Opportunistic Infections

Opportunistic infection refers to illness caused by a microorganism that does not usually cause disease in immunocompetent individuals but is pathogenic in those with compromised immune systems.

A variety of immunocompromised patients are at risk for opportunistic infections (OIs), including patients with HIV/AIDS, patients who have undergone solid-organ or bone-marrow transplantation, and those taking high-dose glucocorticoids or immune modulators (e.g., for rheumatologic diseases, inflammatory bowel disease, multiple sclerosis, and obstructive airway diseases). Recognizing opportunistic infections early and ensuring adequate prophylaxis are crucial for mitigating their complications. In this section, we will cover:

• Common Opportunistic Infections

• Prophylaxis for Opportunistic Infections in Adults with HIV

• Prophylaxis for Opportunistic Infections After Solid-Organ Transplantation

Common Opportunistic Infections

Immunocompromised patients are at increased risk for common infections in addition to the rarer pathogens. The specific organisms that a patient is susceptible to vary based on the patient’s underlying illness. Common opportunistic infections in immunocompromised patients include:

• Pneumocystis jirovecii pneumonia (formerly Pneumocystis carinii pneumonia; PCP)

• toxoplasmosis

• tuberculosis (TB)

• Mycobacterium avium complex (MAC)

• Endemic mycoses: histoplasmosis, Coccidioides, Blastomyces, Cryptococcus, Talaromyces marneffei (endemic in Southeast Asia)

• other fungal infections: yeast (e.g., Candida) and molds (e.g., Aspergillus or mucormycosis)

• cytomegalovirus (CMV)

• herpes simplex virus (HSV) and varicella-zoster virus (VZV)

• Epstein-Barr virus (EBV)

• BK virus

• JC virus

• hepatitis B reactivation

Prophylaxis for Opportunistic Infections in Adults with HIV

Prophylactic Antibiotics

Antiretroviral agents and prophylactic antibiotics have significantly reduced the frequency of opportunistic infections in patients with HIV/AIDS. A patient’s CD4-cell count correlates with the likelihood of contracting an OI, and those with normal CD4-cell counts are not typically considered to be immunocompromised. The following table provides a simple guide for choosing prophylaxis in patients with HIV/AIDS:

Vaccinations

In addition to prophylaxis with drugs, vaccination is another vital component for keeping patients with HIV/AIDS healthy. The following table summarizes general immunization recommendations from the Centers for Disease Control (CDC) for patients with HIV. Other vaccines may be indicated based on additional risk factors. The complete National Institutes of Health recommendations for prophylaxis, treatment, and vaccination of patients with HIV/AIDS can be found here.

Prophylaxis for Opportunistic Infections After Solid-Organ Transplantation

Initial considerations for infection and prophylaxis should be started at the time of transplantation. The following table summarizes recommendations for the prevention of opportunistic infections in solid-organ transplant recipients with HIV.

(Source: Infections in Solid Organ Transplant HIV-Infected Patients. Clin Microbiol Infect 2014.)

The following are prophylaxis recommendations from the American Society of Transplantation Infectious Diseases Community of Practice for solid-organ transplant recipients from the American Society of Transplantation infectious diseases guidelines.

• Valganciclovir is recommended for CMV prophylaxis in the following patients (“D” denotes donor serologic status and “R” denotes recipient serologic status): D+/R−, D+/R+, and D−/R+. Duration of prophylaxis varies by organ transplantation center and risk of developing CMV infection and is usually a minimum of 3 months (but often closer to 6 or 12 months) after transplantation and is restarted for a few months after postrejection treatment with antithymocyte globulin.

• TMP-SMX is typically administered for 6 to 12 months after transplantation, to prevent PJP pneumonia as well toxoplasmosis. Alternative PJP prophylaxis agents include dapsone, atovaquone, or inhaled pentamidine.

• Oral clotrimazole lozenges, nystatin, or fluconazole are given as needed after transplantation or a month after antithymocyte globulin.