GOOD GERMS, BAD GERMS

Chapter and verse on the bugs that outnumber, outwit and no doubt will outlast us.

The good news is that for the most part these bugs, aka bacteria, help or at least do no harm. With us since birth, the resident flora help digest and extract nourishment from what we eat, asking little but leftovers in return. Comfortably lodged in our various niches, they also impede hostile takeovers by the not-so-nice species, which is one reason we suffer diarrhea or other complaints. Sachs (Corpse: Nature, Forensics, and the Struggle to Pinpoint Time of Death, 2001) deals with the well-known problems of human antibiotic abuse that leads to scary headlines about hospital superbugs or extensively drug-resistant tuberculosis, but she also covers the overuse of antibiotics for livestock, which ensures that at least some highly drug-resistant bugs make it to the supermarket. She explains the many ways bacteria acquire resistance: via mutations, but also through the exchange of genes within a strain (bacterial sex) and across species; genes are also ferried into bacteria by invading viruses. Sachs points out that most antibiotics are derived from bacteria species that have a supply of resistance genes sequestered in their main chromosome ready to be turned on to prevent bacterial suicide. Humans’ built-in defenses are largely the components of the immune system, the antibody-producing and killer cells, as well as the ones that trigger allergic sneezes. The latter branch of the system may be in overdrive, she suggests, as we excessively spritz the latest bactericidal sprays and cleaners. This “hygiene hypothesis” posits that the reason for increases in asthma, allergies and autoimmune diseases in the developed world is that the immune system, for want of normal disease-fighting activity, overreacts to any stray molecule it senses, triggering an inflammatory response.

Sachs discusses a variety of proposed solutions for infection as well as allergy, but basically the message is, “Get over it! Learn to live and let live in a natural balance.”