Homegrown Defender: Urinary infections face natural guard

Bacteria are adept at sneaking past our defenses, succeeding most often when swallowed, inhaled, or given free passage via a cut or scratch. But over the past 2 decades, scientists have found that even before the immune system can gin up a response to such intruders, built-in antimicrobial agents in the intestines, lungs, and skin act as a first line of defense.