Treponema pallidum

Treponema pallidum is a Gram-nonreactive spirochete which causes treponemal diseases such as syphilis. Under the light microscope, this organism can only be seen using dark field microscopy. Due to its coat of lipids, it is hard to stain the organism, even though it would be gram-negative. It is a hypotroph (or obligate parasite) that cannot grow on regular lab media.

Transmission
Syphilis is a sexually transmitted disease between humans, but can also spread through the placenta, lesions or fomites. Transmission through fomites is rare because the organism dies within minutes when exposed to dry environments.

Morbidity
The reported number includes people as young as 12 years old. Unreported cases are often healthy carriers.

Reported Number: Estimated:
 * Syphilis: 40,000 cases/year; treatable with antibiotics
 * AIDs: 40,000 cases/year; can’t be cured
 * Gonorrhea: 350,000 cases/year
 * Chlamydia: 1 million cases/year; treatable with antibiotics
 * Genital herpes: 1.5 million cases/year; can’t be cured; 1 in 5 adults actually have it
 * Trichomonas: 7 million; protozoa (usually only women have symptoms and they are very mild)
 * Human Papilloma Virus: 7.5 Million; most prevalent STD; auto-innoculatable

Mortality
Syphilis causes 100 deaths a year in US, but that number is increasing because of AIDS.

Incubation
Syphilis incubates for 2-3 weeks. Its ID 50 is 57 spirochetes. They have hook-like flagella that attatch to damaged skin.

Primary Phase
In the primary phase  a lesion called a chancre (a raised, hard nodule under skin), develops where the initial infection occurs. 90% of those will develop in the genital area, 10 % in fingers, nipples, anus, and lips. Organism eventually breaks down the chancre and forms an ulcer loaded with the organism. During this primary phase the organism is able to spread through contact, but is indolent (painless) to the host. In males, this lesion can be itchy in genital area. If scratched, the chancre can be infected with E coli or Staph. In females, this lesion, 90% of the cases are in the cervix: they are healthy carriers. These chancres last 4-6 weeks.

Primary latent phase
The primary latent phase lasts for 0 to 6, depending on your immune system and the strength of the pathogen, during which there are no visible lesions, and are only slightly contagious. However, the organism is in the blood, and the body still produces antibodies against the organism, but few in number because they can’t stick to lipid coat on bacteria. Syphilis is known as a Teflon pathogen, which don’t stimulate the immune system due to their thick lipid layer.

Secondary phase
Lasts a few weeks to a few months. You have a flu like syndrome, and indolent rashes/lesion that can spread the disease. Lymphadenopathy, swollen lymph nodes.

Late latent
After 4 years after contraction usually not infectious except from mother to fetus,

25% of people become completely cured, no organism, no more symptoms, no more antibodies; amount of antibodies goes down in 6-8 months; no remaining immunity

25% remain in late latent phase indefinitely, there is a slow destruction of tissues and they always test positive for antibodies.

Remaining 50%: go onto tertiary phase, more rapid destruction of tissues

Tertiary phase
Lesion formed is called a gumma (feels granulomatous/ rubbery, indolent but destructive). There are two serious types of tertiary syphilis:

a. Cardiovascular syphilis: damages heart, arteries, enlarged aorta, aneurysms (blood vessels become weak; bubble forms, which can break and cause patient to bleed to death)

b. Neurosyphilis: nervous system, can lead to blindness, deafness, and dementia (killed Al Capone)

Neonatal Syphilis (Prenatal/Congenital syphilis)
Transmitted from mother to fetus before the 5th month of pregnancy, 2% chance of occurrence if treated before 5th month, 50% chance of occurrence if untreated

Incidence: (World wide)
There are about 1 million cases worldwide: 250,000 cases: fetus dies in utero, or are still born, 250,000 cases: fetus dies shortly after birth, miscarriage. 500,000 cases: baby survives but develops neonatal syphilis 60% of those 500,000 cases is latent, with no outward signs 40% of those 500,00 cases get early and late lesions.

Early lesions are seen within a few weeks of birth. They resemble rashes of secondary syphilis, and occurs within few weeks of birth. There are no chancres because point of entry was the umbilical cord

Late lesions appear after 2-5 years. They resemble gumma of the tertiary syphilis.

Stigmata
The Hutchinson’s Triad is used to diagnose kids with neonatal syphilis. The 3 reactions from syphilis are:
 * 1) Hutchinson’s incisors: teeth become notched/misshaped
 * 2) Interstitial keratitis: cornea of eyes become scarred, vision
 * 3) Eighth nerve deafness

Microscopic Examination
Done if there is a chancre or a rash with a dark-field microscope or immunofluorescence.

X-Rays
Look for gummas in tissues.

Serological test
Take sample of blood and test for antibodies in blood with antigens.

Screening Test
A non-Treponemal test, using cardiolipin (antigen), the chemical released from syphilis damaging the mitochondria in the human host. Two tests are under this category: Rapid Plasma Reagen test (RPR) and Veneral Disease Research Laboratory (VDRL). The RPR is a tube test that is more common in the U.S., while the VDRL is a slide test more often performed in Europe. Screening tests determine the presence of antibodies, which are also called reagens, Wasserman antibodies, or immunoglobulins (IgM/IgG)

Screening tests can have false positives and false negatives, but are easy and inexpensive to perform.

Specific Test (Treponemal test)
Uses Treponema palladum organism grown in rabbits. There are two tests:

Fluorescent Treponamal Antibody Absorption (FTAA), which uses the Reiter strain of Treponema pallidum.

Hemagglutination Treponema Test for Syphilis (HTTS), which uses the Nickol strain of Treponema palladium.

Test are very expensive and difficult to run, but have almost no false positives, and almost no false negatives.

Treatment
Benzathine Penicillin G is the DOC. A single dose is given to a patient who has had the disease for less than one year, and a second dose if they have had it for longer.

EPT-Expedited Partner Treatment. The index patient (have the symptoms) will receive drugs to give to their partner to prevent reinfection. 