Salmonella infections remain a significant public health concern across the globe, and in Israel, one specific strain—Salmonella Muenchen—has become the dominant serotype causing infections in recent years. Emerging research highlights the role of poultry, particularly chicken meat, in transmitting this multidrug-resistant pathogen to humans. The increased prevalence of Salmonella Muenchen in both the human population and poultry flocks has raised alarm bells, prompting a call for more stringent surveillance, vaccination, and biosecurity measures in the food industry.
The Rise of Salmonella Muenchen in Israel
Over the last several years, Salmonella Muenchen has emerged as the leading cause of salmonellosis in Israel. According to a study published in the journal Emerging Infectious Diseases, the prevalence of this pathogen has significantly increased, particularly since 2018. In 2017, Salmonella Muenchen accounted for just 2 percent (101 out of 5,072) of all Salmonella infections reported in humans. By 2022, however, this figure had risen dramatically to 35.4 percent (1,124 out of 3,171) of reported cases. This surge is mirrored in poultry-related cases, where the serotype has become increasingly prevalent in commercial poultry farms and food products.
In the poultry industry, isolates of Salmonella Muenchen in animal sources increased from 3.8 percent (63 out of 1,672) in 2017 to 23.6 percent (202 out of 857) in 2021. Similarly, Salmonella presence in food products, particularly ready-to-eat items from poultry slaughterhouses, rose from 4.9 percent (12 out of 245) in 2017 to 20 percent (43 out of 215) in 2021. These statistics point to a growing and persistent problem with this specific strain of Salmonella in Israel.
Genetic Similarity and Multidrug Resistance
One of the most concerning findings in the study is the genetic similarity between Salmonella Muenchen strains found in humans, poultry, and food products. Using whole genome sequencing (WGS), researchers analyzed 109 Salmonella Muenchen isolates from Israel collected between 2020 and 2023. These isolates were compared to 125 global strains, showing significant genetic similarity between Israeli isolates and those from countries such as the United Kingdom, South Africa, and the United States. This finding suggests that there may be a global spread of contaminated poultry breeding stock or travel-associated transmission, leading to the rise of multidrug-resistant strains across multiple regions.
Role of Poultry in the Spread of Salmonella Muenchen
The study’s findings strongly suggest that poultry broilers—young chickens raised for meat production—are an important source of Salmonella Muenchen infections in humans. A major concern is the high genetic similarity between strains collected from broiler flocks and those found in human cases, indicating a direct link between the consumption of contaminated poultry meat and the rise in human infections.
The prevalence of Salmonella Muenchen in commercial broiler flocks was found to be alarmingly high, reaching 61.5 percent. While genetic evidence did not trace the origin of the pathogen to breeder flocks (adult birds used for reproduction), researchers noted the on-farm persistence of the strain. This means that even after hatching, broiler flocks could be exposed to the pathogen through the farm environment, including contaminated soil and barn litter.
While vertical transmission (from breeder to production flocks) remains a concern, horizontal transmission—spread between birds within the same flock after hatching—appears to be an equally significant factor. This complicates efforts to control the spread of Salmonella Muenchen, as the pathogen is able to persist and propagate in farm environments, even if birds are vaccinated.
Vaccination and Control Measures
In response to the increasing prevalence of Salmonella Muenchen, Israeli authorities have taken steps to implement stricter control measures. Starting in March 2024, mandatory vaccination for breeder flocks against Salmonella Muenchen will be required. However, researchers caution that this measure alone may not be sufficient to curb the spread of the pathogen. Given the pathogen’s persistence in the farm environment, vaccination may have a limited impact on reducing overall contamination rates, particularly in broiler flocks where horizontal transmission is more common.
In addition to vaccination, researchers recommend several other strategies to reduce the spread of Salmonella Muenchen. These include improving biosecurity measures to prevent the introduction and spread of the pathogen, using probiotics to enhance gut health and resistance to infection in poultry, and expanding surveillance efforts throughout the poultry production chain—from breeding farms to slaughterhouses and ready-to-eat food products. Increased monitoring and testing of poultry products can also help identify and mitigate contamination before products reach consumers.
Transmission Routes and Public Health Concerns
The potential for Salmonella Muenchen to be transmitted through eggs as well as meat is another area of concern highlighted in the study. While eggs have not been conclusively proven to be a major source of human infections, the genetic similarity of the pathogen between layer flocks (egg-laying hens) and broiler flocks suggests that eggs could play a role in spreading the pathogen. Eggs, especially those that are undercooked or raw, are often a part of many dishes, particularly in households where there is less awareness of proper food handling and cooking practices. The researchers recommend further investigation into the role of eggs in the transmission of Salmonella Muenchen to humans.
From a public health perspective, the rising dominance of Salmonella Muenchen poses significant risks. This strain, which has developed multidrug resistance, is more difficult to treat with standard antibiotics. As a result, infections caused by this pathogen can lead to more severe illness, longer recovery times, and increased healthcare costs. Multidrug-resistant strains of Salmonella present a growing threat to food safety and public health worldwide, making it essential for countries like Israel to invest in comprehensive surveillance and control strategies.
The Global Challenge of Multidrug-Resistant Salmonella
The emergence of multidrug-resistant strains of Salmonella Muenchen is not just a problem for Israel—it is a global issue. The genetic similarity between isolates from Israel and those found in other countries underscores the potential for global dissemination of contaminated poultry breeding stock or travel-associated transmission. International cooperation will be necessary to address the spread of antimicrobial resistance (AMR) in Salmonella and other pathogens.
Conclusion
The growing dominance of Salmonella Muenchen in Israel highlights the urgent need for better control measures in poultry farming, improved biosecurity protocols, and more effective vaccination strategies. The research findings underscore the pivotal role that poultry—especially broiler chickens—plays in the transmission of this pathogen to humans, as well as the challenges posed by the multidrug-resistant nature of the strain.
The situation in Israel is a cautionary tale for other countries dealing with similar issues, and it calls for increased investment in surveillance, antimicrobial stewardship, and food safety education. Without these efforts, the public health risks posed by Salmonella Muenchen and other antibiotic-resistant pathogens will continue to escalate, posing a growing threat to global food safety.
