Usmle Microbiology: Gram Positive Cocci

Front 1

Staphylococcus Species

Back 1

1. S. aureus 2. S. epidermidis 3. S. saprophytics

Front 2

Shared Staphylococcal Properties

Back 2

1. Gram-positive cocci in grape-like cluster 2. Catalase positive 3. Grow in 7.5% salt

Front 3

S. aureus Characteristics

Back 3

1. Large beta-hemolytic mucoid colonies 2. Coagulase positive

Front 4

S. aureus Virulence Factors

Back 4

1. Surface Components 2. Enzymes 3. Toxins

Front 5

S. aureus Virulence Factors: Surface Components

Back 5

1. Capsule 2. Protein A 3. Lipotechoic and techoic acids

Front 6

S. aureus Virulence Factors: Enzymes

Back 6

1. Catalase 2. Coagulase 3. Degradative enzymes 4. Penicillinase (Beta-lactamase)

Front 7

S. aureus Virulence Factors: Toxins

Back 7

1. Leukocidins 2. Enterotoxins (A-E) 3. Exfoliateive toxins (A,B) 4. Toxic Shock Syndrome Superantigen (TSST-1)

Front 8

Catalase

Back 8

Reduces phagocytic killing by converting H2O2 to H2O

Front 9

Coagulase

Back 9

Helps encase infection by forming fibrin layer around abscess

Front 10

Enterotoxins (A-E)

Back 10

1. Act as superantigens 2. Responsible for gastrointestinal food poisoning

Front 11

Exfoliative Toxins (A,B)

Back 11

1. Cause splitting of cell junctions (desmosomes) in epidermis 2. Responsible for scalded skin syndrome

Front 12

TSST-1

Back 12

1. Acts as superantigen 2. Promotes massive cytokine release 3. Causes Toxic Shock Syndrome (TSS)

Front 13

Diseases Caused by S. aureus

Back 13

1. Toxin-mediated diseases 2. Suppurative Infections

Front 14

Diseases Caused by S. aureus: Toxin Mediated

Back 14

1. Food poisoning 2. Toxic Shock Syndrome (TSS) 3. Scalded Skin Syndrome

Front 15

Diseases Caused by S. aureus: Toxin Mediated-Food Poisoning

Back 15

1. Due to preformed enterotoxin 2. Quick acting (staph specific)

Front 16

Diseases Caused by S. aureus: Toxin Mediated-TSS

Back 16

1. TSST-1 (superantigen) 2. Associated with tampons 3. Multisystem organ involvement 4. Rash 5. Fever and hypotension

Front 17

Diseases Caused by S. aureus: Scalded Skin Syndrome

Back 17

1. Exfoliative toxins (A, B) 2. Young children 3. Blister-like lesions all over body 4. Large areas of desquamated epithelium, but no scarring

Front 18

Coagulase-Negative Staphylococcal Species

Back 18

1. S. epidermidis 2. S. saprophyticus

Front 19

S. epidermidis Clinical Manifestation

Back 19

1. Adheres to artificial heart valves, vascular catheters, shunts, and prosthetic joints. 2. Colonizes implant area

Front 20

S. saprophyticus Clinical Manifestation

Back 20

Common urinary tract infection (UTI) in sexually active women - dysuria, pyuria and bacteruria

Front 21

Streptococcal Pathogenic Species

Back 21

1. S. pyogenes 2. S. agalactiae 3. Viridans group 4. S. pneumoniae

Front 22

Shared Streptococcal Properties

Back 22

1. Gram-positive spherical or football-shaped cocci in pairs or chains 2. Catalase negative

Front 23

Alpha Hemolysis

Back 23

1. Incomplete hemolysis (greenish zone around colony) 2. S. pneumoniae and Viridans streptococci

Front 24

Beta Hemolysis

Back 24

1. Complete hemolysis (clear zone around colony) 2. S. pyogenes and S. agalactiae

Front 25

Gamma Hemolysis

Back 25

1. No hemolysis 2. Enterococcus spp. (some)

Front 26

S. pneumonia vs. Viridans: Distinguishing Property

Back 26

1. S. pneumonia: optochin sensitive 2. Viridans: optochin resistant

Front 27

S. pyogenes vs. S. agalactiae: Distinguishing Property

Back 27

1. S. pyogenes: Bacitracin sensitive 2. S. agalactiae: Bacitracin resistant

Front 28

Group A Streptococcal spp.

Back 28

S. pyogenes. 1. Beta-hemolytic 2. Sensitive to bacitracin (A disk)

Front 29

Group A Streptococci: Virulence Factors

Back 29

1. Surface Components 2. Enzymes 3. Toxins

Front 30

Group A Streptococci: Virulence Factors-Enzymes

Back 30

1. Hyaluronidase 2. Streptokinase 3. Streptolysin O and S

Front 31

Streptokinase

Back 31

Promotes bacterial spread into tissue by breakind down blood clots

Front 32

Streptolysin O & S

Back 32

Lyse blood cells and platelets; stimulates release of lysosomal enzymes

Front 33

Group A Streptococci: Virulence Factors-Toxins

Back 33

Pyrogenic/erythrogenic exotoxins (some act as superantigens)

Front 34

Group A Streptococci: Diseases

Back 34

1. Localized suppurative 2. Toxin-mediated 3. Nonsuppurative autoimmune sequelae

Front 35

Group A Streptococci: Diseases-Localized Suppurative

Back 35

1. Erysipelas 2. Impetigo 3. Pharyngitis (Strep throat) 4. Scarlet Fever 5. Necrotizing fasciitis

Front 36

Group A Streptococci: Diseases-Toxin Mediated

Back 36

1. Streptococcal TSS 2. Scarlet fever

Front 37

Streptococcal TSS

Back 37

1. Cellulitis 2. Shock 3. Multisystem organ failure 4. Generalized skin flushing 5. (Adult male)

Front 38

Scarlet Fever

Back 38

1. Child 2. Strawberry tongue 3. Diffuse sandpaper-like erythematous rash over body within 24 to 48 hours after pharyngitis onset 4. Rash fades in 5 to 7 days with desquamation

Front 39

Group A Streptococci: Diseases-Autoimmune Sequelae

Back 39

1. Acute glomerulonephritis 2. Rheumatic Fever

Front 40

Acute Glomerulonephritis

Back 40

1. Child or teenager 2. Hematuria 3. Red blood cell casts 4. Proteinuria 5. Hypertension 6. Periorbital edema 7. History of recently treated skin infection

Front 41

Rheumatic Fever

Back 41

Cross-reaction of antibodies, with antigens against the heart -> pancarditis

Front 42

Group B Streptococcal Species

Back 42

S. agalactiae

Front 43

Group B Streptococci: Identification

Back 43

1. Beta-hemolytic 2. Resistant to bacitracin 3. Positive CAMP test

Front 44

Group B Streptococci: Diseases

Back 44

Neonatal meningitis

Front 45

Viridans Streptococcal: Habitat

Back 45

Major part of normal flora of mouth and teeth

Front 46

Viridans Streptococcal: Identification

Back 46

1. Alpha hemolytic 2. Resistant to Optochin

Front 47

Viridans Streptococcal: Diseases

Back 47

1. Streptococcal endocarditis 2. Dental caries

Front 48

Streptococcus Pneumoniae (Pneumococcus): Identification

Back 48

1. Alpha hemolytic 2. Sensitive to Optochin (P disk)

Front 49

Streptococcus Pneumoniae (Pneumococcus): Pathogenesis

Back 49

1. Aspiration of nasopharyngeal secretions into lower airways leads to rapid growth of pneumococci in alveolar spaces 2. Promoted by reduced clearance of airways due to disruption of ciliated epithelium in upper respiratory tract by viral infections or smoking

Front 50

Streptococcus Pneumoniae (Pneumococcus): Diseases

Back 50

Meningitis
Otitis media
Pneumonia
Sinusitis

Front 51

Enterococcal Species

Back 51

1. E. faecalis 2. E. faecium

Front 52

Enterococcus: Identification

Back 52

1. Gram-positive cocci in twisted chains

Front 53

Enterococcus: Virulence Factors

Back 53

Inherently resistant to many antibiotics