Can Samples Collected From Water Bowls Make Feedlot Antibiotic Resistance Surveillance Easier?

Background

Preventing antimicrobial resistance (AMR) is a major priority for the beef industry, but currently all methods to determine antibiotic resistance in BRD bacterial pathogens require the collection of deep nasal swabs from individual animals. This is costly, labor intensive, and not that easy to do, so it isn’t ideally suited to routine surveillance data collection. In contrast, sampling for AMR in gastrointestinal microbes is easy, because it can rely on fecal samples collected from the pen floor – no individual animal handling or sampling is needed. An ability to collect informative samples for antibiotic resistance in BRD pathogens using pen level samples rather than individual animals would benefit both AMR surveillance and research efforts.

Objectives

• To investigate whether water bowl samples from within feedlot pens can be used in place of individual cattle nasal swabs

• To generate accurate data on pen-level resistance profiles of bovine respiratory disease (BRD) pathogens

What they DID

Since water bowls are known to be a place in which infected animals can pass BRD pathogens to other animals, these researchers saw if water bowl samples could be used to accurately determine pen level AMR in BRD pathogens.  Researchers worked with a commercial feedlot to evaluate sixteen 250 head pens.  Researchers collected water bowl samples from each of these pens on days 0 (before pen filling), and 7, 14, 21, and 28 days after cattle placement.  Researchers then isolated BRD-associated bacteria from the water samples and determined antibiotic-resistant profiles.  They also used DNA-based methods to analyze prevalence of BRD pathogens in water bowls.

What They Learned

Overall, the researchers showed that water bowls in feedlot pens can be a source of BRD-associated bacterial pathogens, with prevalence increasing after cattle placement. While the BRD bacteria Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni could not be cultured from water, their prevalence was high when analyzed by more sensitive molecular methods (i.e. polymerase chain reaction). This was likely due to dilution of BRD pathogens among non-target bacteria making it challenging to identify the pathogens properly, and die-off of those pathogens from the time water was collected, to when it was processed. In contrast, the researchers were able to culture M. bovis from water. The M. bovis showed similar antimicrobial resistance to isolates from other feedlot studies, notably high levels of resistance against chlortetracycline, tilmicosin, and tylosin.

What It Means

Water bowls in feedlot pens may be a reservoir of BRD bacterial pathogens, and thus present a mitigation point for limiting the spread of respiratory pathogens among cattle.  The researchers showed that water bowls can be used as an indicator of pen-level antimicrobial resistance for M. bovis. They also learned that to achieve better isolation of BRD pathogens from water bowls, samples should be processed soon after collection, and with the use of selective growth media. They will employ this knowledge in a new study currently taking place to further evaluate the presence of BRD-associated bacteria in feedlot water bowls.