Risk Factors for the Development of Cytomegalovirus Resistance in Solid Organ Transplantation: A Retrospective Case-Control Study

Background: Cytomegalovirus (CMV) resistance is an emerging problem in solid organ transplant recipients. Risk factors are not well defined. Methods: Recipients with CMV viremia of solid organ transplants who underwent CMV resistance testing between January 2010 and March 2016 were divided in 2 groups: proven CMV resistance and refractory CMV infection. A third group was added to compare patients with viremia during the study period with patients with no resistance proven or suspected. We aimed to identify risk factors associated with the occurrence of CMV genotypic resistance. Results: Forty-nine patients underwent resistance testing. Eleven (22.45%) developed genotypic mutations. Group 1 vs groups 2 and 3 had higher prednisone (P =.01) and tacrolimus levels (P =.03); did not respond to antivirals (P <.0001); and had a higher rate of fungal infections (P =.03). CMV resistance was less common in liver and kidney vs heart, small bowel, and mutivisceral recipients (P =.0007). There was no difference in duration of antiviral prophylaxis, viremia while on antiviral prophylaxis, rate of end-organ disease, graft loss, and overall survival. Persistent clinical disease and viremia despite antiviral therapy was the most important risk factor for development of CMV resistance. Conclusion: Persistent clinical disease despite antiviral therapy is an important risk factor and may in part be due to a high degree of immunosuppression. Graft loss and survival were not impacted by CMV resistance.