Many of the restrictions placed on antibiotic use in livestock in recent decades have been due to factors outside the agricultural world. Medical and government authorities have experienced infectious diseases developing a higher rate of antibiotic resistance in a shorter time frame. While some factors like over-prescription of antibiotics in humans for non-susceptible (viral-based) diseases and ailments; tougher, smarter disease organisms and inadequate hospital procedures have gotten deserved attention, animal agriculture has been accused by some, and assumed by others, to be a major contributor to the development of antibiotic resistance in humans.

The website, meatpoultry.com, now reports that there is a scientific study examining the issue, "using advanced gene sequencing techniques to find out whether some form of antimicrobial resistance material can be passed from food animals to humans through the food supply. In addition, the study examined and tested possible environmental influences

"The study involved 16 researchers from Colorado State University; Agriculture and Agri-Food Canada Research Centre, Canada; University of Saskatoon, Canada and the University of Colorado, Denver School of Medicine. The project tracked antimicrobial resistance genes, genes that some thought could be transmitted from livestock systems through meat products or environmental effluents. While public health officials have made some assumptions about the risk to humans through these two routes, little has been documented," the story said.

The study pooled samples from eight different pens of cattle totaling 1,741 head, in four different feedlots in two different states, collecting samples from incoming feeder cattle to post-slaughter. Any antimicrobial drug administration was tracked and the researchers tested and tracked any antimicrobial resistance genes at key points along the feeding and processing trail. They identified over 300 unique antimicrobial resistance genes. But during the feeding period, the array of antimicrobial resistance genes narrowed, indicating some sort of selective pressures.

"But it is post slaughter, after all the precautions and interventions packers now use during slaughter to drastically reduce the incidence of pathogens, where the researchers hit pay dirt. Testing the beef trimmings from processing -- the most likely place for contamination -- the researchers found no antimicrobial resistance genes. That suggests that the interventions packers use today for pathogens appear to remove the antimicrobial resistance genes that could be transmitted to humans and suggested beef products are not a likely source of antimicrobial resistance. The study did suggest that environment pathways might carry more risk than the food supply," the story noted.

If you haven't read through a scientific study for awhile, the advance of genome sequencing has drastically changed the accuracy and the level of investigation.

"Until recently, we have only been able to investigate how resistance develops in bacteria grown in a laboratory or to look for a handful of specific resistance genes in a sample of bacteria collected from people, animals or the environment. Fortunately, a technology called next-generation sequencing now allows us to look at all the resistance genes within all the bacteria in a sample," the study report explained.

"Noelle R. Noyes, with the department of clinical sciences at Colorado State University, and the team of researchers have used this next-generation sequencing to describe the antibiotic resistance potential (known as the "resistome") found in a sample, whether taken from feedyards, trucks or packing plants. This allowed the team to follow the resistome population, discovering that some groups of resistance genes present at the beginning of the feeding period disappeared by the end of the feeding period. The resistance groups that hung around for the entire period correlated with whatever antibiotics were used in the group of cattle. But when the resulting beef products were sampled, no resistance groups could be found," the story said.

The full text of this study was published in the peer reviewed scientific journal "eLife" March 8, 2016, under the title, "Resistome diversity in cattle and the environment decreases during beef production." Click here to go to study text.