Tag Archives: Infectious Disease

Varicella Zoster – 10/18/17

Primary infection – chicken pox (lesion at varying stage on the trunk, face, and extremities)
Reactivation – shingles (painful, unilateral rash in a restricted dermatome)

Clinical manifestations – 1) Rash – most common location is thoracic and lumbar dermatomes
2) Acute neuritis – 75% of patients have pain/burning/throbbing prior to onset of rash

Complications in immunocompetent hosts – post-herpetic neuralgia (7.9%), ocular complications (1.6%),, meningitis (0.5%), oticus (0.2%)

Disseminated if > 3 contiguous dermatomes or 2 dermatomes on separate parts of the body

Diagnosis for encephalitis/meningitis – elevated WBC with lymphocytic predominance, elevated protein, positive VZV PCR or IgM

Treatment: IV acyclovir

Vaccines: Age > 60 give live vaccine unless immunosuppressed
VZIG – give to exposed pregnant or immunosuppressed patients

Tuberculosis 07/18/2017

  • Definitions
    • Primary Tuberculosis
      • 1-5% of cases
      • Infection directly after inoculation by airborne particles
      • Symptoms
        • Fever (70%)
        • Pleuritic chest pain (25%)
      • 90% of immunocompetent patient enter latent state
        • 10% develop TB pneumonia or progress to distant sites
          • Usually those with poor immune responses (HIV, CKD, DM2, immunosuppressants)
    • Latent TB (LTBI)
      • Non-contageous, quiescent state
      • Only manifestation is positive PPD or Quantiferon (IGRA – interferon gamma release assay)
    • Reactivation TB
      • 90% of adult cases in non-HIV patients
      • Classic symptoms
        • Cough, fatigue, fever, night sweats, weight loss
          • Sometimes hemoptysis –> usually in the setting of cavitary disease
  • Risk Factors
    • For exposure
      • Foreign born
      • Homeless
      • Incarceration
      • Health care workers
    • For reactivation
      • Immunocompromised
        • HIV, malignancy, steroids, DM2
      • Prior untreated or inadequately treated disease
      • Lifetime risk for reactivation
        • Immunocompetent -> 10% lifetime risk
        • Immunocompromised -> 10% per year
  • Physical finding –> non-specific and usually absent in mild-moderate disease
  • Labs
    • Sputum samples
      • AFB smear/culture
        • Obtained by coughing vs induced (inhalation of hypertonic saline from nebulizer)
        • 3 specimens at least 8 hours apart
        • Most rapid and inexpensive test
          • 45-80% sensitive
        • AFB positive smear can represent non-tuberculosis mycobacteria (NTM) as well
          • Must confirm with culture and nucleic acid amplification
      • Nucleic acid amplification (NAA) tests
        • Xpert MTB/RIF Test
          • Detects MTB DNA and rifampin resistance mutations
            • But cannot provide specific sequence information
          • Smear positive sample –> 95% sensitive, 98% specific
          • Smear negative sample –> 80% sensitive, 95% specific
          • Negative Xpert cannot exclude active TB!
          • Watch out for false positives from recent previously treated infection
      • Sequencing assays
        • Sequencing assays provide specific sequence mutations and predicts drug resistance with greater accuracy
          • Not approved by FDA; Remains investigational
    • Tuberculin Skin Test (TST) and quantiferon
      • Only used to diagnose latent TB infection, not active TB!
      • Positive result supports Dx; negative result cannot be used to rule out
  • Imaging
    • CXR
      • Primary TB
        • Hilar and peritracheal lymphadenopathy (65%)
        • Small homogeneous lobar vs perihilar infiltrates (30%)
        • Pleural effusion (30%)
      • Reactivation TB
        • Normal hosts
          • apical-posterior infiltrates (85%)
            • MTB prefers higher O2 tensions in the apical lung areas
            • poor lymphatic flow in apices results in poor organism clearance
          • cavitation
        • Immunocompromised (AIDS) Pts –> Atypical findings
          • Diffuse disease (military)
          • Mid/lower lung zones
          • Hilar and mediastinal LAD
        • CT
          • More sensitive than plain CXR for early or subtle parenchymal and nodal disease
  • Management
    • General approach
      • 6 months of treatment in 2 phases
        • Intensive phase –> 2 months
          • First line drugs –> “RIPE”
            • Rifampin, INH, pyrazinamide, ethambutol
        • Continuation phase –> 4 months
          • Rifampin
          • INH
    • Watch out for hepatotoxicity!
      • Rifampin, INH, and pyrazinamide are all associated with hepatotoxicity
    • All pts in INH should get vit B6
    • Avoid fluoroquinolones in suspected TB cases!
      • Avoid resistance from TB monotherapy

Endocarditis – 7/17/17

Risk Factors for developing Endocarditis

  • Dental procedure that penetrates the gums
  • Prior endocarditis
  • Prosthetic valves
  • IVDU
  • Immunosuppression

Common Organisms

  • Staph
  • Strep
  • Enterococcus
  • HACEK

Symptoms/Signs

  • Fever (most common)
  • Murmur
  • Splinter hemorrhages
  • Janeway lesions (non-tender erythematous macules on palms and soles)
  • Osler nodes (tender, subcutaneous nodules, on pads of fingers and toes)
  • Roth spots (exudative edematous hemorrhages in the retina)

Indications for surgical repair

  • New heart failure
  • Perivalvular abscess/extension
  • Conduction abnormalities
  • Persistent bacteremia
  • Prosthetic valves
  • Septic emboli
  • Large vegetation > 10-15 mm
  • Resistant organisms

 

 

 

AM Report 7/10/17 – Falciparum Malaria

  • Most dangerous form of malaria – highest number of deaths
  • Transmitted by the female Anopheles mosquito (females feed on blood, males feed on nectar)
  • Most commonly seen along in Southeast Asia, Latin America, and Africa
  • Two phases – liver and RBC phase
  • Symptoms:
    • Temperature paroxysms (alternating fevers and chills)
    • Headache
    • Diarrhea
    • Jaundice
  • Considered severe infection if evidence of end organ damage (Falciparum is sticky and can cause ischemia and infarcts as the RBCs get more viscous!)
    • Cerebral malaria – ischemia/infarcts in the brain
    • ARDS
    • Nephropathy
    • Hypotension
  • Physical exam findings:
    • Hepatomegaly (from the parasite replicating in the liver)
    • Splenomegaly (from the spleen taking up the damaged RBCs)
    • Pallor
    • Jaundice and scleral icterus
  • Diagnosis:
    • Thick and thin smears
      • Thick smears give a look at the RBCs in an overall sense to figure out if a parasite is present – are there parasites? If yes, look at thin smear.
      • Thin smears give a closer look at the TYPE of parasite – what type of parasite is it?
    • Rapid detection test – blood test which looks at enzymes on the various parasites to determine the type – only available at certain hospitals
  • Treatment:
    • Start immediately!
    • Determined based on the type of plasmodium, whether the malaria is severe or not, and whether the organisms are from an area with high resistance
    • Use 2-3 medications for treatment – consult ID immediately once you have a suspicion!
  • Prophylaxis
    • Given to anyone going to an endemic area – start a few weeks before travel, continue during travel, and continue for some time after returning depending on the medication
    • Wear long sleeves and pants
    • Use DEET