Challenges of secondary immunodeficiency and drug resistant opportunistic pathogens in developing countries

The immune system is composed of a variety of cells and proteins viz. lymphocytes, phagocytes, and cytokines, for which one of the principal functions is microbial defense. Abnormalities of the immune system (IS), particularly the secondary immunodeficiency, are due to old age, several pathologic conditions (diabetes mellitus, lymphohematologic neoplasias, malnutrition, HIV/AIDS etc.), surgical stress or burns, and immunosuppressive therapies. Such deficits in the IS can therefore lead to unusually severe or uncommon recurrent/opportunistic infections (OIs). These infections take advantage of this weak host IS and manifest their adverse effects. The main clinical manifestation of SI, inclusive HIV/AIDS, is severe OIs with abnormally high mortality. OIs are of endogenous nature because OI-causing pathogens are also present in healthy hosts, though only in limited quantities. It is recognized that the IS normally suppresses opportunistic pathogens, and immunodeficiency causes OIs. Drug-resistant microorganisms are frequently detected in individuals with immunodeficiency, and that this drug-resistance is partially responsible for the frequent lethal outcome of OIs incurable by antibiotics. No apparent link exists between immunodeficiency and drug-resistance of the microorganisms. However, drug-resistance is a natural consequence of antibiotic abuse that results from natural selection of drug-resistant mutants under the selective pressure of antibiotics. Bacterial infections contribute to most human and animal diseases in developing countries and are those in which emerging antimicrobial resistance is most evident. Resistance to antimicrobial agents has become major health concern as a number of people with acquired/secondary immunodeficiency are also infected by drug resistant pathogens and/or opportunistic microorganisms.