MLAB 2434 – CLINICAL MICROBIOLOGY SUMMER, 2005 CECILE SANDERS & KERI BROPHY

1. MLAB 2434 – CLINICAL MICROBIOLOGYSUMMER, 2005CECILE SANDERS & KERI BROPHY Chapter 9 – Use of Colony Morphology for Presumptive ID of Microorganism

2. 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

3. 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

4. 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

5. Chapter – 9- Colony Morphology (cont’d) • β hemolysis – complete clearing of blood around colonies on BAP

6. Chapter – 9- Colony Morphology (cont’d) • No hemolysis (sometimes called γ or gamma)

7. Chapter – 9- Colony Morphology (cont’d) • Size • Margin or edge • Elevation • Density • Color • Consistency • Pigment • Odor

8. 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