Bacterial Infections of the Mouth and Pharynx Flashcards
According to the lecture, what microbe is the “major cause” of pharyngitis?
Group A streptococci / Streptococcus pyogenes
Describe the morphology of Streptococci.
Gram(+) cocci that grow in chains
Streptococci and other beta-hemolytic bacteria can be classified by Lancefield group. What feature of the bacteria does this classification system use?
Carbohydrate antigens in the cell wall
Name 3 virulence factors of Group A Strep.
pili (encoded by pathogenicity islands), capsule, and toxins.
Note: hemolysins are not virulence factors!
Describe the function of the Group A Strep pili and capsule.
pili: attachment to mucous membranes
capsule: resist phagocytosis
Describe the effects of the following 3 toxins: streptokinase, streptodornase, and hyaluronidase. What bacteria makes these toxins?
streptokinase - tissue lysis
streptodornase - DNA lysis
hyaluronidase - connective tissue digestion
made by Group A Strep
Describe the reservoir and transmission of Group A Streptococci / Streptococcus pyogenes.
Reservoir: human pharynx and skin
Transmission: direct contact
What toxin made by Group A Strep causes the skin rash and strawberry tongue associated with scarlet fever?
erythrogenic toxin
What toxin made by Group A Strep is a superantigen that can cause fever and toxic shock?
pyrogenic toxin
Streptococcal pharyngitis can spread to the tonsils, middle ear, and what 3 less common sites?
floor of mouth, mastoids, and meninges
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.
Rheumatic fever
How would you identify a Group A Strep bacteria in terms of Gram staining, catalase, hemolysis, and antibiotics?
Gram(+), catalase(-), β-hemolysis, bacitracin sensitive
Preventive measures for Strep A include which of the following: vaccines, prophylactic antibiotics, and/or treatment of carriers?
Prophylactic antibiotics (for patients who have had post strep diseases) and treatment of carriers. There are no vaccinations.
What 2 antibiotics are routinely used to treat Streptococcus infections? Is drug resistance a problem?
Penicillin G or erythromycin.
Drug resistance is not a serious problem but testing sensitivity is helpful.
How would you identify a Strep viridans bacteria in terms of Gram staining, catalase, hemolysis, and antibiotics?
Gram(+), catalase(-), α-hemolysis, optochin resistant (also insoluble in bile)
Describe the reservoir and transmission of Streptococcus viridans.
Reservoir: normal flora of mouth and female genital tract
Transmission: opportunistic or congenital infection
Name the major virulence factor of Streptococcus viridans and describe 2 ways that it causes dental caries.
sugar-metabolizing enzymes; make high MW sugars (plaque formation) and make acids (decalcification)
Besides dental caries, name 4 problems that could be caused by Strep viridans infection.
Abscesses, cellulitis, bacteremia following dental treatments, and endocarditis following bacteremia
If a patient develops an abscess from Strep viridans, what 2 antibiotics can be used to treat it?
Penicillin or erythromycin
What bacteria appear as Gram(+) rods with clubbed ends and internal beads?
Corynebacterium diphtheriae
How can Strep viridans dental problems be treated and prevented?
Treatment: extraction of caries, possibly antibiotics (penicillin and erythromycin)
Prevention: brush and floss teeth
Corynebacterium diptheria can carry up to 3 copies of what virulence factor, and what type of genetic information encodes this factor?
Diphtheria toxin, encoded by the tox gene on a bacteriophage.
What is the reservoir and transmission method for Corynebacterium diphtheriae?
Reservoir: human skin and mucous membranes
Transmission: respiratory droplets or direct contact
How is Corynebacterium diphtheriae treated?
Immediate IV administration of antitoxin, penicillin or erythromycin to help resolution
How would you culture Corynebacterium diphtheriae and check its virulence?
Grow on tellurite plates; confirm toxin with antibody tests or with PCR for tox gene
Which of the following can be prevented by vaccination: Strep viridans, Strep pyogenes and/or Corneybacterium diphtheriae?
Only C. diphtheriae - DTaP vaccination includes the diphtheria toxoid
Name up to 5 effects of the diphtheria toxin
local tissue necrosis, cardiac necrosis, pseudomembrane formation, systemic muscle paralysis, death
What are “quinsy” and “Ludwig’s angina”?
quinsy = peritonsillar abscess
Ludwig’s angina = infection of the floor of the mouth
Which of the following can be treated with penicillin: Group A strep, Strep viridans, and/or Cornyebacterium diphtheriae?
They are all sensitive to penicillin.
