Overview of Methicillin-Resistant Staphylococcus Aureus (MRSA)

Introduction

MRSA stands for Methicillin-ResistantStaphylococcusAureus.  This is the kind of infection that is much tougher to treat compared to most strains of the Staphylococcusaureus. MRSA is caused by a type of a staph bacteria that tends to be resistant to many antibiotics.  MRSA was first isolated in the United States in 1968 and by the 1990’s it accounted for up to 25% of infections in hospitalized patients.  In 2011 there were approximately 11,000 deaths associated with MRSA.  Several studies have shown the various impossibilities associated with treating the infection associated with the resistance of some commonly used antibiotics such as methicillin, penicillin and cephalosporins (Antonanzas, Lozano and Torres,2015). However, the symptoms of MRSA are dependent upon where a person is infected. Most often MRSA tends to cause mild infections on the patient’s skin which resembles sores or even boils. MRSA can cause skin infections or even infect various surgical wounds, cause bloodstream infections and infect the lungs. Most MRSA infections prove serious and some are life threatening hence MRSA is often referred to as a super bug.  There are two different types of MRSA; one that is associated with healthcare facilities such as hospitals and nursing homes and community-based MRSA that is associated with people who develop the disease but have not been hospitalized and acquired the disease in the community.

Symptoms and Signs

Over a three-month period, my mother-in-law noticed that she had infected areas on her hands and arms that had become swollen and grown more painful; she had red bumps that resembled pimples or even spider bites. The affected areas appeared to be warm and full of puss and she often had a fever.  It wasn’t until the pimples had turned into deep and painful abscesses that required surgical draining that she realized she needed to seek medical attention.  The doctor informed her that the bacteria inside her could result in life- threatening infection in her bones, joints, blood stream, the heart valves as well as her lungs.  He explained to her that she may experience chest pains, shortness of breath, muscle aches and headaches until the disease is treated. 

The Causative Agent

MRSA is caused by a Gram-positive bacterium that is resistant to methicillin; which is a member of the penicillin family; and resistant to many other ß-lactam antimicrobials. It is cocci shaped and forms clumps.  It is coagulase positive; all other staphylococci are coagulase negative.  It is salt tolerant and often hemolytic.  The infections are commonly referred as staph and they are found on the skin and in the nose of the patients. According the CDCs (Centers for Disease Control and Prevention) report, it is believed that 2% of the whole population chronically carries the kind of a staph bacteria referred as MRSA. MRSA is a result of decades of unnecessary usage of antibiotics. For many years, antibiotics have been prescribed for the use of cold prevention, flus and many viral infections across the globe.  However, these infections fail to respond to the prescribed drugs because they are not bacterial.  Even the appropriate use of the antibiotics contributes to rise in drug-resistance as they do not destroy every bacterium that is targeted. Since bacteria live on the evolutionary fast track the ones that tend to survive the treatment of one antibiotic soon learn how to resist the others.

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Pathogenicity and Pathogenesis

Staphylococcusaureus is a very versatile pathogen capable of causing many different types of human disease. Different virulence factors play different roles in the development of the staphylococcus infections in a process that remains incompletely understood by many. The nose is the main location for S. aureus and 20% of people always have the bacteria present and 60% of the population have it intermittently.  Many other locations on the body may be colonized.  These colonies provide the reservoir from which the bacteria can be introduced to the body when its defenses are breach by a cut, by the insertion of a catheter, or during surgery.  The basis for this colonization is not readily understood but seems to involve the ability of S. aureus to adhere to the host cells and to evade the immune response.  There are some MRSA strains that are comprised of factors or even genetic backgrounds that highly enhance their virulence and enable them to act as causative agents.   They have factors such as capsules that inhibit phagocytosis and they can produce toxins that damage host tissue. 

Anatomy and physiology

S. aureus has many surface proteins that allow them to adhere to the host’s cells. These proteins are called microbial surface components recognizing adhesive matrix molecules or MSCRAMMs for short.  These MSCRAMMs play a role in bone and joint infections as well as prosthetic materials.  S. aureus is capable of forming small colony variants that have the ability to contribute to the persistence and recurrent of various infections. They are able to hide in host cells without causing damage and are protected from host defenses.  S aureus can block the chemotaxis of neutrophils, it can sequester host antibodies, and can resist destruction by phagocytosis.  These various characteristics linked with S. aureus help it in evading the host immune system during an infection. Once the infection takes off, the S. aureus manage to produce numerous enzymes with the inclusion of; lipases, proteases and the elastases that work in enabling the infection to destroy all the host tissues and even metastasize to other different sites.

Diagnosis

MRSA is diagnosed by checking tissue samples and nasal secretions from the site of the infection for signs of drug-resistance bacteria. The sample is sent to the lab for testing (Hatcher etal,2017). The sample is then placed in a dish containing nutrients in the laboratory which encourages the bacterial growth of staph colonies.  These test results help indicate which antibiotic to use to treat the infection.  Since the whole process takes 48hours for the bacteria to grow, researcher have invented blood tests that can distinguish between MRSA and methicillin sensitive staph within two hours. 

Treatment

Both the health care and the community associated strains all linked with the MRSA can still respond to a few antibiotics.  In some cases the first line of treatment is with surgical draining rather than with antibiotics; then followed up with ointment and frequent bandage changes.  In other cases, antibiotics are required, and it is often treated with vancomycin, for severe cases it is given intravenously and often for up to six weeks. Antibiotics are often given in combination; vancomycin, gentamicin and rifampin to help combat the bacteria.  My mother-in-law was treated with vancomycin for six weeks, the infection started to return and they put her on a second six week course of vancomycin and she has been free of MRSA ever since. 

The prognosis depends on the type and severity of the infection and the health of the patient.  Most patients with mild cases make a full recovery, patients with compromised immune systems and those with blood infections are hard to treat and have a high mortality rate. 

Epidemiology

MRSA is readily transmitted through skin to skin contact with someone who is either infected with the disease, who is a carrier of the bacteria or with an object that has been contaminated with the bacteria and can enter the body through cuts and scrapes.  The frequency of the methicillin resistance Staphylococcusaureus tends to grow further in hospital linked settings. Recent research shows that the infection is now growing in community setting both globally as well as the United States. The pathogens ability to adapt well to any changing environment is linked with the increased incidence of the S. aureus. Infections arising due to S. aureus tend to impose a higher and an increased burden to all the health care resources required for use and most MRSA infections are healthcare associated. MRSA is a reportable disease in Virginia and several other states.  This disease is not required to be reported in all states. 

Prevention is the key to lowering the infection rates.  Wash your hands often with soap and warm water.  Cover cuts and scrapes with bandages to keep bacteria out.  And avoid sharing personal items such as razors, towels, and toothbrushes.   Visitors and care givers attending to the MRSA patients must wear protective garments to help prevent the spread. Likewise, persons infected with the CA-MRSA are advised to wash their hands, keep their wounds covered and ensure that the personal items are keep personal.

References

• Antonanzas, F., Lozano, C. & Torres, C. (2015), “Economic Features of Antibiotic Resistance: The Case of Methicillin-Resistant Staphylococcus aureus”, PharmacoEconomics,vol. 33, no. 4, pp. 285-325.

• Gordon, R. J., & Lowy, F. D. (2008). Pathogenesis of methicillin-resistant Staphylococcus  aureus infection. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 46 Suppl 5(Suppl 5), S350-9.
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