Micro Lab

Front 1

Staphylococcus aureus

Back 1

o Media: BAP
o large (2-3 mm in diameter), opaque, creamy colonies
o Narrow zone of β-hemolysis.
O Gram-positive cocci in clusters.
o Catalase (positive), Coagulase (positive), Mannitol / Salt (positive)

Front 2

Staphylococcus epidermidis

Back 2

o Media: BAP
o large (2-3 mm in diameter), opaque, white colonies
o No hemolysis
o Gram-positive cocci in clusters.
o Catalase (positive), Coagulase (negative), Sensitive to the drug Novobiocin

Front 3

Streptococcus pyogenes (GAS)

Back 3

o Media: BAP
o very small(.5-1mm), grayish, translucent colonies
o large zone of β-hemolysis around colony
o Gram-positive cocci in chains.
o Catalase (negative), Sensitive to the drug Bacitracin

Front 4

Streptococcus agalactiae (GBS)

Back 4

o Media: BAP
o Medium size (~1.5 mm in diameter), grayish, translucent colonies
o Narrow zone of β-hemolysis around colony, often times seen under colony after scraping it away
o Gram-positive cocci in short chains.
o Catalase test (negative), CAMP test (positive)
*Resembles Listeria monocytogenes.

Front 5

Streptococcus pneumoniae:

Back 5

o Media: BAP
o Small(~1mm ), flat, mucoid (encapsulated) colonies
o Prominent zone of α-hemolysis around colony
o Gram-positive lancet-shaped diplococci
o Catalase test (negative), Bile solubility test (positive),
Sensitive to the drug Optochin

Front 6

Enterococcus faecalis:

Back 6

Media: BAP
o Small to medium size (1-1.5 mm in diameter) grayish-white colonies
o No hemolysis
o Gram-positive cocci in short chain
o Catalase (negative), Esculin (positive), NaCl test (positive)

Front 7

Haemophilus influenzae

Back 7

o Media: chocolate (requires X (hemin) and H (NAD) factors for optimal growth)
o Medium (~2 mm in diameter), grayish mucoid colonies(dew-drop appearance) with a distinctive odor (musty basement)
o No hemolysis
o Gram-negative, pleomorphic (different shapes) coccobacilli
o Oxidase (positive), Satellite test (Positive)
The "Satellite" phenomenon: H. influenzae requires X (hemin) and V (NAD=nicotinamide-adenine dinucleotide) factors for growth. Both factors are available along the streak of S. aureus. S. aureus synthesizes NAD and secretes it into the medium. Hemin is released from ruptured red blood as a result of β-hemolysis caused by S. aureus.

Front 8

Neisseria meningitidis

Back 8

o Media: BAP & Choc
o Colony Morphology:
Small (~1 mm in diameter), grayish, glistening , mucoid colonies
o No hemolysis
o Gram-negative, kidney-bean shaped diplococci.
o Catalase (positive), Oxidase (positive), glucose (positive), maltose (positive),

Front 9

Neisseria gonorrhoeae

Back 9

o Media: chocolate
o Small (~1 mm in diameter), grayish, glistening , mucoid colonies
o No hemolysis
o Gram-negative, kidney-bean shaped diplococci.
o Catalase (positive), Oxidase (positive), glucose (positive), maltose (negative)

Front 10

Corynebacterium diphtheriae

Back 10

o Media: BAP
o Small (~1 mm in diameter), white colonies with distinctive garlic odor
o No Hemolysis
o Gram-positive, straight rods (Chinese characters or X-Y arrangements)
Catalase (positive)

Front 11

Listeria monocytogenes.

Back 11

o Media: BAP
o Small (~1 mm in diameter), white-grayish colonies
o Small zone of β-hemolysis
o Gram-positive, pleomorphic (resembles Corynebacterium & Streptococci)
-at 25 C (RT) G+ rods, motile
-at 37 C (body T) G+ cocci, nonmotile
o Catalase (positive), Motility test at RT (positive), CAMP test (positive)
*Resembles GBS

Front 12

Escherichia coli (on MacConkey agar plate).

Back 12

Most E. coli isolates are lactose positive (break down lactose to yield acid) and therefore, produce pink colonies on MacConkey, surrounded by a zone of bile precipitation due to nascent acid. All E.coli are:
indole (positive)
urease (negative)

Front 13

E. coli O157:H7 (EHEC): (on sorbitol-MacConkey agar plate).

Back 13

On regular MacConkey agar, these bacteria are indistinguishable from other (lactose-positive) E. coli organisms.
Sorbitol fermentation: E. coli O157:H7 is incapable of utilizing sorbitol (sorbitol-negative), and therefore, produces colorless colonies on sorbitol agar, whereas, other E. coli bacteria are sorbitol-positive and appear pink on the sorbitol plate.

Front 14

GRAM-NEGATIVE RODS (ENTEROBACTERIACEAE)

Back 14

By definition, Enterobacteriaceae are fermenters (i.e., utilize glucose even in
the absence of O2) and reduce NO3 (nitrate) to NO2 (nitrite).

Front 15

Shigella spp.

Back 15

produce lactose negative colonies on MacConkey agar.
The organism is non-motile and ferments glucose without gas production.
indole (negative)
urease (negative)

Front 16

Salmonella spp.

Back 16

produce lactose negative colonies on MacConkey agar.
The organism ferments glucose with gas production and produces H2S on TSI (black).
indole (negative)
urease (negative)

Front 17

Proteus spp: (i.e. P. mirabilis and P. vulgaris)

Back 17

produce swarming colonies on nonselective media, i.e., blood agar plate and lactose negative colonies on MacConkey agar. The colonies produce a distinct odor reminiscent of "burned chocolate". Both species ferment glucose with gas production and produce H2S on TSI (black).

Front 18

P. vulgaris P. mirabilis

Back 18

urease (positive) urease (positive)
indole (positive) indole (negative)

Front 19

Klebsiella pneumoniae:

Back 19

is an encapsulated bacterium that produces large, lactose positive, mucoid colonies on MacConkey agar. The organism is the only other member of Enterobacteriaceae family, besides Shigella, that is non-motile.
urease (positive)
indole (negative)

Front 20

Pseudomonas aeruginosa

Back 20

o Media: BAP or Mac
o Flat colonies with a spreading border and a green pigmentation caused by the production of the blue (pyocyanin) and yellow (fluorescein) pigments and a sweet, grape-like odor.
o Gram-negative rods
o Oxidase (positive), utilizes glucose only in the presence of O2 (Oxidizes rather than fermenting)

Front 21

Pasteurella multocida

Back 21

o Media: BAP or Choc, but not Mac
o Large, buttery colonies with a characteristic pungent odor caused by the production of indole
o No hemolysis
o Gram-negative coccobacilli (reminiscent of “safety pins”)
Oxidase (positive), ferments glucose with a weak acid production
(hence the term "sick" TSI), sensitive to penicillin (contrary to antibiotic resistance of many G-negative rods.)