00:01
How do we diagnose histoplasmosis? One way
to do so is to try and grow the organisms
from clinical specimens, like sputum, blood,
tissue samples or other body fluids. But this
is a long process, it takes about six weeks
and it's not always successful. You can demonstrate
the presence of small intracellular yeasts
in other clinical specimens and this is more
rapid because you take the sample, you look
at it under a microscope with the appropriate
stain and you can rapidly confirm the diagnosis.
You can get samples from bone marrow, liver,
lung or lymph. Some of these are more invasive
than others. Examine them under the microscope
and confirm the diagnosis by the morphologic
examination. You can also do enzyme linked
immunosorbent assays (ELISA), and you can
look for the polysaccharide antigen from the
cell wall of the fungus. This can be done
with urine or serum, in particular if the
infection is disseminated, the fungus will
appear in these fluids as well and it's relatively
straightforward and quick to do an ELISA to
look for the fungal antigen. You can also
look for antibody against fungal components,
again using an ELISA format and using serum
from the patient.
01:25
So these are all rapid ways to diagnose it,
in addition to the culture which takes a long
time. Once diagnosis is established, which
can often be done not only by the laboratory
methods, but also considering where the individual
has been. If it's in a place at risk for histoplasmosis,
you can treat with drugs like itraconazole.
This takes a while, it takes 3 to 12 months
to eliminate the organisms, so the drug has
to be taken continuously. This drug is good
for mild to moderate pulmonary or disseminated
histoplasmosis, as long as it's a moderate
infection. If the infection is more severe,
amphotericin B is initially given, followed
by itraconazole. Now how do you prevent getting
a histoplasma infection? Well if you're working
in a contaminated area, if you're involved
in construction or demolition, you really
should be wearing a respirator. Now I pass
construction sites all the time in New York
City and nobody wears respirators, because
they're a little bulky and annoying and it
probably doesn't look very good to be wearing
a respirator, but if you're an at risk person,
in particular if you have lung disease, or
you're on immunosuppressive treatments, you
should be wearing a respirator if you're going
to do this kind of work.