There are several tests that can be considered for the identification for the unknown microorganism. One of these tests is Mannitol Salt Agar (MSA). This culture media isolates Staphylococci species to grow. Since the result of the MSA is negative, it is conclusive that Staphylococci species are not the bacteria in question.
Another test to be considered is the Triple Sugar Iron (TSI), which is a differential medium for several gram-negative bacteria. It can determine if the bacteria can metabolize lactose andor sucrose, produce gas during fermentation, conduct fermentation to produce acid or generate H2S. When the medium turns yellow, it indicates that the bacteria have fermented the phenol red or glucose content of TSI. TSI also can indicate if the bacteria are capable of reducing SO4 to H2S (hydrogen sulfide). When the iron combines with the H2S produces a black compound, thus a black color of this medium indicates H2S production. Since the result of this test is black which means positive for H2S production, then we can rule out Shigella dystenteriae, Klebsiella pneumoniae, Enterobacter aerogenes, Escherichia coli, Pseudomonas aeroginosa and Alcaligens laecalis since all these bacteria have negative result for TSI. This leaves us with Salmonella typhimurium and Proteus vulgaris. This result is supported by the SIM medium which indicated that the unknown microorganism is an H2S producer.
Salmonella typhimurium and Proteus vulgaris have similar characteristics. However, they differ in indole production, urease activity and gelatin liquidation. With regards to TSB for indole, the result was positive, which may indicate that the unknown organism is Proteus vulgaris. However, both urease activity and gelatin liquidation tests was negative, which is indicative of Salmonella typhimurium. Thus, it is safe to conclude that the unknown organism is Salmonella typhimurium.
Another test to be considered is the Triple Sugar Iron (TSI), which is a differential medium for several gram-negative bacteria. It can determine if the bacteria can metabolize lactose andor sucrose, produce gas during fermentation, conduct fermentation to produce acid or generate H2S. When the medium turns yellow, it indicates that the bacteria have fermented the phenol red or glucose content of TSI. TSI also can indicate if the bacteria are capable of reducing SO4 to H2S (hydrogen sulfide). When the iron combines with the H2S produces a black compound, thus a black color of this medium indicates H2S production. Since the result of this test is black which means positive for H2S production, then we can rule out Shigella dystenteriae, Klebsiella pneumoniae, Enterobacter aerogenes, Escherichia coli, Pseudomonas aeroginosa and Alcaligens laecalis since all these bacteria have negative result for TSI. This leaves us with Salmonella typhimurium and Proteus vulgaris. This result is supported by the SIM medium which indicated that the unknown microorganism is an H2S producer.
Salmonella typhimurium and Proteus vulgaris have similar characteristics. However, they differ in indole production, urease activity and gelatin liquidation. With regards to TSB for indole, the result was positive, which may indicate that the unknown organism is Proteus vulgaris. However, both urease activity and gelatin liquidation tests was negative, which is indicative of Salmonella typhimurium. Thus, it is safe to conclude that the unknown organism is Salmonella typhimurium.
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