Unit 1 - Pediculosis and Treponema Flashcards
what are Pediculus humanus capitis? classic presentation? treatment?
hair lice (appearance is thin and cylindrical)
- mostly in schoolgirls that share hair accessories
- treat with insecticidal shampoo twice 10 days apart (to kill any nits that have hatched) plus nit combing
- hot wash all clothes/linen, and check family/classmates for spread
- there can be allergic reactions to louse saliva, and possible secondary Staph infections
what are Pediculus humanus corporis? classic presentation? treatment?
body lice (appearance is thin and cylindrical)
- mostly in homeless people who don’t bath properly
- refer for services to improve hygeine
- discard clothing, or wash plus insecticide treatment
- may transmit typhus, trench fever, and relapsing fever
what are Pthirus pubis? classic presentation? treatment?
pubic hair lice (look like crabs)
- in sexually promiscuous people
- shave pubic hair or coat with Vaseline
- hot-wash all clothing and linens, check partner and children (as crabs can spread easily)
- these are markers for other STDs, and aren’t preventable with condoms
where does syphilis fall in the tree of bacteria?
Spirochetes include: Treponema, Borrelia, and Leptospira
-Treponemia include: Syphilis, Yaws, and Pinta
Treponema pallidum (syphilis) bacteriology
- 0.25uM diamter (invisible to light microscope, so need darkfield; too slender to Gram stain)
- spirochetes (motile in flagellar corkscrew motion)
- not culturable (delicate, and can’t survive outside host)
- human-restricted in nature, but can infect rabbits in lab
- extremely infectious sexually, since virulence based on immune evasion
Treponema pallidum (syphilis) pathogenesis
transmitted by sex, transplacentally, rarely blood-blood
- infects endothelium of small blood vessels, enters lymphatics, bloodstream
- CNS invaded early, but symptoms take years to develop
- -first CNS abnormalities, then meninges, then parenchyma of brain/spinal cord
- host raises ineffective Ab (specific anti-treponema, unspecific reagin, but surface of spirochete is non-immunogenic and down-regulates Th1 cells)
what are the 3 phases of syphilis infection?
primary (weeks): initial replication at site of infection, forming chancre that initiates bacteremia
-highly infectious, inflammatory infiltrate at site fails to clear organism
-disappears in 3-12 weeks
secondary (months): macropapular rash on palms/soles, moist papules on skin and mucus membranes, highly infectious moist lesions on genitals
-high antibody titers
-1/3 resolve, 1/3 enter latency, 1/3 enter tertiary
tertiary (years): get gummas granulomas (liver, bones, testes) and CNS involvement
-early meningitis (~6 mo) low inflammation
-late neurosyphilis (meningovascular syphilis and parenchymal neurosyphilis)
explain syphilis latency
1/3 of secondary syphilis patients
- early latency: symptoms come/go, patient remains infectious
- late latency: symptoms absent, not infectious
congenital syphilis
treponemes easily cross placenta
- 40-50% miscarriage/stillbirth/neonatal death
- survivors develop severe secondary syphilis and physical abnormalities
relationship between syphilis and HIV
ulcerations of syphilis facilitate HIV infection
-HIV immunosuppression accelerates syphilis course, and reduces efficacy of treatment
diagnosing primary syphilis
“the great imitator” (can hide behind other infections)
- time course is 3 weeks
- chancres are red, firm, buttonlike, and not painful unless super-infected
- -disappears in 4-12 weeks
- site may be genital or other intimate spot
- local lymph nodes swell with invasion
diagnosing secondary syphilis
4-10 weeks after primary, peaks 3-4 mo after infection
- subtle, round rash bilaterally symmetrical with nontender lymphadenopathy, round pink spots
- lesions weeks later on palms/soles become necrotic
- patchy alopecia
- condylomata lata cause reddish-brown papular lesions on anogenital area, that coalesce into elevated plaques
- -progress from red to gunmetal
- -may be confused with warts
- may have constitutional symptoms like low fever, malaise, anorexia, weight loss, headache, myalgia, lympadenopathy
diagnosing tertiary syphilis
3-10 years after infection, years of inflammation
- gumma: granulomatous lesions with rubbery necrotic center
- -bone: deep, boring pain worse at night
- -skin: hyperpigmented circle, often grouped close together on leg
- liver: jaundice
cardiovascular syphilis
tertiary (>10 years): aneurysm of ascending aorta caused by chronic inflammation of vasa vasorum
-aorta or other major arterial scarring; diastolic murmur with tambour quality, secondary to aortic dilation with valvular insufficiency
what’s included in tertiary late neurosyphilis?
- meningovascular syphilis 5-10 years after infection
- -endarteritis affects small blood vessels of meninges, brain, spinal cord
- -CNS vascular insufficiency or stroke
- parenchymal neurosyphilis 15-20 years after primary infection
- -tabes dorsalis - damage to sensory nerves in dorsal roots ataxia, and loss of pain sensation, proprioreception, DTR, deep ulcers on feet
- general paresis - widespread parenchymal invasion that causes individual cell death and brain atrophy
- dementia
what is the Argyll-Robertson pupil?
hallmark of neurosyphilis (tertiary)
-one or both pupils fail to constrict in response to light, but they do constrict to focus on a nearby object
how can one exam for syphilis?
- imaging
- CT for gummas, chest radiograph and angiograph for cardiovascular syphilis, CT and MRI for neurosyphilis - lumbar puncture for neurosyphilis or syphilis+HIV
- VDRL, cell point, protein
- PCR for past infection
labs for syphilis?
won’t culture, too small to Gram stain, so can only use darkfield
-serology with rapid plasma reagin (RPR), venereal disease research laboratory (VDRL), or ICE syphilis recombinant antigen test
what does it mean that syphilis has specific Ab?
detectable by IF or hemagglutination, but remain positive for life (tests exposure, not current infection)
histology diagnosis of syphilis
- endareritis caused by binding spirochetes to endothelial cells mediated by host fibronectin
- plasma-cell rich infiltrate: delayed hypersensitivity to syphilis leads to gummas
Syphilis treatment
- full panel of STD tests
- penicillin (single injection of benzathine penicillin G for primary/secondary syphilis, as slow release enhances effectiveness)
- no known resistance, but tertiary neuro/cardio damage may not heal
- if congenital: treat mother by 5th month, and if allergic, use inpatient oral desensitization with penicillin - alternative doxycycline, erythromycin, ceftriaxone are much less effective so followup with repeat reagin tests
explain the Jarisch-Herxheimer reaction
8-24 hours after starting syphilis treatment, there are flulike symptoms and/or rash that resolve in 24 hours
what kind of RPR and VDRL results to yaws and pinta give?
positive for both
Treponema pertenue - yaws
-what it is, where, and how
in tropical areas of Africa, Asia, South America, and Oceania
- a few thousand cases/yr, mostly peds
- due to overcrowding and poor sanitation; transmitted by direct contact with skin lesions
- multiple stages like syphilis, but without neuro or cardio involvement
- treat with penicillin (G)
Treponema carateum - pinta
-what it is, where, and how
Central/South america
- similar to Yaws, but no constitutional symptoms
- hypo and hyper-pigmented skin plaques, primarily young adults through direct contact
- entirely human-restricted
- treat with penicillin (G)
