Superbugs are supervillains. They have become a huge threat to our society and the World Health Organisation estimates that they will become the global leading cause of death by 2050. Clearly this is a growing problem!
‘Superbugs’ is a colloquial term for bacterial cells that have developed resistance to antibiotics. They are becoming increasingly common due to the nature of bacterial cells.
Firstly, lets take a look at why antibiotics are important. We made antibiotics accessible after World War Two which led to a rapid decline in deaths from infectious diseases. The average life expectancy was 47 years old at the beginning of the 20th century because many people would die of cholera, pneumonia, typhoid and tuberculosis. We perceive these infectious diseases as benign because we have antibiotics. But superbugs like Penicillin- Resistant Streptococcus Pneumonia (PRSP) are going to create higher morality rates worldwide. The golden era of antibiotics is beginning to slow as natural selection catches up to scientific developments.
Natural selection and evolution has allowed bacterium to develop resistance to the antibiotics we use. Bacterial cells look like this:
The main part we want to focus on is the plasmid. Plasmids are rings of circular DNA that contain the antibiotic resistant gene in a bacterium. An initial antibiotic resistant gene is a random mutation in the genetic makeup of a bacterium. The mutation proves to be an advantage when a selective pressure is introduced. In this case, antibiotics enter the body and try to kill off the bacteria. The bacterium with the mutation is most likely to survive and live on to reproduce (and pass on the antibiotic resistant gene). Overtime an entire population of bacterium will be resistant to antibiotics.
This is the process of natural selection which allows advantages to be passed down generations. Clearly, this is a natural process that all organisms do to evolve into what they are today. But bacteria are special. Whilst other organisms pass genes from parent to offspring, bacteria also transfer genes from one bacteria to another, so that different types of bacteria can become resistant to antibiotics. Consequently, the rate of evolution is increasing.
Transfer of genes between bacteria is done through Horizontal Gene Transfer (HGT) in which a process called bacterial conjugation takes place. Bacterial conjugation allows plasmid’s from a donor bacterium to pass over a ‘small bridge’ to the recipient cell. The small bridge is called a pilus (seen in the diagram of a bacterial cell above) which is made from a Fertility (F) Factor in the episome of a cell (the F Factor and episome code for the pilus formation).
Here bacterial conjugation can be seen more clearly:
There have been ways to slow the rate of antibiotic resistance in bacteria. Doctors have begun prescribing antibiotics only when absolutely necessary to reduce natural selection and prevention methods of infectious diseases are beginning to be implemented (like vaccines etc). Simple things we can do is to only use antibiotics when given them, to use the antibiotics all the way through (until the prescription ends, not when you ‘feel better’) and to educate ourselves.
Within 30 years we will experience the effects of bacterial conjugation as more and more strains evade antibiotics. Superbugs are becoming a real threat to acknowledge and tackle before it becomes unmanageable.