Bacteriology Practical MSS Module Catalase Test Catalase decomposes
Bacteriology Practical MSS Module
Catalase Test • Catalase decomposes hydrogen peroxide into water and oxygen, causing bubbling during the reaction. Results: • Catalase Positive reactions: immediate bubble formation • Catalase Negative reaction: No bubble formation.
Staphylococcus aureus
Coagulase Test This test used to differentiate S. aureus ( produce coagulase) from S. epidermidis and S. saprophyticus (do not produce coagulase). Two types of coagulase are produced by S. aureus: • Free coagulase: converting fibrinogen into fibrin by activating coagulase –reacting factor present in the plasma ( fibrin clot in test tube) • Bound coagulase ( clumping factor): converting fibrinogen into fibrin directly without requiring coagulase –reacting factor (clumping bacteria in rapid slide test)
DNA Hydrolysis • Used to determine the ability of an organism to hydrolyze DNA (produce deoxyribonuclease or Dnase). • Agar medium: this medium is pale green in color because of DNA-methyl green (indicator) complex (Note: Methyl green is binds to the negatively-charged DNA). organism that hydrolyze DNA fade to colorless zone on the blue/green agar. • Quality control for DNA Hydrolysis • -Positive: Staphylococcus aureus -Negative: Staphylococcus epidermidis
DNA HYDROLYSIS TEST Positive: Staphylococcus aureus Negative: Staphylococcus epidermidis
Lecithinase activity of Clostridium perfringens on egg yolk agar Clostridium perfringens on blood agar
S. aureus on mannitol salt agar
Pseudomonas aeruginosa on Triple Sugar Iron agar: Growth; red slant, red butt, no gas, no H 2 S produced
Gram positive cocci/grape like clusters (Staphylococcus aureus). Gram positive cocci/chains (Streptococcus pyogenes).
Large Gram-positive rod with square ends, in chains. (Bacillus anthracis)
C. perfringens : large gram positive rods stained irregularly
Propionibacterium acnes Pleomorphic, gram-positive rods
- Slides: 15