The bacteria under study was Streptococcus sanguis, the predominant bacterium in dental plaque. It is considered harmless, a normal inhabitant in a healthy mouth. But when these bacteria were mixed with human blood in vitro, clots formed. When billions of these bacteria were injected into rabbits, within a minute, heart abnormalities appeared on the animals' electrocardiograms, along with changes in blood pressure and breathing. The clots were caused by a protein on the surface of the bacterial cells which resembles collagen, a protein involved in the early stages of clotting.
Platelets apparently mistake the bacterial substance for collagen.
Now, the first of those studies, conducted on 393 women in Thailand, is complete. The study found that women who were given AZT during the last four weeks of pregnancy, as well as during labor and delivery, had half the risk of giving birth to a HIV-positive baby as those who received the placebo. Today, as a result of that discovery, HIV-infected women in the United States are routinely given AZT during the last 12 weeks of pregnancy. They also receive intravenous infusions of the drug during delivery, and their babies take the medicine for six weeks after being born. Yet every day, an estimated 1,600 HIV-infected babies are born worldwide, most of them in developing nations.