Download MLAB 2434 – CLINICAL MICROBIOLOGY SUMMER, 2005 CECILE

MLAB 2434 – CLINICAL MICROBIOLOGY
SUMMER, 2005
CECILE SANDERS & KERI BROPHY
Chapter 9 – Use of Colony
Morphology for Presumptive ID
of Microorganism
Chapter – 9- Colony Morphology
(cont’d)

Initial Observation &
Interpretation of Cultures
“Read” routine cultures after 18 to
24 hours of incubation
 If cultures cannot be read after 24
hours, refrigerate to prevent
overgrowth and drying

Chapter – 9- Colony Morphology
(cont’d)
Compare growth on different media
 Examples:

• If good growth on BAP but no growth
on MAC, the bacteria is probably a
gram positive organism
• If MAC growth is pink, the organism is
a lactose frementer
Chapter – 9- Colony Morphology
(cont’d)

Gross Colony Characteristics

Hemolysis on BAP (Chocolate agar
does not show true hemolysis)
• α hemolysis – green discoloration on the
media
Chapter – 9- Colony Morphology
(cont’d)
• β hemolysis –
complete clearing
of blood around
colonies on BAP
Chapter – 9- Colony Morphology
(cont’d)
• No hemolysis (sometimes called γ or
gamma)
Chapter – 9- Colony Morphology
(cont’d)
Size
 Margin or edge
 Elevation
 Density
 Color
 Consistency
 Pigment
 Odor

Chapter – 9- Colony Morphology
(cont’d)

Growth of Organisms in Liquid
Media
Streamers or vines and puff balls
are associated with certain streps
 Turbidity is produced by G- rods
 See pictures on page 321
