Antimicrobial Resistance and Natural Selection:

Here we explore the effects of the use of antimicrobial drugs which began during the World War II era. After more than 50 years of widespread use, many antimicrobial drugs have become ineffective. Health authorities believe that antimicrobial resistance is the greatest health threat of the 21^st century.

 What caused microbes to become resistant to previously effective drugs? Below is a list of four major reasons why this has happened. Using your knowledge of natural selection, explain how each statement contributed to drug resistance. Use the internet to do some research and your article on herbicide resistant Pigweed.  20 points.

Discuss-

Rapid mutation and reproduction rates of microbes.

Widespread use and misuse of antibiotics by prescribing physicians.

 Extensive use of antibiotics in agriculture, food production and as animal food additives.

Patient compliance to prescribed treatment regimes (do they follow directions?).

Rapid mutation and reproduction rates of microbes.

The microbes are killed in the presence of an antimicrobial. In some instances, they are not killed because they carry resistance genes to survive. Genetic continuity is accomplished principally by the replicative and repair activities of DNA polymerases and post replicative repair systems. These survivors will replicate and their progeny will become the dominant type throughout the microbial population will become resistant. Moreover, due to rapid reproduction rates of these microbes, mutations arise in a fast paced manner and help an individual microbe survive exposure to an antimicrobial. The development of a defect in one of the repair mechanisms leads to a high degree of mutation in many genes.

Widespread use and misuse of antibiotics by prescribing physicians.

The use of antibiotics has been an essential aspect in the practice of medicine and has saved millions of lives since its discovery. However, it is encouraged to practice the judicious use of antibiotics in clinical cases so as not to increase the likelihood of antibiotic resistance. Antibiotics strictly target bacteria, and the misuse of antibiotics to treat even viral infections that are self-limiting and non-infectious diseases has paved the way for pathogens to mutate and develop survival mechanisms that eventually lead to resistance.

Extensive use of antibiotics in agriculture, food production and as animal food additives.

The extensive use of antibiotics in agriculture, food production and animal food additives has also contributed to antibiotic resistance. The use of antibiotics to food animals selects for bacteria resistant to antibiotics and when humans consume these animal derived food, these bacteria colonise the gut and transfer resistant genes. The more an antibiotic is utilised, the more likely the development of resistant populations among pathogens and among commensal bacteria of an increasing number of animals in an exposed population. Hence, uncontrolled use of antibiotics creates a reservoir of drug resistant pathogens that can potentially infect humans.

Patient compliance to prescribed treatment regimes (do they follow directions?).

?It is imperative for clinicians to be able to monitor patient intake of antibiotics as to correct dosage, timing and duration. Antibiotic dosages are targeted to eradicate the entire population of pathogens. When patients do not comply with the correct dosage and duration, this give the bacteria the ability to adapt to the presence of low dose antibiotics and eventually form a population that is resistant to the antibiotic regardless of dose.