L29 Bacterial and Fungal respiratory tract infections Flashcards
Name the 3 routes of transmission of RTI.
- Aspiration: oropharyngeal secretions
- Inhalation: droplet nuclei, aerosols
- Hematogenous: e.g. staphylococcus in IVDA
The difference in causative agent(s) between common cold (coryza) and acute pharyngitis?
Common cold:
- Respiratory virus, e.g. rhinovirus, coronavirus, parainfluenza virus
Acute pharyngitis:
- Group A strep
The differences in symptoms (not signs!) between common cold and acute pharyngitis?
Common cold:
- Sore throat, cough, sneezing, rhinorrhea, nasal congestion
Acute pharyngitis:
- Sore throat, headache
The differences in signs between common cold and acute pharyngitis?
Common cold
- fever, erythematous pharynx
Acute pharyngitis
- Tendency for fever, swollen tonsils, enlarged anterior cervical nodes, scarlatiniform rash (diffuse redness over the body)
The difference in treatment and complications between common colda and acute pharyngitis?
Common cold: self-limiting; may occasionally have secondary bacterial infection
Acute pharyngitis: antibiotics; complications include rheumatic fever, acute GN
There are more than 200M. serotypes for the bacteria ______________, and M1 and M12 are epidemics.
Streptococcus pyogenes (Group A strep)
Diagnosis for Group A strep? (2)
- POCT (point-of-care testing, but poor sensitivity/specificity
- Throat swab: exudates from tonsils
Way of doing throat swab?
- Dry swab to prevent normal flora overgrowth, but reduces bacterial survival
- Contraindicated in suspected epiglottis (suspect if dysphagia and drooling)
Treatment for Group A strep?
Penicillin/ amoxicillin x 10 days
Name the 2 possible post-streptococcal diseases.
- Rheumatic fever
2. Acute glomerulonephritis
Which of the following about rheumatic fever as a post-streptococcal disease are correct?
A. It is MC in children from 6-15 years old
B. 2-4 weeks post-strep pharyngitis
C. It is due to circulating immune complex
D. Signs and Symptoms are related to Jones Criteria
E. Diagnosed by ASOT (Anti-streptolysin O titre) > 200 IU/ml + Anti-strep DNase B titre
All except C
C: pathogenesis should be anti-strep cell wall Ab cross-reacts with sarcolemma of heart and other tissues
Acute glomerulonephritis - Circulating immune complex in glomerulus;
Nephritogenic strains: M1, M12, etc. do not cause rheumatic fever
What are the Jones criteria?
J: joint - migratory polyarthritis O: Heart - myocarditis/pericarditis/valvular disease N: nodules - subcutaneous nodules E: erythema marginatum S: Sydenham chorea
Onset of acute glomerulonephritis (post-streptococcal)?
10 days post-strep pharyngitis or pyoderma (skin infection with pus)
Signs and symptoms of acute glomerulonephritis and diagnosis?
SSx: Haematuria and AKI
- increase in ASOT (anti-streptolysin O titre), not in pyoderma
What is the pathological definition of pneumonia?
infection of the pulmonary parenchyma
What is the clinical definition of pneumonia?
- Consolidation (radiological or P/E) +
2. Microbiological proof (30-40%)
Which of the following are clinical symptoms of pneumonia? A. Fever B. Chills and rigors C. Cough D. SOB E. Tachypnea F. Pleuritis
All of the above
Signs: fever, tachycardia, tachypnea, signs of consolidation (dull on percussion, bronchial breathing)
List all the causative agents that cause
A. Typical pneumonia
B. Atypical pneumonia
(both community-acquired pneumonia- CAP)
A. Typical
- Strep. pneumoniae
- Haemophillus influenzae
- Moraxella catarrhalis
B. Atypical
- Mycoplasma pneumoniae
- Clamydophila pneumoniae
- Rare: Legionella pneumophila
What are the differences in signs and symptoms between typical and atypical pneumonia? (4)
- Fever
Typical: High grade fever
Atypical: Low grade fever - Rigors
Typical: common
Atypical: uncommon - Cough
Typical: productive, purulent sputum
Atypical: non-productive - Pleuritis (pleuritic chest pain)
Typical: common
Atypical uncommon
The onset of typical and atypical pneumonia?
Typical: abrupt
Atypical: Gradual (3-4 days)
What are the CXR findings in typical and atypical pneumonia?
Typical: lobar consolidation
Atypical: Bilateral patchy infiltrates
WBC in typical and atypical pneumonia?
Typical: increase neutrophils
Atypical: normal
Culture in typical and atypical pneumonia?
Typical: blood agar! (also for organisms cause HAP e.g. pseudomonas);
Chocolate blood agar for H.influenzae
Atypical: Require special culture, e.g. tissue culture, mycoplasma agar
Treatment for typical pneumonia?
- beta lactams
2. macrolides: resistant in HK
Treatment for atypical pneumonia?
- Macrolides - increase resistance
- Tetracyclines: teeth discoloration
- Fluoroquinolones: note TB prevalence
Streptococcus pneumoniae
A. resides in nasopharynx
B. has 98 serotypes based on polysaccharide capsule with IgA protease virulence factor
C. Enters the bloodstream via nasopharyngeal mucosal epithelium
D. Further invades the CNS
E. Causes pneumonia and bacteremia
All of the above
Pathogenesis: C and D
D: causes spectrum of diseases like acute otitis media, pneumonia, bacteraemia and meningitis
Myocplasmia pneumoniae
A. Causes atypical pneumonia
B. causes malaise and headache 1-5 after chest symptoms
C. Can cause extrapulmonary manifestations like myocarditis
D. Can cause Guillain Barre syndrome
E. With cold agglutinins in blood: clumping of blood in 4 degrees Celcius
B is wrong, should be 1-5 days before chest symptoms
E: correct, it is one of the diagnostic tests (obsolete)
What is the definition of Healthcare-associated pneumonia? (HAP)
Hospital acquired (after 48h hospital admission) or reside in a nursing home
List causative agents that cause HAP.
3
Antibiotic-resistant strains
- GN aerobes, e.g. Enterobacteriaceae (Klebsiella), P.aeruginosa
- GN anaerobe, e.g. Bacteroides
List causative agents that cause Aspiration pneumonia (3)
- GN aerobes e.g. Enterobacetericeae, P.aeruginosa
- Anaerobes from URT
e. g. S.aureus
What are the host factors (2) + disease factors (4) (risk factors) for HAP?
Host factors
- Old age
- Underlying diseases e.g. chronic lung disease, DM
Disease factors
- Mechanical ventilators
- Decreased cough reflex, e.g. opioids
- Broad-spectrum antibiotics
- Immobility and reduced consciousness
What are the risk factors for aspiration pneumonia? (4)
- Unconscious patients
- Alcoholics
- Elderly
- Head injury
List all the laboratory investigations you would order when the patient has pneumonia. (6)
- Sputum
- early morning sputum (more concentrate)
- AFB (acid-fast bacilli) smear (Ziehl Neelsen stain) and TB culture required in call cases of productive cough - NPA (nasopharyngeal aspirate)
- for PCR of atypical organisms + viruses (e.g. RSV, influenza) - Blood culture
- Urine:
- Streptococcus Ag, Legionella Ag - Bronchoalveolar lavage (BAL)
- via bronchoscopy, by injecting saline and draw, distinguish from contamination by quatitative culture (>10000 organisms/mL) - Tracheal aspirate
- in patients intubated or with tracheostomy
To obtain best quality sputum:
A. Deep breathing exercise
B. Retaining in the mouth and spill it out to the bottle
C. Rinse mouth before collecting sputum
D. reject if 10 squamous epithelial cells (SEC) per low power field (LPF)
E. reject if without significant amount of WBC
All except B
Should cough directly to sputum bottle rather than retaining in the mouth
Management for patients with pneumonia includes Empirical treatment and treating the pneumonia of specific etiology. What to give if A. Mild to moderate pneumonia B. Severe pneumonia C. Structural lung disease (e.g. bronchiectasis) D. Pseudomonas suspected E. Aspiration pneumonia F. HAP
A: Augmentin IV/PO - amoxicillin/ clavulanate
B. Ceftriaxone (lung!) + macrolide
C. Tazocin (Piperacillin/Tazobactam)
D. Add gentamicin
E. IV cefuroxime + metronidazole (because food from intra-abdominal??)
F. Tazocin
What to give when it is S.aureus - caused pneumonia?
Cloxacillin (MSSA),
Vancomycin (MRSA)
What to give when it is Strep pneumoniae - caused pneumonia?
Penicillin (IC of penicillin <4 mcg/ml),
Ceftriaxone (MIC of penicillin >8 mcg/ml)
What to give when it is Mycoplasma - caused pneumonia?
Macrolide
Mycoplasma pneumoniae
A. Fried egg colonies on Eaton’s media
B. smallest free-living bacteria with no peptidoglycan wall
C. Walking pneumonia
D. CXR with patchy infiltrate
E. Positive cold agglutinin test (autoantibody to RBC)
F. Treated with macrolides
All of the above!
Walking on Thin Ice Sketchy!
What vaccines can be used for strep pneumonia?
- PPSV23
(23-valent polysaccharide vaccine) - PCV13
(13-valent protein conjugate vaccine)
Which type of vaccine for strep pneumonia is this?
- For adults
- Polysaccharide from capsule
- Weaker immune response
- Poorer memory
PPSV23
23-valent polysaccharide vaccine
Which type of vaccine for strep pneumonia is this?.
- For children, included in childhood immunization programme (CIP)
- Weak Ag (polysaccharide) attached to a strong Ag
- More powerful immune response
- Longer memory
PCV13
13-valent protein conjugate vaccine
List 3 causative agents for pneumonia in the immunocompromised host
- opportunistic infections.
Any 3
- Pneumocystis jiroveci (fungus)
- Aspergillus (fungus)
- Mycobacterium tuberculosis
- Mycobacterium avium intracellulare
- Nocardia species
- Candida species (fungus)
- Strongyloides (parasite)
A big risk factor for chronic pulmonary sepsis is?
Examples include patients who have cystic fibrosis and is a smoker. Viral infection like measles will cause this too.
Impaired mucociliary clearance
impaired ciliary tree + mucus production
What are the causative organisms for bronchiectasis? (6)
- Strep. pneumoniae
- S. aureus
- H.influenzae
- P.aeruginosa
- M. tuberculosis
- Aspergillus
Risk factors for bronchiectasis? (4)
Congenital
- Cystic fibrosis,
- Kartagener’s syndrome (primary ciliary dyskinesia)
Acquired
- post-infection (pertussis, TB)
- airway obstruction (foreign body)
Clinical manifestations for patients with bronchiectasis (3)
- Recurrent cough with hemoptysis
- Purulent sputum
Complications
- Cor pulmonale
Management of patients with bronchiectasis?
- Clear secretions: physiotherapy, postural drainage
- Reverse airflow obstruction
- Medical: Abx, DNase(breaks down DNA to improve pulmonary function FEV1), gene therapy
- Surgical: arterial embolization, resection
Acute exacerbation of COPD (chronic bronchitis) is usually due to total burden of inhaled particles - smoking, occupational dust and air pollution.
What are the commonest causative organisms? (4)
- H. influenzae (MC)
- Strep. pneumoniae
- S.aureus
- P.aeruginosa
Clinical manifestations for acute exacerbation of COPD? (3)
- Increase SOB
- Sputum - increased production, more mucopurulent
- Coughing
What maintenance therapy are given to patients with acute exacerbation of COPD? (3)
- Bronchodilators
- Antibiotics for 7-10days
- Physiotherapy
What is empyema?
Accumulation of pus in pleural space
Causes for empyema?
State the cause and the organism
- Pneumonia due to H.influenzae (MC), Strep. pneumoniae, S.aureus
- Thoracic surgery, trauma: S.aureus, GN bacilli
- Esophageal perforation
- Subdiaphragmatic infection: anaerobes
Clinical manifestations of patients with emypema?
- Non-specific constitutional Sx, e.g. weight loss, fever, night sweats
- Pleural effusion
How to diagnosis empyema? (1)
Tx?
Pleural aspirate
Tx
- Pus drainage (thoracentesis)
- Abx (anaerobic coverage) x2-4/52
[prolonged in long-standing cases and Actinomyces (anaerobe, v. invasive)]
Aspiration, Periodontal disease, Underlying lung disease like bronchiectasis and Immunosuppression are all risk factors to lung absecess.
What are the causative organisms?
- Oropharyngeal flora
- Nosocomial e.g. S.aureus
- Anaerobes e.g. bacteroides
Lung abscess can cause constitutional symptoms liek malaise, LG fever and weight loss, anemia. Productive cough too. Complications include - Empyema - bronchopleural fistula - brain abscess
Dx and Tx?
Dx: BAL, empyema fluid, blood
Tx:
- Abx: anaerobic coverage, 2-4/52
- Pus drainage
