Internal Medicine_Infectious diseases_13 Flashcards
Bacteria_Lyme disease, Leptospira, and Syphilis
What type of bacterium is Borrelia burgdorferi?
A spirochete bacterium (spiral-shaped).
How is Lyme disease transmitted?
Through the bite of the blacklegged tick (Ixodes scapularis).
What serves as the primary reservoir for Borrelia burgdorferi?
The white-footed mouse, which hosts larval and nymphal ticks.
What is the obligatory host of adult Ixodes scapularis ticks?
The white-tailed deer.
In which region of the United States is Lyme disease predominantly found?
Northeastern and MidwestUnited States.
What stains are used to visualize Borrelia burgdorferi?
Wright’s stain and Giemsa stain.
What are the differentials for Lyme disease?
Anaplasmosis, babesiosis, influenza, COVID-19.
EM DDx= cellulitis, nummular eczema, insect bite hypersensitivity reaction, tinea corporis (ringworm), granuloma annulare.
What is the hallmark rash of early localized Lyme disease (Stage 1)?
Erythema migrans, a “bull’s-eye” rash expanding beyond 5 cm.
Absent in 20% of cases.
What flu-like symptoms are associated with Stage 1 Lyme disease?
Fever, chills, arthralgias.
First 30 days of transmission.
What antibiotic is recommended for early-stage Lyme disease?
PO Doxycycline (alternative: Amoxicillin) is used for 14 to 21 days.
Use this treatment regime for mild Lyme disease
(EM or isolated 7th cranial nerve palsy)
How much longer does Stage 2 Lyme disease occur?
1 to 3 months after infection.
What unique skin manifestation occurs with Stage 2 Lyme disease?
Multiple EM rashes.
What cardiac complication is seen in early disseminated Lyme disease (Stage 2)?
Myocarditis leading to A-V heart block (degrees 1 to 3).
Palpitations, Chest pain, dizziness on exertion, syncope.
Differential diagnosis: infectious or autoimmune carditis, Parvovirus, HHV-6, syphilis, sarcoidosis, MI.
What neurological complications occur in Stage 2 Lyme disease?
Peripheral Neuroborreliosis:
- Bilateral Bell’s palsy.
- Radiculoneuritis (radicular pain, sensory and motor changes along dermatomes)
Central Neuroborreliosis:
- Meningitis (gradual onset, waxing/waning headache with fever, nuchal rigidity, photophobia). Diagnosis of Lyme meningitis is based on high pre-test probability, clinical signs and symptoms, and CSF serology.
Differential diagnosis: CVA, GBS, tumors, sarcoidosis, radiculopathy.
When is CSF positive for Lyme serology diagnostic for Lyme disease?
When the CSF titer is higher than serum.
Note: a negative CSF serology does not rule out Lyme disease.
What diagnostic tests are used for Lyme disease?
ELISA followed by confirmatory Western blot.
When does serology become diagnostically significant for Lyme disease?
During Stage 2.
Lyme disease is usually diagnosed clinically (Erythema migrans is pathognomonic).
A 2-step serologic testing can be used for confirmation without Erythema migrans:
1) ElA screen for IgM/IgG
2) if positive –> EIA or western blot for IgG
Migratory polyarthritis (migratory myalgias and transient arthritis) is a symptom of stage ___ Lyme disease?
2
What symptoms characterize late disseminated Lyme disease (Stage 3)?
Encephalopathy and chronic inflammatory arthritis.
Lyme arthritis presents as an inflammatory monoarticular or asymmetric oligoarticular arthritis, most commonly in the
Knee.
- Arthritis is the most common complication of late Lyme disease.
- diagnosis requires history and physical exam findings.
- synovial fluid analysis typically reveals ~25,000 WBCs/mm3 with negative gram stain/culture
- positive 2-step serology is also needed for diagnosis.
Differential diagnosis: septic arthritis, gout, pseudogoat, Baker’s cyst, reactive arthritis, autoimmune (RA, SLE).
Treat with 28 days of doxycycline.
The symptoms of Stage 3 Lyme encephalopathy vs subacute encephalitis (rare) are _______ .
The symptoms of Stage 3 Lyme encephalopathy vs subacute encephalitis (rare) are varied:
Chronic mild-moderately impaired memory/concentration, fatigue, mood changes (depression, paranoia).
Multi-step process for diagnosis:
- Neuropsych evaluation to detect for dysfunction
- High pre-test probability (exposure to tick or physical exam findings)
- 2-step serology (positive CSF Lyme antibodies)
What is the differential diagnosis for Stage 3 Lyme encephalopathy?
Post-treatment of Lyme Disease, Fibromyalgia, chronic fatigue syndrome, Alzheimer’s dementia, Depression, Neurosyphilis.
What antibiotic is used for late-stage or severe Lyme disease?
IV Ceftriaxone.
Then PO Doxycycline (once symptoms improve), for a total of 28 days of antibiotics.
Used when heart or the CNS is involved.
Monitor heart with telemetry.
What is the prophylaxis recommendation for a tick bite of less than 36 hours?
Remove the tick; no prophylaxis needed.
What is the prophylaxis recommendation for a tick bite longer than 36 hours?
Remove the tick and administer doxycycline.
if timing (36 hours) is unknown, the tick is engorged.
must have 20% rate of infection.
must take doxycycline within 72 hours of tick removal.
Can pregnant patients take doxycycline?
No.
What antibiotic is used for Lyme disease in pregnant patients or children (less than 8 years old?
Amoxicillin and cefuroxime (2nd generation β-lactams) can be used to treat Lyme disease in children and pregnant women.
What is a common complication following the treatment of Lyme disease?
Post-treatment Lyme disease syndrome:
Chronic non-specific symptoms that include fatigue, diffuse ache, cognitive difficulties.
Usually resolves in 6-12 months.
What is the causative agent of louse-borne relapsing fever (LBRF)?
Borrelia recurrentis, a spirochete bacterium.
What is the morphology of Borrelia recurrentis?
Spiral-shaped spirochete.
How can Borrelia recurrentis be visualized?
Dark field microscopy
Or
Wright-Giemsa stain on peripheral blood smears.
What mechanism allows Borrelia recurrentis to evade the immune system?
Antigenic variation, frequently changing surface proteins.
What are the risk factors for developing louse-borne relapsing fever?
Crowded living conditions, war, famine, and refugee camps.
What is the vector for Borrelia recurrentis?
The human body louse (Pediculus humanus corporis).
What is the reservoir host for Borrelia recurrentis?
Humans.
How is Borrelia recurrentis transmitted?
Through the bite of an infected louse or crushing a louse on the skin.
Infected lice can transmit Borrelia recurrentis through a bite or when someone crushes a louse by scratching their skin or rubbing their eyes.
What are the main symptoms of louse-borne relapsing fever?
Cyclic high fever, headache, chills, sweats, muscle and joint pain, nausea.
What is the “crisis phase” in louse-borne relapsing fever?
Severe fluctuations in temperature, heart rate, and blood pressure following a febrile episode.
What are the two phases of the crisis in LBRF?
“Fire Frenzy” – hot symptoms such as hyperthermia, tachycardia, hypertension.
“Cold Crash” – cold symptoms such as hypothermia and hypotension.
What is the causative agent of leptospirosis?
Leptospira interrogans, a spirochete bacterium.
What is the morphology of Leptospira interrogans?
A spiral or “question mark” shape (hook-shaped ends)
Observable under dark-field microscopy.
What are the typical symptoms of leptospirosis?
Nonspecific symptoms:
fever
flu-like symptoms (mylagias)
headache
What is the severe form of leptospirosis called?
Weil’s disease (icterohemorrhagic leptospirosis) is a severe and potentially life-threatening manifestation of leptospirosis.
Proressive multi-system illness.
Characterized by fever, jaundice, conjunctival suffusion, anemia, renal failure (azotemia), and respiratory distress.
Which non-treponemal and treponemal tests are often performed to confirm the diagnosis and monitor treatment?
Non-treponemal tests which are used for screening are VDRL or RPR.
These tests detect antibodies against cardiolipin (non-specific antigens).
Often used to monitor treatment response (titers increase with active disease and will decline with treatment).
Treponemal-specific tests which are used for confirmatory test are FTA-ABS and TPPA. These tests detect antibodies specific to Treponema pallidum antigens. Remain positive for life, even after treatment.
What conditions can cause false-positive VDRL or RPR test results?
Pathogens:
Viral infections (Mononucleosis from EBV and Hepatitis)
Lyme disease
Leprosy
Malaria
Conditions:
Pregnancy
Autoimmune issues:
Rheumatoid factor
Systemic lupus erythematosus
Antigens:
IV drug use
Medications like chlorpromazine and procainamide
What are the characteristics of primary syphilis?
Localized
Painless, ulcerative, nonexudative, chancre.
Chancre typically appears at the site of infection.
Heals in a few weeks without treatment.
Regional lymphadenopathy.
During the primary phase of syphilis, use _________ for screening.
Use fluorescent or dark-field microscopy to visualize treponemes in fluid from chancre.
What are the symptoms of secondary syphilis?
Systemic disease with constitutional symptoms
(fever, malaise, flu-like symptoms).
Diffuse lymphadenopathy.
Arthritis, hepatitis, glomerulonephritis.
Widespread maculopapular/pustular rash.
White/gray wart-like plaque lesions on mucosa or genitals
(called condyloma lata).
Alopecia.
What lymph nodes are commonly implicated with
epitrochlear nodes.
The widespread maculopapular/pustular rash seen with secondary syphilis commonly affects what part of the body?
often on limbs, palms and soles.
What is the unique wart-like skin lesion seen with secondary syphilis?
condyloma lata.
Gummas from tertiary syphilis can be present on the skin and _______ .
Bone
What MSK finding is associated with tertiary syphilis?
The knee joint is the most commonly affected joint in tertiary syphilis that leads to a Charcot joint (neuropathic arthropathy).
Diagnosis:
X-rays reveal joint destruction, subluxation, and fragmentation of bone.
A history of untreated syphilis and neurological symptoms consistent with tabes dorsalis can support the diagnosis.
What sort of steppage gait is associated with sensory ataxia?
Stomping Gait.
Patient will slam foot to help localize or feel due to the lack of proprioception (patients are Romberg positive).
Broad-based Ataxia.
What are the early features of congenital syphilis?
Fever
Rhinitis
Jaundice
Maculopapular rash and condyloma lata
Sensorineural Hearing Loss.
What are the linear scars at angle of mouth in a newborn with congenital syphilis?
Rhagades (“Parrot lines”)
Scars at the corners of the mouth due to healed mucocutaneous fissures.
What are the signs of congenital syphilis after 2 years old?
- Frontal bossing
- Saddle nose (collapsed nasal bridge).
- Short maxilla
- Saber shins (anterior tibial bowing).
- Hutchinson’s teeth (blunted, pegged incisors).
- Mulberry molars (enamel growth on molar cusps).
- Gummas
- Intellectual disability
- Sensorineural hearing loss (CN VIII deafness)
