INFORMATIONAL HANDOUT:
Biological diversity in the microbial world is not the first thought that comes to mind when biodiversity comes up
in the general public. The general public tends to think bigger. They think of tropical ecosystems or maybe
elephants. Perhaps they would consider an ecosystem in Yellowstone Park focusing on wolves. However, the
biological diversity of microbes will shortly be on everyone’s mind. Evolution through natural selection is
producing a group of organisms that may not be as charismatic as a tiger, but will surely end up being much
more frightening. A diverse and frightening group of organisms resistant to traditional antibiotics are evolving at
an alarming rate.
Antibiotic resistance is now a worldwide problem. There are a number of reasons for this rapid mutation rate of
bacteria into antibiotic strains. Humans consume 235 million doses of antibiotics annually. It is estimated that
20% to 50% of that use is inappropriate. One survey of physicians concluded that more than 80 percent of the
responding physicians admitted to having written antibiotic prescriptions against their better judgment. In
addition to this problem, people often fail to follow the directions that come with these prescriptions – failing to
finish the full course of antibiotic treatment. Improper dosing will encourage the growth of resistant strains.
Finally in many third world countries, it is possible to buy antibiotics over-the-counter. This leads to widespread
abuse of antibiotics.
The same drugs prescribed for human therapy are widely exploited in animal husbandry and agriculture. Large
amounts of these drugs are given to animals to promote growth. These amounts are too small to combat
infection but perfect for producing more disease resistant bacteria. When humans consume this food, bacterial
strains are transmitted to the people who are eating as well as cooking this food is possible.
Antibiotics are applied as aerosols to acres of fruit trees to control infections. High concentrations may kill the
bacteria on the targeted trees, but the trees at the edge of the target receive low doses which can encourage
the growth of disease resistant bacteria. These resistant bacteria can be inhaled by animals--including humans-at the site. They are also being packaged and shipped with the fruit from sprayed fruit trees all over the world.
Each country is now producing their own antibiotic resistant bacteria as well as sharing this resistance with
countries half a world away.
The above misuses of antibiotics are responsible for many different strains of drug resistant bacteria. Following
are some examples of these strains of disease resistant bacteria. An often deadly bacterium, Staphylococcus
aureus, is responding poorly to a once reliable antidote, the antibiotic vancomycin. It was not long ago when
vancomycin was the drug of choice in killing highly resistant bacterial strains. Tuberculosis, once considered to
be nearly eradicated in the 1940’s, is now the world’s leading cause of death from a single infectious disease
according to the World Health Organization. A particularly dangerous strain of Mycobacterium tuberculosis is
spreading rapidly in Russia and other hot spots around the world. Widespread use of antibiotics have
promoted the proliferation of the once benign intestinal bacterium Enterococcus faecalis, which is naturally
resistant to those drugs. This bacterium can be fatal to persons with compromised immune systems.
Ever since antibiotics became widely available in the 1940s, they have been hailed as miracle drugs or the
magic bullets able to eliminate bacteria. Yet with each passing decade, bacteria that defy not only single but
multiple antibiotics are becoming increasingly common. However, this picture is not totally bleak. Through
education, research and some rather simple changes in human behavior, the production of disease resistant
can be controlled or at least slowed down. Treating physicians will need to be educated in the proper use of
antibiotics. The agriculture world will need to rethink the doses of antibiotic that they are using in their treatment
of animals and orchards. Research will need to focus on the development of new alternatives to our current
arsenal of antibiotic weapons. This research and education will need to be conducted and applied worldwide.
ADAPTED FROM: Hudson, Barbara K. Microbiology in Today’s World Second Edition. Kendall / Hunt Publishing
Company, 1998 and Harley, John P. and Lansing M. Prescott. Laboratory Exercises in Microbiology Fourth Edition. WCB
McGraw-Hill, 1999.
Biology 215, Ruth A. Gyure
Western CT State University