Antibiotic resistent bacteria
In the taxonomy of bad bugs, acinetobacter is classified as an opportunistic pathogen. Healthy people can carry the bacteria on their skin with no ill effects - a process known as colonization. But in newborns, the elderly, burn victims, patients with depressed immune systems, and those on ventilators, acinetobacter infections can kill. When a team of geneticists unlocked the secret of the bug's rapid evolution in 2005, they found that one strain of multidrug-resistant Acinetobacter baumannii carries the largest collection of genetic upgrades ever discovered in a single organism. Out of its 52 genes dedicated to defeating antibiotics, radiation, and other weapons of mass bacterial destruction, nearly all have been bootlegged from other bad bugs like Salmonella, Pseudomonas, and Escherichia coli.
Acinetobacter is only one of many bacterial nemeses prowling around in ICUs and neonatal units in hospitals all over the world. A particularly fierce organism known as MRSA - methicillin-resistant Staphylococcus aureus - infects healthy people, spreads easily, and accounts for many of the 90,000 fatal infections picked up in US hospitals each year. Another drug-resistant germ on the rise in health care facilities, Clostridium difficile, moves in for the kill when long courses of antibiotics have wiped out normal intestinal flora.
Nevertheless, the bug makes an unlikely candidate for the next mass plague. It preys exclusively on the weakest of the weak and the sickest of the sick, slipping into the body through open wounds, catheters, and breathing tubes. Colonization poses no threat to people who aren't already ill, but colonized health care workers and hospital visitors can carry the bacteria into neighboring wards and other medical facilities. Epidemiologist Roberta Carey at the Centers for Disease Control and Prevention calls acinetobacter the Rodney Dangerfield of microorganisms: "It doesn't get a lot of respect because it's not out there bumping off normal, healthy people." But lately the bacteria has been getting its due, because it is rapidly evolving resistance to all of the antibiotics that used to keep it in check.
Until a few years ago, most strains could be dispatched with a wide variety of drugs. For the most tenacious infections, doctors could rely on a family of ultrabroad spectrum antibiotics called carbapenems. But strains of acinetobacter are emerging now that are immune to every known remedy. Multidrug - resistant pathogens are an epidemiologist's nightmare - reminders of the dark ages when millions of people died every year of runaway infections.
By creating the most heroic and efficient means of saving lives in the history of warfare, the Pentagon had accidentally invented a machine for accelerating bacterial evolution and was airlifting the pathogens halfway around the world.
