Respiratory Tract Infections

Question 1

Corynebacterium diphtheriae - morphology

Answer 1

nonmotile, noncapsulated, club-shaped, gram-positive bacillus

Question 2

Corynebacterium diphtheriae - biotypes

Answer 2

Mitis, intermedius, gravis (morphological types found on tellurite media)

Question 3

Mitis

Answer 3

Black colonies with a gray periphery

Question 4

Gravis

Answer 4

Large, grey colony

Question 5

Intermedius

Answer 5

Small, dull gray to black

Question 6

Treatment

Answer 6

ADS + Erythromycin

Question 7

Pneumonia

Answer 7

Pneumonia is a disease of the lung that is caused by a variety of bacteria including Streptococcus, Staphylococcus, Pseudomonas, Haemophilus, Chlamydia and Mycoplasma

Question 8

Streptococcus pneumoniae - serotyping

Answer 8

Quellung (capsular swelling) reaction can be used to demonstrate the presence of a specific capsular type of the bacterium.

Question 9

Streptococcus pneumoniae - culture

Answer 9

Mucoid strain on blood agar showing alpha hemolysis (green zone surrounding colonies)
zone of inhibition around a filter paper disc impregnated with optochin. Viridans streptococci are not inhibited by optochin.

Under anaerobic conditions they switch to beta hemolysis caused by an oxygen-labile hemolysin.

Question 10

• Virulence factors

Answer 10

Contains within itself the enzymatic ability to disrupt and to disintegrate the cells. The enzyme responsible is called an autolysin.

Question 11

Bacteria may reach the lungs via one of three routes:

Answer 11

Inhalation
Aspiration
Haematogenous

Question 12

Mycoplasma pneumoniae

Answer 12

rod-shaped bacterium that lacks a cell wall. It tends to affect a younger demographic and occurs in cyclical epidemics.
Diagnosis can be made with PCR of respiratory samples.

Question 13

Pseudomonas aeruginosa

Answer 13

P. aeruginosa is a gram-negative bacillus that causes HAP.

Question 14

Pseudomonas aeruginosa - treatment

Answer 14

Treatment often involves a cephalosporin and aminoglycoside.

Question 15

Chronic pneumonia

Answer 15

is a pulmonary parenchymal process that can be infectious or non-infectious and that has been present for weeks to months rather than days.

Question 16

Symptoms of pneumonia

Answer 16

Fever
Malaise
Cough (purulent sputum)
Dyspnoea 
Pleuritic pain

Question 17

Pleura

Answer 17

The pleura are thin membranes that line the lungs and the inside of the chest cavity and act to lubricate and facilitate breathing

Question 18

Pleural effusion

Answer 18

Pleural effusion, sometimes referred to as “water on the lungs,” is the build-up of excess fluid between the layers of the pleura outside the lungs.

Question 19

Pleural effusion

Answer 19

Inflammation due to pneumonia can lead to pleural effusion

Question 20

Distinction btw S epidermidis and Staph saprophiticus (UTI)

Answer 20

S. epidermidis does not possess the gelatinase enzyme, so it cannot hydrolyze gelatin. It is sensitive to novobiocin, providing an important test to distinguish it from Staphylococcus saprophyticus, which is coagulase-negative, as well, but novobiocin-resistant.

Question 21

Distinction between S pneumoniae and Alpha hemolytic streptococci

Answer 21

Bile Solubility Test is the test which differentiate Streptococcus pneumoniae (positive- soluble) from alpha-hemolytic streptococci (negative- insoluble). Streptococcus pneumoniae is bile soluble whereas all other alpha-hemolytic streptococci are bile resistant.

Question 22

CAMP test

Answer 22

CAMP test - identify group B β-hemolytic streptococci (Streptococcus agalactiae) based on their formation of a substance (CAMP factor) that enlarges the area of hemolysis formed by the β-hemolysin elaborated from Staphylococcus aureus.