Antibiotic-resistant Campylobacter is more common on foreign chicken than domestic meat, according to an analysis in Sweden.
Research also found the majority of Campylobacter infections in patients infected abroad were resistant to antibiotic groups that are important in healthcare. However, no bacteria from meat or patients were resistant to a group called macrolides that are the first choice to treat severe infections. This group includes azithromycin and erythromycin.
Antimicrobials – including antibiotics – are medicines used to prevent and treat infections in humans and animals. Antimicrobial resistance (AMR) occurs when bacteria, viruses, fungi and parasites no longer respond to medicines making infections harder to treat.
The Swedish Food Agency (Livsmedelsverket) and Public Health Agency of Sweden (Folkhälsomyndigheten) investigated how common it was for Campylobacter from chicken meat in stores and in patients to be antibiotic-resistant. A total of 284 isolates from patients and 111 from chicken meat were included in the study.
Sweden generally has a lower use of antibiotics for both humans and food-producing animals compared with other countries. Most people with a Campylobacter infection recover after about a week and antibiotics are given only in severe and long-term cases.
The work found 85 percent of Campylobacter from Swedish chicken meat and 58 percent from foreign meat were sensitive to important antibiotic groups.
A total of 76 percent of people infected in Sweden had Campylobacter that was not resistant to front line antibiotics but for those infected abroad the figure was 21 percent.
Results for meat
The same types of resistance markers to the clinically important classes of antibiotics quinolones, tetracyclines and aminoglycosides were found in Campylobacter jejuni from chicken meat and patients.
Following a large outbreak linked to domestic chicken meat in 2016-17 the Public Health Agency of Sweden and Swedish Food Agency genetically compared Campylobacter from retail chicken meat and Swedish patients. Similar smaller outbreaks were recorded in 2018 and 2020.
In 67 of the 79 isolates of Campylobacter jejuni from Swedish chicken meat, no mutations or genes encoding resistance to the important classes macrolides, quinolones, tetracyclines, or aminoglycosides, were identified. However, 14 of 24 isolates from meat from other countries lacked such resistance determinants.
For Campylobacter jejuni from Swedish, conventionally bred chicken, 40 of 45 isolates lacked genes or mutations for resistance to quinolones, macrolides, tetracyclines or aminoglycosides. For the 34 isolates from organic Swedish meat, 27 didn’t have such resistance markers.
A total of 87 different sequence types were detected in the 375 isolates of Campylobacter jejuni from chicken meat and patients.
Findings from patients
For Campylobacter jejuni from patients, 162 of the 212 isolates from domestically acquired infections and 11 of 53 isolates from travel-related cases contained no such signs of resistance.
Multidrug resistance was identified in only three isolates from patients, two of whom had likely been infected abroad.
The most common resistance determinant in isolates from chicken meat and patients was genes for resistance to beta-lactams, which are not recommended to treat Campylobacter infections. The main resistance type identified among the clinically important antibiotic classes was a mutation, which confers resistance to quinolones, followed by a tetracycline resistance gene and an aminoglycoside resistance gene.
The aim of the study was to increase knowledge about the resistance situation of Campylobacter in Sweden and to get a basis for source attribution, risk assessment and management regarding the pathogen in chicken meat.
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