Manufacturing MRSA on Our Factory Farms

A federal judge in Denver, Colorado on Tuesday sentenced the two owners of the cantaloupe farm that caused a deadly Listeria outbreak in 2011 to five years probation, six months home detention, and $150,000 each in restitution fees to victims.

As we wrote last November, brothers Eric and Ryan Jensen owned Jensen Farms in Colorado, where they grew the cantaloupes that sickened at least 147 people with Listeria and killed more than 30, making it one of the deadliest foodborne illness outbreaks in U.S. history.

The case has been a landmark in foodborne illness litigation, becoming one of the first instances in which food producers faced criminal charges for their contaminated food.

The Factory Farm

The reason this case matters to us is that researchers are now reporting that MRSA, too, is coming to us via the food production system. As we said in our November post: It’s crucial to understand that this is not a case [just] about listeria, it could have been any pathogen that found its way into the nation’s food supply and ended up hurting people. And … there is a rising tide of foodborne illness – the pathogen studied was MRSA – infecting the community because of the new way we are producing our food, the so-called factory farm system.

The US Environmental Protection Agency defines a factory farm- also called a mega-farm or a CAFO – a confined or concentrated animal feeding operation – as a facility that has at least 1,000 pigs, though most are many thousands larger.

Rows of pigs inside the factory farm

By last summer the science caught up with these factory farms and told us they are incubating disease and spreading it to nearby populations. A report in the Journal of the American Medical Association found an increased incidence of MRSA infections in populations close to factory farms compared to communities not near to them. And a study published in the Public Library of Science compared workers on factory farms to workers on traditional farms (where antibiotics aren’t used) and found significant amounts of livestock-associated MRSA (LA-MRSA) only on workers from the factory farms.

And now it’s being reported that a third study, due out in next month’s Infection Control and Hospital Epidemiology, concludes there’s almost three times the risk of carrying MRSA if you live within one mile of a farm housing 2,500 or more pigs.

In other words, we’re “manufacturing” MRSA because of the way we produce our food. The workers themselves become carriers as do people in nearby communities. And here’s the thing: when any of these people get sick they go to hospitals where they carry and can spread these new strains of MRSA – they bring them from the farms to the cities.

So what does the future hold? As we wrote last November:

The big picture is this: Old MacDonald no longer has a farm. Food production in this century has been taken over by large industrial concerns for the same reason that the production of cars, steel, and oil became dominated by giant corporations last century – there’s just no other way to keep up with the growing demand.  We have entered into a new age of food production and along with it we have given rise to a Third Wave of MRSA [LA-MRSA] that if left unchecked has the potential to outstrip both the hospital  [the First Wave] and the community[the Second Wave] as a source of the pathogen.

Dental Students are at Risk for Increased Exposure to MRSA: What does this mean for their Patients?

Dental student are at a much greater risk of being exposed to methicillin-resistant Staphylococcus aureus (MRSA), the potentially lethal bacteria often found in hospitals and now increasingly in the general community. Known as one of the superbugs due to its ability to resist multiple antibiotics, the mortality rate for a MRSA bloodstream infection is about 20-30%.1  The findings of a recently published study in The Journal of Hospital Infection entitled “Higher prevalence of methicillin-resistant Staphylococcus aureus among dental students  lead to the inevitable conclusion that greater consideration for infection control and prevention is needed for both dental clinicians and their patients.

The study undertaken in Mexico City comparing 100 dental students (exposed to patients for 5-6 years) with 81 non-dental students found that the dental students had a significantly higher rate of carriage of MRSA. The study found that 20% of the dental students versus 6% of non-dental students were colonized with MRSA (odds ratio: 4.04; 95% confidence interval: 1.6–12.6; P = 0.0033). The conclusion of the study is that the dental students were occupationally threatened by exposure to this highly antibiotic resistant pathogen with implications that greater steps are needed to try to address this potential risk to their health. The other worrisome implication of this study is that these dental clinicians are also likely to be vectors for MRSA transmission to their patients if the proper precautions are not undertaken.

A key observation from this Mexican study underscores how widespread MRSA is in Mexico. If our data is to be trusted, North American and UK rates of MRSA colonization are significantly lower than in Mexico…. 2-3% versus the 6% found in the study’s non-dental student population. People colonized with MRSA are at a greater risk of self-infection, especially when immunocompromised as in the case of a surgery or major illness. 20-60% of patients identified as being colonized with MRSA in hospital subsequently develop an MRSA infection 2

Until recently, most antibiotics in Mexico were available over the counter and not by prescription. The ability of patients to self-prescribe (not matching the appropriate antibiotic to the prevailing infection) combined with standard non-compliance practices (taking sub-lethal doses) led to the emergence of high antibiotic resistance rates as evidenced by the finding of this study. Fortunately, there are greater controls over how antibiotics are now dispensed in Mexico which should help to lower antibiotic resistance rates in the Mexican public in the future. A reduction of the overuse and abuse of antibiotics in Mexico should, in the future, contribute to lowering the risk of MRSA colonization in the dental clinician population. In the meantime, however, the results of this study are shocking and must be taken as sign that more must be done to protect the dental clinician and their patients from this potentially deadly superbug.


Antibiotic Resistance: The Inevitable Result of Misuse and Overuse of Antibiotics

One of today’s top global health crisis is the threat stemming from the rise of antibiotic resistance. Antibiotic resistance refers to the ability of potentially harmful microorganisms to be unresponsive to, or unaffected by, the effects of antibiotics. 1 Modern uses of antibiotics (including in livestock as growth promotion) have generated resistance in many of our antibiotics. 2

Diagram: Mechanism of Horizontal Gene Transfer (HGT) in Bacteria (3) (4)

Brought about primarily by exposure to sub-lethal doses of antibiotics, antibiotic resistance occurs because microorganisms adapt and change in order to survive. In the face of hostile environments, these pathogens are able to alter themselves rapidly in order to reduce the effectiveness of our antibiotics. If you like, sub lethal doses of antibiotics act like vaccines for micro-organisms.

One of the most interesting of resistance mechanisms is something called “horizontal gene transfer”, a process by which bacteria are able to swap genetic material. Antibiotics kill only the susceptible bacteria. Resistant strains of bacteria that survive these antibiotics multiply, replacing the susceptible bacteria, and communicate important survival mechanisms to neighbouring bacteria. In this manner, bacteria can become resistant to multiple drugs, and in some cases, all antibiotics. Patients who are regularly subjected to multiple doses, sub lethal doses or even long term doses of antibiotics can find themselves over time, unresponsive to many of today’s antibiotic arsenal, and therefore vulnerable to infection. With so few new classes of antibiotics under development, the prospect of developing multiple antibiotic resistance is truly worrisome.

  2. Tiwari R, Tiwari G. Use of antibiotics: From preceding to contemporary. Scho Res J [serial online] 2011 [cited 2014 Jan 15];1:59-68. Available from:
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