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Flashcards in Bacteria Deck (161)
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1

5 Morphologic characteristics of Staphylococcus aureus

Gram-positive cocci
Catalase+
Coagulase+
Beta-hemolytic
Mannitol fermenter (turns salt agar yellow)

2

Main virulence factor associated with Staph aureus — component of cell wall which binds Fc region of Abs and prevents complement activation thus preventing opsonization and phagocytosis

Protein A

3

What area of the body does Staph aureus tend to colonize

Nares

4

8-9 Clinical manifestations of Staph aureus

Post-viral bacterial pneumonia (patchy infiltrate on CXR)

Septic arthritis (MCC)

Large erythematous abscesses

Rapid onset bacterial endocarditis (IV drug use, often tricuspid valve)

Osteomyelitis in adults (MCC)

Scalded skin syndrome, TSS, food poisoning (meats, mayo, salad, cream-filled pastries), MRSA d/t altered cell wall

5

3 morphologic features of Staphylococcus epidermidis and saprophyticus

Gram+
Catalase+
Urease+

6

What morphologic feature differentiates staphylococcus aureus from Staph epidermidis and saprophyticus?

Staph aureus is coagulase+

Epidermidis and saprophyticus are coag-

7

What organism is a part of normal skin flora and tends to infect hardware, orthopedic joints, heart implants, catheters, etc.?

What virulence factor contributes to its ability to do this?

Staphylococcus epidermidis

Ability to form biofilms to stick to metal and plastic surfaces

8

What organism is associated with contamination of blood cultures

Staph epidermidis

9

What is the major clinical manifestation of staphylococcus saprophyticus?

UTI’s in sexually active females (2nd most common cause to E.coli)

“Honeymoon cystitis”

10

Morphologic features of streptococcus pyogenes (group A strep)

Gram+ cocci in chains
Microaerophilic
Hyaluronic acid capsule
Beta-hemolytic

11

5 Virulence factors associated with S. pyogenes

M-protein (anti-phagocytic, humoral response - Abs to heart)
Strep Toxin
Streptolysin O
Streptokinase
DNA-ase

12

Clinical manifestations of strep pyogenes infection (note which ones are toxin-mediated vs. M-protein mediated)

Pyogenic infections: Impetigo, strep throat, erysipelas, cellulitis

Toxin-mediated: Scarlet fever, TSLS, Necrotizing fasciitis

M protein-mediated: rheumatic fever = arthritis, endocarditis (mitral valve), nodules on extensor surfaces, erythema marginatum, sydenham’s chorea [JONES]

Post-streptococcal glomerulonephritis: facial edema, hematuria, HTN

13

How would you test for a group A strep infection?

ASO antibody titer

14

Symptoms of Scarlet fever

Strawberry tongue
Pharyngitis
Widespread rash that spares the face

15

Which superantigens mediate TSLS vs. Necrotizing fasciitis in strep pyogenes infections?

TSLS = SpeA, SpeC

Nec Fasc = SpeB

16

Post-streptococcal glomerulonephritis tends to occur after what type of strep pyogenes infection(s)?

Either pharyngitis OR superficial infection like impetigo

17

Rheumatic fever tends to occur after what type of strep pyogenes infection(s)?

Pharyngitis only (NOT impetigo!)

18

What organism tends to cause serious infections in newborns, thus pregnant mothers should be swabbed at ~35 weeks?

Streptococcus agalactiae (group B strep)

19

Morphologic features of strep agalactiae

Gram+ cocci in chains
Facultative anaerobe
Beta-hemolytic
Polysaccharide capsule
CAMP test + (increasing zone of hemolysis)
Hippurate test +

20

Clinical manifestations of streptococcus agalactiae

Neonatal meningitis (no nuchal rigidity!)
Strep throat
Pneumonia

21

Morphologic features of streptococcus pneumoniae

Gram + diplococci
Polysaccharide capsule
Alpha-hemolytic
Facultative anaerobe
Optochin-sensitive
Bile-soluble

22

Characteristic feature of otitis media caused by streptococcus pneumoniae

Bullous meringitis

23

Major virulence factors of strep pneumoniae

Polysaccharide capsule
IgA protease

24

Diagnosis of strep pneumoniae involves the ____ reaction, which turns blue in the presence of strep pneumo

Quelling

25

Clinical manifestations of streptococcus pneumoniae

MCC of MOPS:

Meningitis
Otitis media
Pneumonia - often lower lobes, PMN-rich rust-colored sputum
Sinusitis

26

Morphologic features of streptococcus viridans

Gram+ cocci in chains
Facultative anaerobe
Alpha-hemolytic
Optochin-resistant
Bile-resistant
No capsule!

27

Major virulence factor associated with streptococcus viridans

Extracellular dextrans —> adheres to platelets

28

Clinical manifestations of streptococcus viridans

Dental caries

Subacute bacterial endocarditis (only affects previously damaged heart valve — usually mitral valve)

29

Morphologic features of S. bovis

Gram+ cocci in chains
Facultative anaerobe
Usually gamma-hemolytic
Grows on bile

30

Clinical manifestations of S. bovis

Same as enterococcus: subacute bacterial endocarditis, UTI, biliary tract infection