Respiratory infections Flashcards
Where is TB most common?
india, indonesia, pakistan, china, philippines
What organisms cause TB?
mycobacterium tuberculosis is most common, M. Bovis is also seen in cattle and some human, M. africanum is also seen in Africa.
What typeof bacteria is mycobacterium tuberculosis?
non motile rod shaped obliguate aerobe
What is M. tuberculosis cell wall made of and what implications does this have?
Long chain fatty acids
- staining characteristics (no gram stain)
- structural integrity
- withstand harsh envrionments
How quickly does M. tuberculosis divide?
every 15-20 hrs
How is TB spread?
Respiratory droplets released when coughing, sneezing and speaking. The infectious dose is only 1-10 bacteria but you need prolonged close contact exposure- at least 8 hrs a day for 6 months.
Describe the pathogenesis of TB
- inhaled infectious droplets
- engulfed by alveolar macrophages
- taken to local lymph nodes
- forms a primary complex
- 5% progress to active primary disease (if very virulent or immunocompromised)
- most go on to develop latent infection which heals/ self cures (95%) or is reactivated when the pt later becomes immunocompromised to cause post- primary active TB (5%)
What cell is responsible for handling primary TB infections?
T cells- as it is cell mediated immunity
Whats the difference between having a TB infection and having TB disease?
TB disease is when you get symptoms
How can you differentiate between TB infection and TB disease? (3)
If TB disease:
- symptomatic
- abnormal CXR
- sputum samples and cultures may be positive
Post primary TB disease may be due to exogenous reinfection or reactivation of latent TB. What may reactivate the TB?
- HIV
- substance abuse
- steroid treatment/ immunosurpression
- organ transplant
- haematological malignancy
- kidney disease
- diabetes
What are the most common extra pulmonary sites for TB disease to manifest? when do these most commonly occur?
- larynx
- lymph nodes
- pleura
- brain
- kidneys
- bones and joints
HIV or immunosurpressed pts
What is millary TB?
TB spreads through blood and is taken to all parts of the body. It is very rare.
What is a gohn focus?
the site of primary infection of TB
What are the risk factors for TB?
HIV, non UK born, immunocompromised, homeless, drug users, prisoners, close contacts, young adults and elderly
What signs and symptoms of TB are created by chronic T cell stimulation?
- fever (via TNFa, Il-6 and Il-1)
- night sweats
- weight loss and anorexia
- tiredness and malaise
What signs and symptoms does the active TB directly cause?
- cough
- sometimes haemoptysis
- breathlessness if pleural effusion
- consolidation
- cavitation and fibrosis
How should TB be investigated? Describe what should/ may be found?
- CXR- find patchy consolidation +/- cavitation, usually upper lobes/ apices
- Biposy- not often done but caseous necorsis indicates TB
- Sputum samples
- Tuberculin skin testing (mantoux test)- will be positive if they have every had/ have TB infection
- Interferon gamma releasing assays- detects INF-y specific to TB, so will be positive if theyve ever had/ ahve TB
How can sputum samples be used to diagnose TB?
- need 3 samples, with one positive
- smears are stained with zeihl neelson stain or auramine (fluorescent)
- need culturing so can take upto 3 weeks
- NAAT can also be used for quicker diagnosis and check for drug resistance mutations
How is TB treated?
RIPE: - Rifampicin (6 months) - Isoniazid (6 months) - Pyrazinamide (2 months) - Ethambutol (2 months) sometimes also streptomycin Surgery can sometimes be done if just one lobe affected
What are the 2 main side effects of TB drugs?
rifampicin turns wee orange
theyre all hepato and probably nephrotoxic
Why are so many drugs needed to treat TB?
- stop resistance forming
- long term because it multiplies so slowly
What are the diadvantages of the mantoux test?
- prone to false positives if BCG vaccinated
- also false negatives if HIV or immunosurpressed
- also cannot differentiate between latent and active disease
How effective is the BCG vaccine?
70% effective in children, less effective in adults
What is meant by TB being a notifiable disease?
When you diagnose a case you need to let public health england know so they can do contact tracing and monitor outbreaks
What organisms make up the normal flora of the upper respiratory tract?
- viridans streptococci
- neisseria species
- candida species
- sometimes S. pneumonia, strep pyogenes, H. influenza
What organisms make up the normal flora of the lower respiratory tract?
none- there should be no bacteria there
State 4 innate defences of the respiratory tract?
- Alveolar macrophages
- muco- cilary clearance
- cough and sneeze reflex
- MALT tissues of pharynx and tonsils
Whats the most common cause of upper respiratory tract infections?
- viruses- rhinovirus, coroavirus, influenze virus
- most are self limiting
What is acute bronchitis and what causes it?
Infection of the medium sized airways, almost only seen in smokers, usually caused by viruses or S. pneumonia or H. infleunza
How will acute bronchitis present?
Cough, fever, increased sputum production, SOB, smoking history
- CXR usually normal as no parenchyma involvement
How is acute bronchitis treated?
Supportively- rest, paracetamol, fluids, bronchodilation, sometimes physio to remove secretions
Rarely antibiotics
Is chronic bronchitis caused by infection?
No, but exacerbations may have infective causes
What is pneumonia?
Inflammation of the lung alveoli
How does pneumonia present?
- systemically unwell
- fevers +/- rigors
- cough +/- sputum
- pleuritic chest pain (sharp, localised, worse on moving)
- SOB
- consolidation in lungs - on CXR, crackles and dullness to precuss
- malaise/ nausia/ vomiting
- high resp and heart rate
- cyanosis
How is pneumonia investigated?
- CXR (diagnotic)
- FBC, U&E, LFT, ABG
- Sputum sample
- blood culture
- nose and throat swab for viruses
- urine (test for leigonella and pneumococcus)
- serum antibodies
What scoring system is used to asses severity of pneumonia to decide whether to admit to hospital or nor?
CURB 65- score of >2 should be admitted
Confusion// Uraemia// Respiratory rate > 30// Blood pressure low// age >65
What’s the difference between lobar and bronchiopneumonia?
lobar affects all of a lobe
Broncho affects patches in >1 lobe
What are the 1st and 2nd commonest causes of community aquired pneumonia?
1st- streptococcus pneumoniae
2nd- haemophilus influenza
Also staph A, Morazella catarrhalis and klebsiella pneumonia
List 3 atypical causes of community acquired pneumonia?
- Legionella
- Mycoplasma
- chalmydia psittaci
Atypical pneumonia will tend to have extra pulmonary features (hepatitis, low [Na+] ect)
How is community acquired pneumonia treated?
If mild to moderate: amoxicillin or doxycycline if allergic
If severe: use co- amoxiclav and doxycycline
- also o2, Iv fluids, pain releif ect
If pneumonia doesn’t resolve w/ antibiotics, what complications could arise? (3)
Lung abcesses
Bronchiectasis
Empyema
How is atypical community acquired pneumonia treated?
Macrolides, tetracyclines (eg doxycycline) as atypical bacteria dont generally have cell wall so need to target protein synthesis
What may cause viral pneumonia?
Infleunza virus, parainfluenza virus, RSV, adenovirus
What are the 4 most common causative organisms in hospital acquired pneumonia?
- Staph A
- Enterobacteriaciae
- pseudomonas species
- h. influenza
- fungi
How is hospital acquired pneumonia treated?
co- amoxiclav, if this doesnt work ITU + pipperacillin/ tazobactam/ meropenem
What is aspiration pneumonia? When does it most commonly occur?
When you aspirate exogenous or endogenous material into the lower resp tract and this introduces bacteria. Most common in stroke pts, drug ODs, alcoholics, epileptics and drowning.
How is aspiration pneumonia treated?
Co- amoxiclav- need broad range as it generally introduces a few bacteria
What chest infections are more likely w/ HIV?
Aspergillius, TB, PCP
What virus is more common in those who’ve just had bone marrow transplants?
Cytomegalo virus
What type of bacterial infections are more common in someone who’s had a splenectomy?
encasulated bacteria- (S. pneumonia, H. influenza)
How are lower resp tract infections prevented in at risk groups?
flu and pneumococcal vaccine
chemoprophylaxis
smoking advice (stop)
Why does TB treatment have poor complicance and how is this reduced?
It is a long course (6 months) and lots of drugs, and they feel better in first couple of weeks.
Directly observed treatments (someone watches you swallow them) can be done if needed.
