Chlorine dioxide has antibacterial effect on Salmonella--contaminated eggs.

Chlorine dioxide is an antimicrobial pesticide recognized for its disinfectant properties since the early 1900s. It kills microorganisms by disrupting the transport of nutrients across the cell wall of microbes. Chlorine dioxide can be generated in a gas or liquid form.

The contamination of eggs with Salmonella is an ongoing important public health problem. It has been estimated that more than 650,000 illnesses occur and more than 3,000 people are hospitalized each year in the United States alone because of Salmonella-infected egg products. Eggs may be contaminated with Salmonella from feces, infected nests, factory transfer belts, and air and packing materials. The contamination can also occur before the shells form in otherwise-healthy hens that have Salmonella-infected ovaries. This makes any disinfection strategy more complicated.

Scientists at Auburn University and elsewhere compared the bactericidal effectiveness of chlorine dioxide in its solution and gaseous phases against Salmonella on inoculated eggs. They also wanted to find the optimal chlorine dioxide concentration and time needed for microbial disinfection.

Chlorine dioxide in solution and gas forms was used to treat Salmonella-infected eggs in experiments. Researchers made a cocktail of S. enteritidis, S. typhimurium and S. mission and used it to inoculate eggs at [10.sup.7] cfu per ml for 3 minutes. The eggs were then dried for 10 minutes. The inoculated eggs were treated with 5, 10, 25, 50 and 100 ppm of chlorine dioxide solution each for 1, 5, 10 and 20 minutes.

All Salmonella were killed by all of the treatments except by the 5-ppm 1-minute treatment, which generated a 97.9% Salmonella kill. The bacteria was unable to survive on inoculated eggs at 8 ppm and 10 ppm of chlorine dioxide gas that were treated for 10, 30, 60 and 120 minutes. So, it appears that chlorine dioxide has a potential application for disinfecting eggs.

Further information. Tung-Shi Huang, Department of Nutrition and Food Science, Auburn University, Poultry Science Building 101C, Auburn, AL 36849; phone: [phone]; fax: [phone]; email: [e-mail].