TUESDAY, Nov. 25 (HealthDay News) -- Here's something new you can worry about when traveling by car on your next vacation: Don't get too close to one of those huge tractor-trailer trucks if it's carrying a load of live chickens. It's a perfect breeding place for the transmission of germs from the chickens to humans.

And some of those germs may be resistant to many antibiotics, researchers from the Johns Hopkins Bloomberg School of Public Health have discovered. The scientists found increased levels of pathogenic bacteria on surfaces and on the air inside cars traveling behind trucks carrying broiler chickens. Typically, broiler chickens -- scientifically called "intensively raised poultry" -- are transported in open crates on the back of flatbed trucks. These crates are contaminated with feces and bacteria.

The study was conducted on the Delmarva Peninsula, a coastal region shared by Maryland, Delaware and Virginia. The peninsula has one of the highest densities of broiler chickens per acre in the United States. The researchers collected air and surface samples from cars driving two to three car lengths behind poultry trucks for a distance of 17 miles. The cars' windows were fully opened while following the trucks.

Air samples from the cars showed increased concentrations of bacteria (including antibiotic-resistant strains) that could be inhaled. The same bacteria were also found in a soda can inside a car and on an outside door handle. Strains of bacteria collected from the cars were resistant to three antimicrobial drugs used to treat humans and also used as feed additives for broiler poultry.

"We were expecting to find some antibiotic-resistant organisms, since it's pretty clear that the transportation conditions for these chickens are not closed or contained," Ana M. Rule, a research associate in the Bloomberg School's department of environmental health sciences, said in a Johns Hopkins news release. "Our study shows that there is real exposure potential, especially during the summer months, when people are driving with the windows down; the summer is also a time of very heavy traffic in Delmarva by vacationers driving to the shore resorts."

Rule and her colleagues said further research is needed, and more needs to be done to contain bacteria associated with high-intensity poultry operations.

The study was published in the Journal of Infection and Public Health.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about antibiotic resistance.