4. Spirochetes

Structurally spirochetes are closer to gram + or -

gram-negative bacteria

Locomotion of spirochetes

rotation of endoflagellum

Endoflagellum

a type of flagellum located within the periplasmic space of spirochetes that enables rotational movement.

Spirochetes: Treponema

genus that includes syphilis and oral treponemes

Treponema oxygen requirements

anaerobics —> syphilis and periodontal disease

Oral treponemes are implicated in

peridontal disease

Spirochetes: Borrelia

vector born causing relapsing fever and lyme disease

Spirochetes: Leptospira

aerobic genus causing leptospirosis

STIs in the US-syphilis

3rd most common bacterial STI

Syphilis cases in 2024

about 200,000 cases (42% increase since 2020)

Newborn syphilis in 2024

about 4,000 cases —> 82% increase since 2020

MOST common STI in US

HPV

Human papillomavirus (HPV)

most common STI that can cause warts and certain types of cancer

Which ethnic groups have higher rates of syphilis

non-hispanic American Indians
non-hispanic Black/ AA

Age group inwomen most likely to get syphilis

20s to mid 30s have way higher rates

What gender account for most cases of syphilis

males, especially among men who have sex with men

Majority of male syohilis cases occur in which groups

men who have sex with men

Syphilis often occurs in patients with

other STDs

Syphilis often occurs in patients with other STDs, which is important

facilitator of HIV coinfection

Syphilis causative agent

Treponema pallidum.

Treponema pallidum morphology

long, thin, and spiral

Why can T. pallidum not be cultured in lab medium

Rapidly dies on drying

T. pallidum- limited metabolic capacity

Obligate internal parasite (no TCA)

T. pallidum- why is it microaerophilic/anaerobic

Lacks catalase and superoxide dismutase so it cannot tolerate oxygen.

T. pallidum is visualized by

dark field microscopy and silver stain

T. pallidum immune strategy

immune avoidance!

Immune avoidance of T. pallidum

“Stealth pathogen” – few surface antigens

T. pallidum adhesins

Surface adhesins bind fibronectin

What T. pallidum enzyme facilitates infiltration

hyaluronidase

Modes of T. pallidum transmission

Sexual
Transplacental
Contact with lesion
Blood transfusion
Accidental direct inncolulation

T. pallidum- close contact with active lesions

includes sexual and perinatal contact

Accidental direct inoculation of T. pallidum

direct contact through cut in skin

4 years post T. pallidum infection

patient is considered NOT infectious due to low bacterial load

Primary stage of syphilis

3-4 weeks after exposure and you might have a sore called a chancre at the infection site.

Chancre

primary lesion of syphilis that is normally painless but HIGHLY INFECTIOUS!!

Chancre spontaneously heals after

around 14 days

After chancre appears, patient is

seropositive for life

Secondary syphilis stage

2-10 weeks after you might have rash

How often does secondary syphilis occur in untreated patients

Occurs in 25% of those with untreated primary syphilis

Characteristic rash of secondary syphilis is caused by

Bacteremia as T. pallidum multiplies and disseminates through the bloodstream.

Skin rashes of secondary syphilis

Immune system reacting to the widespread bacterial infection in skin tissue

T. pallidum mucous patches

T. pallidum spreads to mucous membranes, mouth, throat, vagina, anus, penis during secondary syphilis

Issue with mucous patches

Leak concentrated T. pallidum fluid. Most highly contagious syphilis symptoms

Fluids that leak out of T. pallidum, mucus matches

are HIGHLY contagious

T. pallidum condylomata lata

Wart-like growths that occur in moist areas that have a lot of friction during secondary syphilis

T. pallidum alopecia

Local immune response against antigens leads to inflammation in the follicular matrix causing “moth eaten alopecia”

Latent syphilis

In between stage 2 and stage 3 where you are seropositive with no symptoms

Latent syphilis can last for

several years to decades

Early latent period of syphilis

more infectious than late latent phase

A pregnant women is more likely to transmit syphilis to fetus during which period of latency

early latent period

How is the syphilis latency period affected in patients with coinfection of HIV

It is shortened, because immune system degrades

Tertiary syphilis (3) occurs

several months to 30 years after infection

In the tertiary phase of syphilis the organisms have spread to

various organs

Gumma

painless, granulomatous lesion associated with tertiary syphilis, often found in the skin, bones, or other organs.

Gummas in tertiary syphilis are caused from

immunological event rather than bacterial multiplication

Gumma in oral cavity can cause

perforated palate

Gumma in joints can cause

charcots joints

Tertiary syphilis- charcots joint

neuropathic joint disease caused by nerve damage from T. pallidum invading CNS

Charcots joint causes

loss of sensation and joint destruction (even collapse of arch of foot)

Gumma in cardiovascular system

Aortic aneurism

Aortic aneurism from tertiary syph gumma

abnormal bulge that occurs in the wall of the aorta caused by inflammation that weakens wall and depletes O2.

Are gummas contagious

No, gummas are not contagious as they result from an immunological response and not from active bacterial infection.

As syphilis disease course moves from primary all the way to tertiary, how does that impact bacterial load

decreases and is lowest in tertiary stage, leading to less infectiousness.

Neurosyphilis

Affects sensory and motor functio

During which stage of syphilis of neurosyphilis associated with

can be any stage

Early neurosyphilis

occurs a few months to a few years after infection

Late neurosyphilis

tertiary stage including general paresis, tabes dorsalis, ataxia

General paresis

Progressive neurological & psychiatric disorder of brain & nervous system from late stage neurosyphilis

Tabes dorsalis

degeneration to dorsal root ganglia which can cause ataxia and loss of sensation ( late neurosyphilis )

Ataxia

wide based gait, foot slap can happen in late neurosyphilis

Congenital syphilis

A form of syphilis transmitted from an infected mother to her fetus during pregnancy, leading to serious health issues for the newborn.

If a provider is made aware of a pregnant women with syphilis, it must be reported

within 24 hrs

What amount of syphilis pregnancies result in miscarriage, still birth, infant death

Approximately 40%

Surviving infants may have

developmental delays
craniofacial anomalies

When a baby is born from a syphilitic women it is

infectious!

Craniofacial anomalies seen in congenital syphilis

oHutchinson's teeth (broader term) / Hutchinson’s incisors

oMulberry (Moon's) molars

oMucous patches

oPerforated palate

oSaddle nose

oKeratitis

Hutchinson's teeth- congenital syphilis

Affects permanent incisors causing crescent shaped notch

Hutchinsons incisors

Triangular shaped deformity of incisors caused by congenital syphilis

Mulberry (Moon's) molars affects which tooth

Affects first permanent molars.

Mulberry (Moon's) molars

The occlusal surface is composed of an aggregate of enamel nodules

Mucous patches in congenital infection of syphilis

can form perforated palate

Saddle nose from congenital infection

is a deformity characterized by the loss of the bridge of the nose.

Interstitial corneal keratitis

Corneal scarring due to chronic inflammation of the corneal stroma, can cause blindness

Prevention of congenital syphilis

antibiotic treatment of mother

Risk factors of syphilis

methamphetamine, injection drug use
Risk sexual behavior
Pregnant women

Why is PCR less reliable for blood samples or late stage (latent) syphilis

low bacterial load as disease progresses so you might get false negative

Syphilis diagnosis

2-tiered serology

Non-treponemal serology

Screening tests for cellular damage (non-specific antibodies that show current inflammation or disease activity)

Non-treponemal tests for antibodies to what

cardiolipin in response to cellular damage

Examples of non-treponemal tests for antibodies to cardiolipin

oWassermann test (complement fixation)

oVDRL (Venereal Disease Research Laboratory)

oDiagnose neurosyphilis in CSF

oRPR (Rapid Plasma Reagin)

VDRL (Venereal Disease Research Laboratory)

non-treponemal serology testing for syphilis antibodies —> just says there has been syphilis exposure at some point in your life

RPR (Rapid Plasma Reagin)

Reagin (in blood from damaged cells) will agglutinate when mixed with cardiolipin antigen (in droppers)

Syphilis confirmation 2nd tier- treponemal serology

Identification of T. pallidum or look for specific antibodies made against the syphilis bacterium itself

Treponemal serology detecting antibodies in spinal fluid

highly suggestive of active neurosyphilis

Examples of treponemal tests

oPCR

oFTA-ABS (fluorescent treponemal antibody-absorption)

oTPPA (Treponema pallidum particle agglutination)

oMHA-TP (micro-hemagglutination to T. pallidum)

Overall traditional syphilis testing

is Non-Treponemal Test (RPR, VDRL) first, then confirm with treponemal test

Reverse testing for syphilis

treponemal test FIRST, then non-treponemal to look at extent of cellular damage

DOC for syphilis

Penicillin single dose IM

Treatment for latent syphilis or pregnant women

Three doses of penicillin recommended

Possible complication of antibiotic therapy of syphilis

Jarisch-Herxheimer reaction, “Herx”