Abstract
BackgroundStudies using highly sensitive molecular techniques have detected bacterial communities below the human epidermis. Depending on their abundance and composition, this finding could be clinically relevant. The aim of this study was to determine if bacteria can be detected in the dermis and subcutaneous tissue of dogs without cutaneous disease using two different approaches: traditional cultures and DNA sequencing of the V4 region of bacterial 16S rRNA gene using next-generation sequencing (NGS).ResultsSeven healthy dogs were included in the study, and two sets of samples were collected from each subject. Sample sets were composed of a 6-mm abdominal skin biopsy, including epidermis, dermis, and subcutis, a skin surface swab, and an environmental blank sample for contamination control. One set of samples from each dog was submitted for bacterial culture and the other one for bacterial DNA amplification and sequencing. Five different bacterial genera (Staphylococcus, Bacillus, Corynebacterium, Streptococcus, and Enterococcus) were isolated in five out of the seven skin surface swab samples with aerobic microbiological culture methods, while no growth was obtained from the other two samples. Although some DNA could be amplified from epidermal, dermal, and subcutaneous tissue samples, the results of the NGS were similar to those of the blanks.ConclusionWhen investigated with aerobic microbiological culture methods, the dermis and subcutaneous tissue of dogs are sterile. NGS techniques lead to the detection of some bacterial DNA, similar to the signal detected in blanks, which does not support the presence of a microbiota in dermis or subcutaneous tissue.
Highlights
Studies using highly sensitive molecular techniques have detected bacterial communities below the human epidermis
Sample sets were composed of a skin surface swab taken prior to surgical skin disinfection, a 6mm abdominal skin biopsy, including epidermis, dermis and subcutis, and an environmental blank sample
One set of samples from each dog was submitted for bacterial culture and the other for bacterial DNA amplification and sequencing (Fig. 1)
Summary
Studies using highly sensitive molecular techniques have detected bacterial communities below the human epidermis. Culture-based techniques have been useful to detect bacterial populations in the epidermal surface but have failed to detect microorganisms in the dermis and subcutaneous tissue [11, 12] This explains why skin microbiota has been traditionally assumed to be restricted to the epidermal surface and appendageal structures, while dermis and subcutaneous tissue have been considered sterile. The use of next-generation sequencing (NGS) techniques to characterize microbial communities has increased in recent years, opening the possibility of readily identifying bacteria that may be elusive to culture-based studies [14, 15]
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