Gram (+) Cocci Flashcards Preview

Microbiology Rapid Review > Gram (+) Cocci > Flashcards

Flashcards in Gram (+) Cocci Deck (28):
1

Catalase positive, coagulase positive, beta hemolytic, ferments mannitol, yellow colonies

Staphylococcus aureus

2

Catalase positive, coagulase negative, gamma hemolytic, novobiocin sensitive

Staphylococcus epidermidis

3

Catalase positive, coagulase negative, gamma hemolytic, novobiocin resistant

Staphylococcus saphrophyticus

4

Catalase negative, coagulase negative, beta hemolytic, bacitracin sensitive, PYR+

Streptococcus pyogenes (Group A)

5

Catalase negative, coagulase negative, beta hemolytic, bacitracin resistant, CAMP+

Streptococcus agalactiae (Group B)

6

Catalase negative, coagulase negative, alpha hemolytic, optochin sensitive

Streptococcus pneumoniae

7

Catalase negative, coagulase negative, alpha hemolytic, optochin resistant

Streptococcus viridans

8

Catalase negative, coagulase negative, alpha/beta/gamma hemolytic, PYR+, esculin agar

Enterococcus (Group D Streptococcus)

9

Catalase positive, gamma hemolytic, associated with endocarditis in IV drug users or catheter infections

Staphylococcus epidermidis

10

Catalase positive, gamma hemolytic, associated with UTIs in sexually active females

Staphylococcus saprophyticus

11

What are the virulence factors of S. aureus?

- TSST-1 toxin - superantigen that overactivates immune system
- Enterotoxin - fast acting and heat stabile
- Exfolatin - skin exfoliating
- Protein A binds Fc of IgG, inhibiting phagocytosis
- coagulase - keeps infection local
- cytolytic alpha toxin forms pores

12

Patient presents with fever, hypotension, sunburn like rash on palms and soles that progresses to multiorgan failure and death

Toxic shock syndrome - vignette will hopefully mention something about recent menses or packed wounds

13

What color is the sputum in S. aureus pneumonia?

Salmon colored

14

Most common cause of osteomyelitis in previously healthy patient?

S. aureus

15

What is the best way to differentiate between Staphylococcus and Streptococcus?

Catalase test. Gram stain is insufficient to tell the difference (even though Staph is clusters and Strep is chains) because the chains can group together to look like clusters.

16

Skin infection with honey crusted lesions

Impetigo - could be S. aureus or S. pyogenes (Group A). Differentiate with catalase test.

17

What is the most common cause of adult meningitis, otitis media/sinusitis in children, and community acquired pneumonia?

Streptococcus pneumoniae

18

What is the major virulence factor of S. pneumoniae? Name some VFs.

- major is polysaccharide capsule (test with Quellung or latex particle agglutination and asplenia predisposes to infection)
- IgA protease
- teichoic acid
- Pneumolysin O: a hemolysin/cytolysin that damages respiratory epithelium

19

Has an antiphagocytic M protein that differentiates strains - M12 is associated with acute glomerulonephritis

Streptococcus pyogenes (Group A)

20

These factors make Streptococcus pyogenes good at spreading

Streptokinase, Streptococcal DNAse, Hyaluronidase, Exotoxins A-C (phage coded superantigen and causes fever/rash)

21

Leading cause of neonatal meningitis

Streptococcus agalactiae (Group B)

22

Abrupt onset of sore throat, fever, malaise and headache followed by a blanchable "sandpaper" rash and strawberry tongue with nausea and vomiting

Pharyngitis then scarlet fever, caused by Streptococcus pyogenes (Group A)

23

Two sequelae of Group A Strep infections and their mechanisms

1) Rheumatic fever - Abs to heart tissue 2 weeks post pharyngitis, Type II HSN

2) Acute glomerulonephritis - M12, immune complexes on glomeruli with pulmonary edema, hypertension, smoky urine, Type III HSN

24

Antibodies to streptolysin O titer > 200

Rheumatic fever (Group A Strep)

25

Pathogenesis factors of Streptococcus agalactiae (Group B)

capsule, beta hemolysin, CAMP factor

26

Treatment of pregnant mother that tests positive for Group B Strep

prophylactic ampicillin, clindamycin, or erythromycin during delivery

27

Virulence factors of Viridans streptococci (S. mutans, S. sanguinis)

Dextran biofilm! Mediates adherence to tooth enamel or damaged heart valve, causing dental caries or infective endocarditis

28

Catheter-associated UTI with G+ cocci in chains, resistant to treatment even after vancomycin

VRE - Vancomycin resistant Enterococcus faecium/faecalis (terminal D-ala-D-ala replaced with D-ala-D-lac)