L17 Pneumonia and lower respiratory tract infections Flashcards
What are the features that differentiate pneumonia and vs influenza (bronchitis) and what are common features
Self- limiting upper airway viral infections give a milder symptom profile of influenza/ pneumonia
Both influenza and pneumonia cause fever, muscle ache and pain, malaise and lack of appetite
In pneumonia there is poor gas exchange due to inflammation/pus in the alveolus so Dyspnoea/SOB/ on exertion,
as well as coughing which can be dry due to cytokine parenchymal irritation rather than pus in some cases
What are common symptoms of pneumonia in elderly (and v young children) and what are investigations that are done to check for pneumonia
- History
- Examination of
- increased Respiratory rate (more in children)
- look for increased work of breathing
- Fevers/chills in elderly only 50%
- percuss the lung for consolidation
- listen for bronchial breath sounds: crackles (common in pneumonia)
3. Chest Xray to determine if consolidation - costodiaphragmatic recess is unclear. If normal then antibiotics are not required
What are the 5 risk factors for developing pneumonia
- very common serious infection seen in GP
- Age <2, or >65
- Chronic lung disease such as bronchial emphysema
- Smoking - links to chronic disease and direct
- Immune dysfunction - eg. late stage HIV infection
- Infection more common in winter - due to interplay with respiratory viruses
What is the main cause of pneumonia - bacterial or viral.
Bacterial
1. 60-75%: Streptococcus pneumoniae bacteria: alpha haemolytic
- 5-10% is Haemophilius influenza bacteria and Viruses: influenza, HMV, Sars COV2
What are the main factors that make Streptococcus pneumoniae virulent
- Polysaccharide capsule + pneumococcal surface protein A preventing C3b opsonisation therefore stops immune system recognition and phagocytosis
- deposition stopped with C3b
This is the main mechanism as non capsuled strep are unable to cause disease
- Pneumolysin lyses neutrophils and epithelial cells
What are the 5 possible investigations done after pneumonia has been confirmed on CXR - which are helpful
- mostly when admitted to hospital
- Urine Immunochromatography - moderate yield for S. pneumoniae filtered bacterial proteins if there is bacteremia, less if confined to the lungs, lower for legionella
- Nasopharyngeal swab:
- Checking for viruses, Viral PCR is done so if positive stop antibiotics - Bronchoscopy which gets a good sample in severe cases but poorly tolerated
- Blood cultures, sputum culture - mostly have low yield due to no bacteremia and poor sample collection/contamination with commensal bacteria of the mouth
- Serology: only done to diagnosing a cluster of infections by finding antibodies against mycoplasma, chlaymidia and legionella
Describe the colonisation of Strep pneumoniae (adults v children, duration), way of getting into the trachea
Strep pneumoniae colonises the nasopharynx and therefore can aspirate into the trachea
- 5-10% of adults colonised
- 20-40% of children
Colonisation persists from weeks- months and prevalence increases in winter for adults, kids all year round
What are problems with treating s. pneumoniae with penicillin - how are these overcome
Treatment with penicillin at IV doses as some strains of s. pneumonia is resistant to penicillin through altered transpeptidase which reduces binding affinity with penicillin.
This means that higher doses than oral dose needs to be used to overcome it as well as other infections like meningitis
Penicillin resistance is associated with resistance to other common oral antibiotics as there is co-expression to convey resistance to antibiotics
so therefore macrolides like quinone can be used
What is the difference in Empiric antibiotic treatment to reduce duration of illness and risk of death approach for mild, moderate vs severe pneumonia- which antibiotics
What is the difference between community acquired vs healthcare associated pneumonia
All treatment for 5 days
Community
1. Mild: Don’t need to investigate cause, as good recovery likely with simple antibiotic, have time to adjust treatment if problems
- Amoxycillin tab
2.Moderate: often in hospital
Amoxycillin oral/IV + roxithromycin
- Severe: ICU, IV. Need to use broad spectrum therapy and investigate germ to target it.
Amoxycillin/clavulanic acid + azithromycin
Hospital assoc :
- higher risk of gram - bacterial causes eg. klebsiella pn. E. coli,
- antibiotic resistant bacteria associated with previous surgery, antibiotic treatment, ventilator use compared to community cause.
- Cefuroxime IV +/- Gentamicin IV daily
Describe how Ribosomes make proteins
- Initiation complex made from tRNA attached to start codon of mRNA binding to the small subunit of ribosome. Then large subunit joins aligning it in the A site.
- The A site is where tRNA binds to mRNA
- Moves to P site where the ribosome catalyses the peptide bone between adjacent amino acids
- Moves to E site where tRNA is released from the ribosome
What are the 5 antibiotic classes that have ribosome targets - which targets are they-4. Which one is bactericidal (others bacteriostatic)
- Macrolides eg. clarithromycin, Lincosamides eg. clindamycin
- Blocks tRNA adding peptide: 50S transpeptidation - Chloramphenicol
- interferes with 50S peptidyl transferase which transfers amino acid to peptide chain. mainly used ocular medicine- chance of agranular cytosis - Aminoglycoside eg. Gentamicin
- interferes with initiation of ribosome subunit 30S function leading to 2ndary message to apoptose: bactericidal - Tetracyclines eg. doxycycline
- interferes tRNA binding to 30S subunit.
Describe what Macrolides are used to treat in pneumonia + 2 other diseases, what they can’t and why,
Broad spectrum:
- Active against streptococci, staphylococci and other causes of pneumonia eg. legionella (untreatable by penicillin as it goes into WBC).
- This is because it is concentrated in pulmonary macrophages and vessels - Used for skin infections if allergic to penicillin drugs
- Used as a single dose (azithromycin) for chlaymidia treatment if non adherence to doxycycline week course suspected)
Not used
- Gram - bacteria (due to reduced cell membrane permeability)
- Pyelonephritis/ cystitis as its not cleared by the kidneys to doesn’t get into urine well.
What are the adverse effects of Macrolide antimicrobials meaning they are not first line treatment and why
- GIT upset; nausea, vomiting, diarrhoea due to effects against gut flora + erythromycin agonism of motilin receptors which cause peristalsis
- Sudden death: due to cardiac conduction problems: prolonged Q-T–> VT–> torsades de pointes–> death
- Drug interactions - synergism with other drugs which interfere with cardiac conduction eg. BB, amiodarone
What should you not use to treat bronchitis and why - when can you use antibiotics
- Antibiotics because Bronchitis is a viral illness: fever, cough, illness caused mainly by Rhinovirus, CVD, adenovirus.
- Antibiotics are recommended for Bordetella pertussis infection (bacteria) not to make illness quicker finish, but rather to break transmission chain)
RCT show harm outweigh benefits.
- NSAIDS eg. ibuprofen
- Sedating antihistamines eg. chloropheniramine :
