Identification of skin microbiota in Saudi female community and their effects on keratinocytes viability (in vitro)

Abstract

Objectives: This study aims to identify the skin microbiota of a Saudi female population and investigate topically applying a specific bacterial strain isolated from the skin to understand its effects on skin cells’ basic functions, including cell viability, using a primary human keratinocyte cell culture system. Methods: Microbiota samples were collected from four body parts of 200 females from AL-Madinah, Saudi Arabia, who were clinically screened for the absence of any disease. The four skin samples were collected by swabbing from the forehead, forearms, underarms, and behind both ears with no prior preparation or clearing of the skin surface. Samples were analyzed with the VITEK®2 Compact system after preparations according to the manufacturer's instructions. Staphylococcus aureus and commensal Staphylococcus epidermidis were isolated from the study participants and grown to investigate their effects on normal human epidermal keratinocyte (NHEK) basic functions, including cell viability in vitro. Results: Three bacterial phyla (Firmicutes, Actinobacteria, and Proteobacteria) were most abundant in Saudi female populations, while Bacteroidetes was not observed in these individuals. The most abundant phylum in the underarm area was Firmicutes (91.01%), whereas Proteobacteria was abundant in the forearm area (76.92%), and Actinobacteria showed up in the behind-ear area (24.28%). Staphylococcus (S. aureus and S. epidermidis) was the most abundant genus, on average making up >80% of the microbial community within every sample. The effect of S. aureus and S. epidermidis on NHEK viability was investigated. Results indicated that S. aureus reduced the viability of NHEKs, while S. epidermidis strains did not. Next, the effects of co-incubating NHEKs with S. epidermidis and S. aureus on NHEK viability were investigated to determine if S. epidermidis could inhibit the effect of S. aureus. Monolayers incubated with S. aureus and S. epidermidis had higher percentage viability than monolayers incubated with S. aureus alone (p = 0.04, n = 3). NHEK monolayers treated with S. epidermidis two hours before adding S. aureus had higher percentage viability than monolayers exposed to S. aureus alone (p = 0.03, n = 3). Conclusions: These data demonstrate that the most abundant bacterial phyla in a Saudi female population are Firmicutes, Actinobacteria, and Proteobacteria, and the most abundant genus is Staphylococcus (S. aureus and S. epidermidis). The data also reveal that S. epidermidis can protect human keratinocytes from the effects of the skin pathogen S. aureus in vitro. Further analysis of the mechanisms behind this is necessary.

Keywords

• keratinocyte
• microbiota
• colonization
• skin flora
• opportunistic pathogens
• staphylococcus