Therapy- and non-therapy-dependent infectious complications in inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) are susceptible to infections.

Independently from immunomodulatory therapy, IBD predisposes to infectious complications. Thus, the incidence of Clostridium difficile infection is increased in IBD patients, and a significant proportion of these patients contracts C. difficile infection outside the hospital and without precedent antibiotic use. Cytomegalovirus infection has been reported in cortico- steroid-naive patients with ulcerative colitis, and infectious gastroenteritis has been linked to initiation and exacerbation of IBD. Finally, in Crohn's disease there is a substantial risk for abscess formation, and urinary tract infections occur more frequently than in a non-IBD control population. Apart from the disease process itself, factors that predispose to infectious complications in IBD are malnutrition, advanced age, immunosuppressive medications, leukopenia from immunosuppressive medications, and surgery. However, the main risk for infections is clearly related to the use of immunosuppressive agents such as corticosteroids, azathioprine, methotrexate, cyclosporine, and TNF-blocking biologicals. A wide spectrum of infectious complications has been reported in patients treated with these medications, including viral (e.g. CMV, VZV, EBV), bacterial (e.g. Mycobacteria, Listeria, staphylococci), fungal (e.g. Pneumocystis jiroveci, Aspergillus, Candida, Cryptococcus) and protozoal (Toxoplasma) pathogens. The greatest risks obviously relate to the combined use of immunomodulating agents rather than to individual drugs. The risk of infections is also aggravated by an insufficient immunization status as frequently observed in patients with IBD.

Physicians treating patients with IBD must be aware of the risk for infectious complications in these patients as well as of strategies to minimize them.