Animal experiment:

Mice: Bacterial challenged mice are treated with methicillin, gentamicin, both methicillin and gentamicin, or no antibiotics. The treatment is given three times a day for up to 3 days. Each dose of methicillin is 75 mg per mouse (3 g/kg of body weight), and the gentamicin dose is 0.75 mg per mouse (0.03 g/kg). The antibiotics are given subcutaneously in 0.1 or 0.5 mL of saline. Mice are sacrificed and serum and aspirate samples are collected[4].

Gentamicin is an aminoglycoside antibiotic, always used the sulfate form, composed of a mixture of related gentamicin components and fractions ,which is used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms.[1]
Gentamicin is a bactericidal antibiotic that works by irreversibly binding the 30S subunit of the bacterial ribosome and 16S rRNA, interrupting protein synthesis. This mechanism of action is similar to other aminoglycosides.The ribosome is a large and complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis (translation). Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules. [2] Ribosomes consist of two major components, the small ribosomal subunit which reads the RNA, and the large subunit which joins amino acids to form a polypeptide chain. Each subunit is composed of one or more ribosomal RNA (rRNA) molecules and a variety of proteins. Ribosomes differ in their size, sequence, structure, and the ratio of protein to RNA from bacteria, archaea and eukaryotes (the three domains of life on Earth).[3] The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. Gentamicin binds to four nucleotides of 16S rRNA and a single amino acid of protein S12 which interferes with decoding site in the vicinity of nucleotide 1400 in 16S rRNA of 30S subunit. The interaction with the wobble base in the anticodon of tRNA leads to interference with the initiation complex misreading, so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and the breakup of polysomes into nonfunctional monosomes.[4]
Gentamicin is a broad spectrum aminoglycoside antibiotic. Aminoglycosides are useful primarily in infection diease include aerobic, Gram-negative bacteria, In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. Symptoms of gentamicin toxicity include: Balance difficulty, Bouncing, unsteady vision, Ringing in the ears (tinnitus), Difficulty multi-tasking, particularly when standing.[5] Gentamicin is very poorly absorbed orally. Injections lead to peak serum concentrations in 30-60 minutes.
References:
1. Moulds, Robert and Jeyasingham, Melanie "Gentamicin: a great way to start". Australian Prescriber 2010 (33): 134–135.
2. Czernilofsky. et al. "PROTEINS AT TRANSFER-RNA BINDING-SITES OF ESCHERICHIA-COLI RIBOSOMES". NATL ACAD SCIENCES. 1974, 71 (1): 230–234.
3. Ben-Shem A. et al. "The structure of the eukaryotic ribosome at 3.0 Å resolution". 2011 Science 334 (6062): 1524–1529.
4. Lopez-Novoa, Jose. "New insights into the mechanism of aminoglycoside nephrotoxicity: an integrative point of view." 2011. Kidney International.
5. Pandya, A. et al. (1993)."Nonsyndromic Hearing Loss and Deafness, Mitochondrial". Book.