You may have read in the news recently that our last line of defence against bacterial infection has come under serious threat. While hospitals are already forced into using ‘last-resort‘ antibiotics, new research results suggest we may reach breaking point soon.
This final stand against the tide of antibacterial infection comes in the form of Polymyxin. A group of antibiotics with a general structure of a cyclic peptide and a long hydrocarbon tail. They kill bacteria by binding with lipids in the phospolipid membrane and thus disintegrating it. While this group of antibiotics was developed around 60 years ago they are rarely used. This is because they are both neuro- and nephrotoxic; affecting both the nervous system and the kidneys.
Researchers in china, however, have recently discovered a strain of E. coli that carries a gene resistant to polymyxins, described as ‘very worrying’ by the scientists. The reason this is such worrying news is that the resistance gene, MCR-1, has been found on a bacterial plasmid. A tiny piece of DNA that can be transferred between bacteria of the same species AND unrelated bacteria, meaning that there is the potential for this resistance to be passed on to all types of bacteria (for an explanation how).
It was discovered, during routine checks at a pig farm in Shanghai, that 21% of animals and 15% of raw meat tested positive for the presence of E. coli carrying the MCR-1 gene. They concluded that it is likely that this gene is widespread among the Enterobacteriaceae which are found in humans and animals worldwide. Luckily most strains of E. coli are harmless, but there some pathogenic strains of E. coli that can cause serious health complications and even death.
Resistance to polymyxins come in the form of lipid modification, rendering the antibiotic useless. And although this resistance has been found before, it is generally less than 10% and thought to be due to individual mutations of bacteria. Thus, finding bacteria that carries this resistance gene on plasmids is very worrying indeed. I have written about the risks of bacterial antibiotic resistance before, but essentially; without effective antibiotics infections we regard as not-serious and things like routine operations can carry a much higher risk.
This has caused scientists to urge people not to use polymyxins in agriculture, or resistance may increase. Professor Nigel Brown, president of the microbiology society, has said that the “careful surveillance to track the global spread of this resistance” is needed to ensure this does not become a global pandemic.
With ever-improving biotechnology and development of drugs, it might not all be doom and gloom. There are a few new antibiotics currently in development that seem to be promising. Teixobactin is one such example, that kills pathogens without ‘detectable resistance’.
I would love to here what your thoughts are on these findings? Is bacterial resistance a product of over-prescription of antibiotics?
Image credit: http://columbiariverkeeper.org/water-quality/water-quality-monitoring/wqm-get-involved/wqm-program-options/wqm-e-coli-monitoring/