I & I Part III > Spirochetes > Flashcards

Spirochetes Flashcards

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1
Q

Spirochetes

A
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2
Q

3 Genera of Spirochetes Pathogenic for Humans

A

•Treponema

  • Syphilis
  • Non-venereal or endemic treponematosis

• Leptospira

  • Leptospirosis

•Borrelia

  • Lyme disease
  • Relapsing fever
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3
Q

T. pallidum subsp pallidum

A
  • cause of syphilis
  • slender (0.2 µM), only seen using special stains

• dark-field, immunofluorescence, Warthin-Starry

  • Few PAMPs, evades host immunity
  • Microaerophilic with slow (30 hr) doubling time
  • Minimal exogenous DNA
  • Not routinely able to be cultured
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4
Q

Other pathogenic treponemes

A
  • 99% related to T. pallidum subsp pallidum
  • Not transmitted venereally
  • Include
  • T. pallidum subsp pretenue (yaws)
  • T. pallidum subsp endemicum (bejel)
  • T. carateum (pinta)
  • Some free-living treponemes are associated with periodontal disease
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5
Q

Syphilis Transmission

A

• Acquired by sexual contact

  • able to penetrate moist mucous membranes
  • uncircumcised glans penis; labia, introitus and cervix of women; anal canal; oral mucosa
  • may also infect abraded keratinized tissue
  • Transplacental transmission
  • soon after maternal infection, crosses the maternalfetal circulation to infect the fetus in utero

• Transmission only occurs during the primary & secondary stages

  • when the number of organisms is high
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6
Q

Syphilis Epidemiology

A
  • Syphilis remains a significant public health problem.
  • While there was a decrease after the introduction of penicillin, there was an increase during the AIDS epidemic in the early 1990’s.
  • After another decline, there has been a recent resurgence since 2000, particularly among men who have sex with men (MSM) and among people using drugs. In the latter case, transmission occurs as part of selling sex for drugs.
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7
Q

Syphilis Pathogenesis

A
  • Entry is aided by at least one adhesin that binds to fibronectin and elements of the extracellular matrix.
  • In the submucosa, it multiplies slowly and induces minimal tissue reaction. This is probably due to the relative paucity of antigens in the outer membrane.
  • The organisms spread from the primary site to the bloodstream and to distant tissues rapidly.
  • The immune response is not complete and the organism persists at low levels. Moreover, there is no long lasting immunity and reinfection may occur.
  • T. pallidum can infect almost any organ of the body, including the central nervous system (CNS).
  • The basic pathologic finding is an endothelial proliferation causing an endarteritis that results in capillary obstruction.

-This accounts for the necrotic ulceration of the primary lesion and subsequent destruction at other sites.

•Although the primary lesion heals spontaneously, the bacteria are already disseminated to other organs by way of local lymph nodes and the bloodstream.

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8
Q

Syphilis Immunity

A
  • The host response in syphilis is imperfect.
  • T lymphocytes infiltrate the site of infection within 3 days and are followed by macrophages. The number of treponemes decreases markedly thereafter, likely due to phagocytosis.
  • However, some organisms evade phagocytosis and persist.
  • The presence of activated lymphocytes and macrophages at the site of the infection may account for the increased risk for HIV-1 infection in those with a primary lesion.
  • While antibodies are produced during infection, these are not sufficient to clear infection but are critical tools for diagnosis (see below).
  • In the end, a state of latency occurs with organisms persisting and not triggering an inflammatory response, due to their relative lack of surface proteins. At this point, the immune response is not sustained and persons can be reinfected.
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9
Q

Primary Syphilis

A
  • The primary lesion, called the chancre, appears as a single, painless papule at the site of inoculation. It rapidly ulcerates with a hard edge.
  • There is often regional arlymphadenopathy that is firm and painless. It usually persists for 4-6 weeks before healing spontaneously.
  • This stage often missed in women and in cases of anal exposure
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10
Q

Secondary Syphilis

A
  • Occurs a few weeks or months after primary disease (with some occasional overlap)
  • Mild, symmetrical non-pruritic rash that is present on the palms and soles
  • Low-grade fever
  • Diffuse lymphadenopathy
  • Alopecia
  • Mucous patches
  • Condyloma lata
  • Hepatitis
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11
Q

Latent Syphilis

A
  • This occurs in patients who have a positive syphilis serology without any clinical manifestations who have not received prior appropriate antimicrobial therapy.
  • It has been arbitrarily divided into early latent syphilis, occurring within one year of infection, and late latent syphilis, where infection has occurred one or more years previously.
  • Some clinicians insist on a lumbar puncture to rule out meningitis prior to making this diagnosis, but this is not routinely done.
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12
Q

Tertiary Syphilis

A
  • Currently uncommon
  • Cardiovascular
  • 10-40 years after initial infection
  • endarteritis obliterans of vaso vasorum of large vessels
  • aortic regurgitation with saccular aneurysm of ascending aorta
  • calcification of the aneurysmal wall

• Late benign syphilis (gumma)

  • granulomatous
  • indolent, painless masses, sometimes ulcerated
  • skin, skeletal system most common

• Late neurosyphilis

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13
Q

Neurosyphilis

A

•Syphilitic involvement of the central nervous system is now recognized as occurring very soon after infection. It is divided into an asymptomatic and a symptomatic stage

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14
Q

Asymptomatic neurosyphilis

A

•Asymptomatic neurosyphilis occurs in patients without attributable symptoms but who have an abnormal CSF profile. This may include a nucleated cell pleocytosis, an elevated protein level, and/or a positive non-specific treponemal test, such as the VDRL. There is some debate, but most experts recommend treating asymptomatic neurosyphilis.

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15
Q

Symptomatic neurosyphilis

A

•Symptomatic neurosyphilis is divided into three types.

  1. Meningeal syphilis usually presents within one year of infection. Headache, cranial nerve abnormalities, and seizures are common. Uveitis (ocular syphilis) and deafness (otic syphilis) may be seen.
  2. Meningovascular syphilis is due to an inflammatory vasculitis and occurs later after infection. Stroke involving the middle cerebral artery is the most common manifestation.
  3. Parenchymatous neurosyphilis is due to late tissue damage and is rarely seen now. General paresis is a cluster of abnormalities including changes in personality, often with delusions of persecution or grandeur, defective judgment, and hyperreflexia.
  • The Argyll-Robertson pupil, where pupillary restriction occurs from accommodation but not from light, is a manifestation.
  • Tabes dorsalis is due to demyelination of the posterior columns, dorsal roots, and dorsal root ganglia, resulting in a loss of sensation and proprioception. The patient presents with a wide-based gait, joint degeneration (Charcot’s joints), and ulcers of the feet and shins.
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16
Q

Congenital syphilis

A
  • Currently uncommon
  • All pregnant women should be tested for syphilis
  • if risk high, retested during third trimester
  • if positive, treat mother

• Manifestations

  • Early (~2-10 weeks)
  • infectious
  • similar to secondary syphilis in adults
  • Late (>2 years)
  • non-infectious, subclinical in 60%
  • interstitial keratitis
  • 8th nerve deafness
  • recurrent arthropathy
  • Hutchinson’s teeth, mulberry molars, saddle nose, saber shins
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17
Q

Diagnosis of Syphilis - Microscopy and NAATs

A
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18
Q

Diagnosis of Syphilis - Serology

A
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19
Q

Syphilis Treatment

A

•penicillin!

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20
Q

Jarisch-Herxheimer reaction

A

• Systemic reaction after therapy

  • most common with 2° syphilis
  • Fever, chills, tachycardia, hypotension 6-8 hr after treatment and lasts ~24 hr - presumed cytokine storm from released lipoproteins of dead treponemes
  • Ameliorated with NSAIDs, corticosteroids
  • Occurs with treatment of other spirochete infections - e.g. relapsing fever, Lyme disease
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21
Q

Leptospira genus

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A
  • Gram -
  • spiral
  • aerobic
  • The genus Leptospira currently has 23 named species
  • previously only L. interrogans recognized as pathogenic
  • thin, tightly wound, with hooked ends
22
Q

Leptospirosis

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A

• Zoonotic infection

  • chronic renal infection in rodent reservoirs

• In humans, occurs most commonly in tropics & subtropics

  • subsistence farmers
  • urban homeless
  • camping, water sports
  • animal handlers
  • Direct or indirect contact with infected urine - soil or water
  • Results in humans in a high-grade leptospiral bacillemia
  • human TL4 does not recognize leptospiral LPS
  • lack of innate immune response
  • results in “cytokine storm
23
Q

Leptospirosis Life Cycle

24
Q

Leptospirosis Clinical Presentation

Study These Flashcards
A
  • Ranges from mild to life-threatening
  • Typically, biphasic
  • Incubation stage: 2–20 days
  • Acute presentation stage: ~ 1 week
  • sudden fever, chills, headache

• associated with leptospiral bacillemia

  • muscle pain
  • conjunctival suffusion
  • multiple organ involvement

• Weil’s syndrome

  • jaundice
  • hemorrhage
  • renal dysfunction
  • Convalescent or Immune stage: ~2–3 weeks
  • Chronic stage (?): months–years
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Leptospirosis Diagnosis
• Culture - Leptospira can be isolated from blood, CSF during the first 10 days of illness - Urine cultures are positive after first week of illness - Requires specialized media * PCR * Serology - Microscopic agglutination test (MAT) • difficult to perform, cross-reactive - Requires 4-fold rise in titer or a single titer of \>1:800
26
Leptospirosis Treatment
* Mild cases - self-limited, no antibiotics necessary * Moderate to severe - β-lactams * Penicillin * Ampicillin * Ceftriaxone - **Doxycycline**
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Borrelia genus
* Gram - * spiral * anaerobic/microaerophilic * Closely related to other spirochetes - at least 15 different species - generally divided into three disease groups - carried by ticks or lice
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Borrelia Relapsing Fever Tick Bourne
• B. hermsii, B. turcatae, B. parkeri, B. miyamotoi, and others
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Borrelia Relapsing Fever Louse Bourne
• B. recurrentis
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Borrelia Lyme Disease
* B. bergdorferi sensu lato * B. lonestari, B. mayonii
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Antigenic Variation and Relapsing Fever
• Borrelia have a genes for surface outer membrane proteins located on extrachromosomal linear plasmids - variable major protein (vmp) genes - multiple copies of each exist • When a vmp is positioned down-stream from a promoter, it is expressed - the other copies are silent * If a silent gene recombines with an active gene on another plasmid, it will be expressed * The result are waves of antigenically distinct organisms over time as the immune response occurs to each antigenic variant * Clinically, this is expressed as recurrent fevers and bacteremia until the antigenic repertoire can no longer escape
32
Tick-borne Relapsing Fever (TBRF)
• Transmitted by the soft-bodied ticks of the genus Ornithodoros - feed on rodents at night - persist in wood piles, cabins - bite is painless * Results in recurrent fevers of about 3 days duration followed by around one week of afebrility * Diagnosis is often not considered until multiple episodes of recurring fevers * Seen principally in the western United States
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Tick-borne Relapsing Fever (TBRF) Diagnosis
• During febrile episode, organisms can be seen on blood smear using routine stains
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Tick-borne Relapsing Fever (TBRF) Treatment
•Treatment is usually doxycycline for 7 days - penicillin, tetracycline, erythromycin are also effective
35
Louse-borne Relapsing Fever (LBRF)
* Due to B. recurrentis * Only currently seen in the Horn of Africa * Is carried by the human body louse - no transovarial transmission * maintained by human infection - lives on clothing * Presentation similar to TBRF with recurrent febrile episodes - blood smear shows organisms * Treatment is tetracycline, doxycycline, penicillin erythromycin * Prevention depends of removing and washing the clothes
36
Lyme disease (Lyme borreliosis)
* • First described in 1977 by Dr. Allen Steere - an outbreak of arthritis among children living in Lyme, CT * A Borrelia was isolated from Ixodes scapularis ticks by Willy Burgdorfer in 1982 - called B. burgdorferi - found to be the causative agent • Currently, the most common vector-borne infection in the U.S.
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B. burgdorferi
• Multiple strains of B. burgdorferi but only one causes disease in North America - B. burgdorferi sensu stricto * Obligate intracellular parasite * In the tick mid-gut, it is dormant and expresses OSP-A * After a mammalian blood meal, OSP-C and ViSE are expressed
38
B. burgdorferi Pathogenesis and Immunity
• In the mammalian host, OSP-C is down-regulated and ViSE is up-regulated - ViSE undergoes antigenic variation • The organism migrates to the skin and disseminates widely - by attaching to various host proteins, including plasminogen and fibrinogen receptor * Host damage shows inflammation around vasculature * Adaptive and innate immunity controls active infection - but the organism may survive for prolonged periods in anatomic niches
39
Lyme Disease
• In the U.S., transmitted principally by two species of hard-bodied Ixodes ticks: - I. scapularis (NE and mid-west) - I. pacificus (west coast) - different ticks and Borrelia species in Europe and Asia • Highest risk of infection is late spring and summer - usually due to bite of nymph form
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Tick Life Cycle
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Life cycle of Ixodes scapularis and Borrelia burgdorferi
42
Lyme Disease Epidemiology
• \>30,000 cases reported annually in U.S. - actual infections perhaps 10-fold higher • Most cases are reported from the NE and upper Mid-West - relates to avidity of ticks for humans - rate of tick infection • Epidemic related to - return of woodlands - increase in deer and mouse population - suburbanization bringing people close to ticks
43
Lyme Disease Clinical Presentation
• Divided into three stages - Early Stage 1 • Rash at site of tick bite - Early Stage 2 * Hematogenous spread * Neurologic and cardiac complications - Late disease • Arthritis
44
Lyme Disease Early Disease Stage 1
• Expanding macular or papular rash with outer border and sometimes central necrosis - called erythema migrans (EM) - occurs at site of bite 3-30 days after * bite often unnoticed * Most common in thigh, groin or axilla
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Lyme Disease Early Disease Stage 2
• Hematogenous spread days to weeks after onset of EM - may be accompanied by secondary EM * Headache, neck stiffness, fever, chills, arthralgias, fatigue * Symptoms tend to abate * Without treatment, may be complicated after several weeks by - Neurological abnormalities (15%) * Bell’s palsy (often bilateral) * Polyradiculoneuropathy * CSF pleocytosis - Carditis (8%) • fluctuating AV heart block • LV dysfunction less common
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Lyme Disease Late Disease Stage 3
* Without antibiotic therapy, 60% develop arthritis * Occurs weeks to years after initial infection * Intermittent, large joints - especially knees - lasts weeks to months - synovitis with ~25,000 cells/µL • Most respond to antibiotic therapy - some are antibiotic-refractory • likely not infectious but autoimmune
47
Lyme Disease Diagnosis
* Observation of EM for early localized disease is diagnostic * Specific tests required for other stages * Culture is difficult and not routinely done * Reliance has been on serology - complex and difficult to interpret
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Serological testing for Lyme disease
• Problems - may be negative early in infection - subsequently remains persistently positive • does not distinguish between active and inactive infection - a positive Lyme serology doesn’t mean that the symptoms are due to Lyme disease • Testing should only be done where there is a high clinical likelihood of active Lyme disease - appropriate exposure history - signs and symptoms suggestive of Lyme disease
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Treatment of Lyme borreliosis
• Erythema migrans (EM) - Doxycycline po 100 mg bid x 14 days • avoid in pregnant women and children - alt: amoxicillin, cefuroxime, erythromycin • Early disseminated infection - As in EM x 21 day • Arthritis or 1° & 2° heart block - As in EM x 30-60 days - IV ceftriaxone 2 gm daily x 14-28 days • Neuroborreliosis or 3° heart block - IV ceftriaxone x 28 days
50
Lyme disease and chronic fatigue syndrome
* A syndrome of persistent fatigue, malaise, body aches, and difficulty concentrating has been ascribed to Lyme disease * This has led to use of intravenous antibiotic therapy for months * Studies have found no improvement with prolonged antibiotics nor has there been evidence of persistent Borrelia infection
I & I Part III
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