The use of
biological agents and
immunomodulators for
inflammatory bowel disease (IBD) has remarkably improved disease management in the current era but at the same time has increased the risk of infectious complications. Patients with IBD on
corticosteroids,
immunomodulators, and
biological agents are considered immunocompromised and are at risk for
opportunistic infections. These are
infections caused by organisms that take advantage of a weakened immune system, and cause disease, when they ordinarily would cause mild illness or no disease in an immunocompetent host. Risk factors for
opportunistic infections include
malnutrition, older age, congenital immunodeficiency,
HIV infection,
chronic diseases, and use of
corticosteroids,
immunomodulators, and anti-
tumor necrosis factor alpha therapy. Apart from immunosuppressive medications and older age, there is only indirect evidence for above risk factors contributing directly to
opportunistic infection risk in patients with IBD.
Opportunistic infections in patients with IBD include
viral infections (herpes viruses, human papillomavirus, influenza virus, and JC virus),
bacterial infections (
tuberculosis,
nocardiosis,
Clostridium difficile infection,
pneumococcal infection,
legionellosis, and
listeriosis),
fungal infections (
histoplasmosis,
cryptococcosis,
Pneumocystis jirovecii infection,
aspergillosis, and
candidiasis), and
parasite infections (Strongyloides stercoralis). Although these
infections lead to high morbidity and mortality, only a minority of patients with IBD develop
opportunistic infections. Currently, we lack a test to accurately predict patients at risk of
opportunistic infection, and future research needs to focus on
biomarkers or predictive models for risk stratification. Until such a test is developed, we need to screen, prevent, diagnose, and treat
opportunistic infections in all patients with IBD in a timely manner.