Horizontal Transfer vs. Vertical Descent Gentamicin is an antibiotic that is used to treat bacterial infections. A hospital reports a sudden outbreak of a new gentamicin-resistant strain of Escherichia coli in 5 out of 25 patients of the intensive care unit. On further investigation, it was determined that this new strain was found only in patients that were also infected with a known gentamicin-resistant strain of Klebsiella pneumonia. What is the most likely explanation for the development of this new antibiotic resistant strain of Escherichia coli?

A.)Spontaneous mutations arose separately in the E. coli strains from each of the 5 patients, leading to the separate evolution of gentamicin resistance in E. coli from each of the 5 patients.

B.)A single spontaneous mutation arose in E. coli from a single patient leading to gentamicin resistance in that patient. This mutation was passed along to the E. coli in other patients by vertical descent.

C.)Klebsiella pneumonia and E. coli can easily exchange genetic material. Antibiotic resistance was passed from Klebsiella pneumonia to E. coli by horizontal gene transfer in each of the co-infected patients.