Practicals

Question 1

Gram Positive Organisms

White, Hemolytic

Answer 1

Staphylococcus aureus

Key Tests for Presumptive Identification
1. Catalase positive
2. Coagulase or Staphaurex postive

Gram positive cocci in clusters

Very common pathogen seen in all sites, especially wound and skin infections.

Question 2

Gram Positive Organisms

White, Nonhemolytic

Answer 2

Staphylococcus epidermidis
Key Tests for Minimal Morhological Identification (MMI)
1. Catalase positive
2. Coagulase/Staphaurex negative
MMI= Coagulase negative staphylococcus

Gram positive cocci in clusters

Definitive ID achieved by MALDI-TOF
Associate w/ skin, common blood culture contaminant and foriegn device infections

Question 3

Gram Positive Organisms

Bright White, Nonheme

Answer 3

Staphylococcus saprophyticus
Key Tests for Presumptive Identification
1. Catalase positive
2. Coagulase or Staphaurex postive
3. Novobiocin resistant

Gram positive cocci in clusters

Associate w/ UTIs in young females

Question 4

Gram Positive Organisms

Yellow

Answer 4

Micrococcus species
Key Tests for Presumptive Identification
1. Catalase positive
2. Coagulase or Staphaurex negative
3. Bacitracin susceptible

Gram positive cocci in tetrads

Associate with skin & environmental contamination

Question 5

Gram positive organisms

Alpha

Answer 5

Enterococcus faecium
Key Tests for Minimal Morhological Identification (MMI)
1. Catalase negative
2. PYR positive
MMI= Enterococcus species

Gram positive cocci in pairs & short chains

Definitive ID by MALDI-TOF or additional biochemicals
Associate E. faecium w/ VRE (vanA or vanB gene)

Question 6

Gram Positive Organisms

Gamma

Answer 6

Enterococcus faecalis
Key Tests for Minimal Morhological Identification (MMI)
1. Catalase negative
2. PYR positive
MMI= Enterococcus species

Gram positive cocci in pairs & short chains

Definitive ID by MALDI-TOF or additional biochemicals
Associate E. faecalis w/ VSE

Question 7

Gram positive organisms

2 variations

Alpha, dimpled (on left) Alpha, mucoid (on right)

Answer 7

Streptococcus pneumoniae
Key Tests for Presumptive Identification
1. Catalase negative
2. Optochin disk susceptible
3. Bile solubility positive

Gram positive cocci in pairs (lancet shaped)

Most frequently associated w/ respiratory infections

Question 8

Gamma

Answer 8

Streptococcus bovis group (Group D Streptococci)
Key Tests for Presumptive Identification
1. Catalase negative
2. PYR negative
3. Bile esculin positive

Gram positive cocci in pairs & chains

Colonizes the GI tract. Associate w/ bacteremia & endocarditis

Question 9

Pinpoint alpha or pinpoint beta

Answer 9

S. anginosus group
Key Tests for Presumptive Identification
1. Catalase negative
2. VP positive
3. Arginine positive
4. Butterscotch smell

GPCPCH

Associate w/ deep tissue abscess

Question 10

Beta

Answer 10

Streptococcus pyogenes
Key Tests for Presumptive Identification
1. Catalase negative
2. Bacitracin disk susceptible
3. PYR positive

GPCPCH

Associate w/ strep throat & soft tissue infections (including necrotizing fascitiis)