Pinpointing pathogens, dead or alive

  • Albert Canturri

    Pinpointing pathogens, dead or alive

    CVM graduate student designing better way to manage respiratory disease in swine

Mycoplasmal pneumonia of swine (MPS) first appeared in pigs a century ago, when producers had a hunch that it wasn’t influenza that was taking their droves. Today, the disease is nearly endemic.

“It exists in just about any country where pigs are raised,” says Maria Pieters, DVM, PhD, director of the College of Veterinary Medicine’s (CVM) Swine Disease Eradication Center. 

When the minuscule bacteria, called Mycoplasma hyopneumoniae, first enter a pig’s lungs, it can easily go undetected. But as the pig approaches the finishing stage, the bacteria cripples its respiratory system and stunts the swine’s growth. The infected pig takes longer to reach market size, elevating costs for producers. They also suffer, something veterinarians strive to eliminate. 

There’s a better way to manage the spread of the disease, and Albert Canturri, a PhD candidate in CVM, is designing it.

Testing the solutions 

Mycoplasma hyopneumoniae is a tricky bacteria to culture, meaning polymerase chain reaction (PCR) tests, like the ones used to test for COVID-19 in humans, are the best way to determine where the bacteria is present. However, the ultra-sensitive tests screen for the presence of genetic material, in this case from a specific bacteria, in any form. But the tests cannot produce vital information about whether or not the bacteria are alive. 

“We know that DNA is not short-lived, meaning DNA from dead bacteria cells can still be present in an animal for days or weeks, even though they are not infectious,” says Canturri, who is also a board-certified pathologist. “But when we are diagnosing a pig, we want to know what is happening right now, and we cannot detect that with a simple PCR test.”

Canturri set out to solve the PCR test problem last year with support from the MnDRIVE Global Food Ventures Research Fellowship.

In recent years, researchers, including teams from the University of Minnesota, have untangled the epidemiology of the bacteria, allowing veterinarians to develop strategies for disease elimination. The bacteria has already been eradicated in Switzerland, Finland, and Norway, and eradication projects are underway across the United States. But to test the progress of these efforts, pathologists need a test that can detect only live, and therefore infectious, bacteria. 

“The distinction between dead and alive bacteria is important because if the bacterium is dead, it can no longer be transmitted to other animals, so it isn’t a problem,” Canturri says. 

According to Pieters, the recent momentum surrounding Mycoplasma hyopneumoniae elimination programs means Canturri’s redesigned PCR test, which can detect the difference between dead and living pathogens, can benefit the entire swine production system.

“Many times we do an elimination program and think we’ve failed because we detect the bacterium, but it isn’t really a failed program, it’s just that the tests are picking up on noninfectious genetic material,” Pieters says. “It’s important to know so we don’t keep pouring resources into programs that have succeeded.”

Antimicrobial stewardship

Not being able to properly monitor the success of elimination programs has a ripple effect for another mounting threat. Since Mycoplasma hyopneumoniae is a bacterium, it’s treated with antibiotics and overuse comes at a steep cost to the future of medicine. 

Our food systems, environment, and healthcare rely heavily on antimicrobial drugs to treat and prevent disease, but each time an antibiotic is used, bacteria are given a chance to evolve the ability to resist the drugs that are designed to kill them. Antimicrobial resistance (AMR) is a major threat and food producers need new technologies, including Canturri’s novel PCR test, that enable them to use fewer antibiotics while maintaining a safe food system.