W4 LRTI Flashcards
Name some acute lower respiratory tract infections
- Pneumonia
- Bronchitis
- Bronchioloitis
- Legionnaires’ disease
- Whooping cough
Name some chronic lower respiratory tract infections
- Tuberculosis
- Aspergillosis
- Cystic fibrosis
What is pneumonia
An acute LRTI associated with recently developed radiological signs. Infection of the lungs due to bacteria, viruses and fungi
How can pneumonia be aquired?
May be acquired in the community (CAP) or in the hospital (HAP); associated risk factors
How many people die from pneumonia each year?
- Approximately 30,000 people die due to pneumonia in the UK per annum
- May present with either TYPICAL or ATYPICAL symptoms
What is peumonia caused by?
•May be caused by several organisms therefore accurate identification is essential to ensure appropriate antimicrobial therapy
How is pneumomia classified?
- Community-acquired pneumonia (CAP)*
- Hospital-acquired pneumonia (HAP)*
- Aspiration pneumonia
- Recurrent pneumonia
Describe Community Acquired Pneumonia (CAP)
- Every year, 0.5% to 1% of UK adults will have CAP (approx. 320,000 – 640,000 people)
- Mainly seasonal: Autumn / Winter
- CAP is diagnosed in 5 to 12% of patients presenting to their GP with symptoms of LRTI
- 22 to 42% admitted to hospital (approx.100,000 patients)
- 5 to14% die in hospital
- 50% of deaths occur in patients 84 years or more
What are the signs and symptoms of typical pneumonia?
Predominantly respiratory; most common in elderly; may occur spontaneously in young adults
What microorganisms are acquired with communiated associated pneumonia?
Most common:
- Mycoplasma pneumoniae
Less common:
- Legionella pneumophila (legionnaires disease)
- Chlamydophila psittaci (psittacosis)
- Chlamydophila pneumoniae
Don’t forget the viruses:
- Influenza A/B
- Rhinovirus
- RSV
Show the radiological appearance of
TYPICAL and ATYPICAL pneumonia
Many organisms cause CAP: What are the associated risk factors
What is the 3rd most common hospital acquired infection?
Hospital acquired infection (HAI)
Patients may present with typical / atypical symptoms
What are the risk factors for HAP?
- Ventilatory support: Klebsiella pneumoniae, Pseudomonas aeruginosa (‘hospital flora’); VAP -48hrs or more following intubation
- Immunosuppression: organ transplantation: Aspergillus fumigatus
- Immobility and vomiting: aspiration pneumonia- oral bacteria eg. viridans streptococci and anaerobic bacteria
What regimens are available for the treatment of different types of pneuomia?
What organism is the most common cause of community acquired pneumonia?
S. pneumoniae
Streptococcus pneumoniae mechanisms of Pathogenicity: Capsule
(Major virulence factor)
- Antiphagocytic (evasion of immune attack)
- 92 different capsular types; serotypes differ in virulence
- 90% pneumonias are caused by about 23 serotypes (used in development of PPSV23)
- Quellung reaction (serotyping with homologous antibody)
Streptococcus pneumoniae mechanisms of Pathogenicity: CbpA adhesin
Major pneumococcal adhesin. The adhesin interacts with carbohydrates on the pulmonary epithelial surface
Streptococcus pneumoniae mechanisms of Pathogenicity:
PspA (Protective Antigen)
Inhibits complement-mediated opsonization of pneumococci
Streptococcus pneumoniae mechanisms of Pathogenicity:
IgA1 protease
Cleaves IgA1 the principal immunoglobulin isotype for the respiratory tract
Streptococcus pneumoniae mechanisms of Pathogenicity:
Autolysins (LytA, LytB, LytC)
Breaks peptide cross linking in cell wall peptidoglycan releasing cell wall components; massive inflammation and pneumolysin release
Streptococcus pneumoniae mechanisms of Pathogenicity:
Pneumolysin
Toxin released during autolysis; inhibits neutrophil chemotaxis, phagocytosis, lymphocyte proliferation and immunoglobulin synthesis
Draw a diagram to show streptococcus pneumoniae
Mechanisms of Pathogenicity
Diagnostic Clinical Microbiology: Case Study
Case: Streptococcus pneumoniae pneumonia
- A 65-year lady presents to A/E complaining of breathlessness, chest pain and has a temperature
- She reports that she has been ‘coughing up’ blood stained sputum for the last 5-days
- Chest X-ray: widespread consolidation in both lungs
- Initial Diagnosis: Community Acquired Pneumonia (CAP)
- Most likely pathogens: Streptococcus pneumoniae, Haemophilus influenzae
- Reasons for laboratory confirmation: Pneumonia is caused by a wide range of organisms; rapid identification of the pathogen and effective treatment is essential
Case: Streptococcus pneumoniae pneumonia
Describe specimen collection and transport
- Correct labelling of samples and form
- Sputum (early morning, before breakfast) for microscopy culture and sensitivity
- Gram stain (non culture technique)
- Culture
•Urine (rapid pneumococcal antigen test)
-Antigen detection (non culture technique)
•Transport <24h
Laboratory investigations for bacterial pneumonia: State the sample required
Sputum
Laboratory investigations for bacterial pneumonia: State the non-culture technqiues
Sputum: Microscopy; Gram stain
Laboratory investigations for bacterial pneumonia: State the non-culture technqiues state the culture technqiues
(a) Blood agar (37oC,5%CO2, 24h) + optochin disc
(b) Chocolate agar (37oC,5%CO2, 24h)
Laboratory investigations for bacterial pneumonia: State the non-culture technqiues state the safety considerations
- S. pneumoniae: category 2 pathogen
- Sputum sample: category 3 laboratory; class I safety cabinet
What are the safety aspects of a class I safety cabinet?
(a) Negative pressure, inward flow of air
(b) 0.74m3/sec air flow rate
(c) HEPA filter (high efficiency particle absorber)
Describe the basic identification of Streptococcus pneumoniae
- Colonial appearance: Strep pneumoniae grow as alpha-haemolytic colonies,1 mm in diameter, sometimes mucoid
- Gram stain of colonies: Gram-positive diplococci
How would you fully idetify Streptococcus pneumoniae?
• Optochin sensitivity: large zone (16mm) of inhibition around optochin disc: differentiates pneumococci from ‘normal’ oral streptococci
S. pneumoniae antigen detection: Describe the non-culture technique
Immunochromatographic assay / lateral flow assay
SAMPLE: URINE
- Rabbit-anti-Strep. pneumoniae bound to a nitrocellulose membrane
- Urine added to test well; read result in 15 minutes
- 86% sensitivity; 94% specificity
- Diagnostic if positive; however a negative result DOES NOT rule out infection
Describe EUCAST Sensitivity Testing / Treatment / Prevention
- S. pneumoniae susceptible to penicillin also are susceptible to nearly all other antibiotics
- Penicillin-Resistant S. pneumoniae (PRSP): strains have become increasingly prevalent worldwide; 50% PRSP
- Drug-resistant S. pneumoniae (DRSP): now widespread eg. tetracycline, macrolides, trimethoprim-sulfamethoxazole
25% multi-drug resistant
•Fluoroquinolones remain active: moxifloxacin
Describe PNEUMCOCCAL VACCINATION
- At risk patients:
23-valent pneumococcal polysaccharide vaccine (PPSV23)
- Childhood immunisation programme:
2010: pneumococcal conjugated vaccine (PCV13)
(< 2 years of age; 4 doses)
What are the key points of LRTI’s?
- LRTI infections are acute or chronic and caused by a wide variety of microorganisms
- Pneumonia may be CAP or HAP and may present with typical or atypical symptoms
- Pneumonia is caused by many microorganisms / associated ‘risk factors’
- Streptococcus pneumoniae the major cause of TYPICAL pneumonia; possesses a wide range of virulence factors to cause disease
- Rapid laboratory confirmation is essential to ensure appropriate therapy
- S.pneumoniae is becoming increasingly resistant to several antibiotics. Moxifloxacin is now recommended for treatment
- Pneumococcal vaccination available
