Tuberculosis Flashcards
describe the basic epidemiology of tuberculosis?
- 1/3 of worlds population are infected with TB
- 9 million new and relapsed cases
- 1.4 million deaths
- incidence increased by 1% each year and peaked in 2005 and now is declining
- mainly Africa and Asia
what are the 4 main mycobacterial species which are collectively known as mycobacterium tuberculosis complex?
Mycobacterium tuberculosis
Mycobacterium bovis
Mycobacterium africanum
Mycobacterium microti
describe the characteristics of mycobacterial species?
obligate aerobes and faculative intracellular pathogens, usually infecting mononuclear phagocytes.
slow growing generation time of 12-18 hours
high lipid content in the cell wall so relatively impearmeable
acid fast bacilli
describe the basic pathogenesis of tuberculosis?
-airborne
-respiratory droplets
-only small number of bacteria need to be inhaled to develop infection but not all those who are infected develop active disease
the outcome of exposure is dictated by a number of factors including the hosts immune response
describe primary tuberculosis infection?
- infection with MTb
- alveolar macrophages ingest bacteria
- bacilli proliferate in macrophage
- release of neutrophils, chemoattractants and cytokines
- leads to inflammatory cell infiltrate reaching lung and draining hilar lymph nodes
- macrophages present antigen to T cells
- development of celular immune response
- delayed hypersensitivity type reaction leading to tissue necrosis and formulation of a granuloma
what is a granulomatous lesion?
central area of necrotic material (caseation) surrounded by epitheliood cells and langhans’ giant cells
caseated areas heal and may become calcified some contain bacteria that can lay dormant for year
what is a ghon focus?
the inital focus of disease
on x-ray is a small calcified nodule in upper parts of lower lobes or lower parts of upper lobes
what is a primary complex of ranke?
a ghon focus that may develop in a regional draining lymph node
what percentage of people develop active disease upon initial contact with infection?
<5%
what is latent TB?
For most people infected with mycobacterium, the immune system contains the infection and the patient develops cell mediated immune memory to the bacteria called latent TB
what are the features of latent infection?
bacilli present in ghon focus sputum smear and culture negative tuberculin skin test usually positive chest x-ray normal (small calcified ghon focus frequently visible) asymptomatic not infectious to others
what are the features of active disease?
-bacilli present in tissues or secretions
-sputum commonly smear and culture positive in pulmonary disease
MTb can usually be cultured from infected tissue
tuberculin skin test usually positive (and can ulcerate)
chest X-ray signs of consolidation /cavitation/effusion in pulmonary disease
symptomatic (night sweats, fevers, weight loss, cough)
infectious to others if bacilli detectable on sputum
what factors are implicated in the reactivation of latent TB?
HIV co-infection immunosuppresant therapy diabetes mellitus end stage chronic kidney disease malnutrition ageing
what are the clinical features of pulmonary TB?
Symptomatic with a productive cough and occasionally haemoptysis along with systemic symptoms of weight loss, fevers and sweats (commonly at the end of the day and at night). When there is laryngeal involvement, hoarse voice and a severe cough are found. If disease involves pleura the pleuritic pain may be the presenting complaint
how is a diagnosis of pulmonary TB made?
Chest X-ray-consolidation with or without cavitation, pleural effusion or thickening or widening of the mediastinum caused by hilar or paratracheal adenopathy
what are the clinical features of lymph node TB?
extrathoracic nodes are more commonly involved and usually presents as a firm non tender enlargement of a cervical or supraclavicular node. Node becomes necrotic centrally and can liquefy and be fluctuant if peripheral. Overlying skin is frequently indurated or there can be sinus tract formation with purulent discharge but characteristically there is no erythema. Nodes can be enlarged for several months before diagnosis. On CT, the central area appears necrotic
what would be appropriate diagnostic investigations for a patient with pulmonary, pleural or laryngeal TB?
smear and culture of
- sputum
- bronchoalveolar lavage if unproductive cough
- aspiration of pleural fluid and pleural biopsy
- nasoendoscopic or bronchoscopic examinations/biopsy
what would be the appropriate diagnostic investigations and findings in a patient with miliary TB?
- blood cultures
- bronchoalveolar lavage (smear negative but culture positive)
- lumbar puncture-assess CNS involvement
what would be the appropriate diagnostic investigations and findings in a patient with CNS TB?
- lumbar puncture (CSF protein high, CSF glucose <1/2 blood glucose
- CSF lymphocytosis
what would be the appropriate diagnostic investigations and findings in a patient with lymph node TB?
- all samples sent for histocytopathological examination
- culture and smear (fine needle aspiration or biopsy of involved lymph / mediastinal nodal sampling)
what microbiological methods are used to make a diagnosis of TB?
- stains
- culture
- nucleic acid amplification
describe the use of stains in making a diagnosis of TB?
auramine-rhodamine staining is more sensitive (but less specific) than ziehl-neelsen so is more widely used)
bacilli are highlighted as yellow/orange on a green background
describe the use of culture in making a diagnosis of TB?
liquid culture
allows detection of drug sensitivity to infection
describe the use of nucleic acid amplification in making a diagnosis of TB?
used to differentiate between mycobacterium and non-mycobacteria
what is directly observed therapy?
widely recommended and employed with an aim to achieve treatment completion
it is treatment supervised by a healthcare professional where the patient is observed swallowing the medication
what is the criteria for the implementation of directly observed therapy?
- patients thought unlikely to comply such as patients with serious mental health problems or with a history of TB non-adherence
- street or shelter dwelling homelessness
- multi-drug resistant TB
what is the usual duration of treatment for pulmonary, extrapulmonary or miliary TB?
6 months
can be extended to 9 months in certain situations
-patient smear positive 2 months into treatment
-HIV co-infection
-high burden of disease
what is the drug choice for TB treatment?
2 months of rifampicin, ethambutol, isoniazid, pyrazinamide plus 4 months of isoniazid and rifampicin
what are the basic steps in treatment once a patient has been diagnosed with TB?
- allocate case manager
- health and social care plan
- drug treatment
- address housing needs
- strategies to encourage adherence
- directly observed therapy needed?
- surgery needed?
- follow up
what drugs are used for treatment of active TB of CNS?
- isoniazid (+pyridoxine), rifampicin, pyrazinamide, ethambutol for 2 months
- isoniazid (+pyridoxine) and rifampicin for 10 months
describe drug resistance in TB treatment?
- due to incomplete or incorrect drug treatment and can be spread from person to person
- multi drug resistance (rifampicin and izoniazind) is low
- mono resistance is fairly common-10% in UK
what is the treatment for isoniazid resistant TB?
2 months- rifampicin, pyrazinamide and ethambutol
7 months - rifampicin and ethambutol
what is the treatment for pyrazinamide resistant TB?
2 months-rifampicin, isoniazid (with pyridoxine) and ethambutol and ethambutol
7 months-rifampicin, isoniazid (with pyridoxine)
what is the treatment for ethambutol resistant TB?
2 months-rifampicin, isoniazid (with peridoxine) and pyrazinamide
4 months-rifampicin and isoniazid (with pyridoxine)
what is the treatment for rifampicin resistant TB
same as treatment for multidrug resistant TB
what methods can be taken to control spread of TB?
- contact tracing
- screen healthcare workers
- screen new entrants to the country, homeless, hostel dwellers, immunocompromised people, BCG vaccination
what is a classic presentation of pneumonia?
shaking chills purulent sputum bacteremia acute cough breathlessness fever
describe pulmonary infarction?
occurs when artery to lung becomes blocked and part of the lung dies
most often caused by pulmonary embolism
what are the clinical features of pulmonary infarction?
Angiographic demonstration of pulmonary thromboemboli
Concurrent condition frequently predisposing to pulmonary thromboembolism. Bloody, non purulent sputum, sanguineous pleural effusion, migratory parenchymal infiltrates and unresponsive to chemotherapy.
Do not dismiss infarction simply due to high fever, leucocytosis, normal JVP, atypical pulmonary lesions, non bloody pleural effusion, failure to detect the source of emboli, or because patient is young or appears healthy
describe pnuemonia?
- inflammation of lung
- usually bacterial cause
- 50% is pneumococcal
- classified by setting is which person contracted their infection
what is the commonest cause of community acquired pneumonia?
pneumococcus (streptococcus pneumonia)
what part of the lungs does community acquired pneumonia affect?
localised with one or more lobes affected (Lobar pneumonia) or diffuse where lobules of lung are mainly affected often due to pneumonia centred on bronchi and bronchioles
how is pneumonia infection spread?
respiratory droplets
what are the clinical features of community acquired pneumonia?
- cough (dry or productive and hemoptysis, rust coloured sputum),
- breathlessness (alveoli filled with pus and impair gas exchange, course crackles , bronchial breath sounds)
- fever
- chest pain (pleuritic, may hear plural rub)
- extrapulmonary features
- other features (confusion or nonspecific symptoms)
what investigations are needed in community acquired pneumonia?
- microbiological tests not needed in mild infection
- CXR if mild disease doesn’t improve in 48-72 hours
- CURB-65
- if admitted to hospital - CXR, bloods, microbiological tests and repeat CXR 6 weeks after discharge
how is mild pneumonia treated?
oral amoxicillin 500mg 3x day OR oral clarithromycin 500mg 2x daily OR doxycycline 100mg daily
what are the radiological findings of strep. pneumonia?
consolidation with air bronchograms, effusion and collapse due to retention of secretions
radiological abnormalities lag behind clinical signs
what are the radiological findings of mycoplasma pneumonia?
usually one lobe affected but infection can be bilateral and extensive
what are the radiological findings of legionella pneumonia?
lobar and multi lobar shadowing, with occasional small pleural effusion
cavitation is rare
what makes up the CURB65 score?
Confusion
Urea level >7mmol/L
respiratory rate >30
BP S<90, D<60
what implication does CURB 65 score have on management?
0-1 = outpatient treatment 2 = admit to hospital 3+ = ICU care
what blood tests are performed in patients with pneumonia?
FBC
urea and electrolytes
biochemistry
CRP
what blood results would be expected in a patient with strep pneumonia?
WCC >15=10^9
inflammatory markers raised
what would WCC be in a patient with mycoplasma pneumonia?
normal WCC
what blood result would you expect in a patient with legionella pneumonia?
lymphopenia without marked leucocytosis
hyponatraemia
hypoalbuminaemia
high serum levels or liver aminotransferases
what investigations should be performed if a patient has a CURB65 score of 2?
- blood cultures
- sputum
- pneumococcal antigen
- serology or PCR if epidemic
what treatment is given to a patient if they have a CURB65 score of 2?
amoxycillin 500-1000mg 3x daily + clarithromycin 500mg 2x daily
if penicillin allergy:
doxycycline 100mg daily with 200mg loading dose
or levofloxacin 500mg 2x daily
or moxifloxacin 400mg daily orally
what investigations are performed in a patient with CURB65 of 3-5?
blood culture sputum pneumococcal antigen legionella antigen serology and viral PCR
what treatment is given to a patient with a CURB65 score of 3-5?
-antibiotics ASAP
-co-amoxiclav 1.2g 3x daily IV + clarithromycin 500mg 2x daily IV (fluoroguinolone if suspect legionella suspected)
OR
penicillin allergy
-IV cephalosporin +clarithromycin
-benzylpenicilin 4x daily or 4 hourly + fluoroquinolone
what are some of the complications of pneumonia?
respiratory failure sepsis pleural effusion emphyema lung abscess organising pneumonia
what is hospital acquired pneumonia?
new onset of cough with purulent sputum with compatible X-ray demonstrating consolidation in patients who have been more than 2 days in hospital or been in healthcare setting within last 3 months
what organisms are commonly implicated in hospital acquired pneumonia?
gram negative bacilli P.aeruginosa E.coli klebsiella pneumoniae acinetobacter MRSA
What bacteria are usually implicated in pneumonia acquired in nursing homes?
gram negative rods
pneumococcus
pseudomonas
what are the clinical features of streptococcus pneumoniae?
acute onet preceded by flu like symptoms cough with rust coloured sputum high fevers pleuritic chest pain bacteraemia more common in women, excess alcohol, dry cough and COPD, diabetes or HIV infection
what are the clinical features of mycoplasma pneumoniae?
usually mild disease in young patient
occurs in cycles every 3-4 years
prominent extrapulmonary symptoms
common complications
what are the clinical features of legionella spp. pneumonia?
causes more severe disease with intensive care needed
acquired by inhaling water mist containing bacteria
neurological symptoms with GI involvement
more common in smokers, men and young people
what are the clinical features of pneumonia caused by staphylococcus aureus?
recent influenza in 40-50%
MSSA which can result in necrotising cavitating pneumonia and bilateral infiltrates
what are the clinical features of chlamydophila pneumoniae?
unclear whether causative or associated organism
causes mild disease but with prolonged prodrome
what are the clinical features of haemophilus influenza pneumonia?
more common in pre-existing structural lung disease (CF, bronchiectasis, COPD) and elderly
what is involved in the management of pneumonia?
oxygen between 94-98% IV fluids antibiotics thromboprophylaxis physiotherapy nutritional supplementation analgesia
