World Antibiotic Awareness Week

Cajsa Isgren was a resident in equine surgery at the PLEH, and is currently undertaking research for her PhD at University of Liverpool. Here she shares some of the issues around antibiotic resistance in horses and how it relates to her research for World Antibiotic Awareness Week (13-19^th November 2017).

Antibiotic resistance is a global problem, which not only affects people, but also our much loved pets and horses. You may wonder how antibiotic resistance applies to you and your horse, especially if your four-legged friend is ‘fit as a fiddle’ and you have been fortunate enough not to call the vet out for anything apart from routine visits. Should your horse get ill in the future it is important to understand why your vet may, or may not prescribe antibiotics.

Antibiotics inhibit the growth or kill bacteria and since the revolutionary discovery of penicillin by Alexander Fleming in 1928, infections that were previously likely to be fatal, could be treated which revolutionised human and animal medicine! since then many other antibiotics have become available and we take it for granted that if we were to suffer from a serious infection, these would always be available to treat the infection. However, bacteria are very adaptable, like animals they are able to evolve and adapt to their environment, except they can do this very quickly, as a bacteria can multiply every 20 minutes, so from one bacteria you can get up to 16 million in 24 hours. When they are challenged with antibiotics some bacteria may develop changes in their DNA, so that the antibiotic can no longer attack their bacterial target, or they may acquire new DNA or ‘resistance genes’ which also stops the antibiotic acting on its target. These ‘resistance genes’ can jump from one type of bacteria to a different types thus making the problem worse. These ’resistant’ bacteria may then further multiply making the infection harder to treat or spread to other individuals and they can also survive in the environment waiting for the next opportunity to cause infection.

You may also presume that drug companies will develop new antibiotics to deal with these resistant bacteria, however no major new types of antibiotic have been found in the last 30 years. The problem is that looking for new antibiotics and getting them to the stage where they can be used in a person or animal is very expensive and it’s a big financial risk for the pharmaceutical companies. Any new novel drug would be kept as a ‘last resort’ and would certainly not be for widespread use and would be kept for human use only. As equine vets, when we are faced with a horse with a bacterial infection the ’gold standard’ is to treat that animal with an appropriate antibiotic based on growing the bacteria in the lab and testing which antibiotics are able to kill it. Sound easy doesn’t it? The problem is time, as culture and antibiotic sensitivity takes at least 48 hours and in the mean time we have to make an appropriate choice of antibiotic based on the type of bacteria likely to be causing the infection.  There is less resistance to some of the more recently developed antibiotics and it may seem like a tempting option to reach for such drugs when in fact these should be preserved for those infections which have failed to improve to ‘first line’ antibiotics and/or where culture and sensitivity results reveal the infection is resistant to all other antibiotics and hence justifies such use.

I am an equine vet and I am currently doing a PhD at University of Liverpool and am in my second year of study. My research project is on ‘The emerging problem of antimicrobial resistance in hospitalised horses’ and my study involves looking at this issue in UK equine hospitals.  Previous research has identified that just like in people; horses may carry certain types of resistant E. coli bacteria in their faeces when they are in the hospital.  Whilst they are in the gut of the horse, they are unlikely to cause any harm and the horse is likely to stop shedding these bacteria a few weeks after they have left the hospital or stopped receiving antibiotics, which may also make them carry such bacteria for longer. You may wonder why this is of any interest if it does not cause any harm.The resistant E. coli may act as a potential source of infection should the horse have a wound or an incision, or become more susceptible from another type of infection if they are poorly. There is also a risk of these resistance genes in these E. coli jumping to other types of bacteria hence we are interested in ways to reduce this. This study is looking at identifying different factors that make the horse more likely to carry these resistant bacteria, such as antibiotic use and how they are managed in hospitals. This work will enable us to identify those horses which are more likely to carry these bacteria and then we can look at what changes we can implement to stop them carrying such resistant bacteria and preserve antibiotics for future use in horses.