RESULTS
Cell Culture
Cell culture was attempted from the fresh tissue. However, no growth occurred after 4 weeks of incubation.
Molecular Identification and Confirmation
We performed Myxogastria and panfungal PCR assays in an attempt to target an unknown eukaryote, but these assays unexpectedly identified H. nana with 99% sequence identity. The presence of H. nana DNA in the specimen was confirmed by cestode- and hymenolepidid-species–specific PCR testing and sequencing. The molecular findings were surprising, since there was no recognizable tapeworm tissue architecture; thus, to confirm that the cells originated from a tapeworm, we performed immunohistochemical studies and in situ hybridization, which localized cestode antigen and nucleic acid markers (Figure 2A, 2B, and 2CFIGURE 2
Confirmation of H. nana Infection.
).
Phylogenetic and Mitochondrial DNA Analysis
The CO1 sequence obtained from the patient was grouped within the clade of known H. nana sequences (Figure 2D). An unexpected feature of the patient-derived sequence was the presence of three single-nucleotide insertions within a span of 12 bp in a highly conserved domain (NCBI Conserved Domain Database, cd01663) (Fig. S4 in the Supplementary Appendix), which was compatible with a deleterious mutation.
Comparative Genomic Analysis
Deep sequencing of the specimen from the patient generated 10.2 million 150-bp, paired-end reads. Removal of contaminating human sequences resulted in 1.7 million remaining reads, of which 1.4 million mapped onto the H. nana reference genome, with 53% coverage, at an average coverage of 2.4 times per base (excluding zero-coverage regions). From the H. nana control specimen, 7.1 million reads were mapped, with 93% coverage, at an average coverage of 7.0 times per base.