Resiratory tract infections tutorial Flashcards
․․․ remains the most commonly identified pathogen in community-acquired pneumonia.
St pneumoniae
Other pathogens have been reported to cause pneumonia in the community and include…
Haemophilus influenzae, Mycoplasma pneumoniae, and influenza A, along with newer pathogens such as Legionella species and Chlamydophila pneumoniae. Other common causes in the immunocompetent patient include Moraxella catarrhalis, Mycobacterium tuberculosis, and aspiration pneumonia. The causative agent of community-acquired pneumonia remains unidentified in 30% to 50% of cases
The causative agent of community-acquired pneumonia remains unidentified in 30% to 50% of cases.T/F
True
purulent sputum, neutrophilia, focal consolidation can also be due to viral pneumonia?
No, it suggests bacterial infection, but the viral infection usually influenza can be complicated by bacterial superinfection and pneumonia.
is the presentation of TB acute or chronic?
TB usually presents with more long-standing symptoms
what specimens need to be obtained and what investigation s need to be requested in a patient with suspected CAP?
- -Sputum for culture
- -Blood for culture
- -Urine for legionella/pneumococcal antigens
- -Nose/throat swab for influenza PCR - (seasonal)
how the sputum is cultured?
Specimen inoculated onto blood and chocolate agar plates and incubated for 18-24 hours
what is the goal of chocolate agar?
Blood agar is incubated aerobically and chocolate agar is incubated in CO2 (picks up organisms such as Haemophilus influenzae)
name a blood agar plate that contains V-factor (NAD) and X-factor (hematin). Used to culture fastidious bacteria (e.g., Haemophilus influenzae, Francisella tularensis)?
Chocolate agar
what pathogen is alpha-hemolytic (greenish discoloration) on blood agar and susceptible to optochin?
Streptococcus pneumoniae
Gram-positive cocci in pairs (i.e. diplococci) and short chains are suggestive of …
Streptococci
how urinary antigen test is performed?
- -Like a pregnancy test
- -Quick- result in 15 mins
- -Useful if positive (but negative in approx. 30% of pneumococcal infections)
which empirical antibiotic therapy should be started based on the CURB-65 score?
- -mild (0-1): POamoxicillin, or clarithromycin or doxycycline
- -moderate: IV amoxicillin + PO clarithromycin
- -severe (3-5): IV co-amoxiclav + PO clarithromycin
what organisms are covered by amoxiclav vs clarithromycin?
- -Co-amoxiclav (rather than amoxicillin alone) to cover Haemophilus influenzae as well as Str. pneumoniae. Give IV (severe pneumonia, sepsis)- higher dose and gets in faster than if given PO.
- -Clarithromycin to cover atypicals (e.g. Legionella spp.) Very good oral bioavailability so can give orally (PO)
what is the CURB-65 score?
A score used to decide whether patients with pneumonia require hospitalization. Confusion, blood urea > 7 mmol/L (20 mg/dL), respiratory rate ≥ 30/min, systolic blood pressure ≤ 90 mm Hg or diastolic BP ≤ 60 mm Hg, and age ≥ 65 years are each assigned 1 point. If the CURB-65 score is ≥ 2, hospitalization is indicated.
what is the clavulanate?
A β-lactamase inhibitor used in combination with β-lactam antibiotics (particularly amoxicillin) to prevent bacteria from inactivating the antibiotic.
what are the management principles of CAP?
- -Empiric antibiotics as per local guidelines
- -Rationalise with culture results and susceptibilities
- -Vaccinate to prevent future episodes
what is the VAP?
A hospital-acquired infection that develops 48 hours after the initiation of mechanical ventilation via either tracheostomy or intubation. Approx. 5–10% of patients on mechanical ventilation develop VAP.
what are the pathogens involved in VAP?
1) Gram- negative bacilli: including multidrug resistant ones
- -E. coli
- -Klebsiella spp.
- -Enterobacter spp.
- -Pseudomonas spp.
- -Serratia marcescens
2) Staphylococcus aureus including MRSA
3) Legionella pneumophila (aerosol inhalation)
4) Anaerobes, e.g. Bacteroides fragilis (aspiration)
6) Viruses: influenza, RSV etc.
7) Fungi e.g. aspergillus (in significantly immunosuppressed patients)
Is candida likely to be the cause of the VAP?
Candida spp. often grow from respiratory specimens of intubated patients but almost always represent colonization, not infection
what specimens need to be obtained and what investigation s need to be requested in a patient with suspected VAP?
–Broncho-alveolar lavage for culture
–Consider TB/ respiratory viral PCR/ fungi also
Blood cultures (from central lines as well as peripheral cultures)
what is the empiric antibiotic therapy for a patient with VAP?
–N.B. Check previous microbiology; is the patient known to be colonized with resistant organisms e.g. MRSA?*
If not:
–Piperacillin-tazobactam
1)Broad-spectrum Gram-positive and Gram-negative cover, including Pseudomonas aeruginosa
2)Pip-taz is recommended empiric treatment for hospital-acquired pneumonia in many hospitals, including Beaumont
3)Choice of antibiotics in ICU patients is usually discussed with the consultant microbiologist
how long is the treatment duration of VAP with Piperacillin-Tazobactam?
Treatment duration usually 7 days, but should be judged on a case-by-case basis
What measures can be taken to prevent VAP?
- -Avoid intubation unless necessary
- -Standard precautions e.g. hand hygiene & decontamination
- -Appropriate endotracheal tube cuff size
- -Aspiration of secretions (subglottic secretion drainage)
- -Head of bed elevated at 30-45oC
- -Oral hygiene with chlorhexidine
