Detection of cytomegalovirus drug resistance mutations in solid organ transplant recipients with suspected resistance

- CMV resistance mutations should be confirmed whenever resistance is suspected.
- Detection of resistance mutations is needed to optimize patients' management.
- Sanger sequencing may not detect all resistance mutations present.
- Other factors may contribute to lack of response to treatment.

BackgroundCurrent guidelines recommend that treatment of resistant cytomegalovirus (CMV) in solid organ transplant (SOT) recipients must be based on genotypic analysis. However, this recommendation is not systematically followed.ObjectivesTo assess the presence of mutations associated with CMV resistance in SOT recipients with suspected resistance, their associated risk factors and the clinical impact of resistance.Study designUsing Sanger sequencing we prospectively assessed the presence of resistance mutations in a nation-wide prospective study between September 2013-August 2015.ResultsOf 39 patients studied, 9 (23%) showed resistance mutations. All had one mutation in the UL 97 gene and two also had one mutation in the UL54 gene. Resistance mutations were more frequent in lung transplant recipients (44% p = 0.0068) and in patients receiving prophylaxis ≥6 months (57% vs. 17%, p = 0.0180). The mean time between transplantation and suspicion of resistance was longer in patients with mutations (239 vs. 100 days, respectively, p = 0.0046) as was the median treatment duration before suspicion (45 vs. 16 days, p = 0.0081). There were no significant differences according to the treatment strategies or the mean CMV load at the time of suspicion. Of note, resistance-associated mutations appeared in one patient during CMV prophylaxis and also in a seropositive organ recipient. Incomplete suppression of CMV was more frequent in patients with confirmed resistance.ConclusionsOur study confirms the need to assess CMV resistance mutations in any patient with criteria of suspected clinical resistance. Early confirmation of the presence of resistance mutations is essential to optimize the management of these patients.