M- Syphilis and Treponemal Infections Flashcards Preview

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Flashcards in M- Syphilis and Treponemal Infections Deck (27):

What are the microbiological features of treponema pallidum [syphilis]?

1. highly motile - periplasmic endoflagella wedged between cytoplasmic membrane and outer membrane

2. slender, long, helical organism

3. NO LPS despite the 2 membranes and peptidoglycan is linked to the the CM so it cannot gram stain


What is unique about cuturing treponema in the lab?

It cannot be cultivated in vitro!
It must be cultivated using rabbits [similar to how leprosy is cultured on the footpads of 9-banded armadillos]


Treponema are associated with what 2 things?

1. syphilis- sexually transmitted
2. non-venereal treponematoses [yaw, pinta, Bejel endemic syphilis] - spread person to person and on fomites


What is responsible for most of the clinical manifestations of treponema infections?

The host immune response [acute and chronic inflammation] in response to the lipoproteins on T. pallidum


What is the reservoir for syphilis?
How is it transmitted?
What is the relationship between syphilis and HIV?

Syphilis is exclusively a human disease.

Mainly venereal transmission but also:
kissing, transfusion, oral sex, breast milk, transplacental.

If someone has syphilitic ulcers, there is an increased risk to both give and receive HIV.


Describe the pathogenesis of syphilis.

1. penetrates abraded skin, deposits in the dermal tissue and replicates.
[a small inoculum size can est. infection

2. Systemic dissemination occurs because the treponema go through the tight junctions of capillaries and enter the bloodstream


What is the incubation period of syphilis?

3-8 wks


What stages of syphilis have dark field microscopy positive for spirochetes?

Primary, secondary and secondary recurrences

There are no serum spirochetes in latency!!!


A patient presents with a firm, well-demarcated, indurated chancre. It is painless. What is the likely cause? What stage of the disease is it?

primary syphilis


Between primary and secondary stages of syphilis, what happens?
How long is this interval?

The syphilis heals w/o treatment.
The time between primary and secondary can be anywhere from 6wks to 6months


When in the course of untreated syphilis does secondary stage typically occur?
How does it manifest ?

Secondary syphilis usually occurs within 6 months of infection.
There are diverse [protean] presentations but >90% have some form of rash. It will typically involve the palms and soles.

Syphilis in second stage also mimics other disorders giving it the name "the great imitator"


If patients go untreated from secondary syphilis, what are the 3 courses the disease can take?

1/3 -->spontaneous resolve
1/3 --> stay in latency
1/3 --> progress to tertiary syphilis


What occurs during tertiary syphilis?

1. benign gummas [destructive, granulomatous lesions of skin, bone, and viscera].
*spirochetes are rarely if ever found in lesions

2. cardiovascular [thoracic aortic aneurysm]

3. neurosyphilis - dementia, erratic behavior, etc


When is a person with syphilis infectious to others?

Soon after inoculation to early latency [however, it depends on the disease manifestations and mode of contact]

Late latency and tertiary infections are NOT infectious


What causes congenital syphilis?

Transplacental transmission in the first trimester (after 18 weeks gestation) om women who have been infected for less than 2 years [still in early latency]


In terms of days, months, years, when does primary, secondary, early latency, late latency and tertiary syphilis usually occur?

Primary - 10 to 90 days [3 to 8 weeks]
Interval between 1 and 2 = 6wks to 6months
Early latency lasts until about 2 years after infection.
Late latency is from 2 years onward


What accounts for the majority of symptoms for ALL stages of syphilis?
What virulence factor of T. pallidum has been implicated?

The host's overlapping acute and chronic inflammation accounts for the majority of symptoms.
The organisms lipoproteins have been implicated as the principal pro-inflammatory mediator during disease pathogenesis


What is meant when they say T. pallidum is a "stealth pathogen"?

Infection by T. pallidum causes a strong Ab response [specific AND nonspecific], however, the Ab play no role in protective immunity because T. pallidum displays the lipoproteins [the major immunogen] on the cytoplasmic inner membrane and not the outer membrane.

Therefore, Ab are made in extremely high titer, but they cannot recognize the bacteria


Can patients acquire syphilis more than once?

Yes because there is no protective immunity elicited by early infections and there is no vaccine


How is the diagnosis of syphilis made?

1. visualization of T. pallidum on dark field microscopy from samples taken from the chancre in primary or lesions in secondary

2. Serology
- nontreponemal/nonspecific titers of RPR and VDLR that measure anti-cardiolipin Ab
- treponemal/specific tests - MHA-TP, FTA-ABS, TP-PA which recognize T. pallidum lipoproteins

3. biopsy - silver stain will show perivascular B-cell lymphocytes with plasma cells


Describe the 2 steps of obtaining serology for syphilis.
Which step is non-specific? Specific?
Which titer decreases over the course of late latency and which remains elevated?
What does each titer give you information about?

1. Non-treponemal [RPR, VDRL]
- non-specific
- anti-cardiolipin Ab [cardiolipin made by treponema]
- serum titers are for screening and to track disease progression [rising titer] or after antimicrobial therapy [falling titer]
- levels fall over the course of late latency

2. Treponemal [FTA-ABS, MHA-TP, TP-PA]
-specific because they react to T. pallidum lipoproteins
- denote present OR PAST infection
- titer remains elevated for life
- cannot distinguish reactive from non-reactive


What can give false positive VDRL?

1. Autoimmune disease
2. pregnancy
3. cancer

[all will have non-reactive specific tests]


How is congenital syphilis diagnosed?
How is it treated?
What are the complications if it is not treated?

50% of infants are asymptomatic at birth.
Routine serological tests are NOT helpful because they detect maternal IgG that crossed the placenta

Measure fetal IgM directed against specific antigens [lipoproteins] which can be an important adjunct to diagnosis

Treatment: IV penicillin for 14 days

If untreated:
"little old man with potbelly"
- long bones are saber shaped
- nasal streaming filled with spirochetes
-aged facial features


What is the most effective treatment against syphilis?
What is an acceptable alternative for early syphilis [except in kids under 8]?
What do you do if there is an allergy to the drug?

How does treatment change when it is neurosyphilis?

IM injection of penicillin is most effective.

Tetracycline can be an acceptable alternative, but penicillin is by and large the best.

If the patient has a penicillin allergy, desensitize them.

Neurosyphilis --> IV at higher doses


What is the most severe complication of penicillin treatment of syphilis?

The Jarisch-Herxheimer reaction can occur within several hours of treatment for primary or secondary syphilis.
Antibiotics kill the T. pallidum which releases the lipoproteins stimulating cytokine cascade {TNFa}.

It manifests as:
Fever, flushing, tachycardia, vasomotor instability, and can be life threatening.

Treat with anti-TNFa


What is Yaws?
Where is it endemic?
How is it transmitted?
How does it present?
How is it diagnosed?
What is treatment?

T. pallidum subspecies pertenue.
It is significant in Africa and Asia.
Transmission: skin inoculation
-stages like syphilis but never attacks CNS
[skin, bones, cartilage]

Dx: dark field, serology, clinical
Rx: penicillin or tetracycline


What is the cause of pinta?
Where is it endemic?
How does it present?
Dx? Rx?

It is caused by T. carateum
Endemic to Central and South America
It presents with skin manifestations only.
Dx: dark field, serology, clinical
Rx. penicillin, tetracycline