The bacterium was determined to be Gram- negative rods. The first attempt of gram stain the unknown appeared to look positive and cocci. But, the next day onwards for 4 consecutive days the unknown showed up as a gram- negative gram stain and appeared pink rods.
Triple Sugar Iron Agar is a differential medium. It differentiates Gram-negative enteric bacteria based on the ability to reduce sulfur and ferment carbohydrates (lactose, sucrose, and glucose). This is indicated by the formation of acid and gas. Different strains of enteric bacteria utilize the nutrients differently hence can be differentiated. TSIA differentiates bacteria by their sucrose, lactose or glucose fermentation. Sodium thiosulfate provides the source of sulfur and the reduction produces hydrogen sulfide gas and forms
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Phenol red- alkaline is the pH indicator used in TSIA. The phenol red turns yellow from red when pH 7.4 drops below pH of 6.8 (Acharya, 2009). The unknown resulted in yellow slant and yellow butt with cracks in full medium. These observations indicate Acid slant/ acid butt and gas production. The production of acid indicates that lactose and sucrose was fermented thus lowered the pH of the butt and slant turning it yellow. Since gas was produced it leads to believe that unknown could be E. coli, E. Aerogenes or K. pneumonia (Leboffe & Pierce, 2016).
EMB is a selective and differential media it differentiates the Gram- negative enteric bacteria. EMB isolates coliforms and inhibits growth of most Gram- positive bacteria. Eosin and methylene blue can differentiates between organisms that ferment lactose and sucrose and those that do not. If dark purple colonies or colonies