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MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ

MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ. Use of Colony Morphology for Presumptive ID of Microorganism. Importance of Colonial Morphology as a Diagnostic Tool. Provide a presumptive diagnosis in times of critical need

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MLAB 2434 – MICROBIOLOGY KERI BROPHY-MARTINEZ

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  1. MLAB 2434 – MICROBIOLOGYKERI BROPHY-MARTINEZ Use of Colony Morphology for Presumptive ID of Microorganism

  2. Importance of Colonial Morphology as a Diagnostic Tool Provide a presumptive diagnosis in times of critical need Best guess giving type of specimen and what is seen before confirmatory tests Help jump-start therapy Enhance quality of patient care through rapid results and cost effectiveness Prevents time-consuming testing that yields few results Play a significant role in quality control Helps maintain accuracy of commercial or automated systems Troubleshoot mixed cultures or errors in commercial systems

  3. 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

  4. 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 fermenter

  5. Fermenting vs. Non-Fermenting

  6. Colony Morphology (cont’d) • Gross Colony Characteristics • Hemolysis on BAP (Chocolate agar does not show true hemolysis) • α hemolysis • green discoloration on the media • Due to partial lysing of the RBC’s

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

  8. Colony Morphology (cont’d) • Gamma hemolysis • Absence of hemolysis, nonhemolytic

  9. Colony Morphology (cont’d) • Size ( large, medium, small, pinpoint) • Margin or edge (smooth, filamentous) • Elevation ( raised, convex, flat) • Density( transparent, translucent, opaque) • Consistency (brittle, creamy, dry) • Pigment (production of color) • Odor (fruity, old sock)

  10. Colony Morphology (cont’d) Shape, edge and elevation of bacterial colonies

  11. Liquid Media Environment

  12. Growth of Organisms in Liquid Media • Streamers or vines are associated with certain streps • Puff balls associated with streps

  13. Growth of Organisms in Liquid Media • Turbidity • Cloudiness of the medium • Often see gas

  14. References • Engelkirk, P., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams and Wilkins. • Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.

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