Chapter 2: Medically Relevant Bacteria (3)

Question 1

List some Viridans group Streptococcal species.

Answer 1

S. mutans; S. sanguinis; S. gallolyticus (bovis)

Question 2

Features of scarlet fever?

Answer 2

blanching, sandpaper rash, strawberry tongue

Question 3

Treatment options for Staphylococcus aureus?

Answer 3

Nafcillin/oxacillin for widespread penicillinase-producing strains

MRSA: vancomycin

VRSA (vancomycin resistant S. aureus) or VISA (vancomycin intermediate S. aureus) quinupristin/dalfopristin

Question 4

Transmission of Streptococcus pyogenes?

Answer 4

direct contact; respiratory droplets

Question 5

Pathogenesis/ Virulence factors for Strep pyogenes.

Answer 5

• Hyaluronic acid: is non-immunogenic
• M-protein: antiphagocytic, associated with acute glomerulonephritis, rheumatic fever
• Streptolysin O: immunogenic, hemolysin cytolysin
• Streptolysin S: not immunogenic, hemolysin/cytolysin

Spreading Factors

• Streptokinase: breaks down fibrin clot
• hyaluronidase: hydrolyzes the ground substance of the connective tissues
• Exotoxins A-C (pyrogenic or erythrogenic exotoxins)
  -phage-coded (i.e., the cells are lysogenized by a phage)
  -cause fever and rash of scarlet fever; superantigens

Question 6

Lab diagnosis for Streptococcus pyogenes?

Answer 6

• Rapid strep test (ELISA-based) misses approximately 25% of infections. Culture all negatives.
• Ab to streptolysin O (ASO) titer of >200 is significant for rheumatic fever
• Anti-DNAse B and antihyalurondiase titers for AGN

Question 7

Treatment for Streptococcus pyogenes.

Answer 7

beta lactam drugs, macrolides in the case of penicilin allergy

Question 8

Prevention of Streptococcus pyogenes?

Answer 8

possible prophylactic antibiotics for at least 5 years post-acute rheumatic fever; beta lactams and macrolides

Question 9

Transmission of GBS?

Answer 9

newborn infected during birth (increased risk of prolonged labor after rupture of membranes)

Question 10

Treatment for GBS?

Answer 10

ampicillin with an aminoglycoside or a cephalosporin

Question 11

Prevention of GBS?

Answer 11

• ampicillin or penicillin are the drugs of choice (to give to mother)
• clindamycin or erythromycin for penicillin allergies

Question 12

Transmission of Streptococcus pneumoniae?

Answer 12

respiratory droplets (not considered highly communicable; often colonize the nasopharynx without causing disease)

Question 13

Predisposing factors for Strep pneumoniae?

Answer 13

• antecedent influenza or measles infection
• COPD
• CHF (congestive heart failure)
• alcoholism
• asplenia predisposes to septicemia

Question 14

What is the major virulence factor of Streptococcus pneumoniae.

Answer 14

• polysacchardie capsule is the major virulence factor

Question 15

How is the pneumonia produced by Streptococcus pneumonia often desribed?

Answer 15

most common cause of typical penumonia presenting with lobar consolidation, blood-tinged, “rusty” sputum

Question 16

How would you diagnose someone with S. pneumonia?

Answer 16

• Gram stain and culture of CSF or sputum
• Quellung reaction: positive (swelling of the capsule with the addition of type-specific antiserum, no longer used but still tested!)
• latex particle agglutination: test for capsular antigen in CSF
• urinary antigen test

Question 17

Treatment for S. pneumoniae?

Answer 17

• beta lactams for bacterial pneumonia; ceftriaxone and cefotaxime for adult meningitis (add vancomycin if penicillin-resitant S. pneumoniae has been reported in community)
• amoxicillin for otitis media and sinusitis in children (erythromycin in cases of allergy)

Question 18

Prevention for S. pneumonia?

Answer 18

• ab to capsule (>80 capsular serotypes) provide type- specific immunity
• vaccine
  -pediatric (PCV, pneumococcal conjugate vaccine) 13 of the most common serotypes; conjugated to diphtheria toxoid; prevents invasive disease
  -adult (PPV, pneumococcal polysaccharide vaccine) 23 of most common capsular serotypes

Question 19

Describe transmission of Viridans Strep?

Answer 19

endogenous

Question 20

Pathogenesis of Viridans group strep.

Answer 20

dextran (biofilm) mediated adherence onto tooth enamel or damaged heart valve and to each to other (vegetation); growth in vegetation protects organism from immune system

Question 21

Strep gallolyticus is associated with what type of cancer?

Answer 21

colon cancer

Question 22

What is the best treatment option of Viridans group strep?

Answer 22

penicillin G with aminoglycosides for endocarditis

Question 23

Best prevention of Viridans group strep?

Answer 23

prophylactic antibiotics prior to dental work for individuals with damaged heart valve

Question 24

2 types of enterococcus species?

Answer 24

• Enterococcus faecalis
• Enterococcus faecium

Question 25

Transmission of Group D strep?

Answer 25

endogenously

Question 26

Best treatment plan for Group D strep?

Answer 26

all strains carry some drug resistance * Some vancomycin-resistant strains of Enterococcus faecium or E faecalis have not reliably effective treatment; or low-level resitance use ampiciliin, gentamicin, or streptomycin

Question 27

Prevention practices for Group D strep?

Answer 27

prophylactic use of penicillin and gentamicin for patients with damaged heart valves prior to intestinal or urinary tract manipulation

Question 28

Which gram positive rod orgamism are facultative intracellular?

Answer 28

Listeria annd mycobacterium

Question 29

Which Gram positive rods are acid fast?

Answer 29

mycobacterium and nocardia

Question 30

Which gram positive rod bacteria have branching rods?

Answer 30

actinomyces and nocardia

Question 31

Distinguishing features of Bacillus anthracis?

Answer 31

* large boxcar-like, gram positive, spore forming rod * capsule is polypeptide (poly-d-glutamate) * potential use in bioterrorism

Question 32

Resovoir for Bacillus anthracis?

Answer 32

animals, skins (animal hides), soils

Question 33

Transmission of bacillus anthracis?

Answer 33

contact with innfected animals or inhalation of spores (bioterrorism)

Question 34

Some virulence factors/pathogenesis of bacillus anthracis.

Answer 34

* capsule polypeptide, anti-phagocytic, immunogenic * anthrax toxin includes 3 protein components. - protective ag (B component) mediates entry of LF or EF into eukaryotic cells -Lethal factor kills cells -Edema factor is an adenylate cyclase (calmodulin-activated like pertussis adenylate cyclase)

Question 35

List the diseases that can be caused by bacillus anthracis.

Answer 35

* cutaneous anthrax * pulmonary (woolsorter's disease) * GI anthrax (rare)

Question 36

Describe cutaneous anthrax.

Answer 36

papule > papule with vesicles (malignant pustules) > central necrosis (eschar) with erythematous border often painful regional lymphadenopathy; fever in 50%

Question 37

Describe Woolsorter's disease.

Answer 37

life-threatening pneumonia; cough, fever, malaise, and ultimately facial edema, dyspnea, diaphoresis, cyanosis, and shock with mediastinal hemorrhagic lymphadenitis

Question 38

Describe GI anthrax.

Answer 38

edema and blockage of G tract can occur, vomiting and bloody diarrhea, high mortality

Question 39

Diagnosis of Bacillus anthracis.

Answer 39

* mediastinal widening on chest x-ray * gram stain and culture of blood, respiratory secretions * serology * PCRT

Question 40

Treatment for bacillus anthracis.

Answer 40

ciprofloxacin or doxycyline

Question 41

Prevention of Bacillus anthracis.

Answer 41

toxoid vaccine (AVA, acellular vaccine adsorbed) is given to high risk occupations (milliary); raxibacumab for prophylaxis

Question 42

Bacillus cereus reservoir?

Answer 42

found in nature