1. Propionibacteriu
m
By Daniel Kang

2. General Information
Propionibacterium species are nonsporulating,
gram-positive anaerobic bacilli that are
considered commensal bacteria on the skin.
These species are slow-growing and require
at least 6 days for growth in culture.

3. History
P. acnes was originally Corynebacterium
acnes until two researchers named
Douglas and Gunter proved that it was
more closely related with the
Propionibacterium. They proposed that
Propionibacterium be modified to include
bacteria that do not ferment lactose into
propionic acid; and that C. acnes should
then be changed to P. acnes. It was later
discovered that P. acnes does actually
ferment lactose into propionic acid under

4. Food
The holes come from a byproduct of some of the microbes added to milk to
make Swiss cheese. Specifically, there are three primary types of bacteria
that are typically used to make Swiss cheese (these can vary slightly
depending on the manufacturer): Streptococcus thermophilus; Lactobacillus
helveticus; and Propionibacterium shermanii.
The first two types of microbes produce significant amounts of lactic acid, which
is, in turn, consumed by the latter type of microbes, Propionibacterium
shermanii. It is this Propionibacterium shermanii that is responsible for the
holes in Swiss cheese. Through the process of consuming the lactic acid,
the shermanii produces acetate, propionic acid, and carbon dioxide as a
byproduct.
The acetate and propionic acid give the Swiss cheese much of its distinct
flavor, while the carbon dioxide forms bubbles within the cheese block or
wheel. These carbon dioxide bubbles are left in as the cheese continues to
ferment, rather than pressing them out, which gives Swiss cheese its
distinctive holes. Historically, however, these holes were seen as an

5. Symptoms
Propionibacterium acnes is found
briefly on the skin of neonates, but
true colonization begins during the 1-
3 years prior to sexual maturity.
During this time, numbers of P acnes
rise from fewer than 10/cm2 to about
106/cm2, chiefly on the face and
upper thorax. P acnes grows in the
lipid-rich microenvironment of the hair

6. Treatment
Acne vulgaris: Topical and oral
agents act at various stages in
the evolution of an acne lesion
and may be used alone or in
combination to enhance efficacy.