Record your reaction and results on the worksheet.Īfter adding sulfanilic acid & alpha-naphthylamine A red color formation after the addition of zinc is a negative test result. If the organism did not reduce nitrate, then the broth will turn red AFTER the addition of zinc because zinc reduces the nitrate to nitrite, NOT the bacteria. This is considered a positive result since the organism reduced the nitrate to nitrogen gas. If the organism reduced the nitrate to nitrogen gas, then no color will develop after the addition of zinc. IF no red color occurs: Dip a wooden applicator stick in the zinc powder (just enough to get the stick “dirty”) and drop it into the nitrate broth. Nitrate Reduction Test After Adding Sulfanilic Acid and Alpha-Naphthylamine Record your reaction and results on the worksheet. This is a positive test result, and no further testing is required. IMMEDIATELY look for a dark red color which indicates the organism reduced nitrate to nitrite. Add 10 drops of 0.8% sulfanilic acid and then add 10 drops of 0.6% N, N-Dimethyl-alpha-naphthylamine. Incubate the nitrate broth in the class test tube rack.ĪFTER INCUBATION –Add reagents to the incubated nitrate broth. Using a sterile inoculating loop, obtain a small amount of bacteria and inoculate the nitrate broth.ģ. Make a tape label writing your name, your assigned culture and the name of the media.Ģ. Other organisms do not have the ability to reduce nitrate at all.ġ. Other bacteria can reduce nitrate to nitrogen gas by also producing the enzyme nitrite reductase which reduces nitrite to nitrogen gas. Some bacteria can reduce nitrate (NO 3) to nitrite (NO 2) by producing the enzyme nitrate reductase. Nitrate broth is used to determine if an organism can reduce nitrate. Each person in the group will work with one of the color dot cultures. Many (but not all) are oxidase positiveįor this exercise: Work in groups of 4.The Non- Enterobacteriaceae also have three common characteristics: The Enterobacteriaceae have four common characteristics: These bacteria are mostly found in the environment, yet some of these organisms can cause wound infections and serious life-threatening infections in immunocompromised patients. Several of the bacteria in this group include bacteria such as Pseudomonas aeruginosa, Alcaligenes faecalis and Acinetobacter baumanii. The Gram-negative bacilli that are not in the Enterobacteriaceae family are composed of several families but are collectively called Non- Enterobacteriaceae or Nonfermenters (of glucose) to differentiate them from the Enterobacteriaceae. These Gram-negative, facultative anaerobes are frequently called “enterics” since they are normally found in the intestinal tract of humans and other animals. coli, Klebsiella, Enterobacter and Proteus. One major group of Gram-negative bacilli is the Family Enterobacteriaceae which contain many genera of organisms such as E. Gram negative bacilli comprise a vast array of bacteria, yet most clinically significant Gram-negative bacilli can be divided into two groups. Gram Negative Rod Biochemical Test color photos (PDF document) Biochemical Test Results Google Photo Album
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