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
