Microbiome Dysbiosis Dominated by Rhodococcus Occurs in Keloids

Background:
A keloid is an abnormal scar that grows excessively, almost like a tumor. Previous studies suggest that long-lasting inflammation plays an important role in keloid formation, but the exact cause is still not clear.

Objective:
Many inflammatory diseases are linked to an imbalance of microorganisms (microbiome dysbiosis). This study aims to find out whether such an imbalance exists in keloids and whether it is related to how keloids form and worsen.

Methods:
Researchers collected 35 keloid samples and 36 normal skin samples. The severity of keloids was measured using the Vancouver Scar Scale (VSS).
Bacteria in the tissues were analyzed using 16S rRNA sequencing, and their relationship with clinical features was examined.
Additionally, 10 keloid samples and 10 normal skin samples were broken down into single cells, and flow cytometry was used to measure the number of T cells in each tissue.

Results:

• Keloids had fewer types of bacteria compared to normal skin.

• The types of bacteria present in keloids were different from those in normal skin.

• At the broad level, the bacteria group Firmicutes was more common in keloids.

• At a more specific level, Rhodococcus was the most dominant bacteria in keloids.

• Acinetobacter was also linked to keloid formation.

• Rhodococcus was better than Acinetobacter at predicting how severe a keloid would be.

• The bacterial makeup of keloids changed over time:

  • In keloids younger than 10 years, Rhodococcus was more common.

  • In keloids 10 years or older, Rhodococcus decreased, while Cutibacterium increased.

• The number of CD4+ and CD8+ T cells was significantly lower in keloid tissue compared to normal skin.

Conclusion

Keloids show an imbalance in their microbiome, mainly involving an increase in Rhodococcus. This imbalance may be linked to the reduced numbers of CD4+ and CD8+ T cells found in keloid tissue. Therefore, correcting microbiome imbalance could be a promising strategy for future keloid treatment and management.

Keywords

Microbiome imbalance; Keloid; Inflammation; Vancouver Scar Scale; Rhodococcus