00:01
The next fungus I’d like to tell you about
is collectively called the Dermatophytes.
00:07
Infections with dermatophytes are the most
common fungal infections of humans; almost
everyone has these at one time or another.
This infection on the skin is often called
ringworm or tinea and that's because the lesions
get bigger and bigger in a serpentine manner,
so they are originally called ringworm, but
no worm is involved. It's a fungus. It's a
dermatophyte and in fact it's better to use
the Latin name 'tinea'. Tinea means 'worm',
but most people don't know that and so it
sounds more medically important. And there
are a number of places where dermatophytes
can cause their typical lesions on your body.
00:52
Depending on where they are, they have different
names. So for example if the infection is
on your head it's called Tinea capitis, if
the infection is on your feet, it's called
Tinea pedis, if the infection is on your body
or anywhere else it's called Tinea corporis,
if it’s in your crotch it's called Tinea
cruris, if it is in your nails, in the actual
substance of your finger or toenails, it's
called Tinea unguium or onychomycosis. There
are street names for all of these afflictions.
Of course when it's on your feet, it's called
athlete's foot, when it's in your crotch,
it's called jock itch or jungle rot, very
colorful names for these afflictions. By the
way, the athlete's foot, you pick up by walking
in a locker room, because other people have
this affliction. Members of three different
genera of fungi, dermatophytes of course,
can cause these infections at different parts
of the body. Microsporum, and these are very
unusual structures, we haven't seen anything
like this before, Trichophyton and Epidermophyton.
So all of these are found environmentally
and they all can cause dermatophyteses. These
are not members of our normal flora, so many
of the fungi we've talked about in these lectures
are not members of the normal flora, a few
are. But most of them are environmentally
acquired and the same goes for the dermatophytes.
02:29
Where do you find these dermatophytes? Well
some grow in the soil as you might expect,
others are found in animals. Your pets may
have them, your pet dog or your pet cat, and
others you acquire from another human, who
in turn acquired it from the soil or from
an animal as well. And when you acquire it
from another human, typically close contact
is needed or you may pick it up off the locker
room floor, as I said, where it was left by
another human before you. These fungi survive
on wet surfaces, the walls of showers, the
floors of locker rooms, and this is how they're
transmitted. You know when you think about
it, the locker room is not a very clean place,
lots and lots of people go there. I’m talking
about locker rooms in school gyms and health
clubs that you may go to, the floor can be
covered with spores from these fungi, you
are likely to pick up athletes foot there,
that's why they call it athlete's foot, because
you typically pick it up in a locker room.
03:28
You should wear flip-flops when you walk around
the locker room, because that's not the only
infection you can pick up, you can also get
warts. People have lots of warts on the bottom
of their feet and those are caused by viruses,
the papilloma viruses. So you can get warts,
you can get athlete's foot, please wear flip-flops.
You know what those are right? Those plastic
things that fit between your feet, you can even
take a shower in them, you never have to take
them off until you're ready to get dressed
and then put a towel on the floor. I know
I am giving you too much advice, but really
you don’t want to get these infections.
04:01
Dermatophytoses, you have to have a break
in the skin to get these infections. You can
get a cut on your arm or hands, even the athlete's
foot, usually you have an abrasion on the
bottom of your foot which is not hard to get,
a little micro abrasions are sufficient, not
a cut as shown in this picture. The fungus
then spreads through the stratum corneum,
stratum coreum does not invade the dermis,
very rarely. So these are superficial mycoses,
and you get these rings shapes when they are
present on your body, and that's because the
organism spreads. It grows outward and you
have this ring formation, and again, people
thought this was a worm so they called it
tinea. Dermatophytes can also invade your
fingernails or toenails or hair shafts, so
that's how you would get these infections,
right in the nail of your finger. Most of
these can be treated with topical antifungal
creams, but if you have one of these dermatophytosis
in your fingernails, a topical antifungal
will not take care of it. You have to take
systemic drugs. You have to take antifungal
agents by mouth, and they will spread throughout
your body and get into your fingernails or
toenails eventually, and this you have to
do for three or four months. The very angry
lesions that you see, these circular lesions,
redness, these are a consequence of our inflammatory
reaction to fungal antigen, so that's our
immune system reacting to their presence there.
05:33
The products of the immune system are often
effective, but not often pretty and they do
cause the redness which is the cardinal feature
of these dermatophytosis, and again as I said
you can treat most of them with topical antifungal
creams and lotions such as tolnaftate, allylamines
and azoles. Just go to your local drugstore,
there is probably a whole aisle for athlete's
foot and other infections such as this.