BIOD 171 Essential Microbiology Portage Learning Module 4 Exam Questions and Answers

Question 11 Not yet graded / 10 pts In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next? Why? Your Answer: The researcher should try Sorbotial MacConkey (SMAC) agar. SMAC is formulated to detect pathogenic E. coli 0157:H7. SMAC has sorbitol instead of lactose which is found in MacConkey agar. Pathogenic E. coli can ferment sorbital but not lactose. Nonpathogenic E. coli can ferment both sorbital and lactose. The microbe should be plated on SMAC (Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7. Pathogenic E. coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-pathogenic) can be differentiated from nonfermenters (neutral to basic conditions; pathogenic