Respiratory TB and Pneumonia: 53-109 Flashcards
What is the microbiology of mycobacterium tuberculosis?
Non-motile rod shaped bacteria
Obligate aerobe
Long chain fatty acids, complex waxes and glycolipids in cell wall
Slow growth compared to others
Where are the regions affected by extra-pulmonary TB?
- Lymphadenitis (Scrofula, Cervical lymph nodes most commonly, Abscesses and sinuses)
- Gastrointestinal (Swallowing of tubercles)
- Peritoneal (Ascitis or adhesive)
- Genitourinary (Slow progression to renal disease, Subsequent spreading to lower urinary tract)
- Bone and joint (Haemotgenous spread, Spinal TB is most common, Potts disease)
- Tuberculous meningitis (Chronic headache, fevers, CSF – markedly raised proteins, lymphocytosis)
What is military TB?
Bacilli is spread through the blood stream
- Headaches suggest meningeal involvement
- Pericardial, pleural effusions small
- Ascites may be present
- Retinal involvement (choroid tubercles seen)
What is the transmission of TB?
- Spread by respiratory droplets –coughing, sneezing
- Droplet nuclei
- Suspended in air
- Reach lower airway
How easy is it to catch TB?
Contagious but not easy to acquire infection. Prolonged exposure to active TB individuals facilitates transmission
What is the pathogenesis of TB?
- Engulfed by alveolar macrophages
- Unique structure allows the TB bacteria to evade destruction by macrophages. Can survive and multiply within the macrophage
- TB bacilli from the macrophage can get carried to the lymph nodes during drainage
- Formation Primary complex (Ghon’s focus + draining lymph nodes)
- Minority (5%) – Can proceed to active disease after the primary complex. Primary TB develops
- Majority of patient – latent infection (95%). Containment of the infection to prevent the bacilli from multiplying. Live organism in the site of infection and lymph node
- Small number of latent infection patient can develop post primary. 2 years after the initial infection.
What is the effect of post primary TB?
Reactivation and hypersensitivity can occur. Massive destruction of the lung due to increased inflammatory response and bacterial damage. This can also occur with reexposure to the bacteria
What determine the formation of the primary complex?
- The infectious dose
- Strain of TB
- Immune response to the TB bacilli which depends on T cells to decide fate of primary complex (HIV)
Compare Latent Tb and Active TB.
Latent TB
- Inactive, contained tubercle bacilli in the body
- TST or IFN gamma test results usually positive.differentiate
- Chest X-ray usually normal
- Sputum smears and cultures negative
- No symptoms
- Not infectious
- Not a case of TB
Active TB
- Active, multiplying tubercle bacilli in the body
- TST or blood test results usually positive
- Chest X-ray usually abnormal
- Sputum smears and cultures may be positive
- Symptoms such as cough, fever, weight loss
- Often infectious before treatment
- A case of TB
Why doesn’t the TST or IFN test differentiate between latent and active TB?
Both Latent and Active have Primary Complex so doesn’t differentiate between the two.
What are the histological features of Tuberculosis?
-Caseating granuloma is lung parenchyma and/or mediastinal lymph nodes
Where are the features of TB on an X-ray?
- Apex of the lung often involved
- Ill-defined paths consolidation
- Cavitatons usually develop with consolidation
- Healing results in fibrosis
How is a TB diagnosis established through investigations?
- Culture is the Gold standard technique
- NAAT
- Chromatography
How are antibiotics tested for effect on a micro-organism?
Drug sensitivity test
What are symptoms of TB?
- Night sweats
- Tiredness and malaise
- Weight loss and anorexia
- Fever
- Cough
- Haemoptysis occasionally
- Breathlessness if pleural effusion
What are the signs seen on examination for TB?
- Often no chest signs despite CXR abnormality
- Maybe crackles in affected area
In extensive disease
- Sings of cavitation
- Fibrosis
-Pleural involvement: typical signs of effusion
What is important about the history of a TB patient?
- Ethnicity
- Recent arrival or travel to high TB burden countries
- Contacts with TB
- BCG vaccination
- Specific clinical features
- Fever
- Weight loss
- Malaise
- Anorexia
What are the risk factors of TB?
- Non-UK born/recent migrants (South Asia, Sub-Saharan Africa)
- HIV – latent infections can reactivate due to the immune system being affected
- People sustpected of TB are tested for HIV
- Other immunocompromised states
- Homeless
- Drug users, prison
- Close contacts
- Young adults
How are People suspected of TB managed?
- Early and adequate treatment
- Close monitoring of compliance to treatment (Direct observed therapy, Video observed therapy)
- Treatment for a long duration due to long duration of TB to multiply
What is the First line medication to treat TB?
- Rifampicin (orange pee)
- Isoniazid
- Pyrazinamide
- Ethambutol
2nd line
Quinolones
What is the BCG vaccination?
- Live attenuated M bovis strain
- Given to babies in high prevalence communities only (0-80% effectiveness)
- Protection wanes
- Little evidence in adults to work
Why is multi drug therapy used?
- The drugs are given for a long time so likely for mutations to occur and resistant strains to develop. Less chance of survival against all drugs of resistant strains which can cause a lot of damage
- Resistance can develop due to inadequate treatment or spontaneous mutation
How is TB transmission prevented?
Notification
- Triggers contact tracing to detect and treat cases and contacts to prevent transmission
- Provides surveillance data to detect outbreak and monitor epidemiological transmission
How is TB controlled in the population?
- Treatment of index case
- Reduces susceptible contacts by vaccinating or addressing risk factors
What are the risk factors for reactivation of latent TB?
- Infection with HIV
- Substance abuse
- Prolonged therapy with corticosteroids
- Other immunosuppressive therapy
- Organ transplant
- Haematological malignancy
- Severe kidney disease/haemodialysis
- Diabetes mellitus
- Silicosis
- Tumour necrosis factor alpha antagonists
What is pneumonia?
Pneumonia is a general term denoting inflammation of the lung parenchyma due to infection.
What is lobar pneumonia?
Pneumonia localised to a particular lobe
What is bronchpneumonia?
Diffuse and patchy pneumonia
What are the common microbes that cause community acquired pneumonia?
- Streptococus pneumoniae
- Haemophilus influenzae
What are atypical organisms causing community acquired pneumonia?
- Legionella - contaminated water
- Mycoplasma
- Coxiella burnetti
- Chlamydia psittaci – exposure to birds
What are the organisms causing hospital acquired pneumonia?
- Haemophilus influenza
- Staphylococcus aureus
- Pseudomonas spp
- Acinetobacter baumanii
What is the pathophysiology of viral pneumonia
- Damage to cells lining the airways/alveoli by the virus and immune cells
- Gas exchanged is hindered by fluid
- Can be mild or severe
- Sevre viral pneumonia can lead to necrosis and haemorrhage
What is the appliance o viral pneumonia on a chest X-ray?
-Patchy and diffuse ground glass opacity on the X-ray
What are the symptoms of pneumonia?
- Malaise, Nausea and vomiting
- Fever
- Cough productive of sputum (purulent or rust coloured)
- Pleuritic chest pain
- Patients often feel breathless
- Rigors
What are the features of pneumonia on clinical examination?
- Tachycardia
- Tachypnoea
- Cyanosis
- Dullness to percussion, tactile vocal fremitus
- Bronchial breathing – Crackles
What are the investigations undertaken for patient suspected of pneumonia?
- Full blood count
- Urea and electrolytes
- C-reactive protein
- Arterial blood Gases
- Chest X-ray
Microbiological
-Sputum / Induced sputum
-Blood culture
-Broncho Alveolar Lavage fluid (BAL)
Nose and Throat swabs or NPAs (viruses)
-Urine (antigen test for legionella / pneumococcus)
-Serum (antibody test) acute and convalescent sera (usually collected at presentation and 10-14 days later)
What is used to assess severity of asthma?
CURB-65
C – New mental confusion
U – Urea > 7 mmol/L
R – Respiratory rate > 30 per minute
B – blood pressure (systolic BP < 90 or DBP <60 mmHg)
Age > 65 years
What are the aetiological features of pneumonia?
- Poor swallow (CVA, muscle weakness, alcohol)
- Abnormal ciliary function (smoking, viral infection)
- Abnormal mucus (cystic fibrosis)
- Dilated airways: bronchiectasis
- Defects in host immunity (HIV, Immunosuppression)
What are general measures for management of pneumonia?
- Maintain a good oral fluid intake to avoid dehydration.
- Anti-pyretic drugs- fever and malaise, together with stronger analgesics for pleural pain
- More severe illness may require intravenous fluids and oxygen.
What are the treatment measures for community acquired pneumonia?
- Target organism is Pneumococcus
- Amoxicillin or Doxycycline for Mild/Moderate pneumonia
- Co-amoxiclav and Doxycycline for Moderate/Severe
What is the treatment for hospital acquired pneumonia?
Hospital acquired pneumonia is more likely to be due to gram negative organisms
use antibiotics which would cover these organisms .
First line: IV Co-Amoxiclav
Second line: Meropenem
What drugs are used to treat atypical organism?
Erythromycin/clarithromycin) or tetracycline (doxycycline)
Why are people with TB checked for HIV?
Dysfunction in the immune system can result in the latent infection activating
What are preventative methods of pneumonia?
- Flu vaccine (annually given)
- Pneumococcal vaccine (5 yrs)
- Chemoprophylaxis – oral penicillin/erythromycin to patients with higher risk of LRT infections
- Smoking advice
What are some complications of pneumonia?
- Pleural effusion
- Empyema
- Lung abscess formation
What are the links between immunosuppression and lower trespiratory tract infection?
- HIV: PCP, TB, atypical mycobacteria
- Neutropenia: fungi e.g. Aspergillus spp
- Bone marrow transplant: CMV
- Splenectomy: encapsulated organisms –e.g. S. pneumoniae, H. influenzae, malaria
What are common respiratory flora?
- Viridans streptoccic
- Neisseria spp
- Anerobes
- Candida sp
Less common
- Streptococcus pneumoniae
- Streptococcus pyogens
- Haemophilus influenzae
- Psedomonas
- E.coli
What are muco-ciliary mechanisms for clearance of respiratory mucosa?
- Nasal hairs, ciliated columnar epithelium of the respiratory tract
- Cough and the sneezing reflex
- Respiratory mucosal immune system. Lymphoid follicles of the pharynx and tonsils, alveolar macrophages, secretary IgA and IgG
What are common upper respiratory infections?
- Rhinitis (common cold)
- Pharyngitis
- Epiglottis
- Laryngitis
- Tracheitis
- Sinusitis
- Otitis media
What are common viruses that infect the upper respiratory tract?
- Rhinovirus
- Coronavirus
- Influenza
- Parainfluenza Respiratory syncytial virus (RSV)
- Bacterial super-infection common with sinusitis and otitis media –can lead to mastoiditis, meningitis, brain abscess
How does aspiration pneumonia occur and how is it treated?
-Aspiration of exogenous material or endogenous secretions into respiratory tract
-Common in patients with neurological dysphasgia (epilepsy, alcoholics, drowning, strokes)
-Risk groups (nursing home residents, drug overdose)
-Mixed infection (viridans streptococci, anaerobes
Treat with Co-amoxiclav)
