Invasive Markers of Staphylococcus Epidermidis

In the hospital, a large proportion of bacteraemia and implantable medical device infections are caused by Staphylococcus epidermidis. This microorganism is the most abundant on human skin and all patients are carriers. Its remarkable ability to form biofilms on most materials explains that catheter-related infections are by far the most common.

S. epidermidis infections are difficult to treat because most strains are multi-resistant and antibiotics are less effective in the presence of biofilms.

In addition, S. epidermidis poses a major diagnostic problem because it is also the first source of contamination of blood culture sample and intraoperative samples (in case of suspected infection of orthopedic material in particular). Thus, when a sample is positive for S. epidermidis, there is less than a 25% chance that it reflects true bacteremia in the patient and 30% of patients would inappropriately receive vancomycin following contaminated blood cultures. Differentiating a contamination of a blood or intraoperative sample from true S. epidermidis infection is therefore crucial for patient management because unnecessary antibiotic therapy is potentially responsible for the emergence of resistant strains, toxicity and additional costs.

The objective of this study is to identify the genetic markers that make it possible to differentiate the strains causing infections from the strains causing contamination by comparing their genomes using high throughput sequencing.

Inclusion criteria

CASE Inclusion Criteria:

Population 1: nosocomial bacteraemia associated with intravascular devices

• Hospitalized patient with intravascular device (peripheral or central, venous or arterial, short or long duration) for at least 48 hours before the development of bacteraemia
• Presenting a definite infection with S. epidermidis according to the categorization criteria,

Sub-Population 1A:

3a) Aged less than 28 days (New-born)

Sub-population 1B:

3b) Aged 28 days or more

Population 2: nosocomial infections of implanted material

• An operated patient carrying implanted equipment following orthopaedic surgery, following cardiac surgery or following neurosurgery,
• Presenting a definite infection with S. epidermidis according to the categorization criteria occurring in the year following surgery

CONTROL Inclusion Criteria:

Population 1: carrier of intravascular devices

• Hospitalized patient with intravascular device (peripheral or central, venous or arterial, short or long duration) for at least 48 hours before positive blood culture with S. epidermidis
• Certain contamination with S. epidermidis according to the categorization criteria,

Sub-Population 1A:

3a) Aged less than 28 days (Newborn)

Sub-population 1B:

3b) Aged 28 days or more

Population 2: carrier of implanted material

• An operated patient carrying implanted equipment following orthopedic surgery, following cardiac surgery or following neurosurgery,
• Presenting a certain contamination to S. epidermidis according to the categorization criteria occurring in the year following surgery

Exclusion criteria

CASE Exclusion Criteria Population 1: nosocomial bacteremia associated with intravascular devices

• Opposition of the patient or the holders of parental authority (minor patients)
• Patient with polymicrobial infection
• Patient with a colonized catheter (positive catheter end culture <103UFC / mL) with no clinical signs of local or general infection and with sterile peripheral blood cultures
• Patient with local catheter infection (positive catheter end culture> 103UFC / mL) with local inflammatory signs only and with sterile peripheral blood cultures

Population 2: nosocomial infections of implanted material

• Opposition of the patient or the holders of parental authority (minor patients)
• Patient with an infection of material concomitant with a catheter-related infection

CONTROL Exclusion Criteria

Populations 1 and 2:

Opposition of the patient or the holders of parental authority (minor patients)