Streptomyces is a genus of soil bacteria that is a virtual biological drug-making factory. It produces a wide range of drugs used to combat infections caused by bacteria (tetracycline, streptomycin, vancomycin, neomycin), fungi (nystatin, amphotericin B), and parasites (ivermectin), as well as anticancer drugs (bleomycin). Chloramphenicol is an antibacterial antibiotic that was isolated from one of the more than 550 Streptomyces species—this one from a soil sample in Venezuela.
When chloramphenicol (Choromycetin) hit the market in 1949, Parke-Davis appeared to have a blockbuster drug. Along with the tetracyclines, it was one of the first broad-spectrum antibiotics that were effective against a wide range of microbes. Moreover, chloramphenicol’s long reach to fluids and tissues throughout the body prevented disease-causing microbes from evading it.
FATAL FLAWS IN A LIFESAVING DRUG. However, its potentially life-threatening effects on the bone marrow—the site of blood cell manufacture in adults—prevented chloramphenicol from achieving its potential in medicine. The most serious effects are pancytopenia (a decrease in red and white blood cells and platelets) and aplastic anemia, in which the bone marrow fails to make enough blood cells—in particular, red cells.
In addition, non-blood-related problems were seen in the very young. Infants, especially premature infants, do not metabolize drugs as effectively as older children and adults. This lesson was tragically learned with chloramphenicol. In the late 1950s, what appeared to be “reasonable” doses were given to premies, after which their bodies became limp, their skin assumed ashen-gray coloration, their blood pressure dropped, and they became cyanotic; 40 percent died within days. This “gray baby syndrome” was found to result from the very low activity of UDP-glucuronyl transferase enzymes. Current uses of chloramphenicol are limited to serious infections when safer drugs are not effective. These include bacterial meningitis, typhoid fever, Rocky Mountain spotted fever, and related infections caused by the Rickettsia genus.
SEE ALSO Drug Metabolism (1947), Streptomycin (1944), Tetracyclines (1948), Nystatin (1954), Amphotericin B (1956).
The female American dog tick or wood tick is the primary carrier of the rickettsia that causes Rocky Mountain spotted fever. In humans, RMSF has a mortality rate of 20–25 percent if untreated and 5 percent if treated with chloramphenicol.