ATLANTA (AP) -- Research by the Centers for Disease Control and Prevention indicates that a common bacteria blamed for food-poisoning has a growing resistance to a drug used to combat the bug.

The reason, scientists say, is the use of similar drugs to fight the bacteria in poultry.

A new study shows that Campylobacteria now has a 19 percent resistance to Cipro, compared with 15 percent in 1997, CDC epidemiologist Robert Tauxe said Tuesday.

In 1990, when the CDC first looked at antibiotic resistance, there was none to Cipro, which is used to treat humans who are sickened by the bacteria. Cipro also is used to combat anthrax and smallpox, which have not displayed a similar growing resistance to the drug.

"That's going from being not a detectable problem at all to being a real problem. That's significant. And there's some evidence that it's increased every year since then," Tauxe said.

The data led a watchdog group, the Keep Antibiotics Working campaign, to deliver 16,000 letters to German pharmaceutical maker Bayer Corp., urging the company to end its two-year battle with the Food and Drug Administration over a proposed ban on Cipro-like drugs for use in poultry.

The organization said the CDC data bolster the FDA's case that continued use of Bayer's Cipro-like fluoroquinolone antibiotic, Baytril, in poultry flocks is undercutting Cipro's effectiveness against food poisoning.

"This new data give even greater urgency to the American Medical Association's recommendation that Bayer should stop fighting the FDA's proposed ban, and stop playing chicken with the public's health," said Rebecca Goldburg, a scientist for Environmental Defense who delivered the letters.

The data on Campylobacter resistance was to be presented Wednesday at the National Antimicrobial Resistance Monitoring Systems 2002 Annual Scientific Meeting at Hilton Head Island, S.C.

Tauxe supervises the group that has been looking at the growing resistance of Campylobacteria to Cipro.

"We estimate that about 2.4 million Americans get this a year. That's about 1 percent, which is a lot," Tauxe said. He said the natural habitat of the bacteria is in the gastrointenstinal tract of birds.

People get infected primarily by eating undercooked poultry, or through handling raw poultry. Symptoms include abdominal cramps, diarrhea, vomiting.

The reason for the growing resistance is the use by poultry farmers of fluoroquinolone antibiotics, very similar to Cipro and made by Bayer, to prevent and treat pneumonia in chickens, he said. The bacteria living in the birds becomes resistant, increasing the chances of a human getting sick with resistant bacteria.

Cipro is the most frequent and effective antibiotic prescribed to treat it.

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