Concern about germs becoming resistant to antibiotics, such as the salmonella linked to a resistant strain recently traced back to ground turkey, prompted a study that found that bacteria in organic poultry is less resistant.

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Poultry farmers who adopt organic practices and stop giving their birds antibiotics significantly reduce the resistance of bacteria to antibiotics in their flocks, according to a study released Wednesday.

Public-health experts have become increasingly concerned about germs becoming resistant to many commonly used antibiotics. Indeed, a current outbreak of salmonella is being caused by a resistant strain of the bacteria traced back to ground turkey.

In the study in the journal Environmental Health Perspectives, Amy Sapkota of the University of Maryland School of Public Health and colleagues studied 10 conventional farms and 10 farms that had become organic in 2008. They tested for the presence of a bacteria known as enterococci in poultry litter, feed and water and for whether the organisms were resistant to 17 commonly used drugs.

All the farms tested positive for the bacteria. But the farms that had recently become organic had significantly lower levels of resistance. For example, 67 percent of enterococcus faecalis from conventional farms were resistant to the drug erythromycin compared with 18 percent of the organisms from the organic farms. Forty-two percent of the bacteria from conventional farms were resistant to multiple drugs, compared with 10 percent from the organic farms.

Study links genes

and intelligence

A new study indicates the extent to which the genes someone is born with play a role in determining intelligence.

Ian Deary of the University of Edinburgh and colleagues conducted a “genomewide association”analysis to try to gauge the role of genes in intelligence. The researchers analyzed DNA from 3,511 unrelated adults to see how much 549,692 common genetic variations known as single-nucleotide polymorphisms were associated with variations in intelligence.

Previous studies involving twins and adopted children have indicated genes play an important role in intelligence, perhaps accounting for about half the variation among individuals.

In the new analysis, published online Tuesday in the journal Molecular Psychiatry, researchers calculated that perhaps 40 to 50 percent of individual differences in intelligence — how much a person knows and how good the person is at problem-solving — are due to genetic variations. But it appears the differences in intelligence are due to many genes, each playing a small role.

That means it will be difficult, if not impossible, to ever identify any genes that play a major role in IQ, researchers say.

Nevertheless, the study “is the first that finds that a substantial proportion of the genetic contribution suggested by” earlier “studies can be found in signals in people’s DNA,” Deary wrote in an email.

Seattle Times news services