ICL 2.11: Borrelia & Leptospira Flashcards
what is the microbiology of borellia?
spirochete
nontoxic, highly invasive, damage from immune system
what is the microbiology of leptospira?
spirochete
nontoxic, highly invasive, damage from immune system
what three bacteria are spirochetes?
- borrelia
- treponema
- leptospira
lyme disease vingette
no localizing symptoms
vomiting, nausea, aches, malaise, slight fever
eventually starts to feel better but large bullseye rash develops
walking through tall grass
which bacteria causes lyme disease?
borrelia burgdorferi
what are the structural features of borrelia burgdorferi?
OUTSIDE
1. outer membrane
contains few proteins in OM; majority of those are lipoproteins
- endoflagella*
- peptidoglycan
- inner membrane
INSIDE
NO LPS
NO lipid A
NO lipoteicocic acid
what are the structural features of gram - bacteria?
- outer membrane
LPS
porins and other surface proteins
- PG
- periplasm
what are the structural features of gram + bacteria?
no outer membrane
- thick PG
- lipoteicoic acid
during what time of the year is Lyme disease most common?
risk of human infection is greatest in late spring and summer
what are the 4 stages of tick growth?
- eggs
- larva
- nymph
- adults
how do ticks become infected with borrelia burgdorferi?
no transovarial transmission of B burgdorferi between parent ticks to their offspring so tick larvae are initially uninfected
but then naive larvae feed on infected mice and will sustain infection through molts to nymph and adult stages and therefore can transmit infection = persistence
nyph ticks then transmit infection to naive mice or humans – this allows maintenance of spirochete pool in wild
adult ticks then feed on deer and lay eggs
deer are not reservoirs for spirochetes, but provide blood meal that allows maintenance of tick population – so the number of Lyme cases correlates with acorn and deer population!
which tick species transmits Lyme disease?
Ixodes scapularis = eastern USA
Ixodes pacificus = california
what populations are most susceptible to Lyme disease?
most prevalent in the young (4-15; especially boys) and the elderly (45-85)
this is due to lack of proper tick surveillance
also in europe and asia and northeast america
which stage of tick usually transmits Lyme disease?
usually transmitted by nymph ticks
> 50% will never notice attached tick or remember bite
what are the risk factors for Lyme disease?
- presence of ticks known to harbor B. burgdorferi
- presence of mammalian/bird hosts to maintain B. burgdorferi reservoir = small rodents, migratory birds
- large terminal blood meal to maintain large tick population = deer
- proximity of humans and deer population (ticks)
what are the stages of Lyme disease?
- early disease = stage 1, primary
2. large disease = stage 2, subacute
what happens during the early stage of lyme disease?
- diagnostic symptom is erythema migrans = expanding bullseye rash at site of bite (70-80%)
may not be seen due to location of bite but believed to represent an inflammatory response to disseminating spirochetes
may be misdiagnosed in absence of erythema migrans
- “flu-like” symptoms: fatigue, malaise, fever, headache; no respiratory complications
- symptoms may occur days to weeks after infection
if diagnosed and treated appropriately, >99% are cured
what happens during the late stage of lyme disease?
occurs from weeks to years after initial infection once spirochetes disseminate to varied organs and tissues
most common complications are arthritis (60%), neurologic (20%) and cardiac (8%)
spirochetes are present in affected tissues
antiobiotics eventually resolve disease
how can you differentiate lyme disease from autoimmune arthritis?
pathology of Lyme arthritis is distinct from autoimmune arthritis because it can occur in the absence of B and T lymphocytes
the arthritis reflects the host inflammatory response to B. burgdorferi lipoproteins
what is causing arthritis in Lyme disease?
the arthritis reflects the host inflammatory response to B. burgdorferi lipoproteins
what are the clinical manifestations of confirmed lyme disease?
- erythema migrans (71%)
- arthritis (28%)
- facial palsy
- radiculoneuropathy (4%)
- meningitis/encephalitis
- carditis
what is radiculopathy?
a problem in which one or more nerves are affected and do not work properly
what is facial palsy?
characterised by facial drooping on the affected half, due to malfunction of the facial nerve (VII cranial nerve), which controls the muscles of the face
what are the neurologic complications that can happen with Lyme disease?
- Bell’s palsy = paralysis of facial nerve
usually resolves with antibiotic treatment
- lymphocytic meningitis
- radiculoneuritis
what are the cardiac complications that can happen with Lyme disease?
- atrioventricular block
- myocarditis
- palpitations
what is atrioventricular block?
one of the cardiac complications associated with Lyme disease
it’s when there’s interferance with the normal movement of
electrical signals from the heart’s
upper to lower chambers
what is acrodermatitis chronica atrophicans?
happens during late stage of european lyme borreliosis; predominantly seen in infections with Borrelia afzelii
it’s progressive fibrosing skin process that’s most evident on extremities – hard to diagnose
the pathophysiology is not understood but ACA develops after spirochetes persist for an extended period
but you don’t see spontaneous remission like other sequella
what happens if you don’t treat Lyme disease?
if left untreated, infection appears able to continue indefinitely
there’s the same range of symptoms as with disseminated lyme and it can be treated with antibiotic treatment
however, if the disease is treated too late in course, symptoms may remain indefinitely even if bacteria are eradicated because not all damaged host tissues repair quickly/completely so extended antibiotic treatments won’t fix this damage
a minor subset may develop an autoimmnune disease
what happens when lyme disease develops into an autoimmune disease?
this is limited to certain MHC haplotypes
MHC presents certain Borrelia antigens in way that resembles certain host tissue proteins
have dual reactive T cells that cause self-reactive immunity
this disease cannot be cured by antibiotics….
how does B. burgdorferi mediate host inflammation?
B. burgdorferi lacks LPS or lipoteicoic acid in outer membrane
but B. burgdorferi can make at least 150 different lipoproteins
all lipoproteins possess the same lipid modification = stimulatory
different lipoproteins are expressed by B. burgdorferi in different host environments
what type of genome does borrelia burgdorferi have?
segmented genome
linear chromosome of 910 kb
contains 21 plasmids with another 610 Kb pairs –> 12 linear and 9 circular plasmids
over 90% of these genes are unique to B. burgdorferi; many of these genes are lipoproteins
they’re believed to be involved in cycling between host species
but they lack genes to produce biosynthetic enzymes = obligate parasites
what are the virulence factors of B. burgdorferi?
- outer membrane lipoproteins
- endoflagella
- inhibits alternate pathway of complement activation
- does not require metabolic iron
how does the outer membrane lipoproteins act as virulence factors for B. burgdorferi?
the lipoproteins are triacylated and can vary expression on surface of bacteria = immune evasion
there’s a huge repertoire of antigenically distinct lipoproteins
they can restrict access of antibodies to integral membrane proteins
what is the function of endoflagella?
B. burgdorferi virulence factor
spirochetal motility