Infectious Disease Board Review

1. Infectious Disease Board Review Dave Fitzhugh, MD June 16, 2009

2. 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

3. 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

4. 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

5. Meningitis Dx • CT prior to LP if seizure, papilledema, AMS, focal neurological deficit, h/o CNS dz, immunocompromised

6. 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

7. Empiric Meningitis Therapy

8. Review Questions • MKSAP 16 • MKSAP 33 • MKSAP 14 • MKSAP 97 • MKSAP 19

9. 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

10. Secondary syphilis

11. 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

12. 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 weeks 3. Neurosyphilis -PCN G 3-4 million units IV q4hrs x10-14 days

13. Relevant question • MKSAP 22

14. 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

15. Actinomycosis

16. 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

17. Relevant question • MKSAP Cardiology 32

18. 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

19. 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

20. Relevant question • MKSAP 73

21. 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

22. Relevant questions • MKSAP 90, 97

23. OI ppx in HIV • Pneumocystis – CD4 < 200 • Bactrim, dapsone, atovaquone • Toxo – CD4 < 100 • Same as above • MAC – CD4 < 50 • Azithro

24. Initiation of HAART Clinical cat CD4 VL Tx recommendations

25. HIV-related questions • MKSAP 111, 122, 20, 27, 7

26. The End Natalie says, “Good luck on the boards, I’ll be at the beach.”