Contributed by Nyasia Jones, Chris Richardson and Kari Tyler
A common misconception regarding evolution it that it is slow, and because it is slow, humans are not influencing it. This is completely false. Humans have and are continuing to make major changes that are not only influencing the course of our own evolution, but are also influencing the evolution of other species we interact with. Especially in medicine, human advancement is occurring at an amazing pace and thus allowing us to witness evolution in response to our actions.
Over the past century, the use of antibiotics to treat bacterial pathogens has become a widespread practice. Starting around 1930, medical practitioners began discovering several drugs that successfully rid patients of a particular bacterial pathogen Neisseria gonorrhoeae. The first successful therapy was administration of a class of chemicals called sulfonamides. For years, treatment with sulfonamides proved successful in patient after patient until about the mid-1940s when reports of N. gonorrhoeae resistance to sulfonamides increased. Fortunately, at this time, the “miracle drug” penicillin was found to be highly effective at bacterial treatment and become the number one treatment option. After ten to fifteen years though, low doses of penicillin were no longer as effective, and by the 1980s strains with high-level penicillin resistance had emerged.
So what happened with both penicillin and the sulfonamides? Nothing.
But something did happen to the N. gonorrhoeae. They evolved.
Sequential chromosomal mutations allowed some bacteria to incur resistance to penicillin. With penicillin treatment, the bacteria with resistance survived while those without it did not. The resistant individuals reproduced thereby creating a new generation of bacteria in which all individuals were penicillin resistant. This, my friends, is evolution.
Unlike the billions and billions of years it took to create modern-day humans, this evolution took less than a century to change these N. gonorrhoeae bacteria into “superbugs” which are becoming increasingly harder to treat. And it doesn’t stop there. N. gonorrhoeae has also become resistant to more recent treatment options, such as tetracycline and fluoroquinolones. Now, with less and less success to current methods of treatment, namely cefixime and ceftriaxone, scientists are worried history will repeat itself and strains of N. gonnorhoeae with complete cefixime and ceftriaxone resistance will emerge. With dwindling options for treatment, N. gonorrhoeae resistance and that of other superbugs remains a major problem in the fields of medicine and epidemiology.
So are humans influencing evolution? N. gonorrhoeae tell us, loud and clear: yes!
For more information:
Anderson, M. T., & Seifert, H. S. (2011). Neisseria gonorrhoeae and humans perform an evolutionary LINE dance. Mobile Genetic Elements, 1(1), 85-87.
Mavroidi, A., Tzelepi, E., Siatravani, E., Godoy, D., Miriagou, V., & Spratt, B. G. (2011). Analysis of emergence of Quinolone-resistant gonococci in Greece by combined use of Neisseria gonorrhoeae multiantigen sequence typing and multilocus sequence typing. Journal of Clinical Microbiology, 49(4), 1196-1201.
Unemo, M., & Shafer, W. M. (2011). Antibiotic resistance in Neisseria gonorrhoeae: Origin, evolution, and lessons learned for the future. Annals of the New York Academy of Sciences, 1230(1), E19-E28.