Donor-derived Mycoplasma hominis and a cluster of M. hominis cases in solid organ transplant recipients

Background: Invasive and disseminated Mycoplasma hominis infections are well recognized, but uncommon complications in solid organ transplant recipients. In a single center, a cluster of M. hominis infections were identified in lung transplant recipients from the same thoracic intensive care unit (ICU). We sought to determine the source(s) of these infections. Materials/methods: Medical records of the donor and infected transplant recipients were reviewed for clinical characteristics. Clinical specimens underwent routine processing with subculture on Mycoplasma-specific Hayflick’s agar. M. hominis identification was confirmed using sequencing of the 16S rRNA gene. M. hominis isolates were subjected to whole genome sequencing (WGS) on the Illumina NextSeq platform. Results: Three lung transplant recipients presented with invasive M. hominis infections at multiple sites characterized by purulent infections without organisms detected by Gram staining. Each patient had a separate donor; however, pre-transplant bronchoalveolar lavage fluid was only available from the donor for Patient 1, which subsequently grew M. hominis. Phylo- and pan-genomic analyses indicated that the isolates from the donor and the corresponding recipient (Patient 1) were closely related and formed a distinct single clade. In contrast, isolates from Patients 2 and 3 were unrelated and divergent from one another. Conclusion: M. hominis should be considered a cause of donor-derived infection. Genomic data suggest donor to recipient transmission of M. hominis. Additional patients co-located in ICU, were found to have genetically unrelated M. hominis isolates, excluding patient to patient transmission.