infectious disease board review dave fitzhugh, md june 16, 2009
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Infectious Disease Board Review
Dave Fitzhugh, MD
June 16, 2009
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Bacterial meningitis
• Strep pneumo is most common cause in US (47%), with 19-26% mortality
• Often develops in conjunction with PNA, otitis media, mastoiditis, endocarditis or s/p head trauma
• All children (and adults >65) should be vaccinated at this point
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Meningococcemia
• #2 cause of bacterial meningitis in US• Typically, kids/young adults• Pts with complement deficiencies (C5-C9) at
increased risk• Vaccine available, typically only high risk
population (college dorm residents, asplenia, travellers, microbiologists)
• Petechial rash which can progress to purpura fulminans, indicating DIC/sepsis
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Other causes of meningitis
• Listeria – associated with GI portal of entry (raw vegetables, milk, cheese, processed meats)
• GBS – typically in neonates. In adults with DM, EtOH, HIV
• Gram negative – Klebsiella, E coli, serratia, Pseudomonas typically Nsrg pt or head trauma
• Haemophilus – rare now given childhood vaccine• Staph aureus – usually Nsrg or head trauma, but
also with DM, EtOH. Coag neg staph with CSF shunt
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Meningitis Dx
• CT prior to LP if seizure, papilledema, AMS, focal neurological deficit, h/o CNS dz, immunocompromised
Bacterial Viral TB Crytpo
WBC count
1000-5000 50-1000 50-300 20-500
Diff PMN Lymph Lymph Lymph
Glu <40 >45 <45 <40
Pro 100-500 <200 50-300 >45
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Meningitis Tx
• Empiric therapy if delay in LP
• Consider adjunctive dexamethasone in suspected or proven S pneumo meningitis (given only with or just prior to 1st dose abx)
• Target Abx if you have Gram stain information
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Empiric Meningitis TherapyAge 2-50 S. pneumo, N.
meningitidisVanc +3rd gen cephalosporin
Age >50 S. pneumo, N. men, Listeria, GN bacilli
Vanc +3rd gen cephalosporin + ampicillin
Basillar skull fracture S. pneumo, H.influ, group A strep
Vanc + 3rd gen cephalosporin
Post-NSG or trauma Staph, Gram negative: Pseudomonas
Vanc + either ceftaz, cefepime, or meropenem
CSF shunt Staph aurues, CONS, GNR
Vanc + either ceftaz, cefepime, or meropenem
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Review Questions
• MKSAP 16
• MKSAP 33
• MKSAP 14
• MKSAP 97
• MKSAP 19
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Syphilis
• Primary syphilis presents as a painless ulcerative chancre approx 3 weeks after exposure to Treponema pallidum
• Primary lesion usually resolves and progresses to secondary syphilis 2-8 weeks later
• Secondary syphilis is characterized by hematogenous dissemination in the skin, liver, lymph nodes usually resolves and progresses to latent, tertiary or neurosyphilis
• Latent syphilis is asymptomatic infection with positive serology • Tertiary syphilis includes CNS, cardiovascular and gummatous disease
involving skin, soft tissues, bones, and internal organs. • Neurosyphilis now most often seen w/ HIV, involves CNS, meninges,
vascular sxs w/ meningitis, CN palsies, tabes dorsalis
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Secondary syphilis
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Syphilis Dx
• Darkfield microscopy• Nonspecific tests: rapid plasma reagin (RPR) and Venereal
Disease Research Laboratory (VDRL) used as screening tests, reported as titer and followed for response to tx
• Specific treponemal tests: fluorescent treponemal antibody absorption (FTA-ABS) assay and the microhemaglutination assay (MHA-TP) used as confirmatory tests
• False positive nonspecific and treponemal tests. FP treponemal tests: SLE, HIV, ESLD, IVDU
• False negative occur prior to development of abs
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Syphilis Tx
1. Primary, secondary or early latent (less than 1year) -Benzathine PCN G 2.4million units IM x1 -PCN allergic, nonpregnant: doxycycline 100mg bid x14
days -In pregnancy, PCN desensitization 2. Late latent, tertiary or unknown duration-Benz PCN G, 2.4 million units IM q week x3 weeks-PCN allergic: doxycycline 100mg bid x4 weeks3. Neurosyphilis-PCN G 3-4 million units IV q4hrs x10-14 days
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Relevant question
• MKSAP 22
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Actinomycosis
• Subacute-to-chronic infection caused by filamentous, gram-positive, non-acid fast, anaerobic bacteria.
• Part of normal oral flora• Infection is characterized by suppurative and
granulomatous inflammation with abscess and sinus tract formation with sulfur granules
• Most often results in cervicofacial infection 50% cases• Presents in pts predisposed to facial infection - dential caries, gingivitis, tooth extractions -underlying DM, immunosuppression, oral malignancies or
radiation
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Actinomycosis
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Antibiotic Ppx for endocarditis• No longer indicated - bicuspid aortic valve, acquired aortic or mitral
valve disease (including MVP with regurgitation and those who have undergone prior valve repair), and hypertrophic cardiomyopathy with latent or resting obstruction.
• Current recommendations –– Prosthetic heart valves, including bioprosthetic and homograft valves. – A prior history of IE. – Unrepaired cyanotic congenital heart disease, including palliative shunts and
conduits. – Completely repaired congenital heart defects with prosthetic material or
device, whether placed by surgery or by catheter intervention, during the first six months after the procedure.
– Repaired congenital heart disease with residual defects at the site or adjacent to the site of the prosthetic device
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Relevant question
• MKSAP Cardiology 32
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Toxic Shock Syndrome
• Caused by S. aureas and group A strept• Fever, n/v/diarrhea, rash, hypotension (latter
required for dx)• Caused by exotoxins that act as superantigen (i.e.,
interact directly with MHCII on APC and crosslink TCR -> massive cytokine release)
• Tx: Clindamycin (reduces toxin synthesis and shedding) + Vanc, unless known MSSA
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Botulism• Caused by C. botulinum toxin, gram pos spore producing rod
– Food borne: usually involving home canned fruit/veg or fish– Wound – typically IVDU– Infant - association with raw honey, but this is minor cause at best. More
likely environmental dust with C. botulinum spores
• Sx: cranial neuropathies with symm descending weakness. Five D’s: diplopia, dysphonia, dysarthria, dysphagia, descending paralysis
• Tx: supportive, including mechanical ventilation prn.• Antitoxin: trivalent for adults, botulism immune globulin for
infants. Of note, pentavalent antitoxin available only within the DoD.
• Abx: unproven, though PenG widely used in wound botulism
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Relevant question
• MKSAP 73
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Traveler’s/Food borne Diarrhea• Most is E coli, usually ETEC (remember HUS). E coli
usually self-limited• Other bacterial pathogens
– Salmonella – meat/poultry– Shigella – severe sx, salads/milk/dairy– Vibrio – shellfish– Campylobacter – poultry
• Viral– Norwalk – cruise ship– Rota – peds exposure– Hep A
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Relevant questions
• MKSAP 90, 97
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OI ppx in HIV
• Pneumocystis – CD4 < 200– Bactrim, dapsone, atovaquone
• Toxo – CD4 < 100– Same as above
• MAC – CD4 < 50– Azithro
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Initiation of HAART
Aids def illness
Any value Any value treat
Asx <200 Any value treat
Asx 200-350 Any value Weigh pros/cons
Asx > 350 >100,000 ?
Asx >350 <100,000 Defer tx
CD4 VL Tx recommendationsClinical cat
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HIV-related questions
• MKSAP 111, 122, 20, 27, 7
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The End
Natalie says, “Good luck on the boards, I’ll be at the beach.”