The Crisis of Antibiotic Resistance

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Whilst we are heading towards the end of a pandemic, there are far more issues to deal with regarding world health, namely the issue of antibiotic resistance. Due to the misuse and overuse of these drugs, lack of correct prescriptions and minimal developments from pharmaceutical companies, antibiotic resistance is rising at an alarmingly rapid rate. Coordinated efforts have to be made to prevent even greater burdens on the healthcare system.

How does antibiotic resistance arise? Within a bacterial population, there is genetic variation caused by mutations. A chance mutation might cause some bacteria to become resistant to an antibiotic, like Methicillin. When the population is treated with this antibiotic, the resistant bacteria do not die. A mutation may change an existing gene within the bacterial genome, causing it to give rise to a nucleotide sequence that codes for a slightly different protein that is not affected by the antibiotic being used. This means the resistant bacteria can continue to reproduce with less competition from the non-resistant bacteria, which are now dead. Therefore the genes for antibiotic resistance are passed on with a much greater frequency to the next generation. As bacteria only have one copy of each gene, a mutant gene will have an immediate effect on any bacterium possessing it. Over time, the whole population of bacteria becomes antibiotic-resistant because the antibiotic-resistant bacteria are best suited to their environment. This is Natural Selection. Some pathogenic bacteria have become resistant to penicillin as they have acquired genes that code for the production of the enzyme β-lactamase, which breaks down penicillin.

There are two ways of spreading antibiotic resistance:

Vertical transmission – Bacteria reproduce asexually by binary fission, the DNA of the bacterial chromosome is replicated and the bacterial cell divides in two, with each daughter cell receiving a copy of the chromosome. Bacteria reproduce like this very rapidly, on average, every 20 minutes. If one bacterium contains a mutant gene that gives it antibiotic resistance, all of its descendants, millions of which can be produced in a matter of hours, will also have the antibiotic resistance.

Horizontal transmission – Plasmids, the small rings of DNA present in bacterial cells, often contain antibiotic-resistant genes. These plasmids are frequently transferred between bacteria, even from one species to another. This occurs during conjugation, when a thin tube forms between two bacteria to allow the exchange of DNA – DNA from the bacterial chromosome can also be transferred in this way. Through horizontal transmission, a bacterium containing a mutant gene that gives it antibiotic resistance could pass this gene on to other bacteria, even those from a different species. This is how Superbugs with multiple resistances have developed like MRSA.

Antibiotics have not only saved patients’ lives, they have played a pivotal role in achieving major advances in medicine and surgery. They have successfully prevented or treated infections that can occur in patients who are receiving chemotherapy treatments; who have chronic diseases such as diabetes, end-stage renal disease, or rheumatoid arthritis; or who have had complex surgeries such as organ transplants, joint replacements, or cardiac surgery.

Antibiotics have also helped to extend expected life spans by changing the outcome of bacterial infections. Although resistance to anti-MRSA agents usually occurs through bacterial mutation, there have been reports of the transfer of resistance to linezolid and glycopeptide antibiotics, some of the only antibiotics that work on MRSA, which is cause for major concern. However invasion of MRSA in the UK dropped by 31% when new hygiene measures were implemented in hospitals. It is not impossible to treat antibiotic resistance bacterial infections, however they will take longer hospital stays and the drugs used to treat these infections are far more expensive.

Coordinated efforts must be made by clinicians, governments and pharmaceutical companies to prescribe correctly and develop new drugs to combat the wave of antibiotic resistance.