Reproduce and Validate Results

A publication from Ohio State University recently reported the detection of bacteria carrying carbapenem-resistant genes on a pig farm in Ohio, which immediately became big news in the popular press. Carbapenems are known as the “last resort” antimicrobials. It is an interesting observation from a project, which basically collected samples from the animals and the environment using the “Swiffer” technique (Swiffer clothes are used to monitor cleanliness of surfaces in truck cabs, cargo areas and wash bays, as well as other areas of interest). But what does all this really mean at this time? 

Let’s look at the facts:

1. These carbanepem-resistance genes were detected in bacteria collected from one pig farm. 

2. They were not found in samples from animals, rather they were recovered only from environmental samples
collected at the sow herd level.

3. No resistance genes were detected in the wean-to-finish flow or in any market animals.

4. Carbapenems are not used in food animals.

5. The researchers have no idea how the genes actually entered the farm.

6. Very intensive methods were used to enhance the growth of the bacteria along with the use of very sensitive techniques to identify the resistance genes.

In my opinion, while it is a very interesting observation, at this time it is an “N of 1,” that is, this observation has only been identified on one farm and has not been replicated and validated across multiple farms. Furthermore, with the advent of very sensitive tests (metagenomics), our ability to scrutinize samples at the genomic level has increased significantly. 

This reminds me of what happened after the PCR test for PRRSV was made available to the public. As many of you recall, we found the virus everywhere, and not all positives were true positives. A lot of incorrect conclusions were drawn early on and a lot of learning was required to sort out what the results actually meant. In regard to the source of these genes, they might have come from several sources that have nothing to do with the pig itself: feed, air, flies, dust, trucks, people, supplies, who knows? The authors surely don’t and made that clear in their paper.

Now, if this observation gets reproduced and validated across multiple investigators, farms and labs, then it will need to be given the proper attention, and plans to mitigate risk will need to be put in place. For example, one idea could be that because the carbapenem antibiotics are related to cephalosporin antibiotics, we might need to consider using a different antibiotic at processing and what public perception would be of this practice.

In the end, I don’t think this calls for termination of cephalosporin use. These are data from one farm, we know that when used responsibly, cephalosporin antibiotics are valuable tools to treat sick pigs, and clearly this study calls for more research in this area. However, we need to acknowledge this observation and pay it the respect it deserves. I am confident that if we follow the principles of responsible sharing of truthful and non-misleading information about medicines with healthcare professionals and payers as recommended, we will be able to use cephalosporin antibiotics to treat our sick pigs safely and efficaciously for years to come.