Microbiology - Shillitoe - Bacterial Infections of the Mouth and Pharynx Flashcards Preview

MS 2 - Unit 2 > Microbiology - Shillitoe - Bacterial Infections of the Mouth and Pharynx > Flashcards

Flashcards in Microbiology - Shillitoe - Bacterial Infections of the Mouth and Pharynx Deck (49):
1

Group A Streptococcus pyogenes is Bacitracin sensitive or resistant?

Sensitive
Gram +
Catalase (-)
Cocci
Beta hemolytic
react with Lancefield group A antiserum

2

What are the virulence factors for Strep A?

Pili
Streptokinase - tissue lysis
Streptodornase - digests DNA
Hyaluronidase - digests connective tissue
Pyrogenic toxin - fever, super antigen, toxic shock
Erythrogenic toxin - skin rash

**middle ear infection, throat, mastoids**

3

What are the antibiotics for Strep A?

Cephalosporins
Penicillin
Erythromycin
Amoxicillin

Drug resistance not an issue

Patients with hx of rheumatic fever need special attention.

4

What is Ludwig's angina?

Swelling of maxilla
Strep A

5

Mastoiditis is a complication of:

Strep A

6

What are the characteristics of scarlet fever?

Strawberry tongue
skin rash
Strep A

7

Rheumatic fever is caused by:

Strep A
infection --> recovery --> fever, endocarditis, arthritis

8

Viridans Streptococci is part of what family?

Gram +
Catalase (-)
Alpha hemolytic
Optochin resistant

Includes: Strep mutans, Strep sanguis

Cause dental carries

9

What are the virulence factors for viridans Strep?

Sugar-metabolizing enzymes
acid --> decalcification
turns low MW sugar to high MW sugar causing plaque

can cause bacteremia associated with dental procedures
--> bacterial endocarditis

10

What are some signs of bacterial endocarditis?

Splinter hemorrhages
Small hemorrhages in conjuctiva
metastatic abscesses

prolonged penicillin is treatment but significant morbidity bc of heart damage

11

What kind of bacteria is Corynebacterium diphtheriae?

Gram +
club-shaped rods
strains may be toxigenic or not

Bacteria inhabit skin & mucus membranes, carriage may be asymptomatic

12

The toxin in corynebacterium causes:

local and cardiac necrosis

“Pseudomembrane” – a necrotic coagulum of bacteria, epithelial cells, fibrin, leukocytes, erythrocytes forming a gray-brown “pseudomembrane” covering oro-pharynx.

13

How is diptheria diagnosed?

Swab nose & throat, beneath pseudomembrane

Culture requires tellurite plates – alert lab

PCR confirmation of tox gene

14

What is the treatment for diptheria?

Penicillin and erythromycin as needed
Equine antitoxin

**prevent with vaccine**

15

What are main players in the differential of a sore throat/pharyngitis?

VIRAL
EBV
Adenoviruses
HSV-1
Coxackie virus

FUNGAL
Candida albicans

BACTERIAL
Strep pyogenes
Corynecaterium diphtheriae
Neisseria gonorrhoeae
Hemophilus influenzae

16

Test for Strep A

rapid antigen assay
has some issues with false negatives

17

What is scarlet fever?

Due to endotoxin encoded by bacteriophage that carries the gene for the erythrogenic toxin
Complication of Strep Pyogenes

18

T/F: Meningitis can be a complication of Strep Pyogenes.

True

19

When does rheumatic fever occur?

Only some strains of Strep A cause it ie M5, M3
Happens 3 weeks out from an infection
Fatality 2-5%
IgM antistreptolysin O ab
No bacteremia

20

Treat dental abscesses with:

penicillin
erythromycin
cephalosporins
dental extraction most effective

21

T/F: Antibiotics do not penetrate vegetations in bacterial endocarditis.

True

22

Causative agents of bacterial endocarditis commonly:

viridans strep - dental
staph aureus - IV drug users
HACEK gram (-)

23

What are the bacteria responsible for gingivitis?

Mix of anaerobes

24

Release of toxin in diphtheria can cause what?

Muscle paralysis (myocarditis)
death

25

Why is examination of smears not useful in diagnosing diphtheria?

There are corynebacteria that are diphtheroid w/o the toxin present

26

diagnostic criteria of group A streptococci aka S. pyrogenes?

beta-hemolytic,
bacitracin-sensitive and react with Lancefield Group-A antiserum.

27

What are the toxins of group A streptococci aka S. pyrogenes?

Streptokinase - Tissue lysis
Streptodornase - Digests DNA
Hyaluronidase - Digests connective tissue
Pyrogenic toxin - Fever, Super antigen, Toxic shock
Erythrogenic toxin - Skin rash

28

If hemolysins of group A streptococci aka Strep. pyrogenes are not virulance factors, what are they used for?

useful in identification of streptococci since
they produce hemolysis on blood agar plates

Streptolysin O is highly antigenic,
inducing short-lived IgM antibody which can be diagnostically useful

29

What are complications of strepticoccal pharyngitis?

Tonsillitis - peritonsillar abscess - Ludwig's angina
Middle ear infections (also caused by S. pneumoniae or H. influenzae)
Mastoiditis
Meningitis (also caused by N. meningitides and S. pneumoniae)
Scarlet fever - Due to exotoxin encoded by bacteriophage that carries gene for the erythrogenic toxin.
Skin rash and tongue rash (strawberry tongue).
Rheumatic fever

30

Should step pharangitis be treated with antibiotics?

Is bacterial resistance a problem for antibiotic treatment of strep pharyngitis?

Not essential as infection is self-limiting. Antibiotics can shorten symptoms by 16 hours and reduce complications.

No. Systemic Penicillin G, amoxicillin, erythromycin or cephalosporins are suitable

31

What is Rheumatic fever? What are the symptoms? Who does it affect? Can it recur? What remains as a life long consequence?

Post-streptococcal autoimmune condition with fever, polyarthritis, and inflammation of heart leading to permanent deformations.

arises around 3 weeks after
resolution of a sore throat that was caused by some strains of Group-A streptococci

affects children aged 6– 15

Recurrences are common.

life long risk of endocarditis - prophylactic antibiotics needed for dental procedures etc.

32

How is the diagnosis made for Rheumatic fever? Do any variants of strep predispose?

Clinical features plus presence of IgM anti-streptolysin O antibody. Heart lesions
and inflamed joints are sterile. There is no bacteremia.

Certain M-protein types of Strep (eg M5, M3) are more likely to be associated with Rheumatic Fever.

33

What is the treatment for Rheumatic fever?

Anti-inflammatory drugs (aspirin / steroids). No antibacterial therapy is indicated.
Later, replacement of heart valves may be necessary.

34

What organism causes dental caries? What distinguishes these bacteria from others?

Streptococcus viridans

Alpha hemolytic. Optochin resistant.

35

How do Strep. viridans cause dental caries?

Organisms produce high molecular weight carbohydrates that form biofilm on tooth surfaces. Organisms break down sugars to make acid that demineralizes enamel and dentin.

36

How do you diagnose dental caries?

Six-monthly dental examinations show early demineralization. Lab testing is not
informative since the bacteria are part of the normal flora of the mouth of 100% of people.

37

What are the virulance factors for S Viridens

Extracellular polysaccharides. Acids.

38

What are possible complications of dendal caries?

Pulpitis, abscesses and cellulitis.
Bacteremia and Endocarditis may follow dental treatment of susceptible patients.

39

What is most common bacterial cause of post-rhumatic endocarditis?

What about post IV drug use?

Viridans streptococci

Staph aureus

40

What is diphtheria?

How is it transmitted?

How is it treated?

Infection of the pharyngeal mucous membrane causes necrosis and “membrane” with
respiratory obstruction. Release of toxin causes systemic muscle paralysis including
myocarditis and death in 10-20% of cases. Mostly a childhood condition.

Air born droplets

Antitoxin, given as soon as possible. Penicillin or erythromycin helps resolution.

41

What is the virulance factor in diphtheria?

Diphtheria toxin, encoded by bacteriophage.

42

How is diptheria diagnosed?

Is examination of smears useful?

Growth of Corynebacterium diphtheria on tellurite plates. Appearance of Grampositive
rods with clubbed end and internal beads. Lab cultures are confirmed to produce toxin
by antibody tests, or to have the toxin gene by PCR

No, because of the existence of non-pathogenic Corynebacteria
(diphtheroids)

43

Can Diphtheria be prevented?

Diphtheria vaccine. DTaP includes diphtheria toxoid. In New York State,
diphtheria vaccine is required for all school children.

Diphtheria is now rare in the western
world.

44

1. Post-streptococcal conditions, such as Rheumatic fever, are associated with variants in which aspect
of the streptococcus?
A. The M protein
B. The cell wall acid
C. Host bacteriophages
D. The capsule

A

45

2. What is the value of penicillin in the management of Rheumatic fever?
A. Can reduce the duration of symptoms
B. Can prevent damage to heart valves
C. Can prevent a recurrent attack in a patient with a history of the condition
D. Is of no value

C

46

3. In which of the following conditions is the responsible coccus likely to be found in the blood?
A. Streptococcal pharyngitis
B. Streptococcal tonsillitis
C. Bacterial endocarditis
D. Rheumatic fever

C

47

4. The use of the blood test for anti-streptolysin antibodies may assist the diagnosis of which condition?
A. Streptococcal pharyngitis
B. Pneumococcal pneumonia
C. Bacterial endocarditis
D. Rheumatic fever
E. All of the above

D

48

5. Hemolytic anemia in a patient is a sign of infection by streptococci that are:
A. Alpha hemolytic
B. Beta hemolytic
C. Gamma hemolytic
D None of the above

D

49

6. Post-streptococcal conditions, such as Rheumatic fever, are associated with variants in which aspect
of the streptococcus?
A. The M protein
B. The cell wall acid
C. Host bacteriophages
D. The capsule

A