Staphylococcal infections

Content

Introduction

Staphylococci are bacteria that commonly live on the skin, nose, throat (pharynx) and intestines of people without creating problems. In particular conditions, however, they can penetrate the human body and develop infections that are sometimes mild, others so serious life endangering.

There are different types (species) of staphylococci, more or less capable of causing disease (pathogens). The most fearful is it staphylococcus aureus both for the number of cases in which it is involved, and because it can be resistant to some antibiotics, including methicillin. Staphylococci methicillin-resistant (MRSA) they cause infections that are very difficult to cure, due to their resistance to a large number of antibiotics.

Staphylococci can cause both localized infections, usually in the skin, and deep infections affecting various organs. Some diseases are caused not so much by the presence of the bacterium as by the spread of substances produced by the bacterium itself (toxins).

The most common staphylococcal infections are:

  • cutaneous forms, such as abscesses, boils, impetigo (infection with scabs or blisters, often itchy, which mainly affects the face, neck, hands), erysipelas (infection that also involves the deep layers of the skin with pain and redness), the sty, the patereccio (the "giradito"), infectious cellulite, pustules
  • deep forms, such as pneumonia, endocarditis, septic arthritis, osteomyelitis, lymphangitis, acute lymphadenitis

When staphylococci invade the blood, and multiply there, they can cause a "generalized infection (septicemia / sepsis) sometimes accompanied by localized abscesses in the organs.

Among the diseases caused by toxins produced by staphylococci:

  • burn skin syndrome (SSSS), also known as Ritter's disease or Lyell's disease, caused by exfoliative toxin which, by damaging the skin, leads to the formation of large blisters similar to those produced by a burn
  • toxic shock syndrome (TSST) caused by the enterotoxin from which it takes its name, associated with an infrequent replacement of vaginal swabs
  • skin infections, in non-hospitalized subjects, caused by a toxin that infects leukocytes, called Panton-Valentine leukocidin (PVL)
  • food poisoning caused by the ingestion of staphylococcal enterotoxins

Symptoms

The disorders caused by staphylococcal infections are closely related to the affected organ:

  • in skin and deep infections, such as osteomyelitis or septic arthritis, redness, swelling, localized pain, pus appear
  • in food poisoning, nausea, vomiting and / or diarrhea occur after 2-6 hours after ingestion of contaminated food. In these cases, fever is not present
  • in pneumonia, in addition to high fever, breathing difficulties, cough, purulent sputum as in pneumococcal pneumonia, lack of strength (asthenia) and deterioration of the general condition appear

In sepsis, the following can occur:

  • fever above 38 ° C
  • feeling of general malaise
  • muscle aches
  • chills
  • confusion

A sharp drop in blood pressure is the main manifestation of an aggravation of sepsis leading to septic shock.

Causes

One in three people safely harbor harmless staphylococci in the skin, mucous membranes, respiratory and intestinal tracts. However, if these bacteria enter the body they can cause infections, in some cases negligible, in others so serious as to be fatal.

Transmission between people can occur through close contact or through the sharing of contaminated objects such as, for example, towels, toothbrushes, rarely through coughing and sneezing.

The main ways of penetration into the human organism are:

  • skin, due to local infections, such as boils or backstairs, cuts, grazes, burns, insect bites
  • mucous membranes, in particular those of the genitals and urinary tract, more rarely the mucous membranes of the mouth and throat (oropharynx)

The infection is favored by poor hygiene and by the presence of foreign bodies (prostheses, catheters, various medical devices).

The ingestion of foods polluted with staphylococcus aureus, especially creams or ice creams, in which it multiplies easily, but also in sausages, causes the appearance of food poisoning.

As in all infections, contagion and spread within the body are strictly dependent on the reaction (response) of the body's defense system (immune system).

Diagnosis

When a "staphylococcal infection" is suspected, in addition to the observation of typical disorders (symptoms) it is essential to ascertain (diagnose) the presence of bacteria in the body by analyzing clinical samples that are different depending on the site of the infection:

  • tampons vaginal, pharyngeal, rectal, cutaneous
  • urine (urine culture), blood (blood culture), faeces (copro culture), sputum

Subsequently, if the analyzes show the growth of bacteria in the materials examined, an antibiogram is carried out to identify the most suitable antibiotic for treating the infection.

In food poisoning infections, the toxin or bacterium is also searched for in the suspected food, as well as on the skin and nose of food operators.

Therapy

Less severe staph infections, including skin infections and foodborne infections, do not generally need specific treatment (therapy) and tend to heal spontaneously within a few days or weeks.

In some cases, local antibiotic-containing creams may be recommended. Sometimes, minor surgeries may be required to clear collections of pus under the skin using a needle or scalpel.

For deep infections, therapy depends on the organ in which the infection is located and the severity of the disorders (symptoms), but antibiotic therapy is generally required.

Invasive staphylococcal infections often require hospitalization, because the specific treatment of the infection is usually based on the administration of intravenous antibiotics.

MRSA infections, due to the bacterium's resistance to antibiotics, are difficult to cure, although antibiotics suitable for these infections are also available today.

Prevention

To reduce the chances of developing staph infections, it is useful to follow common hygiene rules:

  • wash your hands regularly with warm soapy water (Video), especially if you come into contact with someone who has a "skin infection."
  • keep wounds clean and covered
  • do not share towels, washcloths, bedding, toothbrushes and razors with other people
  • cook and properly store food
  • disinfect tools and surfaces

In hospitals, the prevention of transmission of staphylococcal infections, as occurs for other hospital infections (nosocomial), is based on 4 points of which the first is the most important:

  • hand washing by healthcare personnel
  • identification and isolation of infected patients or colonized with antibiotic resistant strains (MRSA)
  • elimination of staphylococcus aureus (especially if MRSA) that the patient hosts as a carrier (decolonization) before major surgery or transfers to critical wards
  • cleaning and environmental decontamination

Complications

Deep or invasive staph infections, especially if caused by antibiotic-resistant strains, can be difficult to cure. Mortality in these cases reaches 30%.

The most serious complications are sepsis and septic shock which can lead to a failure of the functioning of several organs of the body (multi-organ failure) with a mortality rate of around 70%.

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