Distinct Skin Microbiome and Skin Physiological Functions Between Bedridden Older Patients and Healthy People: A Single-Center Study in Japan

Abstract

With the increase in the older populations, the number of bedridden older patients is becoming a matter of concern. Skin microbiome and skin physiological functions are known to change according to lifestyle and community; however, such changes in case of movement- and cleaning-restricted bedridden older patients have not yet been revealed. To address this issue, we analyzed skin microbiome and skin physiological functions, including pH, hydration, sebum level, and transepidermal water loss (TEWL), of bedridden older patients, compared with those of ambulatory older and young individuals. For this analysis, we enrolled 19 healthy young and 18 ambulatory older individuals from the community and 31 bedridden older patients from a single, long-term care hospital in Japan. The area of interest was set to the sacral (lower back) skin, where pressure injuries (PIs) and subsequent infection frequently occurs in bedridden older patients. We observed a higher number of gut-related bacteria, fewer commensals, higher skin pH, and lower TEWL on the sacral skin of bedridden older patients than on that of young or ambulatory older individuals. In addition, we observed that 4 of the 31 bedridden older patients developed PIs during the research period; a higher abundance of pathogenic skin bacteria were also observed inside the PI wounds. These findings imply distinct skin microbiome and skin physiological functions in bedridden older patients in comparison with healthy individuals and may suggest the need for more stringent cleaning of the skin of bedridden older patients in light of the closeness of skin and wound microbiome.

Keywords: microbiome; pressure injury; skin; skin physiological function; wound.

Figure 1

Comparison of bacterial relative abundance. (A) Relative abundance of top 20 genera. (B) Genera with significant differences among the groups (refer to Supplementary Table 1 for the actual P-values). The heatmap shows log10-transformed relative abundance of genera, with dendrograms created using Manhattan distance and the unweighted pair group method with arithmetic mean method (C). Colors above the heatmap indicate the three participant groups: blue for healthy young (HY), green for ambulatory older people (AO), and red for bedridden older patients (BO).

Figure 2

Results of beta diversity analyses. (A,B) Biplots based on weighted UniFrac (A) and unweighted UniFrac (B) are shown. Each color represents a participant group: blue for healthy young (HY), green for ambulatory older people (AO), and red for bedridden older patients (BO). Ellipses represent 95% confidence region of each group. Arrows represent the projection of each genus on the principal coordinate analysis. PC, principal coordinate.

Figure 3

Results of alpha diversity analyses. Rarefaction analyses of the number of observed operational taxonomic units (OTUs) (A), phylogenetic diversity (B), Chao1 (C), and Shannon index (D) are shown. Box plots show each metric value at 13,783 depth. *P < 0.05 and **P < 0.01 in Steel–Dwass test compared to each other.

Figure 4

Relationship between skin physiological functions and skin microbiome. The results of skin hydration (A), skin pH (B), and transepidermal water loss (TEWL) (C) are shown. (D) The result of canonical correspondence analysis (CCA). *P < 0.05 and **P < 0.01 in Steel–Dwass test compared to each other. ^†P < 0.01 in the significance of constraints.

Figure 5

Similarity between before and after pressure injury (PI) onset. Spearman's correlation coefficients (ρ) are shown above the bar graphs. The positions of PI onset were coccyx (ID: 20 and 23; d2 and d1) and sacrum (ID 27; d1) (refer to Supplementary Figure 1).