1-20 Spirochetes and Vibrios Flashcards
Recurring themes of spirochetes
cross easily into bloodstream/cross blood brain barrier - spread through entire body quickly (unlike anaerobes that wall themselves off from bloodstream)
primary virulence factor involves immune evasion
diagnosis challenging
once correctly diagnosed, treatment simple
jarish herx reaction to treatment
The primary virulence factor of spirochetes
for immune evasion
- little inflammation
- few exotoxins
- low immunogenic surface (no LOS or LPS)
- no vaccines
describe the issues of spirochete diagnosisis
wide variety of symptoms. illness comes in phases. history taking critical
syphillis too small for standard microscopy
lyme has no reliable lab diagnostic
Argyll-robertson?
hallmark of neurosyphillis. loss of light pupil constriction.can still constrict when focusing
conjuctivitis?
redness with exudate, found in leptospirosis
caught early vs caught late
early-curable by standard abx
late- infection still cured easily, but recovery of nerves/immune system takes months/years if ever
Herx?
24 hours after abx, body “wakes up” to infection. spirochete evasion tactics fail. flulike, 24-48 hours
treponema pallidum (syphillis) bacteriology
spirochetes are motile (corkscrew), not culturable, very slow growing, too slender to gram stain
tranmission of treponoma pallidum
intimate contact - sex, mother-baby, rarely through blood transfusion
what does syphilis infect? incidence?
endothelium of small blood vessels
increasing in US
treponema pallidum is a _______ infection
triphasic
primary syphilis
primary (weeks) - initial replication at site of infection, ulcer/chancre. initiates bacterioemia
secondary syphilis
months. macropapular rash on palms, soles. papules on mucuous membranes. patchy alopecia. low fever, malaise, anorexia, headache, myalgia,
____ syphilis will resolve, _____ will enter
1/3, 1/3 latency
early latency - symptoms come and go, patient remains infectious
late latency - symptoms absent, not infectios
remaining ____ will enter tertiary syphilis
1/3
granulomas “gummas”, CNA involvement
congenital syphilis
crosses placenta, stillbirth or fetal abnormality
immunity is _____
incomplete - reinfection can occur. doesnt cause strong enough immune response
pathogenesis of syphilis does not seem to involve
toxins.
diagnosis of syphilis
chancre, rash, granulomas, cns symptoms
lab - darkfield microscopy or IF
serology -
efficacy of antibiotics against spirochetes
spirochetes are still sensitive against older antibiotics
describe the syphillis bacteria
delicate, small, .25mM in size
Describe how to culture T.pallidum
cannot culture, syphillis will not grow in culture
highest risk groups for contracting syphillis
gay/poor
describe the path of infection by syphillis
penetrates mucous membrane, hits bloodstream, enters lymphastics, hits CNS early in infection
what factor most complicates treatment of syphillis at the primary/secondary stages?
the fact that the lesions go away. Patients will not present primary or secondary lesions.
Also patients who are economically disadvantaged or don’t know a doctor will wait until it goes away, which it does
neurological syphillis
neurosyphillis - CNS breached
meningitis - within 6 months
meningovascular syphillis - damage to blood vessels of brain, spinal cord
parenchyma neurosyphillis - grows in brain
prevent syphillis?
penicillin & condoms. if allergic, treat with other abx then check up later
Describe the borrelia burgdorferi bacteria
motile spirochete, flat wave shape
can you get lyme without ever knowing?
asymptomatic clearance is possible - but how common this is unknown for obvious reasons
weeks after being bitten by tick
early localized infection (75%) with erythema migrans (bullseye, getting larger)
months after tick bite
early disseminated infection. bloodborn bacteria colonize CNS
meningitis, facial palsy, AV block, other rashes
takes time for body to recover after lyme cleared
final stage of lyme disease progression
late disseminated
bacteria colonize large joins and brain (encephalitis). damage will persist or be permanent
describe the proper examination for lyme.
- testing is not clear
- no known exposure or substantial risk of exposure? do not test. “history of outdoor activity?”
how will a patient likely present with lyme?
EM, high fever, coinfections, flu-like
Serology of lyme?
available but not useful. cant tell if current or past infection or if received vaccine while still on market
treatment of lyme?
14 days doxy if early, 30 if late. refer for symptoms (psychiatry, rehumatology)
how to treat pregnant woman with lyme?
avoid doxy. give approved antibiotic for time being, prescribe doxy after delivery
Describe vibrios appearance and resovoir
curved, gram neg. rods
mostly ocean dwelling. infected humans are resovoir
tranmission of vibrios
fecal-oral
infection of wounds exposed to ocean water
what can vibrios cause?
gastroenteritis and peptic ulcers.
vibrio example?
cholera
two types of cholera?
non-pathogenic, and pathogenic that received virulence factors from horizontal gene transfer
how does cholera spread?
-fecal oral
-shed by asymptomatic carriers
-untreated water/under cooked shellfish
ussually killed by stomach acid
-surviving bacteria reach small intestines and colonize
growing cholera excrete _____
cholera toxin (enterotoxin) called choleragen
-AB subunit, overactivates adenylate cyclase
presentation of cholera if little penetration of gut wall
watery, not bloody diarrhea
what causes morbidity to cholera?
dehydration from the toxin
When examining a cholera patient, what to look for? treatment?
look for dehydration, treat with antibiotics and rehydration with electrolytes (most important)
what kind of virulence factor is choleragen?
an enterotoxin
what is an enterotoxin?
gastroenterology
a toxin produced in or affecting the intestines, such as those causing food poisoning or cholera.
Transmission of spirochetes
Transmission – Sexual contact (Treponema pallidum – syphilis), vector-borne transmission (deer ticks carrying Borrelia burgdorferi – Lyme disease), and environmental transmission.
pathogenesis of spirochetes
Pathogenesis – They cross easily into the blood stream, and their primarily virulence factors are for immune evasion. They can further immunomodulate the host to suppress any immune response. As a result, no effective vaccines exist. Both syphilis and Lyme disease occur in three stages that can happen over the course of years.
diagnosis of spirochetes
Spirochetes are particularly challenging to diagnose. Symptoms appear in stages, so a patient history is essential. What’s more, Treponema pallidum are too small to see with a standard light microscope, and there is no quick and clear lab test for Borrelia burgdorferi exposure. In patients with neurosypilis, Argyll-Robertson pupil (one or both pupils fail to constrict due to light) is a good diagnostic tool.
treatment of spirochetes
Treatment – Treat syphilis with penicillin, prevent by practicing safe sex. Treat patients with early Lyme disease with a ten-to-twenty-day long doxycycline regiment unless pregnant. Antibiotics will cause Jarisch-Herxheimer reaction (about twenty-four hours of flu-like symptoms) twenty-four hours after the beginning of the regiment.
tranmission of vibrios
Primarily by fecal-oral route, but can also infect wounds contaminated by seawater or ocean debris. V. cholerae in particular is more likely to be transmitted by fecal-oral route in individuals with higher stomach pH (on antacids) or gastrectomies.
pathogenesis of vibrios
Vibrios have specialized virulence factors for survival in the GI tract. In the case of V. cholerae, when it reaches the small intestine, it secretes mucinase to clear out mucus and reach the brush border where it attaches and colonizes. There, it releases the enterotoxin choleragen. It follows the typical exotoxin AB structure. B binds the ganglioside receptor GM1 on intestinal lining, and A causes massive water and ion loss by the cells while simultaneously blocking microvilli absorption. Massive watery diarrhea results, and patients can die within hours in severe cases.
diagnosis of vibrios
When testing for V. cholerae, a pinch test is effective to determine if the patient is moderately dehydrated. For severe dehydration, signs to look for include sunken eyes, weak pulse, and coma.
treatment of vibrios
Rehydration and rebalancing electrolyte levels are critical steps. Then treat with a short course of tetracycline, doxycycline, or furazolidone after IV rehydration to shorten course and reduce shedding.
treat c.jejuni with abx but not c.butulinum with abx. Why?
c. botulinum dies during ingestion, it is the toxin we are worried baout. even if some bacteria survived, they don’t have any virulence factors we would worry about.
c. jejuni is an enteric bacteria with virulence factors for survival of stomach acid. Needs antibiotics.
why do we vaccnate against chickenpox?
the virus is very immungenic. raises a strong, long-lived response that prevents reinfection to a host that has been previously exposed.
