Chlortetracycline

Chlortetracycline is a broad-spectrum antibiotic originally isolated from S. aureofaciens. It inhibits growth of both Gram-positive and Gram-negative bacteria at a range of 0.1-100 μg/ml against A. aerogenes, D. pneumoniae, E. coli, K. pneumoniae, P. morganii, and several species of Haemophilus, Neisseria, Salmonella, and Staphylococcus. Chlortetracycline protects mice from infection by various strains of S. aureus with protective doses (PD50s) of 0.2-7.5 mg/kg, and from infection by E. coli (PD50 = 3 mg/kg) and K. pneumoniae (PD50 = 75 mg/kg). It acts by inhibiting protein synthesis, and it binds to a single site on the 30S ribosome subunit. Chlortetracycline is an ionophore and is selective for calcium over sodium, potassium, magnesium, strontium, and barium. It transports calcium from an aqueous phase into an organic phase environment or into multilamellar vesicles. Chlortetracycline is also a fluorescent dye that can be used to monitor calcium flux.