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Tips from the Journals of the American Society for Microbiology: July 2001

American Society for Microbiology

ANTACIDS MAY INCREASE SUSCEPTIBILITY TO OYSTER-ASSOCIATED DISEASE

If you pop antacids you may be more susceptible to disease from eating raw oysters, say researchers from the Food and Drug Administration's Gulf Coast Seafood Laboratory. They report their results in the July 2001 issue of the journal Applied and Environmental Microbiology.

Using a simulated gastric environment, the researchers found that antacids significantly increased the survival rate of Vibrio vulnificus. Most commonly found in marine waters of the U.S. Gulf Coast, V. vulnificus has the highest case fatality rate of all the foodborne diseases in the United States, and is commonly contracted by ingesting tainted oysters.

In order to cause disease, though, the bacteria must first survive the highly acidic environment of the stomach, and it is the use of antacids that may help these bacteria get past the stomach and to the intestines where they can cause disease.

"Presence of antacid in the gastric compartment of the model greatly increased the ability of both V. vulnificus and its phage to survive simulated gastroinestinal transit and may be a factor involved with oyster-associated illness," say the researchers.

(J. Koo, D.L. Marshall and A. DePaola. Antacid increases survival of Vibrio vulnificus and Vibrio vulnificus phage in a gastrointestinal model. Applied and Environmental Microbiology, 67: 2895-2902.)

BAN ON ANTIBIOTIC USE IN DENMARK LOWERS RESISTANCE IN FOOD ANIMALS

Five years after the country of Denmark began banning the use of antibiotics as growth promoters in food animals, resistance rates of bacteria to these antibiotics have fallen significantly, suggesting that it is possible to reduce resistance by curbing antibiotic use in food production.

Researchers from the Danish Veterinary Laboratory in Copenhagen report the results of their research in the July 2001 issue of the journal Antimicrobial Agents and Chemotherapy.

The researchers analyzed antibiotic resistance patterns of over 2,500 samples of enterococcal bacteria taken from pigs and broiler chickens in Denmark over a five year period beginning in 1995, the year when Denmark first banned the use of the antibiotic avoparcin in food animals. During that time the resistance rate for avoparcin and related antibiotics fell from 72.7% in 1995 to just over 5% in 2000. In addition, the researchers also noted a significant decrease in resistance rates associated with the ban on use of the antibiotic virginiamycin in 1998.

"Our observations show that it is possible to reduce the occurrence of antimicrobial resistance in a national population of food animals when the selective pressure is removed," say the researchers. "The results discussed [in this study] represent the first documented effects of large-scale interventions to reduce the occurrence of antimicrobial resistance. They demonstrate that the exposure of humans to bacteria resistant to antimicrobial drugs and to resistance genes through food can be reduced effectively by intervention."

(F. M. Aarestrup, A.M. Seyfarth, H.-D. Emborg, K. Pedersen, R.S. Hendriksen and F. Bager. Effect of abolishment of the use of antimicrobial agents for growth promotion on occurrence of antimicrobial resistance in fecal enterococci from food animals in Denmark. Antimicrobial Agents and Chemotherapy, 45: 2054-2059.)

Full text of the above articles can be access through the ASM homepage at: http://www.asmusa.org/pcsrc/tip.htm.

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