Lecture 11 - treatment of resp infections Flashcards
Which groups of people are at a higher risk of CAP?
the elderly, males, alcoholics, and those with chronic disease
Percentage of CAP caused by conventional bacteria? atypical? virus?
conventional 60-80
atypical 10-20
viruses 10-20
What are the two main causes of CAP
S. pneumoniae
H. influenzae
(other ones are pneumonia M C L )
Name the 4 steps in the investigation of CAP
confirm the diagnosis, assess the severity of the disease, define the aetiological agent (important when treating) and identify for complications
What is antimicrobial management of CAP based on
assessment of likely pathogen
severity of the illness
likelihood of resistance
What microbiological investigations can be taken for CAP
sputum analysis and culture
immunoflorescence on sputum samples
blood cultures
urinary pneumococcal legionella antigen
What is the criteria for CAP?
Confusion
Urea >7mmol/l
Resp rate over 30
Blood pressure
Describe mycoplasma CAP
patchy consolidation on CXR, prominent extra pulmonary disease. more likely in young patients. has prolonged gradual onset
What is characteristic of S aureus CAP?
abscess formation on CXR, very aggressive disease increased tissue lysis
What is characteristic of legionellosis CAP
hyponatraemia, multi lobe involvement, confusion and neurological symptoms
Which two groups in the UK are more likely to have TB
socially disadvantaged and ethnic minority
Describe the two phases of TB
Latent phase - where granulomatous forms - controlled by cell mediated response and lays dormant.
Active phase - where disease is reactivated and extracellular growth occurs. bacteria disseminate from granulomatous
Which factor keeps TB in latent phase and how
DosR maintains the organism in hypoxic environment inside the granulomatous - ensuring organism homeostasis
Name three typical TB CXR appearences
Reactivated TB usually appears in the upper lobes of chest X rays
Reactivated TB in immunocompromised spreads throughout lung
Millary TB is disseminated
Which TB drugs are bactericidal
Rifampicin, Isoniazid, Ethambutol (moderate), Streptomycin
Side effects of Rifampicin
rash, hepatitis, fever, flu syndrome, drug interactions e.g. pill
Side effects of Isoniazid
hepatitis, peripheral neuropathy, cutaneous hypersensitivity
Side effects of Pyranzinamide
hepatitis, anorexia, flushing, cutaneous hypersensitivity, hyperuricaemia
Side effects of Ethambutol
optic neuritis which can cause blindness - never give to someone who cannot report visual changes e.g. a child
Side effects of Streptomycin
ototoxicity (blood levels should be monitored in renal impairment)
How do TB drugs work
Rifampicin inhibits RNA polymerase
Ethambutol inhibits synthesis of cell wall polysacherides
Streptomycin binds to mycobacterial ribosome and inhibits protein synthesis
What are the principles of chemotherapy for TB
- mycobacteria within an infected individual are in two phases of replication
- the population contains natural occurring resistance
Why is TB treated with two phase therapy and combination therapy
2 phase - as bactericidal phase to kill majority of active organisms and sterilising phase which persisting organisms (latent) are eliminated
combination - resistance is frequent- more drugs means less likely to be resistant to all of them (single drug therapy always selects resistant organisms)
Why is 6 months required for eradication of TB?
persisting organisms undergo intermittent metabolic activity
What is DOT in TB testing?
nurse of surrogate directly observes all doses taken - increases compliance. UK dont do much but do in US
Which TB drug has the highest resistance rates?
isoniazid
Which patients are more likely to have acquired a MDR TB? (5)
- if the individual has previously been treated for TB
- contact with known MDR TB case
- got infection in country with high prevalence of MDR TB
- patients dont respond to treatment
- co-existing HIV
How is MDR TB managed?
- initial treatment should be with at least 4 TB drugs the organism is sensitive to and should last 3-6 months PAST the sputum becomes culture negative
- the second phase should be continued with 3 drugs for 15-18 months
What else must be done if a patient is found to have MDR TB?
notifying TRACE
infection control measures
BCD
