Download Microbiology: Spirochetes and Rickettsiae pg. 1 Jenny V. Seibert

Microbiology Transcriber: Jenny V. Seibert
09/26/2008
33:07
Spirochetes and Rickettsiae
Slide 3: Treponema pallidum-this is the agent of syphilis. Gonorrhoeae and chlamydia are two causes of
urethritis. Syphilis is a very different microorganism in the group referred to as spirochetes. They are
spiral shaped organisms like you see here. They are 5-15 microns in length. We don't think of them as
gram + or gram – because they don't stain well with gram stain due to very little peptidoglycan. You
have to use other ways to look at them.
Syphilis is not an organism you can take to the laboratory and stick in a culture to grow because
you cannot grow it on artificial media. You can grow the organism in epithelial cell cultures. They are
typically grown in rabbit epithelial cell cultures for research purposes.
They are like gonorrhoeae; they are fastidious organisms in the sense that they are very
susceptible to the environmental conditions. Have to have mucosa to mucosa contact to spread the
organism. It can't be spread by droplets.
Slide 4: Syphilis has been known for hundreds of years as a cause of human disease. For many years
gonorrhoeae was thought to be the same organism as syphilis due to the very similar symptoms. Only in
the last hundred years, when we began cultivating the organisms in the laboratory, have we been able
to distinguish the differing characteristics of the organisms.
Chlamydia and gonorrhoeae, they primarily produce urethritis. Syphilis does NOT produce
urethritis. Typically it produces an ulcer somewhere on the genitals at the point of contact. Or whatever
mucosal surface is contacted.
The first stage of syphilis is the primary phase which is the chancre(ulcer). It will appear one to
three weeks after the organism has been inoculated. It is painless and has a raised edge. The herpes
virus produces a lesion that is painful so this is one way you can distinguish syphilis lesion from one
caused by herpes.
The secondary stages of syphilis: this is where you have manifestations of the disease remote
from the site of infection. You've spread the organism through the body.
Slide 5: After the primary stage and secondary stage you go into a latent period. By this time, the rash
you see with secondary syphilis is gone, and this may last several years.
Finally, if you've not had any treatment, you can get the tertiary syphilis, which is the immune
response to the spirochetes over the years. You can get heart valve lesions, gummas (granuloma
lesions), tabes dorsalis (loss of proproiception in spinal cord), general paresis of the insane (it affects the
cognitive parts of the brain).
Slide 6: The first stage is chancres. And depending on what part of the body is exposed to spirochetes,
that's where the chancre will occur. See, here's a chancre on a penis (middle photo), here's one in the
throat(left picture), one in the roof of the mouth (bottom right) and one in the corner of the lips (upper
right). It's not unlikely that you all will see something like this. So it's pertinent to get appropriate history
on the patient to see how it got there, if they'll tell you.
Microbiology: Spirochetes and Rickettsiae
Jenny V. Seibert
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Slide 7: Remember that the chancre is the point of entry for the spirochete. They invade the body
through the chancre. Then the chancre will heal on its own. Then a few weeks later, after the organism
has spread throughout the body, you can get the rash of secondary syphilis that can occur all over the
body and you can get raised patches on the genital area. Everyone that gets syphilis more or less goes
through these stages.
Slide 8: Then you can get these chronic lesions of chronic syphilis that occur called a gumma. It's
essentially a granuloma. They are the immune response of the body to syphilis.
Slide 9: Congenital syphilis can cause dental manifestations. Syphilis can be transmitted across the
placenta, especially in the third trimester of pregnancy. When this occurs, the baby can be born with the
rash of secondary syphilis. They can have nasal and oral secretions that contain live spirochetes, so
they're infectious. The baby can be born with pneumonia and hepatitis due to the syphilis that spread
throughout the body. If you get the syphilis involvement early in gestation, you can see some of the
effects of congenital syphilis on the development of the teeth. Hutchinson's incisors are notched incisors
you see here. These mulberry molars you see here are examples of congenital syphilis. You can get
saber shins, which is a bowing of the shins, making them look like a bowed saber. Invasion of the
spirochetes during gestation in the fetus brain can cause congenital deafness if it invades the 8th cranial
nerve.
Slide 10: Syphilis can masquerade as a lot of things. And there again, you can be asymptomatic or in
between the stages and you can spread it. Now I told you that you couldn't culture it, but if you
aspirated some fluid from a lesion, something you thought contained the spirochetes, even a rash
lesion, you could put it on a slide and do a darkfield examination. This is done under a darkfield
condenser of the microscope and you can see motile spirochete.
Darkfield analysis is not useful for oral lesions. If you have oral lesions or a chancre in the mouth,
the test will not be useful because we all have spirochetes in our mouths. The spirochetes normally
occurring in the mouth look enough like the syphilis that you'd be confused. The darkfield examination is
only useful for genital lesions. This is a test you can do immediately. If you see spirochetes from a genital
lesion, then you know it is syphilis.
Slide 11: But the cornerstone for diagnosing syphilis, that has been available for over a hundred years,
is the serological test (measuring antibodies). It's important for you to have an understanding of what
these serological tests are and how they work.
We have two different types of tests. We have the non Treponemal tests, which are primary
screening tests, and the Treponemal tests. Of the non Treponemal tests, the most important ones that
you need to know about are the RPR (Rapid Plasma Reagent) and the VDRL (Venereal Disease Research
Laboratory test). The RPR is a basic serological test you do on serum to look for antibody. With the
VDRL, you are looking for antibodies in the spinal fluid.
The RPR is an inexpensive test; it's also easy and quick. You take an antigen and bind it to
carbon particles. Then you take the serum and mix it with these bound carbon molecules to see if you
Microbiology: Spirochetes and Rickettsiae
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get agglutination. When you make antibodies to the Treponemes, when you have an acute phase of
syphilis, you make antibodies that will cross react with cardiolipin and lecithin and cholesterol antigens.
These are the antigens put on the carbon particles. If you get a reaction, then you dilute the serum
out,and then measure the titer of the antibodies. If you have an increasing titer, you have active disease.
If your titer is falling then you are getting active treatment or it's being resolved.
This is a good screening test because it's simple, easy and cheap. This test can be positive in the
late stage of the chancre and before you get the rash and by the time you get the rash, unless you are
immune compromised, you will always have a positive reaction to this test. The test is very reliable. If
you don't get treated and you launch an immune response but then you get treated and don't have an
active state of syphilis, you will still be positive to this test.
It's a very good, sensitive test, but you get some false-positives sometimes. Autoimmune
diseases, such as lupus, can cause false-positives. Some viral diseases or other Treponemal diseases can
cause false-positives. Even being pregnant can cause a false-positive test. Before you would tell
someone they have syphilis from a positive RPR, you would want to confirm that with a more specific
test that tests for an antibody more specific to the Treponeme and that's what we call a Treponemal
test.
Slide 12: This is an example of an RPR. You take a card, out the patient's serum on the card, you mix it
with the carbon particles that have the non treponemal antigens on there, you mix it up and you see if
you get agglutination on there.
Slide 13: The Treponemal tests, there are several different types of these. In the ones that we do in the
clinical laboratory at UAB, you take serum that you suspect has the syphilis and you react it with gelatin
particles that have the Treponema antigen coated on them. If you see agglutination, that's a positive. It
works just like the RPR except that you've got gelatin particles and you have the actual Treponemal
antigen on there rather than a cardiolipin antigen. So if this one is positive, you can be pretty sure that
the patient does have syphilis.
Slide 14: Another test that is sometimes done, that requires a fluorescent microscope, is called the FTA.
You do need to know this terminology because depending on where you practice, you will have patients
with this and you need to know the associated terminology. With FTA, you have the Treponemal
antigens fixed onto a microscope slide, and then you put the patient's serum on top of it. If the patient's
serum has antibodies, they will bind to the treponemal antigen. So then you take a fluorescent dye
coated anti-human IgG. When you put it on the slide, it will attach to the IgG antibody and it will shine
under the microscope. Good test, becomes positive very early in the disease, but it does require a
fluorescent microscope, so it's more expensive.
Slide 15: So let's move on and mention another organism that's in the spirochete group, the Borrelia.
These are long spirochetes, longer than syphilis. Sometimes they can stain with Giemsa stain. This is a
blood smear that has a Borrelia in it. They stain better than the syphilis. Some of the Borrelia can be
grown in laboratories.
Microbiology: Spirochetes and Rickettsiae
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Slide 16: So what are the diseases we can get from Borrelia? One of them is relapsing fever. This disease
is mainly found in the Western US carried by lice and ticks. So you get recurrent febrile illnesses.
Someone you suspect has this, you could test for antibodies to the Borrelia, leading to the proper
diagnosis. Like gonorrhoeae, this organisms have antigenic shifts and that makes the serology and
diagnosis sometimes difficult. Often the patient history of living out west, being exposed to ticks and lice
and having recurrent febrile illnesses can be a deciding factor for diagnosis of Borrelia.
Slide 17: Probably a more prominent disease that you've heard about is Lyme disease. This is Borrelia
burgdorferi. This is found in a lot of places in the US, but it is not common in AL because it requires
several different vectors. The Ixodes ticks carry the live spirochete. There's a reservoir in mice. The tick
and the mouse carry the disease back and forth, but sometimes the tick will transmit the disease to
humans. There are several different species of tick that can carry the live spirochete. In AL, we don't
have those species. Those ticks are mainly found in the midwest and the northeast. The disease is
named after Old Lyme Connecticut, where the disease is more common. It's not likely you'll get Lyme
disease here unless you travel to some of these locations.
The spirochete invades the bloodstream from the tick and it carries all over the body. An easy
way to make a clinical diagnosis is from a characteristic bulls-eye rash that the spirochete creates after
being bitten by the tick (shown in Slide 18). With this rash, one can make a definitive diagnosis.
However, you don't always get the rash, or the rash may be on your head, not visible through the hair.
Since the disease develops slowly, you might get joint aches, heart problems, or a facial nerve
paralysis causing a Bell's palsy. You may not remember a tick bite and these symptoms may occur
several days or weeks after you've been bitten. With this vague history of not feeling well, it's difficult
for the doctor to think about Lyme disease. And often, to make the diagnosis, you would have to do an
antibody test. But if you are not in the right stage of the disease, you may miss the rise and fall of the
antibody. In some cases, you never can confirm the presence of the disease.
Slide 19: Here is the vector for Lyme disease, the Ixodes tick. The one on the right has not been fed yet.
And remember, ticks are not insects. Insects have six legs; ticks have eight legs. They are like spiders, the
arachnids.
Slide 20: Leptospira. This is probably not a disease you'll hear much about; it's not real common. These
are tightly coiled spirochetes. They're anaerobic bacteria. Usually you diagnose these serologically, but it
can be cultivated.
Slide 21: Leptospira interrogans can cause disease after being exposed to animal urine. If you work on a
farm around livestock and you walk barefooted, these spirochetes can invade the skin of the feet or
mucous membranes on the body. They get in the bloodstream and spread throughout the body and
especially go to the liver and kidney. They especially go to the kidney because that's where they are
carried in livestock animals. They can cause a diagnostic dilemma because they produce a lot of nonspecific symptoms such as fever of unknown origin. If they affect the liver, they can cause hepatitis. If
you have someone with liver disease and jaundice, it's a good thing to ask if they've been around
animals or livestock. The hepatitis virus, however, is a much more common cause of hepatitis. But it can
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produce a disease that is indistinguishable from viral hepatitis. Usually serology is what's used in the
diagnosis. If you are in the early stages, urine can be collected and a darkfield analysis can be performed.
Slide 22: So we want to say a few things about the Rickettsiae and the Ehrlichia pathogens now. Like the
chlamydia, Rickettsiae are obligate intracellular organisms. Most of them, except for Coxiella, are
transmitted to humans by arthropods, ticks and lice primarily. They are not viruses; they contain both
DNA and RNA. And their cell walls are similar to Gram- bacteria. They stain with Giemsa and reproduce
by binary fission like bacteria. You cannot grow them in the laboratory; it's much too dangerous because
they aerosolize. You usually measure antibody responses as a diagnosis. You use patient's serum to
measure a rise and fall in antibodies. They are easily killed by heat, drying and chemicals.
Slide 23: This is Rickettsiae inside a host cell. They are rod shaped organisms here in this electron
micrograph.
Slide 24: The pathology and pathogenesis is fairly simple. Rocky Mt Spotted Fever is caused by R.
rickettsii, the prototypical Rickettsiae organism. What typically happens is the tick with the Rickettsiae
in its saliva bites you, it injects the Rickettsiae into your body and these Rickettsiae seek out the
endothelium of small vessels and capillaries. They invade the endothelial cells and stimulate the immune
response causing vasculitis. As a process of the inflammatory action in the cells, the cells swell, causing
thrombosis. Ultimately you can get DIC (disseminated intravascular coagulation) from this. What you
get is a vasculitis rash. They spread throughout the blood stream to more and more endothelium and
eventually what you end up with is a spot on the skin all over the body. The spots are groups of
Rickettsiae invading blood vessels, creating spots, hence Rocky Mt Spotted Fever. The Rickettsiae
replicate inside host cells, including phagocytes.
Slide 25: So the pathogenesis is always associated with rashes and usually associated with an arthropod.
The most important ones are the tick-born disease such as R. rickettsii. There can be reservoirs of
several different animals. You can have dogs, rabbits, rodents. Rocky Mt. Spotted Fever is very common
in AL and the Southeastern US.
Some other diseases associated with Rickettsiae are Typhus fever and Q fever. Q fever doesn't
have a vector. You would get this directly from contact with the infected animal. Several different types
of arthropods, ticks, fleas, lice, can be vectors for Rickettsiae.
There are two other organisms grouped within the Rickettsiae, Ehrlichia chafeensis and
Anaplasma phagocytophilum. This are also tick-born diseases that have vectors and reservoirs and they
cause infection of white blood cells. The Ehrlichia causes infection of the monocytes while the
Anaplasma cause infection of the granulocytes.
Slide 26: This rash here can diagnosis this as Rocky Mt Spotted Fever. Another way you can diagnose this
is by taking a biopsy of the skin and you can stain with an immunfluorescent stain for R. rickettsii. If you
saw fluorescence, then you could make the diagnosis.
Microbiology: Spirochetes and Rickettsiae
Jenny V. Seibert
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Slide 27: This is Ehrlichia in a monocyte. These inclusions you see in white blood cells are the Ehrlichia.
You can do serology to confirm the diagnosis, but if you see something like this, you know it's a Ehrlichia
disease.