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Antibiotics are drugs that kill or prevent the growth of bacteria.
During the colonization of New Caprica, Samuel Anders contracts pneumonia. Dr. Cottle is unable to treat Anders because there are no antibiotics available. He can only advise Thrace to make sure Anders gets enough rest in order to recover. Later, Colonel Tigh mentions to Thrace that Lee Adama keeps a store of backup medical supplies for the pilots on Pegasus, so she calls him to request the antibiotics. However, she is interrupted by the untimely arrival of the Cylon fleet (Lay Down Your Burdens, Part II).