How Evolution Complicates the Fight Against Infectious Disease
Tuberculosis (TB) has been successfully fought with antibiotics for decades, but the emergence of antibiotic-resistance TB bacteria has resulted in numerous complications in the battle against this disease.
Misuse of antibiotics via their frequent introduction into an individual’s body may destroy certain weaker strains of the TB bacteria, but will leave in place the few bacteria that have by chance been born with the ability to resist the antibiotics used. These bacteria will then have no obstacle toward proliferating and thus contributing to the evolution of a strain almost fully resistant to that particular antibiotic. The resistant bacteria are naturally selected to survive and multiply as the fittest under such conditions.
When an environment rich in bacteria for a particular disease exists, it may be possible for several afflicted persons to be treated with a different antibiotic each and for those persons to develop strains of bacteria immune to that particular antibiotic. Due to frequent contact between these individuals, the various specifically immune strains can transfer from one individual to another. Within a given individual’s body a strain immune to antibiotic A is free to undergo genetic recombination with a strain immune to antibiotic B, thus sometimes transferring immunity to two or more antibiotics to a given set of bacterial organisms, whose multiplication can bring about a populous multi-resistant strain.
An example of environments where antibiotic-resistant bacteria mutate readily is the Russian prison system, which remains alarmingly overcrowded. Inmates live in constant close contact with one another, facilitating a rapid rate of infectious disease proliferation. The TB bacteria, often latent in healthy individuals, more frequently manifests itself in the malnourished prisoners, many of whom additionally undermine their health via alcoholism. Whenever they cough or speak, the bacteria can infect those nearby. Moreover, antibiotics, especially second-line drugs for treating resistant strains, are in short supply. Thus there exists no real barrier to the spread of tuberculosis within the prison network and beyond.
Transportation, a key factor in the global economy, can also be an agent for the spread of a particular infectious disease on a worldwide scale, as travelers from an epidemic-stricken part of the world can transmit the bacteria a continent away. In cities near the Siberian prisons, many college students have already become afflicted with lung consumption, while trains carry the disease to Moscow, where some Russian travelers to the United States can reach any destination in the world, including the United States, by airplane. In New York, strains of the Tomsk TB bacteria have already been discovered.
An understanding of evolution in bacteria may cause doctors to be more prudent in prescribing antibiotics to patients and compel them to realize that such drugs have their limitations and must not be over-indulged in. Antibiotics may be used for treating severe cases of a disease, whereas milder manifestations should be suppressed by other means. Also, second-line drugs, which are currently expensive and dangerous, can be researched in greater depth, seeing as they provide a resort when resistant strains have already developed. If a mass-manufacturing industry for those drugs develops, their abundance will increase, and thus their prices will drop, rendering them available to quell epidemics within populations, such as the Siberian inmates, which do not possess optimal purchasing power.
Scientists can also keep a step ahead of the bacteria by artificially breeding strains resistant to known antibiotics in lab cultures and developing new antibiotics that would eliminate those strains based on studies of the organisms’ physiological systems and weaknesses. In this manner, future mutations can be anticipated and cures made available to preempt the spread of the mutant strain in the early stages of its development. If most future mutations are likewise suppressed, it may be possible to stagnate the general trend toward emergence of more resistant bacteria.