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

Question

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

Quizplus · Accepted Answer

The dull, wrinkled brown colonies and single bacilli morphology suggest B. subtilis. The lack of hemolysis on blood agar and growth with fermentation on MSA are also consistent with B. subtilis. E. coli would have a different colony morphology and is typically lactose fermenting. Pseudomonas aeruginosa would have a different colony morphology and is typically oxidase positive. B. cereus would have beta hemolysis on blood agar.

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