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Methicillin-resistant Staphylococcus aureus

What is methicillin resistant? Staphylococcus aureus?

MRSA is the term used for bacteria of the Staphylococcus aureus group that is resistant to the usual antibiotics used in the treatment of infections with such organisms. Traditionally, MRSA stood for methicillin (methicillin) resistance, but the term increasingly refers to a multi-drug resistant group. Such bacteria often have resistance to many traditionally used antibiotics against S. aureus.

MRSA is now generally classified into two types.

  • Hospital Acquired (HA) MRSA
  • Community Acquired MRSA (CA)

What causes MRSA?

Methicillin resistance is due to the presence of mec gene, placed on staphylococcal cassette Chromosome mec (SCCmec). This alters the site where methicillin binds to kill the organism. Therefore, methicillin cannot effectively bind to the bacteria. CA-MRSA is phenotypically and genotypically similar to HA-MRSA. CA-MRSA houses SCCmec type IV, V, or VII. However, the distinction between the two types becomes less and less over time.

Infections caused by MRSA are the same as other staph infections because the organism itself is not more virulent (or infectious) than the usual type S aureus.

As another S. aureusMRSA can colonize a person's skin and body without causing disease, and in this way it can be passed on to other people without knowing it. Problems arise in the treatment of overt infections with MRSA because the choice of antibiotics is very limited.

Where is MRSA located?

MRSA is found worldwide, predominantly in hospitals and institutions such as nursing homes, where it is known by the name of Hospital Acquired MRSA (HA-MRSA). Less frequently, MRSA is found in the general community (CA-MRSA).

There are three main reservoirs (and, therefore, sources of spread and infection) for MRSA in hospitals and institutions: personnel, patients and inanimate objects such as beds, sheets and utensils. By far the most important reservoir is patients, who can be colonized with MRSA without evidence of infection.

Common MRSA colonization sites are:

  • Nostrils
  • Groin
  • Armpit
  • Wounds

Most health professionals who are colonized with MRSA do not develop an infection, and many spontaneously cleanse the body without treatment. Once colonization has been around for more than three months, it becomes much more difficult to remove.

However, patients have a 30 to 60% infection risk after colonization. This is probably due to factors related to the disease for which they are hospitalized, which affect their ability to heal or control colonization with the organism.

Most MRSA infections occur in wounds (eg, surgical wounds), skin (eg, intravenous access sites), or in the bloodstream. Mortality from these infections is not significantly different from those seen with the usual type S aureus infections.

Community-acquired MRSA infections mainly occur:

  • In overcrowded places, due to frequent skin contact and sharing things. Examples include sports clubs, kindergartens, schools, and military barracks.
  • In people with a drainage cut or pain or who are carriers from MRSA
  • In people who undergo tattoos or body piercings.

Risk factors for severe skin infections with MRSA include:

  • Diabetes with obesity.

  • Previous antibiotics (within 90 days)
  • Chronic kidney disease / hemodialysis
  • Intravenous drug use.
  • Previous exposure to MRSA / infection (within 12 months)
  • Previous hospitalization (12 months)

  • Infection with the human immunodeficiency virus or AIDS.

What are the clinical characteristics of MRSA?

Hospital acquired MRSA is presented as:

  • Skin infections: abscesses, boils and anthrax, impetigo and cellulite.

  • Wound infection: trauma and surgical sites.

CA-MRSA is mainly presented with:

  • Bacterial folliculitis
  • Boil

  • Impetigo.

MRSA Complications

Left untreated, MRSA can lead to septicemia with eruption, headaches, muscle aches, chills, fever, chest pain and shortness of breath, and in some cases, the death of the patient. This is more common in HA-MRSA than CA-MRSA.

How is MRSA diagnosed?

The standard method of diagnosing MRSA is by culture and antibiotic sensitivity tests for Staphylococcus aureus bacteria from the infected site.

  • Antibiotic sensitivity tests guide treatment
  • PCR tests can also be used to detect MRSA

What is the treatment for MRSA?

The following steps are used for the treatment of MRSA carriers:

  • Current application of an antibiotic ointment as mupirocin or fusidic acid in the nostrils, 2 to 3 times a day for 3 to 5 days.

  • Antibacterial soaps and hand sanitizers.

Treatment of active infection involves draining pus from boils and abscesses, and antibiotics.

  • The antibiotic of choice for an infected hospitalized patient is intravenously administered vancomycin.
  • Daptomycin is an alternative intravenous antibiotic.
  • Oral clindamycin can be used in children Soft fabric outpatient infections.

These antibiotics are no better than flucloxacillin in the treatment of common type S aureus, but they are much more effective in MRSA infections.

Other antibiotics are less effective and are used if there is resistance to vancomycin / clindamycin or in case of Adverse reactions to these drugs.

  • Fluroquinolones
  • Trimethoprim + sulfamethoxazole
  • Minocycline

In life-threatening infections like infectious ones. endocarditis, multiple antibiotics are often prescribed simultaneously (eg vancomycin plus a aminoglycoside plus rifampicin).

How can MRSA be prevented?

In hospitals, patients who have been transferred from another hospital or institution should take swab samples upon admission for colonization or MRSA infection.

Common swab collection sites are the nostrils, armpits, groin, genital region, and any areas of broken skin (for example, surgical wounds, ulcers, sores).

New or transferred hospital staff are also screened. Swab results take a few days to report.

If an inpatient is found to have colonization or MRSA infection:

  • You should isolate yourself from unnecessary contact with staff and other patients in a single room, or share a room with other patients who have MRSA.
  • Bedding and clothing must be carefully sterilized.
  • Staff and visitors must take barrier precautions (gloves and gowns).

The above precautions should be applied strictly until repeated patient samples are negative for MRSA. This may take a few weeks. Personnel colonized with MRSA should withdraw from contact with the patient.

The following basic hygiene practice can help reduce incidence from CA-MRSA:

  • Wash your hands with antibacterial soap or hand rub / sanitizer
  • Avoid sharing personal items
  • Cover all wound sites.

Concerns about MRSA in the future

There is a growing concern about MRSA infections. They appear to be increasing in frequency and showing resistance to a broader range of antibiotics.

Of particular concern are the VISA strains of MRSA (intermediate susceptibility to vanusycin S aureus). They are beginning to develop resistance to vancomycin, which is currently the most effective antibiotic against MRSA. This new resistance has arisen because another species of bacteria, called enterococci, relatively commonly expresses resistance to vancomycin. In the laboratory, enterococci are capable of transferring the vancomycin resistance gene to S. aureus.

Newer antibiotics, such as linezolid and synercid, show promise for treating infections that do not respond to vancomycin. Many newer medications, including glycopeptides (dalbavancin, oritavancin, and telavancin), beta-lactams anti-MRSA (ceftobiprole), and diaminopyrimidines (iclaprim) are being tested for use against MSRA.