Facts About MRSA Treatment
What is MRSA, and Why is it Resistant to Antibiotics?
MRSA is a type of drug-resistant bacterial infection caused by a mutated strain of Staphylococcus aureus. MRSA is an acronym that stands for "methicillin-resistant Staphylococcus aureus." Methicillin is a specific type of antibiotic drug from the beta-lactam family of antibiotics, which are antibiotics that have a specific type of ring, called a beta-lactam ring, in their chemical structure. Methicillin is a chemical that is not used for treatment of infections in the clinic because it is less effective and has more potential side effects than other types of drugs in the same family, but it is used for susceptibility testing of bacteria to antibiotics in the laboratory.
If a bacterium like Staph aureus is resistant to methicillin, that means that it is resistant to other antibiotics with a beta-lactam ring in their structure, like penicillin and cephalosporin. The reason that MRSA is resistant to beta-lactam antibiotics is because the bacteria have acquired a gene that allows them to make an enzyme called beta-lactamase that cuts the beta-lactam ring open and renders the antibiotic chemicals biologically inactive by changing their structure.
The resistance gene can either come from the plasmids of other resistant bacteria or be present in the genetic material of the bacterium, originally in an inactive form, and become activated or expressed later on. Bacteria have one main chromosome with their genetic information on it, but they have the ability to uptake DNA from their environment which comes from other types of bacteria. Plasmids are small rings of genetic material that can be transferred from one bacterium to another. This DNA can then be used by the bacterium to make enzymes that it wasn't able to before, including enzymes for drug resistance, that may increase its chances of survival. This is the mechanism of action for many types of antibiotic drug resistance. Other cases are said to be inducible: The bacterium has the gene for antibiotic resistance in its chromosome all along, but the enzyme is not produced when there are no antibiotics in the environment of the bacterium so the gene is "quiet." When someone starts taking antibiotics, then the enzyme is expressed, the bacteria survive the use of antibiotics, and the infection is not cured.
Although there are multi-drug resistant strains of MRSA that are resistant to more types of antibiotics than just beta-lactam antibiotics, there are still antibiotics available to treat MRSA infection.
Picture of MRSA
MRSA Treatment Facts
Not all MRSA infections may be treated with antibiotics. If a person has a superficial skin infection or an abscess caused by a MRSA skin infection, a doctor taking a needle and draining the abscess and disinfecting the area may be sufficient to allow the infection to heal. This should be done by a doctor in a clinic, however, and not attempted at home. A medical professional will use their experienced judgment to determine whether antibiotics are necessary to treat an infection, and draining an abscess at home could cause serious problems, such as injury or making the infection worse, or result in someone else being exposed to the infectious agents.
For drug-resistant strains of bacteria, such as MRSA, it becomes necessary to take a culture of the infection and test the bacteria for susceptibility to certain antibiotics in the lab so that an effective antibiotic regimen is prescribed. Treating MRSA with penicillin, cephalosporin or other antibiotics with a beta-lactam ring will not do anything to clear up the infection. These drugs are usually the first line of treatment for an infection because they are effective and have relatively few side effects compared to some other antibiotic drugs, but they do not have an effect on MRSA.
Some infections that are resistant to beta-lactam antibiotics can become susceptible to the drugs when the drugs are given in combination with chemicals that inhibit the beta-lactamase enzyme that the bacteria produce. These chemicals are called beta-lacatamase inhibitors. However, this type of treatment is not recommended for MRSA infections. It is more effective to find another antibiotic that the infection is resistant to than to try the beta-lactamase inhibitor approach.
When antibiotics are prescribed to treat a MRSA infection, it is extremely important that the patient take the entire course of antibiotics, even if the infection starts to look like it is clearing up. If antibiotics are stopped early, before all of the bacteria have been eliminated, it contributes to the drug resistance problem. In the future, MRSA may evolve and become resistant to new kinds of antibiotics.
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