1 / 11

Microbiology

Microbiology. Medically Important Staph and Strep Labs 24 - 26. MSA plates. Media pH Phenol Red Mannitol Pathogenic ferment mannitol and acids change phenol red to yellow Nonpathogenic grow no color change 7.5% NaCl

taini
Download Presentation

Microbiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microbiology Medically Important Staph and Strep Labs 24 - 26

  2. MSA plates • Media • pH Phenol Red • Mannitol • Pathogenic ferment mannitol and acids change phenol red to yellow • Nonpathogenic grow no color change • 7.5% NaCl • Selective medium for staphylococci since most other pathogenic bacteria cannot survive in high salt

  3. MSA plates

  4. Coagulase Production • Used to differentiate S. Aureus from other gram positive cocci • S. aureus is an opportunistic pathogen known to be highly resistant due to production of coagulase • Coagulase works in conjunction with normal serum components to form protective fibrin barriers around bacterial cells which shields them from phagocytosis and other types of immune attacks

  5. Coagulase Production • Coagulase enzymes occur in two forms • Bound • Attached to cell wall reacts directly with fibrinogen in plasma causing fibrinogen to precipitates which causes clumping • Free • Extracellular enzyme that reacts with plasma component coagulase reacting factor (CRF) which causes normal clotting mechanisms to begins

  6. Coagulase Production • In our test the yellow colonies from the MSA plate are presumed pathogens • However, virulence of the organism is not established until coagulase test is done • Rabbit plasma is treated with sodium citrate a natural anticoagulant • If coagulase is present then it inactivates the sodium citrate and allows the plasma to clot

  7. Coagulase Production • Substrate: Sodium citrate • Enzmye: Coagulase • pH indicator/reagents: none • Pos: Clotting • Neg: Liquid

  8. Hemolysin Production • Blood agar is used for isolation and cultivative of many types of fastidious bacteria • Used to differentiate bacteria within the genera Streptococcus, Enterococcus, and Aerococcus

  9. Hemolysin Reaction • Several species of gram positive cocci produce exotoxins known as hemolysins • Hemolysins able to destroy RBC’s and hemoglobin (except gamma hemolysin) • Beta – complete destruction of RBC’s and hemoglobin results in clearing • Alpha – partial destruction of RBC’s heme group not used greening ting seen • Gamma – non RBC hemolysis only plasma protein appears as simple growth no change to medium

  10. Alpha (Left) and Gamma (Right) Hemolysis Greenish ting Heme group not broken down agar remains red color

  11. Beta Hemolysis

More Related