**1.4. Definition of MRB**

in the United States has estimated that the problem of antibiotic resistance is responsible for 2 million infections and 23,000 deaths per year with a direct cost of 20 billion dollars, and losses of productivity equivalent to 33 billion dollars [1]; the European Center for Disease Control, ECDC, have estimated that accounts for 25,000 deaths and 1.5 billion € per year by infections by multiresistant bacteria (MRB) [2]. Some consequences of this problem are: increased cost of health care, increased rates of failure of antibiotic treatment and increased mortality. This is not a problem limited to certain regions or countries and resistance can spread quickly in our globalized world.

Intensive care unit (ICU) accounts for less than 10% of total beds in most hospitals, but more than 20% of nosocomial infections are acquired in ICU [3]. Acquired in ICU infections pose significant morbidity, mortality and expense; they are the most frequent cause of death in non-cardiac ICUs and 40% of all ICU expenses [4]. In comparison with patients from other areas of the hospital, ICU patients have higher chronic comorbidity, more severe acute physiological deterioration and are relatively immunosuppressed [5]. Its management also implies a high degree of invasiveness, with use of intravascular catheter, contact with a large number of health personnel—predisposing to colonization and infection—and are subjected to an

When a patient goes to the hospital today, he undergoes a more effective and complete care than in previous years. Advances in diagnostic and therapeutic methods mean improvements in care and may be accompanied by a greater number of associated complications. All these data are magnified in ICU; ICU patients are more vulnerable to develop infections during their stay and to become colonized/infected with MRB. Overcrowding in closed areas of these severely ill patients with multiple comorbidities and subjected to invasive devices are risk

There is a clear relationship between the appearance of resistance and the highest antibiotic consumption. Infections due to resistant germs/MRB have limited therapeutic options, so inadequate empirical treatments are prescribed, the start of the correct treatment is delayed and therapeutic failures increase. All this leads to longer ICU stay, costs and mortality, with

The highest density of MRB is observed in ICU. The importance of adequate and early treatment is greater in critically ill patients; for all above, it is necessary to implement programs for the prevention and treatment of multiresistant bacteria MRB, both in the ICU and in the community—a great number of MRB can be related to inadequate or excessively prolonged

The mechanisms related to the emergence of resistance are varied. Resistance can be intrinsic or acquired. the first occurs in certain germs that are not innately sensitive to certain antibiotics, by a special membrane structure or related to the mechanism of the antibiotic. There may be at the molecular level: modifications in the targets (nucleic acid, ribosomes, action points

**1.2. Intensive care unit generalities**

38 Current Topics in Intensive Care Medicine

increased colonization pressure [5].

worse prognosis of the patient.

**1.3. Antibiotic resistance mechanisms**

factors for the development of nosocomial infections.

treatments in the general ward or outside the hospital.

MRB are defined as those microorganisms resistant to three or more antibiotics, which must also have clinical relevance. The exception to this rule is methicillin-resistant *Staphylococcus aureus* (MRSA) and vancomycin-resistant enterococcus (VRE) cases, in which the resistance condition is given by only one antibiotic. The phenomenon of resistance constitutes a medical problem, since it becomes a difficulty for the treatment and also epidemiological relevance, given the possibility of transmission of the outbreak. The ESKAPE (*Enterococcus faecium*, *Staphylococcus aureus*, *Klebsiella pneumoniae*, *Pseudomonas aeruginosa* and Enterobacter especies) are a specific group of bacteria with clinical relevance, associated with health care, and with the capacity to develop antibiotic resistance [6].
