I Colistin sulfate is an antibiotic primarily used to treat bacterial infections, especially those caused by multidrug-resistant strains. It is often used when other antibiotics are ineffective. Colistin sulfate is particularly active against gram-negative bacteria. However, it's important to note that its use is generally reserved for serious infections due to the risk of potential side effects and the emergence of antibiotic resistance. Always follow your healthcare provider's instructions when using colistin sulfate.