likely in individuals whose level of consciousness is altered, due to anaesthesia, alcohol or drug abuse or having swallowing related problems due to neuromuscular problems or oesophageal disease.
- Aspiration of exogenous material (e.g. people who are drowning) or endogenous secretions (most commonly bowel flora) into the respiratory tract.
- Common in patients with neurological dysphagia (strokes), epilepsy, alcoholics, drowning
- Causative organisms include oral flora and anaerobes – organisms primarily from throat and GI tract.
- Mixed infection – Viridans streptococci and anaerobes
What is interstitial pneumonia and chronic pneumonia?
[*] Interstitial Pneumonia: inflammation of the intersticium of the lung (alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues)
[*] Chronic Pneumonia: inflammation of the lungs that persists for an extended period of time.
How may pneumonias be classified?
[*] Pneumonias may be classified by the infecting organism (bacterial, atypical, viral, fungal or protozoan) but different organisms do not lead to different, well-recognised clinical syndromes.
[*] Hence a more useful classification depends on source of infection and other aetiological factors. This classification offers a logical approach to treatment because different organisms and factors are involved in each case.
Describe community-acquired pneumonia
[*] The commonest causative organism of community acquired pneumonia is Streptococcus Pneumoniae (~30%). It is less commonly caused by Haemophilus influenzae (13%), Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus pyogenes.
- May also be caused by ‘Atypical bacteria’ (10% such as Mycoplasma pneumoniae (the commonest of the atypical organisms), Chlamydia pneumonia and Legionella pneumophila
- Atypical bacterial have different structures / characteristics to typical bacteria
- Mycoplasma has no cell wall therefore antibiotics such as amoxicillin have no effect.
- Viruses (10%) such as influenza, parainfluenza, respiratory syncytial virus (RSV), adenovirus
- Mixed infections (10%)
Describe Nosocomial pneumonia
[*] Nosocomial/Hospital Acquired pneumonia: defined as an infection of the lower respiratory tract in hospitalised patients, which was not incubating at the time of admission.
- Often occurs 2-3 days after admission. Here the infection is more often associated with impaired defences.
- A different range of organisms is usual. Important causative organisms include Gram negative enteric bacteria (10%), pseudomonas and Staphylococcus aureus including MRSA.
What could also lead to pneumonia?
M tuberculosis and Atypical Mycobacteria can also lead to pneumonia
Describe Viral Pneumonia and Influenza
- Direct damage to cells lining the airways / alveoli by the virus and immune cells.
- Fluid filled air spaces interferes with gas exchange
- Most of the time but severe pneumonia can lead to severe viral pneumonia necrosis/haemorrhage into the lung parenchyma – picture similar to adult respiratory distress syndrome. There is diffuse bilateral necrosis which leads to respiratory failure as there is no normal lung tissue to compensate (due to diffuse damage)
- Patchy or diffuse ground glass opacity on chest X-ray
Influenza is the most important viral infection in terms of highest mortality – caused by a RNA virus
- ‘Flu’ seen predominantly in the winter months
- Genetic makeup of the virus changes constantly through mutations => can also acquire large genetic elements => have lead to epidemics and pandemics (immunity from a previous strain is not protective against next seasonal strain)
- The current circulating strain of the virus is H3N1
- Severe infection/infection in pregnancy and in the immunocompromised offer antiviral drugs (oseltamivir and zanamivir)
List the aetiological clues for the common respiratory tract pathogens
[*] Streptococcus pneumoniae: elderly, co-morbidities, acute onset (become unwell within a couple of days), high fever, pleuritic chest pain
[*] H. influenza: COPD (damaged lungs)
[*] Legionella: recent travel, younger patient, smokers, illness, multi-system involvement
[*] Mycoplasma: young, prior antibiotics, extra-pulmonary involvement (haemolysis, skin and joint)
[*] Staphyloccus aureus: post-viral pneumonia, intra-venous drug user, secondary infection
[*] Chlamydia: contact with birds – parrots, budgerigars, cockatoos, pigeons, turkeys
[*] Coxiella: animal contact (sheep, cattle goats)
[*] Klebsiella: thrombocytopenia, leucopenia
[*] S. milleri: dental infections, abdominal source, aspiration
Understand the spectrum of clinical features of acute community acquired and acute hospital acquired pneumonias
[*] The presentation of pneumonia can be variable but there is almost always malaise, fever and cough productive of sputum.
- The sputum may be purulent, or rusty coloured (due to blood) or frankly blood stained.
- There is commonly pleuritic chest pain
- Patients often feel breathless (dyspnoea)
- Pneumonias may be of very rapid onset, particularly if pneumococcal or staphylococcal, with a fatal outcome in a short period of time.
[*] Symptoms of pneumonia
- Fever, chills, sweats, rigors
- Cough
- Sputum: clear/purulent/’rust-coloured’/haemoptysis
- Dyspnoea
- Pleuritic chestp ain
- Malaise
- Anorexia and vomiting
- Headache
- Myalgia
- Diarrhoea
[*] Atypical pneumonias e.g. Mycoplasma pneumonia may have a more prolonged prodromal period with symptoms lasting for several weeks
[*] Factors such as the age of the patient, whether it was community acquired or hospital-acquired, the presence of chronic lung disease, immunosuppression, ownership of a pet, may give clues to the underlying cause/organism of the pneumonia
[*] The chest x-ray will usually reveal shadowing in at least one section of the lung field
What are the Specific Chest Signs?
Bronchial breath sounds
Crackles
Wheeze
Dullness to percussion
Reduced vocal resonance (if consolidation is present)
Describe hospital acquired pneumonia
- Pneumonia occurring 48 hours after hospital admission
- Makes up ~15% of all hospital acquired infections
- Common in ITU and ventilated and post surgical patients
- Organisms: Enteric Gram negative bacteria (E coli), Pseudomonas, Anaerobes, S aureus / MRSA, mixed infections
- Usually require treatment with broad spectrum antibiotics
How would you assess the severity of pneumonia?
[*] Assessing the severity of pneumonia: the severity can be assessed using the CURB 65 score, where the presence of 2 or more of the following features is an indication for hospital treatment, and patients with high scores may require ICU treatment.
- C: New mental confusion (AMT <8)
- U: Urea > 7 mmol/L
- R: Respiratory rate > 30 per minute
- B: Blood pressure (systolic BP <90mmHg or diastolic BP <60 mmHg)
- Age > 65
Describe the non-microbiological investigations of pneumonia
- CXR (very reliable, rarely radiological signs can lag behind clinical characteristics 24-48 hours)
- O2 saturation and blood gases
- FBC, WBC, platelets
- WCC (>20 or <4) indicates severe disease
- Urea Liver Function Test and CRP - C reactive protein useful in assessing response to treatment
Explain about microbiological examinations in pneumonia
[*] Microbiology: it may be possible to identify the infecting organism by gram stain and culture of the sputum.
[*] In severely ill patients blood culture is important.
- Macroscopic (mucoid, purulent, blood stained)
- Microscopy (gram staining, acid fast and special stains)
- Culture (bacteria and viruses)
- PCR (respiratory viruses)
- Antigen detection (legionella)
- Antibody detection (serology)
Describe the common clinical signs associated with disease and understand the structural abnormalities underlying them
[*] Paraneoplastic Syndrome is the presence of a symptom or disease due to the presence of cancer in the body but not due to the local presence of cancer cells.
They are mediated by humoral factors (cytokines and hormones) secreted by tumour cells or the immune response against tumour cells.
Endocrine
- Hypercalcaemia
- Cushing’s syndrome
- Inappropriate Antidiuretic Hormone Secretion (SIADH)
Neurological
- Encephalopathy
- Peripheral neuropathy
- Eaton-Lambert syndrome
Skeletal
- Finger clubbing
Haematological
- Anaemia
- Thrombocytopenia
- Disseminated intravascular coagulation (DIC)
Other
- Nephrotic syndrome
- Anorexia or cachexia
Describe Squamous Cell Carcinoma
- Often central tumours (when bronchial epithelium undergoes metaplasia into squamous cell)
- Angulate cells
- Eosinophilic (pink) cytoplasm (due to production of keratin)
- Keratinisation
- Intercellular bridges – “prickles”
- Keratin pearls
- Immunohistochemistry (monoclonal antibodies recognize particular proteins “markers”: CK5/6 and P63+, TTF-1-)
Describe Adenocarcinoma
- Often peripheral tumours
- Columnar/cuboidal cells
- Form glands (acini)
- Papillary structures
- May line alveoli
- Some produce mucin
- Immunohistochemistry: Most TTF-1+, CK5/6-, p63-
Describe Small Cell Carcinoma
- “oat cell carcinoma”
- Very cellular tumour
- Small nuclei = approximately size of lymphocyte
- Little cytoplasm
- Nuclear moulding
- Often necrosis, lots of mitoses
- Immunnohistochemistry: CD56+, Sytaptophysin+, Chromogranin+
