The abbreviation MRSA originally stands for “Methicillin-resistant Staphylococcus aureus” and not for “Multi-resistant Staphylococcus Aureus” as is often wrongly assumed. Staphylococcus aureus is a gram-positive spherical bacterium that can be found almost everywhere in nature and in many people (about 30% of the population) is also part of the natural flora of the skin and upper respiratory tract. This means that these individuals are colonized by the germ without showing any symptoms under normal circumstances. In principle, however, Staphylococcus aureus is a pathogenic bacterium, which means that it is capable of causing a variety of different diseases. Therefore, if it can spread under favorable conditions or if it encounters a weakened immune system, it can become dangerous for humans with the help of various so-called pathogenicity factors.
Among the most frequently caused clinical pictures are infections of the skin (often purulent: folliculitis, boils, etc. ), food poisoning and muscle or bone diseases. In worse cases, however, this bacterium can also be the cause of pneumonia, endocarditis (inflammation of the innermost layer of the heart), sepsis (colloquially blood poisoning) or the Toxic Shock Syndrome (TSS) specific to this germ and can even become life-threatening.
Normally, Staphylococcus aureus responds well to a variety of antibiotics, which is why a simple illness with this bacterium can usually be treated well with a 1st or 2nd generation cephalosporin (for example cefuroxime). The special thing about MRSA strains is that they do not respond to the usual broad-spectrum antibiotics. It is said that this germ is resistant to these antibiotics.
The resistance to methicillin is due to the fact that the bacterium changes its surface structure in such a way that the antibiotic can no longer bind to its surface as well, which would be necessary, however, in order to develop its effect. Unfortunately, however, resistance is rarely limited to methicillin, but also affects various other antibiotics that may otherwise be used. Hence the common term multi-resistant Staphylococcus Aureus.
Consequently, infections with MRSA are difficult to treat and require a different treatment than the standard Staphylococcus Aureus. This is usually done with glycopeptides such as vancomycin. This is the reason for the special significance of this germ: although its spectrum of diseases is similar to that of the other strains, diseases cannot be cured so quickly and thus put patients at greater risk.
Infection with MRSA in hospitals and nursing homes is of particular relevance, especially in the context of so-called nosocomial infections (infections that have a temporal connection with an inpatient medical task and did not exist before). It is assumed that the prevalence of MRSA in the general population is about 0.4%, in nursing and old people’s homes already about 2.5% and in hospitals even 25%. For this reason, a distinction is made between two groups of MRSA:
- The MRSA infection acquired in hospital: Hospital aquired MRSA.
Elderly people and those with a weak immune system have an increased risk for this type of infection
- The MRSA infection that occurs outside the hospital: Community aquired MRSA c-MRSA. This form is comparatively rare and also occurs in younger persons. It is also associated with a somewhat different clinical picture, for example necrotizing pneumonia and is more common in people who have a certain gene.