Infection: The Uninvited Universe.

INFECTION: The Uninvited Universe

GERALD N. CALLAHAN

The proliferation of antibacterial soaps and drugs suggests that people have come to regard bacteria as the enemy. It's not without good reason: From syphilis to anthrax and the plague, bacterial infection is one of the biggest threats to human health. But what few people realize is that bacteria are also vital to our well-being Callahan, author and associate professor of immunology at Colorado State University, notes that as much as 90 percent of the cells in our bodies are bacteria. Bacteria have played an integral part in shaping human evolution, supplying us with important genes. Disturbances in the flora inside our gastrointestinal tracts lead to a host of ailments, and beneficial bacteria protect us from infectious diseases. Callahan also acknowledges the dark side of bacteria: Infectious diseases remain the leading cause of death in developing countries without adequate access to antibiotics. Callahan notes that the indiscriminate use of antibiotics is leading to an increase in illness caused by bacteria. Scientists are also investigating whether bacteria play a role in the development of diseases such as multiple sclerosis, heart disease, and epilepsy. New conditions such as SARS and the spread of evolving versions of the influenza virus remind us of bacteria's ever-changing threat against humanity. St. Martin's Press, 2006, 288 p., hardcover, $24.95.