In Lab, a Student Observes Some Dull, Wrinkled Brown Colonies

question 39

Multiple Choice

In lab, a student observes some dull, wrinkled brown colonies growing on their agar.They Gram stain the sample and observe single bacilli.Their blood agar does not reveal any hemolysis while their MSA has growth and fermentation.Using the following table and the given observations, determine which microorganism this would most likely be.
$$\begin{array} { | l | l | l | } \hline \text { Bacilli } & \text { B. cereus } & \text { B. subtilis } \\\hline \text { Colony morphology } & \text { Dull, frosted colonies } & \begin{array} { l } \text { Dull, wrinkled colonies cream to } \\\text { brown colors }\end{array} \\\hline \text { Microscopic arrangement } & \text { Chains } & \text { Single bacilli } \\\hline \text { Catalase } & + & + \\\hline \text { Blood agar } & \text { Beta } & \text { Gamma } \\\hline \text { Mannitol salt agar } & -& + \text { growth and } + \text { fermentation } \\\hline\end{array}$$
$\begin{array}{|l|r|}\hline \text { Pseudomonas }&\text { P. aeruginosa }\\\hline \text { Catalase }&+\\\hline\text { Oxidase }&+\\\hline\text { Motile }&+\\\hline\text { Blood agar }&\text { Beta }\\\hline\text { Glucose fermentation }&+\\\hline\text { Escherichia }&\text { E. coli }\\\hline\text { Lactose fermentation }&+\\\hline\text { Motile }&+\\\hline\text { Citrate fermentation }&-\\\hline\text { Urease }&-\\\hline\text { Catalase }&+\\\hline\end{array}$

• A)E.coli
• B)Pseudomonas aeruginosa
• C)B.subtilis
• D)B.cereus

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