You want to determine if the source of fecal contamination is from dairy cows or wild deer. Which antibiotic would give you the most clear results and why

Piperacillin and tazobactam, imipenem and cilastatin, or meropenem may be used.

Explanation:

Antibiotics such as piperacillin and tazobactam, imipenem and cilastatin, or meropenem can be used for the treatment of Fecal coliform bacteria that causes fecal contamination. There are some other methods also used to avoid Fecal contamination i.e. boiling of water, treating water with chlorine, or UV disinfection are the methods that are used to reduce Fecal coliform bacterial infection.

it would be heredity

that is wrong, its not thymus.