Infections of the Lungs Flashcards
What is CAP?
Community Acquired Pneumonia
What is the Mortality if admitted of CAP?
15%
What is the Aetiology?
Streptococcus pneumoniae 60%
Haemophilus influenzae 15%
“Atypicals” 20%
Staphylococcus aureus (post influenza
What is the 2nd most common Hospital Acquired Infection (HAI) after UTI
Nosocomial Pneumonia
Aetiology of Nosocomial pneumonia
Enterobacteriaceae 40%
Staphylococcus aureus 25%
Pseudomonas aeruginosa 15%
Others: multiresistant Gram negative rods
Why is ‘atypical’ pneumonia known as this?
“Atypical” as many do not have typical bacterial cell wall structures
How and who does ‘atypical’ pneumonia infect?
community acquired
RELATIVELY COMMON IN OTHERWISE HEALTHY INDIVIDUALS
What are the causative organisms?
Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella,
Chlamydia psittaci
How are aspiration pneumonias caused?
FOLLOWS INHALATION OF VOMIT OR FOREIGN OBJECT
Who do they usually infect?
OFTEN UNCONSCIOUS PATIENT
What are the causative organisms?
upper respiratory and gastrointestinal commensals, including anaerobic organisms
What is the associated complication?
LUNG DAMAGE DUE TO ACIDIC GASTRIC CONTENTS
Where can specimens for diagnosis be found?
SPUTUM
BRONCHIAL-ALVEOLAR ASPIRATE
what methods can be used for detection?
BLOOD CULTURE
ANTIBODY (SEROLOGY) OR ANTIGEN DETECTION
What are the two Sputum constituents?
Purulent exudate from infected site
- Incorporating pathogen
Other respiratory tract secretions
- Incorporating normal flora
What does a Good sputum sample contain and when can it be taken?
Purulent
First morning specimen: generally most purulent
How is the Sputum processed?
Purulent sputum homogenised
Cultured on blood and chocolate agar in 5% CO2
Antimicrobial (optochin) disc placed on blood plate
what do the colonies look like?
α haemolytic “draughtsman” colonies on blood agar
Shape? Gram? Catalase?
Gram positive diplococcus, catalase negative
Other identifications?
Optochin sensitive
Soluble in bile salt (10% desoxycholate) solution
Benefits of Bronchial Aspirate?
Better specimen than sputum
Point of sampling is lower in respiratory tract
Can be directed to site of infection
Disadvantages of Bronchial Aspirate?
Uncomfortable and Invasive procedure with associated morbidity
In which circumstances must it only be used?
Serious respiratory tract infection
No other positive samples
Examples of use: TB, Legionaires’ disease
When is Antibody and Antigen detection used?
when culture difficult
Mycoplasma, Chlamydia, Legionella
What does antibody detection detect?
rise in concentration of antibodies against infecting organism
What samples are required?
Requires acute and convalescent samples at least 10 days apart
Look for >4 fold increase in antibody titre
What is required for Antigen detection?
Use labelled antibodies
Bind to cell surface antigens in clinical samples
Name two examples of samples that antigen detection is used on?
Sputum smears for legionella, mycoplasma
Urine for legionella pneumophila serogroup 1
