Infectious Disease Board Review

Dave Fitzhugh, MD

June 16, 2009

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

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

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

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

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

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

Review Questions

• MKSAP 16

• MKSAP 33

• MKSAP 14

• MKSAP 97

• MKSAP 19

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

Secondary syphilis

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

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

Relevant question

• MKSAP 22

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

Actinomycosis

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

Relevant question

• MKSAP Cardiology 32

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

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

Relevant question

• MKSAP 73

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

Relevant questions

• MKSAP 90, 97

OI ppx in HIV

• Pneumocystis – CD4 < 200– Bactrim, dapsone, atovaquone

• Toxo – CD4 < 100– Same as above

• MAC – CD4 < 50– Azithro

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

HIV-related questions

• MKSAP 111, 122, 20, 27, 7

The End

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