Colonization is the presence of a microorganism in the body without affecting the body tissues in that area, nor causing organ dysfunction. In most cases colonization does not require antimicrobial treatment.

The human microbiome is the set of genetic material of microbes living in the human body. Most commonly, this term is used to refer to all the microbes present in the human body, but it is rendered slightly differently in English (human microbiota).

The microbiome consists mainly of microorganisms of the gastrointestinal tract, respiratory system, genital tract, and skin. The predominant components of the microbiome are various types of bacteria, followed by fungi, viruses (which are not considered microorganisms in the strict sense of the term) and parasites. Many of these microorganisms live symbiotically with humans, performing critical functions, such as the body’s defense, various metabolic processes, etc. The microbiome is therefore considered to be an additional organ.

Any disturbance of the normal structure, composition and function of the human microbiome can cause issues with how the body functions overall. In fact, there has been an enormous interest in recent years in research on permanent or prolonged disturbances of the microbiome and their association with serious diseases such as chronic neurological diseases and various forms of cancer.

Antimicrobials are natural or artificially synthesized substances used to fight infections by either killing microorganisms or inhibiting their proliferation to give the human body time to eliminate them. They fall into the following four broad categories: antibacterials, antifungals, antivirals and antiparasitics.

All approved antimicrobials are considered safe. However, side effects cannot be ignored, and vary greatly depending on the type of antimicrobial and the health status of the person taking it, including any possible comorbidities they may have. Many of these side effects cannot be predicted in advance. Furthermore, there are specific criteria for each antimicrobial based on the patient’s medical history and underlying conditions.

The correct use of antimicrobials has revolutionized medicine and in nearly a century of administering them to humans, they have saved billions of lives. It is, however, their overuse or misuse that creates major problems. On one hand, they kill microorganisms that are vital components of our natural microbiome, dramatically disrupting its function. On the other hand, the frequent use of antimicrobials makes the microorganisms they combat resistant to them, rendering them useless.

The result is the creation of multidrug resistant strains of microorganisms, which are easily transmitted between people, especially in healthcare facilities (hospitals, nursing homes, welfare facilities, etc.). Cyprus and Greece, as well as other Mediterranean countries are considered global incubators of multidrug resistant microorganisms, mainly due to the indiscriminate use of antimicrobials, but also due to inadequate (or non-implemented) infection prevention and control measures.