An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severely on those with a weakened immune system. These types of infections are considered serious and can be caused by a variety of pathogens including viruses, bacteria, fungi, and parasites. Under normal conditions, such as in humans with uncompromised immune systems, an opportunistic infection would be less likely to cause significant harm and would typically result in a mild infection or no effect at all. These opportunistic infections can stem from a variety of sources, such as a weakened immune system (caused by human immunodeficiency virus and acquired immunodeficiency syndrome), when being treated with immunosuppressive drugs (as in cancer treatment), when a microbiome is altered (such as a disruption in gut microbiota), or when integumentary barriers are breached (as in penetrating trauma). Opportunistic infections can contribute to antimicrobial resistance in an individual making these infections more severe. Some pathogens that cause these infections possess intrinsic resistance (natural resistance) to many antibiotics while others acquire resistance over time through mutations or horizontal gene transfer. Many of these pathogens, such as the bacterium Clostridioides difficile (C. diff), can be present in hosts with uncompromised immune systems without generating any symptoms, and can, in some cases, act as commensals until the balance of the immune system is disrupted. With C. diff and many other pathogens, the overuse or misuse of antibiotics can cause the disruption of normal microbiota and lead to an opportunistic infection caused by antibiotic resistant pathogens. In some cases, opportunistic infections can be labeled as a hospital-acquired infection due to individuals contracting them within a healthcare/hospital setting. In terms of history, there is not one individual that can be attributed for discovering opportunistic infections. Over time and through medical advancement, there have been many scientists that have contributed to the study and treatment options for patients affected by these infections.
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Immunosuppressive drug in the context of Tacrolimus
Tacrolimus, sold under the brand name Prograf among others, is an immunosuppressive drug. After an allogenic organ transplant, the risk of organ rejection is moderate; tacrolimus is used to lower the risk of organ rejection. Tacrolimus is also sold as a topical medication for treating T cell-mediated diseases, such as eczema and psoriasis. For example, it is prescribed for severe refractory uveitis after a bone marrow transplant, exacerbations of minimal change disease, Kimura's disease, and vitiligo. It can be used to treat dry eye syndrome in cats and dogs.
Tacrolimus inhibits calcineurin, which is involved in the production of interleukin-2, a molecule that promotes the development and proliferation of T cells, as part of the body's learned (or adaptive) immune response.
Immunosuppressive drug in the context of Dexamethasone
Dexamethasone is a fluorinated glucocorticoid medication used to treat rheumatic problems, a number of skin diseases, severe allergies, asthma, chronic obstructive pulmonary disease (COPD), croup, brain swelling, eye pain following eye surgery, superior vena cava syndrome (a complication of some forms of cancer), and along with antibiotics in tuberculosis. In adrenocortical insufficiency, it may be used in combination with a mineralocorticoid medication such as fludrocortisone. In preterm labor, it may be used to improve outcomes in the baby. It may be given by mouth, as an injection into a muscle, as an injection into a vein, as a topical cream or ointment for the skin or as a topical ophthalmic solution to the eye. The effects of dexamethasone are frequently seen within a day and last for about three days.
The long-term use of dexamethasone may result in thrush, bone loss, cataracts, easy bruising, or muscle weakness. It is in pregnancy category C in the United States, meaning that it should only be used when the benefits are predicted to be greater than the risks. In Australia, the oral use is category A, meaning it has been frequently used in pregnancy and not been found to cause problems to the baby. It should not be taken when breastfeeding. Dexamethasone has anti-inflammatory and immunosuppressant effects.