Introduction
Normally non-pathogenic and non-invasive staphylococcus, it Staphylococcus epidermidis it is a gram positive bacterium almost omnipresent in human skin, sometimes also found in the mucous membranes. Despite being one of the commensal microorganisms, it is Staphylococcus epidermidis it takes on a pathogenic significance when - in some predisposed subjects and in conditions favorable to it - it creates damage.
Before analyzing the infections carried by this staphylococcus let's briefly analyze it from a microbiological point of view.
Microbiological description
From the numerous biochemical tests performed on Staphylococcus epidermidis, interesting results emerged, summarized below:
- Weakly positive reaction to the nitrate-reductase test
- Staphylococcus epidermidis it is not able to hydrolyze gelatin → absence of the gelatinase enzyme
- It uses glucose, sucrose and lactose to form acid products
- It is positive for the production of urease (enzyme that catalyzes the hydrolysis of urea into ammonia + carbon dioxide)
In bacterial detection tests, it is imperative to distinguish Staphylococcus epidermidis from Staphylococcus saprophyticus: Both bacteria are coagulase negative and are similar in many respects. What sets them apart is novobiocin resistance / sensitivity: Staphylococcus epidermidis is sensitive to this antibiotic, while it Staphylococcus saprophyticus it is resistant.
Staphylococcus saprophyticus causes urinary tract infections. The diseases carried by this pathogen mainly affect young women
Related infections
The Staphylococcus epidermidis constitutes a good portion of the normal cutaneous and mucosal flora: in physiological conditions, the bacterium does not create any disturbance to the host. Staphylococcus epidermidis it represents 65-90% of all staphylococci that usually populate the skin, vagina, urethra and oral cavity.
- However, under certain conditions, it is Staphylococcus epidermidis he can transform his guise from being a diner to an opportunistic pathogen. This bacterium tends to cause damage in immunocompromised, catheterized, surgical or transplanted individuals.
When compared to Staphylococcus aureus, Staphylococcus epidermidis it is a less common cause of opportunistic infections. However, similarly to Enterococcus faecalis, S. epidermidis occupies an important position in nocosomal infections. In fact, most of the infections sustained by Staphylococcus epidermidis it is documented in a hospital setting. This phenomenon may be the result of the continuous use of disinfectants and antibiotics in health facilities: a similar condition seems to have favored the selection of new strains of Staphylococcus epidermidis, virulent for the organism.
- The Staphylococcus epidermidis they have a particular extracellular structure (glycocalyx) which covers the external tissue surface. This outer layer to the cell wall acts as a tool for adhesion of the bacterium to many and varied surfaces, such as skin and catheters. The aforementioned polysaccharide film therefore gives the bacterium the ability to adherence.
It is precisely because of the extraordinary ability to bind to catheters that it Staphylococcus epidermidis it has become an enemy of hospital environments.
To avoid the spread and transmission of the Staphylococcus epidermidis the sterilization of every hospital environment of intervention is essential.
In patients with severely compromised immune systems, in transplanted or catheterized subjects, lo Staphylococcus epidermidis it can create sepsis or septicemia (especially in the newborn), endocarditis in subjects with artificial valves and infections of the central venous catheter. Dialysis patients are also at risk of getting infections from Staphylococcus epidermidis.
Antibiotic Therapies and Resistance
The Staphylococcus epidermidis it turns out to be quite resistant to antibiotics: this characteristic seems to be due precisely to the presence of the glycocalyx. This polysaccharide film, in fact, does not only give the bacterium the ability to adhere to the most varied surfaces: the glycocalyx also constitutes a sort of protection from phagocytosis and antibiotics.
However, patients affected by infections sustained by Staphylococcus epidermidis they seem to respond positively to antibiotic treatment with vancomycin, possibly associated with rifampicin and aminoglycosides.
The best cure for Staphylococcus epidermidis it is prevention, therefore the correct hygiene of hospital environments and medical instruments, and the continuous and careful washing of hands.
