Spirochetes & Vibrios Flashcards
List 8 recurring themes for spirochetes
- wide variety of transmission
- cross very easily to bloodstream
- primary virulence factors = immune evasion
- very low inflammation
- no vaccines b/c not very immunogenic
- diagnosis is challenging
- little acquired abx resistance b/c doesn’t pass around plasmids
- Jarisch-herxheimer rxn to treatment
What is the Jarisch-herxheimer rxn to treatment?
It is one of the recurring themes found in spirochete infections and is when patient develops flu-like symptoms 24 hrs post-abx treatment.
Spirochetes belong into 3 genus
1) treponema (syphillus, yaws, pintas)
2) leptospira (leptospirosis)
3) borrelia (lyme disease, relapsing fever)
Describe the movement of the small treponema pallidum
flagellar “corkscrew” motion
Can treponema pallidum survive outside of humans?
Treponema pallidum is human restricted and cannot survive outside of host.
Can treponema pallidum be grown in culture?
No
Treponema pallidum will cause syphilis. What’s the difference btw acquired and congenital syphilis?
Congenital syphilis is transferred from mom to fetus thru blood. Acquired syphilis is gotten from sex.
In acquired syphilis, there’s full body infection in day 1 due to what characteristic of spirochetes?
it can readily cross membranes and into bloodstream, but it’s not immunogenic enough to cause shock
In acquired syphilis, CNS is invaded relatively early. Do symptoms develop immediately? What are the signs of CNS involvement?
Symptoms make take years to develop. First, CSF is abnormal (subarachnoid space), then meninges then brain parenchyme.
In acquired syphilis, host raises humoral immunity against treponema syphillis, but don’t clear infection. Why?
B/c surface of spirochetes is non-immunogenic. Also spirochetes downregulate TH1 cells, which help activate macrophages.
Primary syphilis is highly infectious. What are the symptoms and what is the treatment?
Patient will present with painless chancre at site within 3-6 weeks of infection. The chancre will heal, but syphilis will remain. Treatment is one shot of penicillin.
Why is secondary syphilis, which occurs when primary syphilis isn’t cured harder to diagnose?
it is much harder to diagnose because of variable symptoms. Patient can present with fever, malaise, myalgias. Nothing that will directly tie it to syphilis, especially if patient doesn’t mention chancre that has gone away.
What is reagin?
useless antibodies found in someone with secondary syphilis
2/3 of secondary syphilis will become
latent syphilis serving as reservoir of treponema pallidum
The other 1/3 of secondary syphilis will become tertiary syphilis, which can cause a wide range of symptoms
- cardiovascular syphilis (aneurysm of ascending aorta)
- gummatous syphilis in liver, bone, testes seen as granulomas with rubbery, necrotic centers
- neurosyphilis
What are the 3 kinds of neurosyphilis?
- syphilitc meningitis (usu. occurs early on around 6 months post-exposure)
- meningovascular syphilis will damage blood vessels of meninges, brain and spinal cord
- parenchymal neurosyphilis leading to impaired sensation, wide-based gait and loss of pain and sensation due to disruption of dorsal roots.
neurosyphilis can cause general paresis and dementia
What does the Argyll-Robertson Pupil Exam test for?
It can detect neurosyphilis.
- 1 or both pupils will fail to constrict in response to light (neg pupillary reflex uni or bilaterally)
- but both pupils will constrict when testing for accommodation (positive accommodation test).
Infants with congenital syphilis will develop what kinds of symptoms within first two years of life?
severe secondary syphilis (fever, malaise, myalgias, etc)
Often times, fetuses infected with treponema pallidum will
be stillborn, miscarried in 40-50% of cases
Borrelia burgdorferi is a spirochete that can cause which disease
Lyme Disease
Treponema pallidum is motile and so is borrelia burgdorferi. Describe their movements
Treponema pallidum has a flagellar corkscrew motion. Borrelia burgdorferi has a flatwave, not spiral movement
Unlike treponema pallidum which is too small to be seen under std light microscopy, borrelia burgdorferi can be seen. But it needs special stain, such as
silver stain
What are the 2 general reservoirs of borrelia burgdorferi?
- small mammals carrying nymph (immature, young ticks)
2. large mammals carrying adult ticks
How long does it take ticks to transmit lyme disease?
about 24-48 hours, which is why checking oneself for ticks everyday in endemic areas can be a great preventative measure
How to remove a tick?
1) use gloves bc tick’s saliva is infectious
2) remove with tweezer
What is the abx of choice to treat lyme disease? Are there any contraindications of this abx?
Use doxycycline for 10-20 days, but cannot be given to pregnant women or people allergic to tetracycline
Lyme disease has 3 phases after tick injects borrelia burgorferi into host. Explain the 1st phase.
1st phase; organisms will spread in the next 6 months; 70% of people will have bullseye rash at site; erythema migrans rash (which will increase in size); autoantibodies
The 2nd stage of lyme disease
- no more rash
- immune and/or neurological disorders
- *harder to diagnose b/c no erythema migrans
The 3rd stage of lyme disease aka Post-Lyme
-more severe immune and neurological disorders
Can someone get lyme disease more than once?
Yes, reinfection can occur.
What is important in diagnosing lyme disease?
Taking a careful history (season, geographic location, timeframe) -patient can have co-infection and present with fever
What are some lab tools that can diagnose lyme disease and who might have false positives?
serology, ELISA, and IFA can confirm Lyme Disease but not until 6 months laters. A problem is there are some people vaccinated against Lyme so will have false positives.
Treponema requires special technique to be visualized
dark field
With these spirochete infections, treatments are easy once diagnosis is made. The problem is with diagnosing. Explain
In syphilis, after it passes the primary syphilis phase, there will not be clearly identifiable chancres. Likewise, in lyme disease, after the first phase, there will be no presentation of erythema migrans. Hence, with these, it’s best to diagnose early and treat early.
At times, people in endemic areas of lyme disease will get treated with prophylactic abx, what reaction can actually confirm diagnosis of lyme disease?
Jarisch-herxheimer rxn which is when patient presents with flu-like symptoms after abx treatment of spirochete infections (lyme, syphillis)
Vibrios are not cocci, bacilli or spirochetes. Describe their shape.
Vibrios are gram negative rods, and are mostly ocean dwelling halophiles (love salt).
Are spirochetes gram negative or gram positive?
Spirochetes are not classified as either gram negative or gram positive
In addition to causing gastroenteritis, vibrios are now known to be linked to
peptic ulcer disease
Describe the shape of Vibrio Cholera
Vibrio Cholera is a curved, comma-shaped motile Gram negative rod.
Is Vibrio Cholera an obligate anaerobe, obligate aerobe or facultative anaerobe?
Facultative anaerobe
What are the two reservoirs of Vibrio Cholera?
- in humans
2. planktonecosystem of Indian Ocean
Vibrio Cholera is usually not pathogenic. How does it become pathogenic?
Vibrio Cholera undergo genetic changes via lysogenic bacteriophage colonization to become pathogenic
What are two ways V cholera is transmitted?
- fecal-oral route
2. shed by asymptomatic carriers
Vibrio Cholera has a high infectious dose that is normally killed by stomach acid. Explain the pathogenesis of V. Cholera
- bacteria that survive the stomach will go to the small intestines
- secrete mucinase, which will clear path to brush border, attach, colonize inside lumen of intestine
- growing bacteria secrete cholera toxin (aka chloragen)
- chloragen (ab subunit) -will persistently activate adenylate cyclase leading to loss of water and ions
- blocks absorption by microvilli while also promoting secretion from crypts
What toxin does Vibrio Cholera secrete?
Chloragen (ab subunit) -b unit for docking and a unit with enzymatic activity to stimulate adenylate cyclase leading to loss of water and ions
Where does Vibrio Cholera get its virulence factors?
from a lysogenic bacteriophage CTX
What is the major symptom of Cholera?
MASSIVE watery diarrhea
Will Abx help with treating Cholera?
No, the infection is self-limiting; will clear within a week. The problem is due to dehydration and electrolyte imbalance.
If your patient presents with cholera, what should you focus on in terms of treatment?
Make sure that the patient is well hydrated and his/her electrolytes are balanced
How to evaluate how dehydrated someone with cholera is?
There’s a pinch test in which you pinch the patient and watch to see how long it takes the site to get back to normal coloration. The more dehydrated the patient, the longer it takes for the skin to get back to normal.
Another Vibrio is Helicobacter pylori. Describe its shape.
Helicobacter pylori is a curved gram negative rod.
What is helicobacter pylori (Vibrio) hallmark virulence factor?
Urease + which will break down urea into ammonia
How is helicobacter pylori transmitted?
Unknown; probably human to human
Explain the pathogenesis of H. Pylori
- bacteria with flagella swim and attach to mucus-secreting cells of stomach
- produce urease to break down urea (normal in stomach) to ammonia (abnormal)
- increased levels of ammonia will increase pH allowing bacteria to grow and form ulcers and irrate gut wall
What are the two ways to diagnose someone with peptic ulcer disease caused by h. pylori?
Radiolabeled Urea-breath test
1. Pt drinks radiolabeled urea
2. if infected, will exhale radiolabeled CO2
Check stool sample for antigens to h. pylori but very expensive
How to treat people with h. pylori?
- peptobismol
- proton pump inhibitor
- 10-14 days of trio of abx
What’s the most pathogenic strain of v. cholera?
most pathogenic strain has O1 genetic marker of colonization by lysogenic bacteriophage
When was H. Pylori discovered?
1983
What clinical conditions are linked to infection with h. pylori?
peptic ulcer disease and gastric cancers
Who is more susceptible to getting cholera?
People who are on antacids and have had gastrectomies.
