Scientists Never Expected to Discover Antibiotic-Resistant Bacteria Here…

Analysis by Dr. Karen Shaw Becker

Howler Monkey

Story at-a-glance -

  • Wildlife experts have discovered animals in the jungles of Mexico that carry strains of antibiotic-resistant bacteria. This is both a surprising and alarming finding, since these animals rarely encounter people, much less antibiotics
  • Superbugs resistant to clinical antibiotics were found in the feces of wild howler monkeys, spider monkeys, tapirs, jaguars, a puma, a dwarf leopard, and jaguarundis
  • Researchers found isolated bacteria that were resistant to synthetic antibiotics such as fluoroquinolones. This suggests the resistance is acquired rather than natural

By Dr. Becker

Antibiotic-resistant bacteria have been a serious health concern in human and veterinary medicine for several years now, and increasingly, scientists are discovering the problem among wildlife as well, most recently in monkeys inhabiting the remote jungles of Mexico.

Antibiotic Resistance and Superbugs

Antibiotic resistance describes a situation in which bacteria are able to survive and multiply despite the presence of an antibiotic that once was able to kill them off or stop them from proliferating.

In most cases, even when bacteria are exposed for the first time to a particular antibiotic, the majority will die, but some will survive and pass on that resistance to other bacteria. Unlike higher organisms, bacteria can transfer DNA not only to bacteria that is not their offspring, but even to bacteria of other species.

The problem is not that certain disease-causing bacteria are antibiotic resistant, it’s that the resistance genes in any type of bacteria can transfer their survivability to billions of other bacteria. This is how superbugs are born. A superbug is a strain of bacteria able to survive an assault by multiple types of antibiotics.

Antibiotic Resistance Found in Wildlife in Southeast Mexico

In a research article published recently in the journal PLoS ONE,1 wildlife biologist Jurgi Cristóbal-Azkarate documented his 2014 discovery of superbugs in the feces of wild howler monkeys near Veracruz, Mexico. These monkeys are rarely exposed to humans, much less antibiotics.

Antibiotic resistance is typically found in settings where the drugs are heavily used (and abused), for example, hospitals in urban areas and factory farms. That’s why Cristóbal-Azkarate was both surprised and alarmed to find resistant bacteria in the jungle, far from civilization.

Cristóbal-Azkarate and a team of researchers documented their findings of a profusion of superbugs resistant to clinical antibiotics in the feces of seven types of wildlife in the Veracruz region of southeast Mexico. These included the howler monkeys, plus spider monkeys, tapirs (large herbivores that resemble pigs), jaguars, a puma, a dwarf leopard, and jaguarundis.

The team also learned that monkeys living far from humans were just as apt to harbor drug-resistant bacteria as those living closer to settled areas.

According to Randall Singer, an epidemiologist at the University of Minnesota, “Resistance is everywhere. It is found in places that are ‘pristine’ and in places that are ‘polluted.’”2 Additional discoveries of superbugs in wildlife include enterobacteria discovered in wild rodents in Britain,3 and terrestrial iguanas on the Galapagos Islands.4

Evidence of Acquired vs. Natural Resistance

It’s conceivable that some antibiotic resistance is naturally occurring. Most antibiotics are created from bacteria and fungi, and most bacteria have been exposed to these microbial by-products for millions of years.

However, Cristóbal-Azkarate found isolated bacteria that were resistant even to relatively recently developed synthetic antibiotics such as fluoroquinolones. This suggests the resistance is acquired vs. natural, and has spread from human-populated areas. The wildlife in Mexico may have been exposed to human or animal waste that carried the resistant bacteria.

The superbugs don’t appear to be harming the wildlife that harbor them, but some experts are concerned they could mutate further and ultimately reappear in the human population in the form of unfamiliar infections that could prove extremely difficult or impossible to treat.

According to study co-author and microbiologist Carlos Amábile-Cuevas, currently “we are completely in the dark [about] which kind of processes led to this type of resistance.”5

Antibiotic Resistance and Human Health

According to the Keep Antibiotics Working organization, due to widespread overuse of antibiotics, the spread of resistance is intensifying in the human population. Today, some strains of bacteria have grown resistant to several previously effective drugs.

Resistant bacteria can cause longer illnesses and increase the risk of dying from an infection. For certain infections, only one or two medicines “of last resort” are now effective.6


  • Staphylococcal bacteria are common causes of infection, including life-threatening illnesses such as toxic shock syndrome, and infections of the heart valves. In the US, nearly every strain of Staphylococcus aureus has become resistant to penicillin. Many strains are also resistant to newer medicines related to the drug methicillin. Even vancomycin has been losing its effectiveness since 1997.7
  • Campylobacter bacteria are the most common cause of bacterial food-borne illness, causing over 2 million cases of food poisoning annually. Most Campylobacter infections do not require treatment, but of those that do, one in six are resistant to a fluoroquinolone antibiotic, the treatment of choice for food poisoning. Ten years ago, such resistance was negligible.8

Per Keep Antibiotics Working:

“While medical use of antibiotics is a major contributor to the emergence of antibiotic resistance, agricultural uses also pose a significant problem since they promote the development of resistant bacteria that can reach humans through several different pathways - directly via contaminated food or indirectly via environmental contamination.

“U.S. meat producers routinely put low levels of antibiotics into feed given to non-sick animals, both to spur faster growth and to compensate for raising animals in the crowded industrial-scale conditions which now predominate in the US. Many of the 17 antibiotics used to promote livestock growth are identical or closely related to those used to treat sick people.”9

Antibiotics and Pets

Antibiotic resistance is not only a serious concern for humans, it is also a rapidly growing problem for our companion animals. Veterinarians are seeing dramatic increases in bacteria strains that are resistant to multiple classes of drugs.

As the problem of antibiotic resistance in pets continues to grow, vets will have fewer and fewer options for treating infections in your dog or cat.

It is my belief that antibiotics are overprescribed in too many conventional veterinary practices. Not only can overprescribing cause your pet to develop an allergy to the medication over time, even worse, too frequent and unnecessary use of these drugs is contributing to the escalating problem of antibiotic resistance in pets, just as it is in people.

When your veterinarian can no longer cure bacterial infections in your pet with antibiotics, the life of your beloved dog, cat or other animal is threatened. The MRSA bacteria is the most widely recognized example of a potentially fatal staph infection that is resistant to even the most powerful antibiotics in use today.

How You Can Help

The next time you buy meat or poultry, choose products from animals raised without the routine use of antibiotics. You can use the Eat Well Guide to find local, sustainable, organic food sources.

Also look for meat products labeled “certified organic,” or “raised without antibiotics,” or “no antibiotics administered.” Every time you make a choice to avoid factory-farmed food, you help the effort to put food producers on notice and to change public policies regarding the use of antibiotics in food animals.

When it comes to your pet, if an infection is suspected, your veterinarian should without fail do a culture and sensitivity test to determine exactly what type of bacteria is involved and the best drug to treat it. It’s no longer appropriate for vets to make an educated guess about what pathogen is involved, given the growing danger of antibiotic resistant strains of disease-causing bacteria.

Deciding a treatment protocol should also involve using an appropriate antibiotic that can also be administered (by injection, orally, or topically) for optimum result in the specific area of the body harboring the infection.

A culture and sensitivity test takes a little extra time, so prepare to leave your vet appointment without a definitive diagnosis or antibiotics the day the culture is taken. But the additional time it takes to identify the bacteria and the drugs it best responds to will allow precise treatment of your pet's infection rather than a hit-or-miss approach. Your dog or cat will heal more quickly and thoroughly, and you have also dramatically reduced her exposure to antibiotics.