Bacterial Infections of the Mouth and Pharynx

Question 1

According to the lecture, what microbe is the “major cause” of pharyngitis?

Answer 1

Group A streptococci / Streptococcus pyogenes

Question 2

Describe the morphology of Streptococci.

Answer 2

Gram(+) cocci that grow in chains

Question 3

Streptococci and other beta-hemolytic bacteria can be classified by Lancefield group. What feature of the bacteria does this classification system use?

Answer 3

Carbohydrate antigens in the cell wall

Question 4

Name 3 virulence factors of Group A Strep.

Answer 4

pili (encoded by pathogenicity islands), capsule, and toxins.
Note: hemolysins are not virulence factors!

Question 5

Describe the function of the Group A Strep pili and capsule.

Answer 5

pili: attachment to mucous membranes
capsule: resist phagocytosis

Question 6

Describe the effects of the following 3 toxins: streptokinase, streptodornase, and hyaluronidase. What bacteria makes these toxins?

Answer 6

streptokinase - tissue lysis
streptodornase - DNA lysis
hyaluronidase - connective tissue digestion
made by Group A Strep

Question 7

Describe the reservoir and transmission of Group A Streptococci / Streptococcus pyogenes.

Answer 7

Reservoir: human pharynx and skin
Transmission: direct contact

Question 8

What toxin made by Group A Strep causes the skin rash and strawberry tongue associated with scarlet fever?

Answer 8

erythrogenic toxin

Question 9

What toxin made by Group A Strep is a superantigen that can cause fever and toxic shock?

Answer 9

pyrogenic toxin

Question 10

Streptococcal pharyngitis can spread to the tonsils, middle ear, and what 3 less common sites?

Answer 10

floor of mouth, mastoids, and meninges

Question 11

What autoimmune condition can occur 3 weeks after a streptococcal pharyngitis infection and is especially associated with the M18 strain of Group A strep? It is characterized by fever, polyarthritis, and heart deformations.

Answer 11

Rheumatic fever

Question 12

How would you identify a Group A Strep bacteria in terms of Gram staining, catalase, hemolysis, and antibiotics?

Answer 12

Gram(+), catalase(-), β-hemolysis, bacitracin sensitive

Question 13

Preventive measures for Strep A include which of the following: vaccines, prophylactic antibiotics, and/or treatment of carriers?

Answer 13

Prophylactic antibiotics (for patients who have had post strep diseases) and treatment of carriers. There are no vaccinations.

Question 14

What 2 antibiotics are routinely used to treat Streptococcus infections? Is drug resistance a problem?

Answer 14

Penicillin G or erythromycin.

Drug resistance is not a serious problem but testing sensitivity is helpful.

Question 15

How would you identify a Strep viridans bacteria in terms of Gram staining, catalase, hemolysis, and antibiotics?

Answer 15

Gram(+), catalase(-), α-hemolysis, optochin resistant (also insoluble in bile)

Question 16

Describe the reservoir and transmission of Streptococcus viridans.

Answer 16

Reservoir: normal flora of mouth and female genital tract
Transmission: opportunistic or congenital infection

Question 17

Name the major virulence factor of Streptococcus viridans and describe 2 ways that it causes dental caries.

Answer 17

sugar-metabolizing enzymes; make high MW sugars (plaque formation) and make acids (decalcification)

Question 18

Besides dental caries, name 4 problems that could be caused by Strep viridans infection.

Answer 18

Abscesses, cellulitis, bacteremia following dental treatments, and endocarditis following bacteremia

Question 19

If a patient develops an abscess from Strep viridans, what 2 antibiotics can be used to treat it?

Answer 19

Penicillin or erythromycin

Question 20

What bacteria appear as Gram(+) rods with clubbed ends and internal beads?

Answer 20

Corynebacterium diphtheriae

Question 21

How can Strep viridans dental problems be treated and prevented?

Answer 21

Treatment: extraction of caries, possibly antibiotics (penicillin and erythromycin)
Prevention: brush and floss teeth

Question 22

Corynebacterium diptheria can carry up to 3 copies of what virulence factor, and what type of genetic information encodes this factor?

Answer 22

Diphtheria toxin, encoded by the tox gene on a bacteriophage.

Question 23

What is the reservoir and transmission method for Corynebacterium diphtheriae?

Answer 23

Reservoir: human skin and mucous membranes
Transmission: respiratory droplets or direct contact

Question 24

How is Corynebacterium diphtheriae treated?

Answer 24

Immediate IV administration of antitoxin, penicillin or erythromycin to help resolution

Question 25

How would you culture Corynebacterium diphtheriae and check its virulence?

Answer 25

Grow on tellurite plates; confirm toxin with antibody tests or with PCR for tox gene

Question 26

Which of the following can be prevented by vaccination: Strep viridans, Strep pyogenes and/or Corneybacterium diphtheriae?

Answer 26

Only C. diphtheriae - DTaP vaccination includes the diphtheria toxoid

Question 27

Name up to 5 effects of the diphtheria toxin

Answer 27

local tissue necrosis, cardiac necrosis, pseudomembrane formation, systemic muscle paralysis, death

Question 28

What are “quinsy” and “Ludwig’s angina”?

Answer 28

quinsy = peritonsillar abscess

Ludwig’s angina = infection of the floor of the mouth

Question 29

Which of the following can be treated with penicillin: Group A strep, Strep viridans, and/or Cornyebacterium diphtheriae?

Answer 29

They are all sensitive to penicillin.