Infections of the Lungs

Question 1

What is CAP?

Answer 1

Community Acquired Pneumonia

Question 2

What is the Mortality if admitted of CAP?

Answer 2

15%

Question 3

What is the Aetiology?

Answer 3

Streptococcus pneumoniae 60%
Haemophilus influenzae 15%
“Atypicals” 20%
Staphylococcus aureus (post influenza

Question 4

What is the 2nd most common Hospital Acquired Infection (HAI) after UTI

Answer 4

Nosocomial Pneumonia

Question 5

Aetiology of Nosocomial pneumonia

Answer 5

Enterobacteriaceae 40%
Staphylococcus aureus 25%
Pseudomonas aeruginosa 15%
Others: multiresistant Gram negative rods

Question 6

Why is ‘atypical’ pneumonia known as this?

Answer 6

“Atypical” as many do not have typical bacterial cell wall structures

Question 7

How and who does ‘atypical’ pneumonia infect?

Answer 7

community acquired
RELATIVELY COMMON IN OTHERWISE HEALTHY INDIVIDUALS

Question 8

What are the causative organisms?

Answer 8

Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella,
Chlamydia psittaci

Question 9

How are aspiration pneumonias caused?

Answer 9

FOLLOWS INHALATION OF VOMIT OR FOREIGN OBJECT

Question 10

Who do they usually infect?

Answer 10

OFTEN UNCONSCIOUS PATIENT

Question 11

What are the causative organisms?

Answer 11

upper respiratory and gastrointestinal commensals, including anaerobic organisms

Question 12

What is the associated complication?

Answer 12

LUNG DAMAGE DUE TO ACIDIC GASTRIC CONTENTS

Question 13

Where can specimens for diagnosis be found?

Answer 13

SPUTUM
BRONCHIAL-ALVEOLAR ASPIRATE

Question 14

what methods can be used for detection?

Answer 14

BLOOD CULTURE
ANTIBODY (SEROLOGY) OR ANTIGEN DETECTION

Question 15

What are the two Sputum constituents?

Answer 15

Purulent exudate from infected site
- Incorporating pathogen
Other respiratory tract secretions
- Incorporating normal flora

Question 16

What does a Good sputum sample contain and when can it be taken?

Answer 16

Purulent
First morning specimen: generally most purulent

Question 17

How is the Sputum processed?

Answer 17

Purulent sputum homogenised
Cultured on blood and chocolate agar in 5% CO2
Antimicrobial (optochin) disc placed on blood plate

Question 18

what do the colonies look like?

Answer 18

α haemolytic “draughtsman” colonies on blood agar

Question 19

Shape? Gram? Catalase?

Answer 19

Gram positive diplococcus, catalase negative

Question 20

Other identifications?

Answer 20

Optochin sensitive
Soluble in bile salt (10% desoxycholate) solution

Question 21

Benefits of Bronchial Aspirate?

Answer 21

Better specimen than sputum
Point of sampling is lower in respiratory tract
Can be directed to site of infection

Question 22

Disadvantages of Bronchial Aspirate?

Answer 22

Uncomfortable and Invasive procedure with associated morbidity

Question 23

In which circumstances must it only be used?

Answer 23

Serious respiratory tract infection
No other positive samples
Examples of use: TB, Legionaires’ disease

Question 24

When is Antibody and Antigen detection used?

Answer 24

when culture difficult
Mycoplasma, Chlamydia, Legionella

Question 25

What does antibody detection detect?

Answer 25

rise in concentration of antibodies against infecting organism

Question 26

What samples are required?

Answer 26

Requires acute and convalescent samples at least 10 days apart
Look for >4 fold increase in antibody titre

Question 27

What is required for Antigen detection?

Answer 27

Use labelled antibodies
Bind to cell surface antigens in clinical samples

Question 28

Name two examples of samples that antigen detection is used on?

Answer 28

Sputum smears for legionella, mycoplasma
Urine for legionella pneumophila serogroup 1