Abstract
Because the human skin microbiota may play roles in the causation or modification of skin diseases, we sought to provide initial quantitative analysis from different cutaneous locations. We developed quantitative PCRs to enumerate the total bacterial and fungal populations, as well as the most common bacterial and fungal genera present in six locales, in eight healthy subjects. We used a set of primers and TaqMan MGB probes based on the bacterial 16S rRNA and fungal internally transcribed spacer region, as well as bacterial genus-specific probes for
Propionibacterium
,
Corynebacterium
,
Streptococcus
, and
Staphylococcus
and a fungal genus-specific probe for
Malassezia
. The extent of human DNA contamination of the specimen was determined by quantitating the human housekeeping
GAPDH
gene. The highest level of 16S rRNA copies of bacteria was present in the axilla (4.44 ± 0.18 log
10
copies/μl [mean ± standard error of the mean]), with normalization based on
GAPDH
levels, but the other five locations were similar to one another (range, 2.48 to 2.89 log
10
copies/μl). There was strong symmetry between the left and right sides. The four bacterial genera accounted for 31% to 59% of total bacteria, with the highest percent composition in the axilla and the lowest in the forearm.
Streptococcus
was the most common genus present on the forehead and behind the ear.
Corynebacterium
spp. were predominant in the axilla. Fungal levels were 1 to 2 log
10
lower than for bacteria, with
Malassezi
a
spp. accounting for the majority of fungal gene copies. These results provide the first quantitation of the site and host specificities of major bacterial and fungal populations in human skin and present simple methods for their assessment in studies of disease.