Mrs. Kovacs had complained of diarrhea and stomach cramps for four days, but what finally brought her in was the weakness. "She can barely move," her husband had told the triage nurse. A healthy 65-year-old, Mrs. Kovacs had seen the inside of a hospital only to deliver her babies. As for doctors, she had needed their services for mild high blood pressure.
The diarrhea had started out watery, not bloody, not too copious, with no fever. According to her husband, she didn't have any risk factors that might explain the persistent diarrhea. She hadn't been out of the country, she hadn't eaten any spoiled food, and she hadn't taken any antibiotics lately.
Two IVs dripped saline in, but her blood pressure would not rally.
"This morning she was walking around," one of her daughters said fearfully. "We thought she had a stomach flu."
The lab results had come back sky-high, with a white blood cell count of 25,000 (normal is 4,000 to 11,000). Her diarrhea had made her so dehydrated that her kidney function was one-third of normal.
The surgeon, still puzzled as to how a gastrointestinal infection could fell a healthy woman, went back over the history.
"No antibiotics in the past few months?" he asked. "You're sure?"
Another daughter had since arrived. "Oh, yes," she exclaimed. "She had a tooth infection about three weeks ago. The dentist gave her something. I brought the container."
She fished in her pocket and handed a plastic vial to the surgeon.
"Clindamycin," he read aloud.
Mr. Kovacs, understandably, had forgotten. His wife had finished the drug treatment two weeks earlier.
"This finally makes sense," the surgeon said. Then, as gently as he could, he addressed the family. "She's in for a very rough time."
In the 1960s, reports of a bizarre and sometimes lethal colon affliction appeared in the medical literature. Because the cell debris and inflammatory gunk that lined the colon looked like a yellow-green membrane, researchers called it pseudomembranous colitis, but its direct cause remained elusive. Clear from the start, however, was that antibiotics—clindamycin in particular—were implicated.
The human colon harbors a complex ecosystem of bacteria. By and large, our bacterial companions behave like a big happy family in which all mind their place and do their part. Some of the bacteria use oxygen; some don't. Many aid in digestion and make nutrients like vitamin K. The social order is fragile, however. Add antibiotics and the good bacteria die, allowing nasty competitors to move in. The most common side effect is diarrhea. Most cases occur because the bacteria-depleted intestine cannot fully digest carbohydrates, and the unabsorbed sugar provokes the runs.