Gram Stain + Blue
Morphology
Cocci
Catalase Test
+ Bubbles
BAP
Beta hemolysis (double zone)
Staphylococcus aureus
Confirm: MSA - Yellow
Gamma hemolysis
Staphylococcus epidermidis
Confirm: MSA - Pink
- No Bubbles
BAP
Gamma hemolysis
Enterococcus faecalis
Confirm: TSA Small white
colonies
Beta hemolysis (single zone)
Streptococcus pyogenes
Confirm: TSA - Tiny pinpoint white colonies
Bacilli
Bacillus subtilis
Confirm: BAP – Alpha hemolysis
BIO 260L – Microbiology Gram+ Dichotomous Key
SP 14 - Fairborn
Gram Stain - Red
Green pigmentation on
TSA (48h)
- Not green
Lactose Test
+ Yellow
Urease Test
+ Pink (delayed)
Klebsiella pneumoniae
Confirm: SIM: -Indole No red ring
- Yellow
Escherichia coli
Confirm: SIM:+Indole, red
ring
- Pink
SIM Test: Indole
+ Red ring
Proteus vulgaris
Confirm: SIM: Moderate Motility
- No red ring
Proteus mirabilis
Confirm: SIM: Highly Motile
+ Green
Pseudomonas aeruginosa
Confirm: Oxidase+ Blue
BIO 260L – Microbiology Gram- Dichotomous Key
SP 14
Gram Stain + Blue
Morphology
Cocci
Catalase Test
+ Bubbles
BAP
Beta hemeolysis (double zone)
Staphylococcus aureus
Confirm: MSA - Yellow
Gamma hemeolysis
Staphylococcus epidermidis
Confirm: MSA - Pink
- No Bubbles
BAP
Alpha hemolysis
Streptococcus pneumoniae
Confirm: TSA Small white
colonies
Beta hemolysis (single zone)
Streptococcus pyogenes
Confirm: TSA - Tiny pinpoint
colonies
Bacilli
Bacillus subtilis
Confirm: BAP – Alpha
hemeolysis
BIO 260L – Microbiology Gram+ Dichotomous Key
WI 13
Gram + (Blue- purple) Morphology
Coccus Rods
Staphylococcus aureus Staphylococcus epidermidis
Enterococcu faecalis Streptococcus pyogens Micrococcus leuteus
Bacillus subtilis
Catalase (H2O2) + Bubbles - Bubbles
S. aureus S. epidermidis Micrococcus
Enterococcus S. pyognes
BAP : Alpha hemolysis
TSA-Pigment
Off white Yellow/Orange
S. aureus S. epidermidis
Micrococcus
Confirm: BAP Gama hemolytic
MSA Pink Yellow
S. aureus
Confirm: Double zone of
Beta hemolysis
S. epidermidis
Alpha/Beta hemolysis
BAP Alpha
hemolytic Beta
hemolytic
Enterococcus S. pyogenes
Confirm: TSA Tiny Pinpoint Colonies
Confirm: TSA Small Off White
Colonies
Gram – (Pink – Red)
Lactose + Yellow - Pink
Pseudomonas aeurginosa Serratia marcescens
Proteus vulgasris Proteus mirabilis
SIM - Sulfur +
Black ppt
- No Black ppt
Proteus vulgaris Proteus mirabilis
SIM -Indole + red ring - No red ring Proteus vulgaris
Confirm: SIM
Slightly motile
Proteus mirabilis
Confirm: SIM
Highly motile
Pseudomonas Serrita
Oxidase + -
Pseudomonas Serratia
Confirm: Green on TSA
48hrs
Confirm: Pink on TSA
25 C
E. coli Confirm: citrate
(blue)
Gram – (Pink Red) Oxidase
Blue + -
White
Pseudomonas Confirm: Green on
TSA 48hrs
E. coli Klebsiella
Serrtia Proteus vulgaris Proteus mirablils
TSA pigmentation
White - Yellow
+
E.coli Klebisella
Serrita
Proteus vulgaris Proteus mirabilis
Lactose + Yellow
- Pink
E. Coli Confirm: Citrate
Green
Serratia Confirm: TSA 25C
SIM - Motility Motile Highly Motile
Proteus vulgaris Confirm: Indole
+ red ring
Proteus mirabilis Confirm: Indole – No red ring
Klebisella Confirm:
Citrate + Blue
GRAM STAIN
Gram Negative
Rod
Oxidase TEST
—
Lactose ferm on MAC
—
H₂S prod in SIM
+
P. vulgaris
+
E. coli
+
P. aeruginosa
Cocci
Gram Positive
Rod Cocci
Catalase TEST
—
Hemolysis TEST
Alpha
Optochin InhibiDon
S. pneumoniae
Beta
S. pyogenes
+
Mannitol plate / acid
—
S. epidermidis
+
S. aureus
Gram Stain +blue -red
S. aureus S. epidemidis
E. faecalis S. pyogens
E. coli Salmonella P. mirabilis
Pseudomonas
Catalase Mackonkey’s + bubbles - bubbles
S. aureus S. epidermidis
E. faecalis S. pyogens
Red Colorless
E. coli Pseudomonas Salmonella
P. mirabilis
MSA Pink Yellow
Staphyloccous epidermidis
Confirm: Coagulase –
BAP: Gamma-hemolytic
Staphyloccous aureus
Confirm: Coagulase + BAP: Double zone of Beta-
hemolysis
Bacitracin Resistant Inhibited
Enteroccous faecalis
Confirm: BAP: Gamma-
hemolysis
Streptococcous pyogens
Confirm: BAP: Beta-hemolysis
TSI A A
Gas +
K K Gas -
Escherichia coli
Confirm: TSA: white
pigmentation
Pseudomonas aeruginosa
Confirm: TSA: green
pigmentation after 48hrs
TSI K A Bppt
K Bppt
Salmonella enteritidis Confirm:
TSA: white pigmentation
Proteus mirabilis
Confirm: TSA: yellow
pigmentation
BIO 260L – Microbiology Lab 8 and 9 Dichotomous Key for Lab Exercises 45, 46, 48 Bacterial Diseases of the Skin, Respiratory, and GI Systems