By Maggie Fox, Health and Science Editor

WASHINGTON, Nov 11 (Reuters) - A common and sometimes deadly cause of diarrhea is far more common in U.S. hospitals than people thought, and only better hygiene and more judicious use of antibiotics will help, experts reported on Tuesday.

As many as 13 out of every 1,000 hospital patients are infected with Clostridium difficile, the Association for Professionals in Infection Control and Epidemiology reported.

This is as much as 20 times greater than previous, admittedly loose, estimates, the group said, and adds up to about 7,000 patients on any given day.

And as the U.S. population gets older and more frail, more patients are at risk of serious C. dificile that can kill them, said health-care epidemiologist Dr. William Jarvis, who led the study.

"You can get disease that ranges all the way from simple diarrhea all the way to perforation of the bowel requiring surgery, ... shock and death," Jarvis said in a telephone interview.

APIC's 12,000 members collected data about all of diagnosed C. dificile patients on one day between May and August 2008 at 648 hospitals. They covered 12.5 percent of all U.S. medical facilities including acute care, cancer, cardiac, children's, and rehabilitation hospitals.

ONLY BLEACH EFFECTIVE

Jarvis said the sample was representative of the nation as a whole and showed a surprising number of people were infected.

"We are still trying to get a grip on it," he said. Because the bacteria are hard to grow in culture, usually doctors order a test that misses the infection 25 percent of the time, he said. And because C. dificile is not a reportable disease, few records are kept.

Antibiotics kill natural bacteria in the gut and allow invaders such as C. dificile to flourish, Jarvis added. And it makes spores that cannot be killed by non-bleach cleaners or alcohol-based hand rubs.

"Antibiotics don't kill it and most germicides used for environmental cleaning don't kill it. Only bleach does," he said.

And by the time patients are diagnosed, they have had a day or two to contaminate their rooms and everyone who has had contact with them, he said.

The study will be published in the American Journal of Infection Control.

U.S. federal government figures released in April showed a 200 percent increase in the number of hospital patients infected with C. difficile from 2000 to 2005.

The most commonly used antibiotic for C. difficile is metronidazole, but some severe and antibiotic-resistant forms must be treated with vancomycin.

In July, Britain's Health Protection Agency said the C. difficile cases rose by 6 percent in the first three months of 2008.

Other studies have shown other types of hospital infections are on the rise in many countries, including drug-resistant forms of Staphylococcus aureus.

(Editing by Julie Steenhuysen and Eric Walsh)

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