Raw Milk, Cheese, Beef... Where is the Infection? The Spread of Antibiotic-Resistant "S. Dublin" in the U.S.: How This Threat, Impervious to Antibiotics, Affects Our Tables and Workplaces

On August 24 (local time), Brazil's InfoMoney reported that "antibiotic-resistant 'superbugs' are spreading in cattle in the United States, posing a threat to humans." Behind the article is a large-scale genomic analysis study of Salmonella Dublin (hereafter S. Dublin) led by Penn State University. The study compared 2,150 strains collected from cattle, humans, and the environment, showing that many strains are genetically very close despite different hosts, and that characteristics indicating antibiotic resistance are expanding. In other words, the same "face" of bacteria circulating between farms, processing environments, and humans is reducing the options for treatment. InfoMoneypsu.eduASM Journals

Key Points of the Study: Why "One Health"?

The paper published in the journal Applied and Environmental Microbiology conducted a cross-sectional analysis of three "reservoirs": cattle (581 strains), humans (664 strains), and the environment (905 strains). It showed that the SNP differences between strains are small, indicating close genetic relationships, and that it is not safe to assume differences based on origin. Resistance profiles also diverged, with genetic changes related to drugs commonly used in human medicine (e.g., fluoroquinolones) being prominent in food and environmental strains, suggesting a transfer of "selective pressure" from livestock to the human domain. The research team emphasizes that countermeasures should be implemented within the One Health framework, which encompasses livestock, humans, and the environment. ASM Journals

Why It's Not Just "Ordinary Food Poisoning"

S. Dublin is a salmonella adapted to cattle, causing severe conditions such as pneumonia and septicemia in calves. Although human infections are infrequent, they tend to be severe, with past U.S. data showing hospitalization rates rising from 68% to 78% (1996–2004 vs. 2005–2013) and mortality rates from 2.7% to 4.2%. The proportion of bloodstream infections is also high, deviating from the general image of "just gastroenteritis." PMC

How It Reaches Humans

There are three main routes.
(1) Food: Unpasteurized milk, natural cheese, undercooked beef, etc. There have been many historical reports of S. Dublin cases related to raw milk.
(2) Occupational Exposure: Direct contact at farms and meat processing, exposure to feces, saliva, and aerosols.
(3) Environment: Transmission via "objects" such as barns, equipment, clothing, and boots.
The study indicates signs of resistance-related mutations associated with human antibiotics accumulating in food and environmental strains, underscoring the importance of hygiene management in kitchens and workplaces. ASM JournalsCDCAmerican Association of Bovine Practitioners

Impact on U.S. Livestock and Food Safety

S. Dublin is notable for "multidrug resistance (MDR)" when isolated from U.S. cattle, complicating treatment and culling decisions. Recent estimates of economic losses have progressed, with European estimates suggesting additional costs of over 10,000 euros per farm annually. The decline in productivity, culling, biosecurity costs, and impact on distribution could potentially affect consumer prices. bovine-ojs-tamu.tdl.orgDairy ProducerFood Poisoning News

Reactions on Social Media: What's Spreading and Being Discussed

On X (formerly Twitter), accounts of researchers and research institutions introduced the paper, highlighting keywords like "cross-sectional analysis of over 2,100 strains," "close genetic relationships across livestock-human-environment," and the "spread of AMR (antimicrobial resistance)," promoting One Health-type measures. In contrast, general users expressed behavior changes such as "avoiding raw milk and natural cheese for the time being" and "ensuring thorough cooking of raw meat," while the livestock industry made earnest appeals to "avoid reputational damage and promote scientific communication." Both sides strongly call for transparent information disclosure and standardized measures, rather than "excessive fear." X (formerly Twitter)

Common Misunderstandings and Correct Understanding

• "Salmonella = Just Stomach Pain" is a Misunderstanding: S. Dublin has a high proportion of bloodstream infections, increasing the risk of hospitalization and death. Caution is needed for the elderly, infants, and immunocompromised individuals. PMC

• "Increasing Antibiotics Will Solve It" is Also a Misunderstanding: Multidrug resistance is the core issue. Overuse selects for further resistance. Optimization of use (stewardship) within One Health is essential. ASM Journals

• "Is Heating 100% Safe?": Managing core temperature is effective, but cross-contamination (e.g., raw meat juices getting on salad) measures are equally important.

• "Raw Milk is 'Natural' and Therefore Safe": There have been repeated reports of S. Dublin cases related to raw milk in the past. Choosing pasteurized is fundamental. CDC

What Should Be Done: Practical Action List

Individuals and Households

• Cook beef to a core temperature of 71°C, especially ground meat. Use separate cutting boards and knives for raw meat, and wash with detergent and hot water after use.

• Avoid raw milk and unheated cheese (especially if pregnant, elderly, infants, or with underlying conditions).

• Avoid food preparation by those who are unwell; keep refrigerators below 4°C and freezers below -18°C.

Livestock and Food Chain

• Antibiotic Stewardship: Adhere to treatment guidelines, review prophylactic routine use, and provide data for surveillance.

• Enhance Biosecurity: Quarantine and unify origins of introduced cattle, separate movement lines, categorize clothing, boots, and equipment, manage visitors, and implement rodent control. FrontiersAmerican Association of Bovine Practitioners

• Network Management: Visualize and restrict livestock movement, and quickly isolate, clean, and disinfect upon infection confirmation. journalofdairyscience.org

• Monitoring and Information Disclosure: Utilize disease diagnosis and WGS (whole genome sequencing) to expedite origin identification and recall decisions. ASM Journals

For Those Still Anxious

The headlines may be alarming, but the measures we can take are clear.Choose pasteurized milk, cook thoroughly, and prevent cross-contamination—by adhering to these three practices, the risk can be realistically reduced. For the industry, smart use of antibiotics and farm hygiene, along with data-driven rapid actions, are key. The message of the research is not to incite fear but to "view humans, animals, and the environment on a single map." psu.edu

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