Guest post: Will new FDA guidelines reduce threat from superbugs?

Guest post by Tim Fothergill, Ph.D.

In January of this year the British Chief Medical Officer urged her government to add  threat posed by superbugs to the official list of "Apocalypses to Worry About" along with catastrophic terrorist attacks and massive flooding. With typical British understatement, its actual name is the National Risk Register of Civil Emergencies but a very stark picture was painted of a post-antibiotic world in which routine operations, such as hip replacements, could prove fatal. In September, The Centers for Disease Control in the US issued a similar statement which estimated that 23,000 people die every year in the US from antibiotic resistant infections. So what is it that has Dame Sally Davies and so many others so worried?

"Superbug" is a term used to describe bacteria which are resistant to many common antibiotics which are used to treat infection. Resistance to these drugs makes treatment more difficult and has increased mortality rates. As resistance to individual antibiotics becomes more prevalent the number of deaths is only set to increase, especially because there is a dearth of research into new antibiotics. Antibiotics are used medically in the short term, so don't offer the same kind of return on investment for the pharmaceutical companies as drugs for chronic diseases or long-term treatments, such as anti-depressants or hypertension medications. Even more worryingly of all is that strains of potentially deadly infectious bacteria, such tuberculosis have already been identified that are resistant to every potential drug.

Against this background the FDA's announcement of a plan to phase out the agricultural use of antibiotics is very welcome. Many animals raised for human production are fed antibiotics as a matter of course to boost growth rates. The animals are not suffering from infection, but the drugs can help them grow faster, resulting in a more efficient production of meat for the market. For most drugs, there is a mandatory withdrawal period during which the animals are fed no antibiotics so that they will clear out of the meat prior to slaughter. However, the antibiotics can impact the food supply and human health in other ways. Not only is there concern about meat contaminated with resistant bacteria but the standard agricultural practice of using animal waste as fertilizer only increases the risk of releasing resistant bacteria into the environment contributes to the spread of resistance. This is of particular concern if the land fertilized in this manner is subsequently used to grow food crops that are typically consumed raw. Previous recalls due to bacterial contamination have included spinach and cantaloupe melons. The potential for harm would only have been greater if these cases had involved superbugs, but this possibility is becoming more and more likely. Resistant bacteria that are spread onto crops via animal manure fertilizer have been demonstrated to not only persist in the soil but to also pass the genes for antibiotic resistance onto other species. As we have no control over this genetic transfer it is quite possible that they spread to even more pathogenic species.

The FDA's proposal to limit antibiotics in cattle feed would seem like good news then. However, the most significant caveat with this plan is that it is voluntary and as such is dependent on the cooperation of the drug producers and farmers. Two of the largest antibiotic producers, Zoetis and Elanco, have indicated that they will no longer labelling their products as suitable for growth promotion. Any subsequent use of these antibiotics for growth promotion would be "off-label" and something that the FDA can and does regulate. However, as with all regulation the devil will be in the details. We do not know yet what the change in labelling will actually say. If their new label can be interpreted in such a way that cattle are still regularly fed antibiotics then nothing will have been achieved.

For example, in Denmark they found that after introducing a ban on antibiotic use for growth promotion in cattle that the quantities of antibiotics actually increased. Animals no longer fed a sub-therapeutic level of antibiotic became more susceptible to infection and thus need therapeutic treatment more often. At first glance this might seem as if little has changed but antibiotics taken at therapeutic levels for the prescribed duration will result in fewer occurrences of resistance to the antibiotic in question. Anybody who has been told by their doctor to ensure that they take the full course for an infection will know this. By reserving antibiotic use for therapeutic use only, where it is needed in greater quantities to fight infections, not only will there be fewer superbugs released into the environment, but the drug companies will stand to increase their sales. This might explain their willingness to cooperate with these proposals. Their other option would be to switch production to antibiotics which are not regarded as being important for human health (such as the ionophores) as these are not covered by these new proposals. However, this is something that would presumably involve some cost to them.

It is also worth comparing the timescale for voluntary phase-out (three years) with the length of time it would take the FDA (presumably in collaboration with the USDA) to implement a strategy for an obligatory regulatory framework, which might have more teeth in terms of enforcement, but which is not yet on the table. The FDA has many admirable qualities but turning on a dime is not one of them. This process would take at least that long if not longer. What we do not know at this point is whether there are plans for the FDA to pursue such mandatory regulation if this voluntary arrangement is found not to be working. Such efforts would presumably require specific budgeting and it seems unlikely that this will happen any time soon given the current state of Congressional deliberations on budget matters. Another possible mandatory option would be Louise Slaughter's PAMTA bill which is currently with the Health Subcommittee.

If our goal is to reduce the spread of antibiotic resistant bacteria from agriculture then the FDA plan may in fact be the best option, and it is certainly better than doing nothing. Mandatory regulation seems unlikely at this point. However, accountability is still vital to the success of this voluntary agreement. What form could this accountability take? The FDA must be prepared to state publicly if insufficient progress is being made. Also, it is to be hoped that increased demand from major chains like Chipotle, McDonalds and KFC will help. If they were to make this demand then cattle production would change at a much faster pace than that proposed currently. This means that consumers are in a position to contribute by choosing to support suppliers of meat produced in a way consistent with these new guidelines.

********************