Methicillin-resistant staphylococcus aureus

background

Staphylococcus aureus (S. aureus) is an extremely versatile bacterium that can cause infections ranging in severity from mild to severe in humans and animals. S. aureus is normally found on the skin or in the nasal passages of about one third of the population. Most individuals harboring S. aureus are not ill but are "colonized" with the bacteria. Individuals who are colonized with S. aureus may develop infection if the bacteria enter the body through a break in the skin or nasal passages. Individuals who are colonized have the ability to spread the organism, even if they are not ill. If the bacteria are transmitted to another individual, they may cause infection in that individual. The ability of bacteria to resist the effects of an antibiotic is called antibiotic resistance. During the past decade, antibiotic resistance has increased tremendously worldwide.
Methicillin is a type of penicillin that was developed in 1959 to treat infections from S. aureus and other bacteria that were resistant to earlier forms of penicillin. Since that time, however, S. aureus and other bacteria have developed resistance to methicillin. Methicillin-resistant Staphylococcus aureus (MRSA) is now a global health concern. MRSA is highly virulent and can cause a large number of serious illnesses that do not respond well to current medical treatment.
MRSA has adapted in ways that allow it to be resistant to a number of antibiotics, including penicillin, methicillin, and cephalosporins. This adaptation or evolution, has been accomplished by mutation of the genetic material contained in S. aureus. The mutated bacteria are less or no longer susceptible to damage from methicillin.
MRSA was first noted in 1961, about two years after methicillin was initially used to treat S. aureus and other infectious bacteria. The resistance to methicillin was caused by a penicillin-binding protein coded for by a mobile genetic element (MGE). An MGE is a type of genetic material that has the ability to move genetic material from one organism to another. The MRSA MGA gene is called the methicillin-resistant gene (mecA). This gene has continued to evolve and, thus, many MRSA strains are currently resistant to several different antibiotics.
MRSA infections commonly occur in hospitals and other healthcare facilities, such as nursing homes. MRSA acquired in a hospital is known as hospital-acquired-MRSA (HA-MRSA) and infections transmitted within a hospital are known as nosocomial infections. Patients in healthcare facilities often have had a recent bacterial infection and have received antibiotics. A number of these patients have become colonized with bacterial strains that are resistant to antibiotics. Hospital workers who care for these patients may also become colonized.
MRSA infections that occur in healthy people who have not undergone a medical procedure or hospitalization within the past year are known as community-associated-MRSA (CA-MRSA) infections. These infections are usually located on the skin and appear as abscesses, boils, and other pus-filled lesions. Currently 10% of all MRSA infections in the United States are CA-MRSA. Individuals with a weakened immune system are particularly susceptible to MRSA.
Not only has S. aureus developed resistance to methicillin, it has developed resistance to newer antibiotics. As new antibiotics are developed, it is likely that this highly-adaptable bacterium will develop resistance to them as well.
Research in the field of genomics may aid in the treatment of MRSA infection. As researchers gain further understanding of the MRSA genome, the outlook for patients with this disease may improve.

Related Terms

Antibiotic pressure, antibiotic resistance, antibiotics, CA-MRSA, community-associated-MRSA, enterotoxin, HA-MRSA, hospital-acquired-MRSA, mecA, methicillin resistance, MRSA, mutation, SFP, SSSS, staphylococcal food poisoning, staphylococcal scalded-skin syndrome, Staphylococcusaureus, toxic shock syndrome, TSS.

types of the disease

Methicillin-resistant Staphylococcus aureus (MRSA) infections commonly occur in hospitals and other healthcare facilities, such as nursing homes. MRSA acquired in a hospital is known as hospital-acquired-MRSA (HA-MRSA) and infections transmitted within a hospital are known as nosocomial infections. Patients in healthcare facilities often have had a recent bacterial infection and have received antibiotics. A number of these patients have become colonized with bacterial strains that are resistant to antibiotics. Hospital workers who care for these patients may also become colonized.
MRSA infections that occur in healthy people who have not undergone a medical procedure or hospitalization within the past year are known as community-associated-MRSA (CA-MRSA) infections. These infections are usually located on the skin and appear as abscesses, boils, and other pus-filled lesions. Currently 10% of all MRSA infections in the United States are CA-MRSA.

research

Ongoing research is being conducted by pharmaceutical companies to develop new antibiotics as well as new forms of existing antibiotics. Studies have been conducted on the use of an antibiotic regimen to decolonize individuals who harbor MRSA. One study reported an 87% success rate in decolonizing MRSA carriers.
Interleukin-8 (IL-8) is a protein secreted by immune system cells. The level of IL-8 is under investigation as a predictor of outcome in patients with toxic shock syndrome. Patients with a lower IL-8 level at the time of hospital admission or diagnosis tend to have a higher chance of survival.
Apelin is a ligand molecule secreted by many tissues in the body. Apelin acts as a mediator for the control of blood pressure and blood flow. Serum apelin rises in patients with sepsis, which is a generalized infection of the body, and with septic shock, which comprises low blood pressure and a weak and rapid heart rate secondary to an infection. Research on serum apelin levels may provide clues for the diagnosis and prognosis (medical outcome) of septic shock.
Mitochondria are tiny subunits within a cell that are responsible for energy production. These subunits, or organelles, take in nutrients, break them down, and then produce energy for the cell. Many researchers believe that mitochondria are particularly susceptible to sepsis and that a breakdown of mitochondrial function is a key factor in organ failure in septic shock. One focus of current research, then, is on the understanding of mitochondrial mechanisms when a patient develops sepsis.
Genomics research has uncovered a specific mutation (a point mutation) in the MRSA gene that provides the bacterium resistance to vancomycin, which is the principal drug used to treat MRSA infections. In the process, two other factors were discovered that produce resistance. Identifying the specific genetics involved in MRSA is the first step in developing an effective treatment for this disease.

future research

Future research will focus on the development of new antibiotics and the investigation of the genetic mechanisms involved in antibiotic resistance. Thiazolyl peptides have the potential to become potent antibiotics effective against MRSA. Recently developed agents are not very effective because of poor solubility (ability to dissolve in solution) and pharmaceutical properties (activity against infection). However, researchers are developing new types of thiazolyl peptides that may be very effective against MRSA infections.
Computer techniques exist for comparing S. aureus genomes. These techniques allow rapid comparison of genomes with only subtle differences (i.e., one that is resistant to a specific antibiotic and one that is not). This will lead to further experiments and ultimately to the development of new antibiotics or other therapies that can combat MRSA infections.
A fermented culture of the bacterium Streptomycesfulvissimus was found to secrete an antibacterial protein that inhibits MRSA and other disease-causing bacteria. This protein has the potential to become a source for the development of new drugs effective against MRSA and other pathogenic bacteria.
Research is ongoing to identify substances found in the blood of patients with toxic shock syndrome, such as apelin and interleukin-8. This research should improve the diagnosis of toxic shock syndrome and help predict disease outcome.
Future mitochondrial research will provide a better understanding of organ failure associated with toxic shock syndrome. A better understanding of this process may lead to improved methods of treatment.