The Rise of the Superbugs

Until the discovery of the sulfa drugs and the antibiotic penicillin in the 1930s, a simple bacterial infection could easily be a life-threatening illness. Even the most trivial cut or scape could be cause for alarm, should an infection occur. Soldiers feared infectious disease or wound infection more than death from battle trauma, because many more deaths occurred from the former. After the advent of the new wonder drugs, many thought that infectious disease would soon be a thing of the past. Then, drug resistance began to rear its ugly head.

Drug resistance is a consequence of Darwin’s principle of natural selection. Bacteria that are resistant to antimicrobial agents are present in the environment ̵ exposure of a population to a particular agent results in proliferation of the resistant strains, because as the more prevalent sensitive strains die, more nutrients are available to the resistant bugs. Put another way, “Everything is everywhere, but the environment selects”.

Drug resistance arises through spontaneous mutation; that is, a random change in the DNA of a particular organism. As the mutated cell divides, a small clone of drug resistant organisms arises. That clone will likely be only a tiny fraction of the total population of bacteria present in a particular environment. However, if selective pressure is brought to bear: for example, a particular drug enters the environment, that small clone will multiply at the expense of everything else, and become the dominant species.

To make matters worse, drug resistance can be passed around. The instructions for drug resistance are often contained on small, circular pieces of DNA called plasmids. These can be transferred between two bacteria of different species; for example, a species that is not infectious to humans can transfer the resistance to one that is.

As more and more drugs are released in the environment, more and more drug resistant organisms arise. Genes for drug resistance can also accumulate on a single plasmid, so by a single transfer of genetic material, one previously sensitive organism can become resistant to multiple drugs. This results in the so-called superbugs.

One superbug that has caused considerable trouble is MRSA – short for methicillin resistant Staphylococcus aureus .S. aureus is a common inhabitant of human skin, and its presence is usually innocuous, however it can cause infections if it invades the soft tissue beneath broken skin. These infections can become life-threatening if they move into the bloodstream. Since S. aureus is found on humans, MRSA can be prevalent in a hospital setting. Even though MRSA is resistant to multiple drugs, antimicrobial treatments for MRSA do exist. However, the best strategy is prevention, by means of proper hygiene and good disinfection practices.

Another group of superbugs that the CDC has designated as an urgent threat are the CRE bacteria. This group contains multiple species, including E. coli, a common inhabitant of the human gut, and Klebsiella pneumoniae, a human pathogen. CDC has documented 9,000 + infections in hospitals, with a mortality rate approaching 50%.

Sexually transmitted diseases have been a scourge of humanity since antiquity. One of the most common causes, a bug called Neisseria gonorrhea, has also been designated as an urgent threat by the CDC, because strains resistant to numerous antimicrobial drugs are becoming prevalent. Untreated gonorrhea infections can cause infertility, and can be passed on to newborns.

Some scientists think that reducing the amount of antibiotics in the environment might slow the rise of superbugs. Doctors are cautioned not to prescribe antibiotics to patients unless necessary – for example, antibiotics are useless against viral infections and should not be used unless complications are likely. However, the majority of antibiotic use is veterinary. Animals raised in a crowded condition are more susceptible to disease than free-ranged animals, and routine administration of antibiotics in feed helps reduce infection and improves profits. However it also creates environment conditions favorable for the development of antibiotic resistance. Regulatory agencies are concerned about this problem, and new regulations prohibiting prophylactic antibiotic use in animals are being considered.

It is almost a foregone conclusion that we will see another global pandemic. Most experts think that this is likely to be viral, in which case, antibiotic resistance will not be a factor. But historically, some of the worst plagues were bacterial, and the death tolls they racked up in the pre-antibiotic era were staggering. However, the strength of humanity has always been its adaptability. A combination of prudent preventive measures and new technology will likely be our salvation.


Photo credit: estherase / / CC BY-SA

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