By Alex Dominguez
BALTIMORE — Antibiotic-resistant bacteria continued to be found in chickens bought at area supermarkets a year after two large poultry producers stopped using an antibiotic blamed for creating the resistant strains, Johns Hopkins researchers report.
The researchers say the findings suggest antibiotic-resistant bacteria may persist in the poultry industry after the use of the antibiotics, known as fluoroquinolones, has stopped and may contaminate more poultry than previously thought.
However, one of the producers and a researcher not involved with the study said the study did not show whether the amount of bacteria found presented a health risk. They also said the findings were not clear on whether the resistant strains were naturally present or use of the antibiotic caused the resistant strains.
In 2000, the Food and Drug Administration (FDA) proposed banning the two fluoroquinolones used in poultry. Abbott Laboratories of Abbott Park, Ill., agreed immediately to pull its version, Sara Flox.
But Pittsburgh-based Bayer Corp. is appealing the decision and the FDA commissioner is considering the case involving Bayer’s product, Baytril.
The bacterium, campylobacter, is responsible for 2.4 million cases of food-borne illness a year in the United States, the Centers for Disease Control and Prevention report.
The antibiotic-resistant form of the bacterium is especially troubling because the fluoroquinolone family of antibiotics includes the popular drug Cipro, and fluoroquinolones are a leading treatment for food poisoning from campylobacter, found mostly in raw chicken.
In February 2002, Perdue Farms Inc. of Salisbury, Md., and Tyson Farms Inc. of Springdale, Ark., stopped using fluoroquinolone antibiotics.
The researchers in the study said they bought chicken produced by Perdue, Tyson and two antibiotic-free producers.
Tyson noted the study’s sample size was small and limited to one area of the country, did not measure the amount of bacteria present, and included strains of campylobacter that may be naturally resistant to the antibiotics without having been exposed to them.
Study author Lance Price said if natural immunity were responsible, “you would expect all the products to come out the same, but that’s not the case.”
Perdue said it had no information on the origin of the samples, and “cannot comment on the conclusions regarding antibiotic resistance.”
Perdue said less than 1 percent of its flocks receive any antibiotics, which are limited to the “humane treatment of ill or at-risk chickens, treating as few birds as possible, and prescribing that treatment no longer than deemed medically appropriate by a poultry veterinarian.”
“Perdue does not use antibiotics for the purpose of growth promotion nor do we use any antibiotics continuously for any reason whatsoever,” said a statement the company issued.