You are given a Tube of contaminated water. The number of bacteria in the tube a

Question

You are given a Tube of contaminated water. The number of bacteria in the tube are too many to count. You prepare a tenfold dilutions in 5 tubes, so that #1 has 1:10 dilution, tube #2 has 1:100 dilution #3 has 1:1000 dilution, tube#4 has 1:10,000 dilution and tube #5 has 1:100,000 dilution. The second tube has 210 cells and the third tube has 26 colonies. What is the number of bacteria per ml in the original sample? Several individuals have food borne poisoning due To Salmonella from a common source. Later several individuals went to The local emergency rooms of the hospital complaining of similar symptoms. How could you determine and be sure that these individuals have the same infection? What would be the effect of a urine sample being left at room temperature Overnight before transported to the laboratory for culture?

Explanation / Answer

1. The number of colonies in the original tube would be 210*102 CFU/ml. Or it can also be written as 2.10*104 CFU/ml.

2. If the people are suffering from Salmonella infection then stool and blood samples are taken, and cultured on the culture media.Colonies obtained after incubation period of bacteria are examined . Staining can also be performed to make sure of the presence of Salmonella infection.If similar colony characteristics are observed on the culture of different patients ,it means that they all have same infection.

3. If a urine sample has been left overnight at room temperature, then its turbidity will increases due to bacterial proliferation. Its glucose content will decrease due to glycolysis by bacteria . The bilirubin will be oxidized to biliverdin.

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