Understanding Antibiotic Resistance

Contributed by Brian Lubbers, D.V.M., Ph. D., Diplomate ACVCP, director of the Microbial Surveillance Lab, a unit of the Kansas State Veterinary Diagnostic Laboratory

Antibiotic resistance is a natural phenomenon. Resistance itself is a property, a characteristic of bacteria. Knowing that, some might say there’s nothing that producers or veterinarians can do to stop resistance. But that’s not the case, and there should be a discussion on what role producers and veterinarians can play in helping alleviate the pressure antibiotics put on increasing resistance. 

Why Antibiotic Resistance is Important to Discuss
Using antibiotics has the potential to enhance a resistant population within an animal. It’s the same situation in humans – every time someone takes an antibiotic, they are potentially enhancing resistance in that population of bacteria as well. A lot of focus is on the relationship between antibiotic use in animal agriculture and potential human resistance, but another area that doesn’t get as much attention is the impact of multi-drug resistance in livestock.

Take bovine respiratory disease (BRD) for example. BRD is the most costly disease in beef cattle in the United States.¹ There are four bacterial agents that are most often associated with BRD: Mannheimia haemolytica, Pasteurella multocida, Histophilus somni and Mycoplasma bovis. The amount of antimicrobial resistance in BRD bacteria hasn’t been studied very well, so Kansas State Veterinary Diagnostic Lab (KSVL) took a closer look into the disease and examined bovine lung tissue samples that were submitted through a three-year period. Results from the KSVL study indicated that more than 60 percent of Mannheimia haemolytica isolates (the primary bacterial agent in BRD) were resistant to three or more types of antibiotics commonly used to treat BRD. Of that 60 percent, half were resistant to five of the antibiotics used to treat BRD.
"Antiobiotic resistance is a real, natural phhenomenon. It's also very complex and not fully understood."
–Dr. Brian Lubbers, D.V.M.
To put that in perspective, there are only about six classes of antimicrobials used in BRD treatment. When the bacteria become multi-drug resistant, our choices of effective antibiotics become severely limited for treating cases of BRD.

What We Know About the Future of Antibiotic Resistance
Antibiotic resistance is a real, natural phenomenon. It’s also very complex and not fully understood. As antibiotics continue to be used in both animal agriculture and human medicine, the potential for resistance will increase. Meanwhile, the number of new antibiotics brought to market is declining. Our role is to better understand antibiotic stewardship and what part we should be playing in that initiative. 

1. Lubbers, Brian, Kansas State University College of Veterinary Medicine, Director of Clinical Microbiology. Animal Agriculture’s Contribution to Antibiotic Resistance – What Should & Shouldn’t Be On the Table. 2014 NIAA Symposium on Antibiotic Use and Resistance: Moving Forward Through Shared Stewardship. Atlanta, Georgia. November 12-14, 2014.