I'm working on a project to make beads containing antibiotics to treat osteomyelitis. To test the efficacy of these beads, I performed an antibiotic diffusion test on the beads using TSA plate streaked with S. aureus. Zone of inhibition was present but I wonder why the plate turns green. I wonder why this happened?
Please apply antibiogram studies on your Staphylococcus aureus by Methicillin Resistance Test.This outcome may result for hetero resistance.Tryptic Soy Agar contains digests of casein and soybean meal. The combination renders the medium nutritious by supplying organic nitrogen. So Staphylococcus aureus utilize its α-acetolactate synthase (ALS) enzyme to neutralize nitrogenous peptide. Again ALS contributes to the resistance of S. aureus to beta-lactam antibiotics such as methicillin and oxacillin. On this contrary, the observation can be followed in two ways: 1. Positive MRSA 2. Negative MRSA. In my conclusive suggestion, for MRSA testing, Muller Hinton Agar can be used on replacing TSA.Than observation of findings will play the lead role for the next test of TSA beads. On both of these experiments, Minimum Inhibitory Concentration can be determined by Epsilometer test.Thank you.
If your Staph aureus culture is contaminated with some forms of Pseudomonas it is possible they are creating the green pyocyanin or pyoverdin. Pseudomonas is a frequent cause of contaminated cultures.
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