Course: SAT 170 Introductory Biotechnology

Unit 9 Reading and Multimedia Assignment

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“Understanding Antimicrobial (Drug) Resistance," by National Institute of Allergy and Infectious Disease, public domain

http://www.niaid.nih.gov/topics/antimicrobialresistance/understanding/pages/default.aspx

Reading Assignment: Antibiotic Resistance
Microbes are living organisms that multiply frequently and spread rapidly. They include bacteria (e.g., Staphylococcus aureus, which causes some staph infections), viruses (e.g., influenza, which causes the flu), fungi (e.g., Candida albicans, which causes some yeast infections), and parasites (e.g., Plasmodium falciparum, which causes malaria). Some microbes cause disease and others exist in the body without causing harm and may actually be beneficial.

Antimicrobial (Drug) Resistance

Microbes are constantly evolving enabling them to efficiently adapt to new environments. Antimicrobial resistance is the ability of microbes to grow in the presence of a chemical (drug) that would normally kill them or limit their growth.

Antimicrobial resistance makes it harder to eliminate infections from the body as existing drugs become less effective. As a result, some infectious diseases are now more difficult to treat than they were just a few decades ago. As more microbes become resistant to antimicrobials, the protective value of these medicines is reduced. Overuse and misuse of antimicrobial medicines are among the factors that have contributed to the development of drug-resistant microbes.

Causes

Microbes, such as bacteria, viruses, fungi, and parasites, are living organisms that evolve over time. Their primary function is to reproduce, thrive, and spread quickly and efficiently. Therefore, microbes adapt to their environments and change in ways that ensure their survival. If something stops their ability to grow, such as an antimicrobial, genetic changes can occur that enable the microbe to survive. There are several ways this happens.

Natural (Biological) Causes

Selective Pressure

In the presence of an antimicrobial, microbes are either killed or, if they carry resistance genes, survive. These survivors will replicate, and their progeny will quickly become the dominant type throughout the microbial population.

Mutation

Most microbes reproduce by dividing every few hours, allowing them to evolve rapidly and adapt quickly to new environmental conditions. During replication, mutations arise and some of these mutations may help an individual microbe survive exposure to an antimicrobial.

Gene Transfer

Microbes also may get genes from each other, including genes that make the microbe drug resistant.

Societal Pressures

The use of antimicrobials, even when used appropriately, creates a selective pressure for resistant organisms. However, there are additional societal pressures that act to accelerate the increase of antimicrobial resistance.

Inappropriate Use

Selection of resistant microorganisms is exacerbated by inappropriate use of antimicrobials. Sometimes healthcare providers will prescribe antimicrobials inappropriately, wishing to placate an insistent patient who has a viral infection or an as-yet undiagnosed condition.

Inadequate Diagnostics

More often, healthcare providers must use incomplete or imperfect information to diagnose an infection and thus prescribe an antimicrobial just-in-case or prescribe a broad-spectrum antimicrobial when a specific antibiotic might be better. These situations contribute to selective pressure and accelerate antimicrobial resistance.

Hospital Use

Critically ill patients are more susceptible to infections and, thus, often require the aid of antimicrobials. However, the heavier use of antimicrobials in these patients can worsen the problem by selecting for antimicrobial-resistant microorganisms. The extensive use of antimicrobials and close contact among sick patients creates a fertile environment for the spread of antimicrobial-resistant germs.

Agricultural Use

Scientists also believe that the practice of adding antibiotics to agricultural feed promotes drug resistance. More than half of the antibiotics produced in the United States are used for agricultural purposes.1, 2 However, there is still much debate about whether drug-resistant microbes in animals pose a significant public health burden.