Upper Respiratory Tract Infections (URTIs)

Question 1

What is the main component of the normal flora in the upper respiratory tract?

Answer 1

Alpha Streptococci.

Question 2

Most common colds are caused by:

Answer 2

rhinoviruses.

Question 3

Describe rhinoviruses (size, enveloped or not, DNA/RNA).

Answer 3

Small, non-enveloped RNA.

Question 4

How are rhinoviruses usually transmitted?

Answer 4

Direct contact, some by droplet.

Question 5

Why do rhinoviruses only grow in the upper respiratory tract?

Answer 5

They don’t grow at 37ºC - their optimal temperature for growth is 33ºC.

Question 6

How long is the incubation period for rhinoviruses?

Answer 6

10-12 hours.

Question 7

What is the second most common cause of common colds?

Answer 7

Coronaviruses.

Question 8

Infectious mononucleosis (IM) is causes by:

Answer 8

HHV-4 (Epstein-Barr virus - EBV).

Question 9

Describe EBV (enveloped/non-enveloped, DNA/RNA).

Answer 9

Enveloped DNA virus.

Question 10

In IM, EBV remains latent in:

Answer 10

B cells.

Question 11

Most IM infections in children are ____ while infections in older demographics (teens, adults) are more ______.

Answer 11

mild; severe.

Question 12

IM can have systemic effects on:

Answer 12

cardiovascular & lymphatic systems.

Question 13

What are some common symptoms of IM (5)?

Answer 13

Fever.
Sore throat.
Swollen lymph glands in neck.
General weakness & fatigue.
Enlarged spleen.

Question 14

EBV produces heterophile antibodies, which are:

Answer 14

weird antibodies that agglutinate other animals’ RBCs.

Question 15

Heterophile antibodies can be used for:

Answer 15

lab tests (ex: monospot).

Question 16

Ampicillin rash is a complication in IM patients who:

Answer 16

are given beta-lactam antibiotics.

Question 17

Strep throat is caused by:

Answer 17

GAS (group A strep), which is beta-hemolytic.

Question 18

Rapid tests for strep throat are ________ but not __________, which means:

Answer 18

specific; sensitive; a positive result is meaningful (with symptoms) but a negative result is not.

Question 19

Why do we need to treat all cases of strep throat with antibiotics?

Answer 19

To prevent sequelae (complications).

Question 20

Patients can get Scarlet Fever from strep throat if (2 conditions):

Answer 20

1. The strain can produce an erythrogenic toxin (superantigen).
2. This is their first time getting infected with any toxin-producing strain.

Question 21

What are 3 characteristics of scarlet fever?

Answer 21

1. Pink/red sandpaper-like rash.
2. High fever.
3. Strawberry tongue (loses upper membrane & becomes inflamed).

Question 22

Scarlet Fever can progress to:

Answer 22

glomerulonephritis or rheumatic fever.

Question 23

Diphtheria is caused by:

Answer 23

Corynebacterium diphtheriae.

Question 24

Describe the Gram morphology of Corynebacterium diphtheriae.

Answer 24

Aerobic, G+, non-spore forming bacillus.

Question 25

If pathogenic C. diphtheriae do not invade tissues, how do they cause disease?

Answer 25

They produce an exotoxin to inhibit protein synthesis in host cells & cause epithelial cells to die in the throat.

Question 26

What must happen for C. diphtheriae to become pathogenic?

Answer 26

Must be lysogenized (transduced) by a bacteriophage to transfer the exotoxin gene.

Question 27

What are some common effects of diphtheria toxin?

Answer 27

Myocarditis, cardiac failure, polyneuritis, death.

Question 28

What are some common symptoms of diphtheria?

Answer 28

Sore throat, fever & malaise. Neck swelling ("bull neck"). Nerve paralysis. Pseudomembrane across back of throat.

Question 29

How do we treat diphtheria?

Answer 29

Antibiotics & antitoxin.

Question 30

What are the 3 most common causes of bacterial URTIs and their Gram morphologies?

Answer 30

Streptococcus pneumoniae: G+ diplococci. Haemophilus influenzae: G- bacilli. Moraxella catarrhalis: G- diplococci.

Question 31

What causes whooping cough?

Answer 31

Bordetella pertussis.

Question 32

What is the Gram morphology of Bordatella pertussis?

Answer 32

Small aerobic G- coccibacillus.

Question 33

If B. pertussis does not invade tissues, how does it cause disease?

Answer 33

It colonizes the ciliated respiratory epithelium and produces many exotoxins to cause cellular damage.

Question 34

What is the mode of transmission for B. pertussis?

Answer 34

Droplet.

Question 35

Describe the 3 stages of disease for whooping cough.

Answer 35

1. Catarrhal: cold-like. 2. Paroxysmal: gasping, cough. 3. Convalescence: healing.

Question 36

What are the 6 mechanisms for pathogenicity for B. pertussis?

Answer 36

1. FTA (filamentous hemagglutinin): for adherence. 2. Pertussis toxin: systemic effects. 3. Tracheal cytotoxin: damages ciliated cells. 4. Lethal toxin: tissue necrosis. 5. Adenylate cyclase: reduced phagocytic activity. 6. LPS.

Question 37

What are the common causes of otis media (5)?

Answer 37

``` Streptococcus pneumoniae. Haemophilus influenzae. Moraxella catarrhalis. Staphylococcus aureus. Steptrococcus pyogenes. Other "cold viruses". ```