Strains of the Propionibacterium acnes type III lineage are associated with the skin condition progressive macular hypomelanosis

Abstract

Progressive macular hypomelanosis (PMH) is a common skin disorder that causes hypopigmentation in a variety of skin types. Although the underlying aetiology of this condition is unclear, there is circumstantial evidence that links the skin bacterium Propionibacterium acnes to the condition. We now describe the first detailed population genetic analysis of P. acnes isolates recovered from paired lesional and non-lesional skin of PMH patients. Our results demonstrate a strong statistical association between strains from the type III phylogenetic lineage and PMH lesions (P = 0.0019), but not those representing other phylogroups, including those associated with acne (type IA1). We also demonstrate, based on in silico 16S rDNA analysis, that PMH isolates previously recovered from patients in Europe are also consistent with the type III lineage. Using comparative genome analysis, we identified multiple genomic regions that are specific for, or absent from, type III strains compared to other phylogroups. In the former case, these include open reading frames with putative functions in metabolism, transport and transcriptional regulation, as well as predicted proteins of unknown function. Further study of these genomic elements, along with transcriptional and functional analyses, may help to explain why type III strains are associated with PMH.

Propionibacterium acnes phylogenetic type III is associated with progressive macular hypomelanosis

“…In contrast, the present study showed a striking predominance of subtype III in PMH lesional samples from the lower, middle, and upper back, and abdomen. This corroborates the previous finding of a unique, unidentified P. acnes type in PMH patients [22], and the recent report that type III strains were cultured from lesions of 14 of 34 PMH patients [24]. …”

“…Previous studies have found a highly significant increase in P. acnes numbers in PMH lesions [11, 24]. In accordance, we could also confirm that P. acnes is more abundant in lesions compared to nonlesional skin: a semiquantitative analysis revealed that all PMH samples from patients had a higher colony-forming unit count as compared to adjacent nonlesional skin (data not shown).…”

“…In contrast, Barnard et al cultured P. acnes from nonlesional skin in only one of 34 patient samples, indicative of low P. acnes numbers in nonlesional skin. Therefore, the type distribution at normal skin sites could not be assessed in their study [24]. In addition, the difference may reflect different sampling and sample processing approaches in the two studies.…”

“…Interestingly, a regional difference in prevalent type III clones was suggested, based on comparisons of PMH isolates from Europe and Brazil [24]. …”

“…A previous study based on bacterial cultivation has indicated that certain subtypes of P. acnes may be associated with PMH: an abundance of a specific but unidentified type of P. acnes was observed in PMH lesions that is different from P. acnes types isolated from acne lesions [22]. Recently, we cultured P. acnes isolates belonging to the otherwise uncommon type III from lesions of PMH patients and sequenced their genomes [23], and a very recent study revealed an abundance of P. acnes type III in bacterial cultures from lesional skin in 14 of 34 PMH patients [24]. …”