By D.S. Toft

By now most of you all have heard of Staph or MRSA (pronounced “mursa”), the skin infection that has experienced a recent outbreak, mostly on the East Coast, leading to several deaths. You’ve heard some easily-comprehensible characteristics about the infection: what it looks like, that it is transmissible by direct contact and that you can increase prevention by being careful.

If not, you are surely reminded every time you enter the bathroom and see the posters, “Sharing Isn’t Always Caring” and “Your Health Is in Your Hands.”

Maybe you’ve even heard the news reporter mention phrases like Staphylococcus aureus and antibiotic resistance. You’ve picked up on some of the talk about how over-prescribing antibiotics has made the infection worse and harder to treat. Because of this, some reports in the past month on CNN even refer to it as the “Superbug.”

But what does it all mean? How do bacteria infect? How do antibiotics fight them off? And how can a species of bacteria suddenly become resistant to the antibiotics that have worked before?

First off Staph is short for Staphylococcus aureus, the genus and species name for a bacterium that can cause Staph infection. Staph aureus is not the name of a disease, and it is not a cause of death. But it can weaken an immune system, leading to disease and possibly death.

There are around 30 species of Staphylococcus. Staph aureus is the most common species that can lead to a Staph infection. Other Staph infections, caused by different species of Staphylococcus, are different from the recent MRSA wave.

MRSA stands for Methicillin-resistant Staphylococcus aureus. This is a more specific name for a strand of Staph aureus that has become resistant to the antibiotic methicillin.

Methicillin is a class of penicillin antibiotics once used to fight off bacteria. These gram-positive bacteria have a different cell wall structure than gram-negative bacteria and are therefore treated differently. Some bacteria can be exterminated by inhibiting the synthesis of the cell wall while others interfere with the assembly of proteins.

Methicillin was once used to exterminate bacteria but is no longer used as an antibiotic and has been replaced by others such as dicloxacillin and flucloxacillin. These antibiotics are also classes of penicillin, but unlike others, are not resisted by MRSA and can be used to exterminate the bacteria. Although methicillin is not the only class of penicillin that MRSA has become resistant of, the name has been retained.

So how has over prescribing antibiotics like methicillin led to a growing generation of resistant strands of bacteria such as MRSA?

In a given colony of bacteria there may be thousands of mutated bacterial strands. While most of the strands are not mutated, those that are may hold properties that prevent them from being exterminated by antibiotics. When this given colony of bacteria is treated with antibiotics, all of the bacteria will die except for those with mutations that provide resistant qualities.

Now that the colony only exists of these antibiotic-resistant strands, they are the strands that reproduce. Eventually you end up with a colony of bacteria entirely existent of antibiotic-resistant strands. This is the equivalent of the generation of a new species, a “superbug,” and is why MRSA is a more specific name for the Staph aureus strand that resists antibiotics.

So what kinds of mutations have allowed bacterial strands to adapt bacterial-resistance? Two different types of mutations would be necessary to resist the two major categories of antibiotics: those that attack the cell wall and those that attack the ribosomes.

The Howard Hughes Medical Institute (HHMI) published an article on Sept. 19, 2005, called “Gaining Ground in the Race Against Antibiotic Resistance.” The article abridges the research of HHMI international research scholar Alejandro Vila, a researcher at the University of Rosario’s Institute of Molecular and Cellular Biology in Argentina and at the Biotechnology Institute of the National Autonomous University of Mexico.

During his research, Vila may have discovered one of the ways that mutated bacteria resist certain antibiotics, which would normally disrupt the bacterial cell wall. These antibiotics are those that would be used to treat MRSA infections and are one of the two major categories of antibiotics.

Normally, these antibiotics bind to the cell wall and inhibit the bonds that hold it together. The cell wall falls apart, and the cell dies as a result of exposure to the extracellular environment. Vila’s research team has discovered mutated bacterial strands that have adapted a defensive enzyme. An enzyme is a protein-based catalyst that bends, contorts or cuts molecules. These mutated bacteria release the enzyme from their cell wall, which “cut” antibiotic molecules in proximity before they can reach the bacterial cell wall. The enzymes “chop” the antibiotics in half, rendering the drugs useless. It is this adaptation that has generated bacteria that can resist cell-wall-targeting antibiotics.

However, constantly releasing these enzymes from the bacteria is a waste of material and energy during times when the bacteria are not being threatened by antibiotics. As a way to avoid misspending this material, the release of the enzyme can be turned on and off based on antibiotic concentration. When antibiotics attack the bacteria, the cell signals the transcription of the defending enzyme. And when there are no antibiotics in cell proximity, the cell signals to stop the transcription of the defending enzyme.

Another HHMI article, published on April 22, 2005, titled “Researchers Make Gains in Understanding Antibiotic Resistance,” discusses the research of Thomas A. Steitz of HHMI and Peter B. Moore, professor of chemistry at Yale. These researchers may have found one of the ways that mutated bacteria resist certain antibiotics that would normally inhibit the sites of protein synthesis, called ribosomes, from manufacturing proteins. These are the second of the two major categories of antibiotics.

Normally, these antibiotics bind to the ribosome at the “tunnels” where synthesized proteins are released into the cell, blocking their exit. The antibiotic works like a cork to block up these “holes.” However in mutated strands of bacteria, according to the article, the “tunnels” have become enlarged so that the “cork” is not big enough to completely block the release of protein molecules. This adaptation has generated bacteria that continue to synthesize proteins even after antibiotic treatment.

The scientific journal, “Science,” reported in 2005 that U.S. hospitals see some 2 million cases of infections caused by antibiotic-resistant bacteria every year. And 90,000 of these cases end in quietuses. The MRSA flare-up is only the most recent effect of these types of bacteria.

To cure diseases caused by antibiotic-resistant strands of bacteria like MRSA, the generation of these types of bacteria must be stopped rather than the mere treatment of individual cases of infection. Steitz asserts that, “It is becoming critical to understand the precise structural basis of resistance and even more important to do something about it.”