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Study Highlights Trends in Drug-Resistant Campylobacter Infections in the U.S.

Campylobacter infections remain the leading cause of foodborne illness in the United States, affecting approximately 1.5 million individuals annually. Recent research assessed Campylobacter jejuni infection records across ten states, revealing insights into regional trends, age demographics, and antibiotic resistance from 2013 to 2019.

This study indicated a higher prevalence of drug-resistant C. jejuni infections among individuals aged 20 to 39. Notably, the proportion of quinolone-resistant strains surged from 22.6% in 2013 to 33.54% in 2019. Researchers observed substantial regional disparities in the resistance patterns of C. jejuni to quinolones and six additional antibiotic classes. These findings were published in the International Journal of Antimicrobial Agents.

The U.S. Centers for Disease Control and Prevention identifies contaminated poultry as the primary source of Campylobacter infections in humans. Inadequate sanitation practices and improper cooking methods significantly contribute to the contagion’s spread. Other animals, including pigs, cows, and sheep, also carry Campylobacter in their gastrointestinal systems, posing further risks of transmission.

While most infected individuals recover from Campylobacter infections within a week, certain populations, such as children under five, seniors over 65, and those with weakened immune systems, may experience more severe illness, sometimes necessitating hospitalization. In the U.S., more than 100 deaths annually are attributed to these infections.

The study utilized publicly available data from the National Antimicrobial Resistance Monitoring System (NARMS), which monitors bacterial infections and antimicrobial resistance across various foodborne and intestinal bacteria in the U.S. NARMS concentrated on ten states that illustrate regional variations, namely California, Connecticut, Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee.

“These sites are actively monitoring foodborne pathogens within the local populace,” noted Csaba Varga, a professor of pathobiology at the University of Illinois Urbana-Champaign and the lead researcher of the study. “They analyze infections involving Campylobacter, E. coli, Salmonella, and other pathogens, with a subset of isolates being tested for antimicrobial resistance. We delve into this surveillance data to investigate emerging and long-term trends.”

The analysis revealed significant variations in drug-resistant C. jejuni cases across the studied states. Connecticut exhibited the highest rates of resistance for all antibiotics examined, except for tetracyclines and quinolones. In contrast, Tennessee and Georgia showed notable percentages of drug-resistant infections for three of the seven antibiotics assessed, while New Mexico reported the lowest overall resistance levels.

Varga highlighted that the reasons behind these discrepancies are multifaceted. Factors such as varying climate conditions, the prevalence of poultry farms, differences in reporting methods, and additional variables could influence the resistance rates detected in national data.

Interestingly, the study also noted a decline in overall tetracycline-resistant C. jejuni infections from 49.13% in 2013 to 41.36% by 2019, contrasting with the rising quinolone-resistant cases. Quinolones, including medications like ciprofloxacin and levofloxacin, are generally utilized to treat campylobacteriosis, which may influence the emergence of quinolone-resistant strains.

“Most human cases of C. jejuni do not require antibiotic treatment,” Varga pointed out. “When treatment is necessary, azithromycin, a macrolide antibiotic, is typically the preferred choice. Our findings indicate low resistance levels to macrolides, which is encouraging.”

In light of this study, Varga noted that the poultry industry is actively decreasing its usage of antibiotics. “Despite the rise of quinolone resistance in Campylobacter, these antibiotics are infrequently applied in poultry production,” he stated. Previous research from Varga’s lab, involving samples from chickens and turkeys between 2013 and 2021, showed significant resistance levels to tetracyclines in chickens and both tetracyclines and quinolones in turkeys.

Taken together, both this and the preceding study underscore the urgent need for further investigation to comprehend these trends more thoroughly and to develop new strategies aimed at mitigating and containing the proliferation of antibiotic-resistant pathogens within the food supply and beyond, according to Varga.

While NARMS data plays a critical role in tracking trends, Varga cautioned that they likely underestimate the total incidence of foodborne infections. “This represents merely the tip of the iceberg,” he remarked. “There is substantial underreporting of these cases, as many individuals do not seek medical attention based on their symptoms, and not everyone undergoes testing.”

Additionally, Varga is affiliated with the Carl R. Woese Institute for Genomic Biology and the Program in Ecology, Evolution, and Conservation Biology at the University of Illinois.

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