impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

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C. Cafarchia, D. Otranto - Malassezia spp. as a pathogenic yeasts
(Continuho and Paula, 2000; Mancianti et al, 2001) of
which, the latter, could contribute to pruritus as mediators
of itch (in Chen and Hill, 2005). Lipases, contribute
to produce fatty acids on the skin which can be
used by yeasts for nutrition providing protection by
other inhibiting organisms (in Chen and Hill, 2005).
M. pachydermatis also produces phospholipase and a
higher phospholipase activity was found in isolates
from skin lesion than in strains from healthy skin
(Cafarchia and Otranto, 2004). Further studies demonstrated
that β-endorphin (a class of endogenous opioid
peptides) induces M. pachydermatis cell differentiation
towards the production or non -production of phospholipase
(Cafarchia et al, 2007a). The presence of muopioid
receptors on the M. pachydermatis cells and the
effect of naloxon (i.e. an opioid antagonist receptor),
on the phospholipase activity has been investigated
(Cafarchia et al, 2007b) and results indicated that mu
opioid receptors are expressed in M. pachydermatis cell
walls. The above results suggested that this receptor
may be involved in mediating the effects of both opioid
agonist (β-endorphin) and antagonist (Naloxon) on
phospholipase production of M. pachydermatis thus
opening new avenues for topical control of Malassezia
lesions.
The host, the Malassezia and the Leishmania infantum
protozoa.
The relationship among the frequency, population size
and phospholipase activity of M. pachydermatis was
investigated for dogs with (Li + ) and without (Li - )
Leishmania infantum infection. A significantly higher
mean population size of M. pachydermatis was cultured
from the skin of L + compared with L - dogs. For
M. pachydermatis, most phospolipase-producing cultures
and the highest phospholipase activity were
recorded for L - dogs with lesions and L + dogs without
lesions. Although M. pachydermatis was a common
commensal on dogs with or without L. infantum infection,
L. infantum infection in dogs without skin lesions
are associated with increased growth of M. pachydermatis
and production of phospholipase in vitro
(Cafarchia et al, 2008a).
Conclusive remarks
The pathogenic role of Malassezia yeasts is related to
changes in the normal physical, chemical or immunological
mechanisms of the skin which may enhance or
down regulate the molecular production of yeast virulence
factors or antigens. As an example the chemical
composition of Malassezia cell wall (i.e. the expression
of mu -opioid receptors) may be strictly related to the
chemical composition of the skin (presence of β-endorphin)
and may play a fundamental role in influencing
the pathogenic or commensal phenotype of Malassezia
yeasts. Without any doubt further studies and researches
are needed in this field in order to better understand
the complex interactions between Malassezia and host
immune system by investigating genomic and proteomic
aspects of this relationship.
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