Final answer:
Neomycin is the aminoglycoside that can be administered rectally for an enterococcal infection, as it is not easily absorbed from the GI tract into the bloodstream.
Step-by-step explanation:
Among the options provided, neomycin is the aminoglycoside that can be administered by the rectal route for treating an enterococcal infection. Neomycin is not absorbed easily from the gastrointestinal (GI) tract into the bloodstream, which makes it suitable for treating local infections within the intestinal tract. Aminoglycosides such as neomycin bind to the 30S subunit of bacterial ribosomes, leading to the production of aberrant proteins and eventually bacterial cell death.Other antibiotics such as amikacin, gentamicin, and tobramycin in the aminoglycosides category are more commonly administered parenterally due to better systemic absorption and distribution to treat infections. Levofloxacin and ciprofloxacin are antibiotics as well, but they belong to the fluoroquinolone class and are not aminoglycosides, thus not being the correct choices for this question.