The Unique <i>hmuY</i> Gene Sequence as a Specific Marker of <i>Porphyromonas gingivalis</i>

<div><p><i>Porphyromonas gingivalis</i>, a major etiological agent of chronic periodontitis, acquires heme from host hemoproteins using the HmuY hemophore. The aim of this study was to develop a specific <i>P. gingivalis</i> marker based on a <i>hmuY</i> gene sequence. Subgingival samples were collected from 66 patients with chronic periodontitis and 40 healthy subjects and the entire <i>hmuY</i> gene was analyzed in positive samples. Phylogenetic analyses demonstrated that both the amino acid sequence of the HmuY protein and the nucleotide sequence of the <i>hmuY</i> gene are unique among <i>P. gingivalis</i> strains/isolates and show low identity to sequences found in other species (below 50 and 56%, respectively). In agreement with these findings, a set of <i>hmuY</i> gene-based primers and standard/real-time PCR with SYBR Green chemistry allowed us to specifically detect <i>P. gingivalis</i> in patients with chronic periodontitis (77.3%) and healthy subjects (20%), the latter possessing lower number of <i>P. gingivalis</i> cells and total bacterial cells. Isolates from healthy subjects possess the <i>hmuY</i> gene-based nucleotide sequence pattern occurring in W83/W50/A7436 (n = 4), 381/ATCC 33277 (n = 3) or TDC60 (n = 1) strains, whereas those from patients typically have TDC60 (n = 21), W83/W50/A7436 (n = 17) and 381/ATCC 33277 (n = 13) strains. We observed a significant correlation between periodontal index of risk of infectiousness (PIRI) and the presence/absence of <i>P. gingivalis</i> (regardless of the <i>hmuY</i> gene-based sequence pattern of the isolate identified [r = 0.43; <i>P</i> = 0.0002] and considering particular isolate pattern [r = 0.38; <i>P</i> = 0.0012]). In conclusion, we demonstrated that the <i>hmuY</i> gene sequence or its fragments may be used as one of the molecular markers of <i>P. gingivalis</i>.</p>