In Vitro: Ceratotoxin A is a 29-residue peptide isolated from the accessory gland secretion fluid, shows anti-E.coli activity, and is heat stable. Ceratotoxin A is effective against Escherichia coli ATCC 23739, Pseudomonas aeruginos ATCC 27853, and Bacillus subtilis ATCC 6633 with minimal inhibitory concentration (MIC) of 7, 7, and 3.5 µM.