Transmission of methicillin-resistant Staphylococcus aureus infection through solid organ transplantation: confirmation via whole genome sequencing

Abstract

We describe two cases of donor-derived methicillin-resistant Staphylococcus aureus (MRSA) bacteremia that developed after transplantation of organs from a common donor who died from acute MRSA endocarditis. Both recipients developed recurrent MRSA infection despite appropriate antibiotic therapy, and required prolonged hospitalization and hospital readmission. Comparison of S. aureus whole genome sequence of DNA extracted from fixed donor tissue and recipients' isolates confirmed donor-derived transmission. Current guidelines emphasize the risk posed by donors with bacteremia from multidrug-resistant organisms. This investigation suggests that, particularly in the setting of donor endocarditis, even a standard course of prophylactic antibiotics may not be sufficient to prevent donor-derived infection.

Figure 1. A single maximum parsimony tree was reconstructed using 508 SNPs from 15 whole genome USA300-0114 sequences of 3 MRSA recipient isolates, 1 donor isolate, 1 reference (FPR3757) and 10 background USA300-0114 isolates

Background genomes are labeled with the state and year collected. Donor and recipient isolates are labeled as such with the clinical source indicated. Branch lengths represent the genetic distance with the numbers on each branch indicating the number of SNPs between genomes. The bar represents 10 SNPs. Tree constructed using MEGA5. *BAL, bronchoalveolar lavage. MRSA, methicillin-resistant Staphylococcus aureus; SNPs, single nucleotide polymorphisms.

Figure 2

(A) Gross appearance of a perforating bacterial vegetation on the posterior leaflet of the mitral valve in the heart of the donor. (B) Gross appearance of a cystic lesion in the white matter of the right cerebral hemisphere of the donor formed by a large intracerebral hematoma. (C) Histological appearance of the mitral valve vegetation showing fibrin (pink) admixed with innumerable clumps of bacteria (blue). Hematoxylin and eosin stain, original magnification × 12.5. (D) Tissue Gram stain of mitral valve lesion showing coalescing colonies of Gram-positive, coccoid bacteria. Lillie-Twort stain, original magnification × 100. (E) Occlusive septic embolus in a small vessel in the cerebral cortex, revealing numerous coccoid bacteria enmeshed in fibrin. Hematoxylin and eosin stain, original magnification × 158. (F) Same vessel as image (E), demonstrating immunohistochemical evidence of infection with Staphylococcus aureus (red). Immunoalkaline phosphatase technique with naphthol-fast red and hematoxylin counterstain, original magnification × 158.