Salmonella more common on larger commercial farms, study reveals

News brief

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.

Teen vaccination cut COVID-19 cases by 37% in California, new data show

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Stephanie Soucheray, MA

JAMA Network Open has published a new study showing that, from April 1, 2020, to February 27, 2023, in California, an estimated 146,210 COVID-19 cases were averted by vaccination in teens aged 12 to 15 years, representing a 37% reduction.

Researchers also estimated that 230,134 cases were averted in kids aged 5 to 11 years, a 24% reduction.

The study looked at COVID-19 infections in post-vaccination evaluation periods consisting of 141 days (June 10 to October 29, 2021) for adolescents aged 12 to 15 years, 199 days (November 29, 2021 to June 17, 2022) for children aged 5 to 11 years, and 225 days (July 17, 2022, to February 27, 2023) for those aged 6 to 59 months, according to study authors.

Biggest reduction in teens

From April 2020 to February 2023, California recorded 3,913,063 pediatric COVID-19 cases and 12,740 hospitalizations. During those times, statewide vaccine coverage reached 53.5% among adolescents aged 12 to 15 years, 34.8% among children aged 5 to 11 years, and 7.9% among those aged 6 to 59 months.

The biggest reduction attributed to vaccination occurred with older kids, and there was no evidence of reductions in COVID-19 cases statewide among children aged 6 to 59 months (estimated averted cases, −259; 95% prediction interval, −1,938 to 1,019).

Though there was no evidence in case reduction in the youngest kids, vaccination prevented an estimated 168 hospitalizations among children aged 6 to 59 months during the 225-day evaluation period.

These results support the use of COVID-19 vaccines to reduce COVID-19 incidence and hospitalization in pediatric populations.

"These results support the use of COVID-19 vaccines to reduce COVID-19 incidence and hospitalization in pediatric populations," the authors concluded.

US study shows post-COVID rebound in inappropriate antibiotic prescribing

News brief

Chris Dall, MA

Antibiotics in package — Ralf Liebhold / iStock

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."