An article published in the November 2006 Journal of Infectious Disease found that antibiotic resistant bacteria was far more prevalent in conventionally raised chicken (raised using subtherapeutic antibiotics) than in "Organicically raised" chicken. Antibiotic resistant bacteria was negligible or non-existent in birds raised without antibiotics.

Further data was collected from fecal matter in hospital patients. Patients who had recently consumed conventionally raised commercial chicken were found to be infected with antibacteria resistant bacteria. The antibiotic resistant bacteria remained in their intestinal tract for fourteen days from ingestion. Hospital patients who consumed vegiterian diets had very low counts of the same antibiotic resistant bacteria.

There was a strong correlation between the patients with high counts of antibiotic resistant bacteria and the consumption of commercial, antibiotic fed chicken, leading to the conclusion that bacteria develop antibiotic resistance within the chickens raised on subtherapeutic antibiotics and the resistant bacteria is passed on to humans when they consume the meat of the chickens.

The entire article is available here: http://www.journals.uchicago.edu/doi/pdf/10.1086/508189