There has been a new discovery of the mcr-1 resistance gene originating from bacteria in both animals and humans. This has led to the emergence of an epidemic that has strong resistance to most drugs. Other similar strains of these bacteria that do not possess the same strength of resistance to many drugs have always been around. These bacteria are from Enterobacteriaceae family that include popular bacteria such as E. coli and other rare ones such Klebsiella and Enterobacter. This has been evidenced by several past incidences of resistance from these bacteria.
What is alarming about the occurrence of the mcr-1 resistance gene is its prominent resistance to the extremely effective microbial infection resistant drug called colistin. This has been a great cause of concern as colistin is the drug of choice that most doctors turn to when encountered with infections. This causes a significant vulnerability as there is no drug capable of successfully counteracting the effects of such infections. Renowned drugs have unfortunately also fallen victim to this drug resistant strain of bacteria such as Enterobacteriaceae. In the past few years there have been worrying reports of extended spectrum beta-lactamase popularly known as ESBL creating resistant Enterobacteriaceae bacteria in horses.
These bacteria have a high resistance to even traditional drugs such as penicillin and variations of cephalosporins that have been established repeatedly as highly effective against serious infections. This has crippled antimicrobial treatment a great deal reducing options available for such treatments. What has grown to be a normal occurrence is their vulnerability to carbapenems such as meropenem and aminoglycosides such as amikacin. Extended spectrum beta-lactamase that are responsible for the production of these bacteria have been cited in healthy colonized and clinically infected horses. This has been the case in numerous countries.
Although carbapenems is rarely used with horses, Acinetobacter and carbapenemase-producing Enterobacteriaceae popularly known as CPE have been located in meager numbers in horses. These are resistant to antimicrobial drugs such as penicillins, carbapenems, cephalosporins and other highly effective drugs.
Due to their multi-drug resistance capabilities, the infections they cause have been classified as pan resistance. What is important to take note of, is that extended spectrum beta-lactamase found in horses are the same ones found in human beings. A good example is CTX-M-15. This emphasizes the huge potential of transmission of a zoonotic nature and indicates high probability equine infections having a human origin. The probability of meeting a horse that is infected with mcr-1 bacteria is low. However, equine infections will be uncontrollable if cases of bacteria that carry these genes increase in number in hosts such as humans, animal foods such as meat and the environment. Currently high levels of resistance to fluoroquinolones, cephalosporins and aminoglycosides are only of great concern to horses. This is because of high frequency of occurrence and few treatment options that are available for them.
Despite there being less threat to people, it is equally important that people are made aware of the situation. Since developments of these infections are occurring in humans, it is only a matter of time before horses follow the trend. This is due to the close relationship between horses and people. There is a high possibility of transmission between species and even from sources that are common to both species such as those of food and the environment. Veterinary doctors are reporting more and more cases of such infections in horses. More alarming is that these bacteria keep evolving.
Two decades ago Staphylococcus aureus that is resistant to Methicillin and extended spectrum beta-lactamase in horses were of little significance. Today they have gained popularity for the wrong reasons and will continue to do so in the coming years. The worry is that they will have evolved by then and will present new challenges and bacterial strains altogether.
There is no standard procedure for dealing with infections that are resistant to bacterial treatment. Nonetheless, creating awareness on the matter, making the most use of anti-bacterial drugs and paying close attention efforts meant to control spread of infection will go a long way. Such efforts should be undertaken by veterinary doctors and people employed to take care of horses.
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