617 Pentapeptide to Control Acne
molecule), or the solvent control. Cell growth was evaluated up to 72 hours (n =3 data
not shown). Neither the isolated compounds nor their combination exerts any significant
effect on bacteria growth compared to the solvent control, confirming the unique limiting
the growth of C. acnes activity of the pKTSKS peptide.
Remnant effects of pKTSKS on C. acnes. A study was conducted to evaluate the remnant effect
of the peptide on C. acnes RT-1 cells and to determine whether the inhibition can be rapidly
lifted in its absence. Bacteria were treated with either 9 ppm pKTSKS or 0.1% DMSO as
a control. After 48 hours, bacteria were centrifuged and rinsed to remove residual peptide
or solvent. Cells from both populations were seeded at same concentrations in fresh cell
culture medium (without pKTSKS nor solvent). Cell growth was estimated over time.
Figure 3 shows a clear increase in cell growth for control (OD
600nm
=0.650 after 48 hours)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
21h 29h 45h 53h
Time (h)
Effect of pKTSKS on C. acnes growth
Solvent control pKTSKS 6ppm pKTSKS 9ppm pKTSKS 12ppm
Figure 2. Effect of pKTSKS on C. acnes growth kinetic over time (n =3). Turbidity measurements (OD600nm)
on C. acnes (RT-1), to evaluate the effect of pKTSKS on C. acnes growth. Bacteria were treated with pKTSKS
in anaerobic conditions. OD600nm measurements were performed at different time-points (21 h, 29 h, 45 h,
and 53 h).
Figure 3. Evaluation of the remnant effect of pKTSKS on C. acnes growth after 48 h of contact (n =3).
C. acnes (RT-1) was treated with 9 ppm pKTSKS or its control for 48 h. Growth was monitored by OD600nm
measurements before and after pKTSKS wash-out.
OD
600nm

618 JOURNAL OF COSMETIC SCIENCE
while marginal growth is observed for 9 ppm of peptide as expected. The similarity of the
second part of the curves indicates that cells regained growth potential identical to the one
observed for the control. Thus, the peptide possesses an inhibitory effect when in contact
with C. acnes, but this effect is lifted in its absence.
Effect of pKTSKS on C. acnes biofilm formation. Because of inhibitory effect of pKTSKS
has on C. acnes growth, we decided to investigate its impact in biofilm. Indeed, C. acnes
biofilms have a significant impact on acne development. Biofilm form makes C. acnes
more resistant and triggers an important inflammatory response.11–14 We therefore tested
the effect of pKTSKS on C. acnes biofilm by focusing on two steps: adhesion and biofilm
formation. C. acnes adhesion was evaluated on the surface of plastic plates after crystal
violet extraction. For the solvent (DMSO), OD
600nm was 2.74 ± 0.12 units, the presence
of pKTSKS almost completely reduced this bacterial adhesion by 98% and 99% after
72 hours at 6 and 12 ppm respectively (Figure 4). Regarding biofilm formation, for solvent,
OD
600nm was 2.22 ± 0.34 after 72 hours. The presence of pKTSKS strongly prevented
this biofilm formation by C. acnes for 6 and 12 ppm (–97% and –98% respectively both
p 0.01). DMSO itself had only a slight effect on biofilm adhesion assay: +18.1% compared
to untreated control, (p 0.05) and no effect on biofilm formation (–4.3%, ns). Effect of
DMSO on biofilm adhesion is marginal when compared to effect of the peptide. Prevention
of C. acnes adhesion and of biofilm formation by pKTSKS both reduce C. acnes ability to
reach its quorum and would avoid a quorum sensing effect.
Growth of S. epidermidis with pKTSKS. S. epidermidis is one of the most abundant commensal
microorganisms on human skin. While it serves as repellent for its pathogenic cousin,
S. aureus, it can also control the excessive development of C. acnes.26 It is therefore of interest
to evaluate whether pKTSKS could affect S. epidermidis growth. S. epidermidis was seeded
at 7 × 107 CFU/mL in TSY medium. Its growth was monitored over time. Neither 0.1%
0
0.5
1
1.5
2
2.5
3
3.5
Biofilm Biofilm dhesion a formag415on
Axis Title
Effect of pKTSKS on C. acnes biofilm adhesion and
formag415on
Untreated control DMSO pKTSKS 6ppm pKTSKS 12ppm
Figure 4. Evaluation of the effect of pKTSKS on C. acnes biofilm adhesion (left) and formation (right) after
72 h treatment with solvent (DMSO) or pKTSKS (6 ppm and 12 ppm). The biofilm was quantified using the
crystal violet staining method. The amount of crystal violet retained by the biofilm was then measured by
assessing the optical density at 600 nm (OD600).
OD
600nm