Used primarily as an antibiotic to treat infections caused by Gram-negative bacteria, especially multidrug-resistant strains. Commonly applied in topical formulations such as ointments, creams, and eye drops for skin, eye, and ear infections. Also used in combination with other antibiotics to enhance effectiveness against serious infections like pneumonia, urinary tract infections, and sepsis. Frequently included in selective culture media to suppress Gram-negative bacteria during microbial isolation. Due to high nephrotoxicity and neurotoxicity, systemic use is limited and reserved for severe cases when other antibiotics fail.