HEALTHCARE-ASSOCIATED INFECTIONS: EVOLUTION BY NATURAL SELECTION

Introduction:Since "nothing in biology makes sense except in the light of evolution," the biological basis of infections associated with health care cannot be clearly and effectively explained, understood, or combated if we ignorethe evolutionary process of Natural Selection, which is also influenced by actions for its prevention, treatment, and control and by modifying the Hospital and organic environment of the hosts.Methods: Using a descriptive, longitudinal, and retrospective analytic method, the main components of the complex evolutive process of 12513 infections and 2473 deaths associated with health care were studied for 11 years: their incidence and fatality due to medical services and surgical procedures, their causal agents with their sensitivity and resistance to antimicrobials (with 7758 cultures and antibiograms) and, concomitantly, hospital actions for their prevention, treatment, and control.Results:The evolutionary process of healthcare-associated infections (HAI) was confirmed by observing their variations over 11 years, with differential upward trends due to morbidity, mortality, typology, hospital service, hosts, and, above all, its causal agents and their sensitivity and resistance to antimicrobials. Variations in HAI occurred through particular ups and downs and contradictions but generally tended to increase, exceeding the expected reference rates. This behavior indicates an evolutionary process that is neither rectilinear nor unidirectional but dialectical in its development.Conclusion:Healthcare-associated infections are subject to a dialectical process of Evolution, basically due to competition, Natural Selection, and adaptation of their causal agents, both to the hospital environment and the tissular and organic microenvironments of the hosts. Their Evolution depends, in principle, on their genomic potential to contaminate and colonize inert surfaces, adapt to the crossed transmission of contagion, colonization, and infection of a host, and concomitantly, their interaction with the conformation and variations of the hospital environment and the organic microenvironment of the host.