In a new comparison of different size poultry farms, researchers at North Carolina State University found that rates of Salmonella and multidrug resistance in fecal and environmental samples were higher on larger commercial farms compared to smaller backyard farms. The study is published in Foodborne Pathogens and Disease.

The researchers focused on backyard broiler farms. Broiler chickens are those being raised for meat and not eggs. 

"Broiler chickens are the top consumed meat in the U.S. and the world, but there's not much research on backyard farms, which are growing in popularity in the U.S.," said first study author Jessica Parzygnat, PhD, with the College of Veterinary Medicine at NC State, in a university press release. 

To conduct the study, Parzygnat and her colleagues tested 10 backyard and 10 commercial flocks at three time points across bird production. They sampled feces, soil, litter/compost, feeders, and waterers. 

All backyard flocks lived outside, and they ranged from 22 to 1,000 birds. Commercial birds were housed indoors, and those flocks consisted of tens of thousands of birds. 

Evidence of antibiotic resistance in backyard birds

Salmonella was detected in 52.3% of commercial farm samples, and in 19.1% of backyard farm samples. Kentucky (sequence type (ST) 152) was the most common serotype found in both backyard and commercial farms, the authors wrote.

Multidrug-resistant isolates (those resistance to three or more antimicrobial classes) were found in both commercial and backyard flocks. Ciprofloxacin- and nalidixic acid-resistant and intermediate isolates were found in 33% of commercial samples but in just 1% of backyard samples.

The proportion of Salmonella in backyard farms and commercial farms that were multidrug resistant—meaning that they showed resistance to three or more classes of antibiotics—was actually not significantly different

"There's a feeling that backyard birds are safer than commercial birds, but even though we found less Salmonella, the proportion of Salmonella in backyard farms and commercial farms that were multidrug resistant—meaning that they showed resistance to three or more classes of antibiotics—was actually not significantly different," Parzygnat said. 

An analysis of outpatient antibiotic prescribing in the United States from 2017 through 2021 shows that rates of inappropriate prescribing returned to baseline levels following a brief dip at the beginning of the COVID-19 pandemic, US researchers reported this week in Clinical Infectious Diseases.

The interrupted time series analysis included more than 37.5 million enrollees in national commercial and Medicare Advantage claims database and looked at prescriptions for antibiotics dispensed to children and adults each month from 2017 through 2020. They used a previously developed antibiotic appropriateness scheme to determine whether diagnostic codes on the medical claims "always," "sometimes," or "never" justified antibiotic use.

Among the 60.6 million antibiotics dispensed during the study period, 15.6% were appropriate, 29.4% were potentially appropriate, 25% were inappropriate, and 30% were not associated with a recent diagnostic code. 

The proportion of enrollees with one or more inappropriate prescriptions was 1.7% in December 2019. In April 2020, it dipped to 0.9%. But by December 2021, the proportion of enrollees with one or more inappropriate antibiotic prescriptions was back to 1.7.%. Notably, from March 2020 through December 2021, one of the two most common diagnoses among people who received inappropriate antibiotics was "contact with and suspected exposure to COVID-19."

Increase highlights need for outpatient antibiotic stewardship

The authors of the study suggest the decline in inappropriate antibiotic prescribing in March 2020 was likely the result of fewer visits to providers, while the subsequent increase in inappropriate prescribing was partly because overall antibiotic dispensing rebounded and partly because the proportion of antibiotic prescriptions that were inappropriate increased.

"Our study shows that the decline in exposure to inappropriate antibiotic prescriptions during the pandemic was only temporary," lead author Kao-Ping Chua, MD, PhD, a pediatrician and healthcare researcher in the Department of Pediatrics at the University of Michigan Medical School, said in a press release. "Our findings highlight the continued importance of quality improvement initiatives focused on preventing unnecessary antibiotic prescribing and antimicrobial resistance, which kills 48,000 Americans per year."