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Infectious Disease Board Review


A neg latex agglutination test for staph pneumoniae r/o this organism as a cause ... E The sensitivity of the latex agglutination (LA) test for the S. ... – PowerPoint PPT presentation

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Title: Infectious Disease Board Review

Infectious Disease Board Review
  • Kathryn Robinett
  • 6/11/07

What We Missed on ID
  • Recognize and Treat Pinworms
  • Management of FUO
  • Presentation and Treatment of Bacterial Meningitis

Enterobius vermicularisPinworms
  • Most common helminth infection in the USA
  • Primary symptom is perianal itching worse at
  • Worms live in bowel lumen and females migrate to
    anus to lay up to 10,000 immature eggs which
    become infective w/in 6hrs
  • Hand to mouth passage highly infective

Enterobius vermicularisPinworms
  • Pt do not have eosinophilia or elevated IgE
  • Stool is often negative because eggs are not
    released into the lumen
  • Dx w/ scotch tape to anus first thing in the
    morning and look for eggs 3 consecutive days
    90 sensitivity
  • Treat pt and family w/ mebendazole 100 mg x 1 and
    then again in 2 weeks.

Pinworm Eggs
Pinworm eggs are flattened asymmetrically on one
side, ovoid, approximately 55 mm x 25 mm in size
Question IV-41
  • A migrant worder is seen in the clinic for
    progressive weight loss and occasional diarrhea.
    A helminthic infection is strongly suspected.
    The patient collects a stool sample and it is
    submitted for lab analysis. Cultures are ngative
    and stool OP are not seen. A CT w/ oral and IV
    contrast is unremarkable.

Question IV-41
  • Which of the following statements is most
  • A minimum of three stools should be obtained to
    examine of OP to r/o helminthic infection
  • The pt can be reassured that his symptoms are not
    due to a helminthic infection
  • All submitted samples would be from sequential
    bowel movements
  • Stool analysis w/ not be affected by ingestion of
    oral contrast
  • Empirical albendazole is indicated

Answer IV-41
  • A- In the evaluation o helminthic infection,
    stool analysis is the mainstay of diagnosis.
    Stool should be collected in clean cardboard
    containers on alternate days for a minimum o 3
    samples b/c of the cyclic nature o parasitic
    shedding. Oral contrast and antidiarrheal agents
    can change the consistency of feces, making lab
    diagnosis more challenging. At this point there
    is no urgent indication for empirical therapy,
    which should be avoided until diagnosis is made.

Definition of a FUO
  • Fever 38.3 on at least 3 occasions
  • Duration of fevers for at least 3 weeks
  • Uncertain diagnosis after one week of study in
    the hospital
  • (Some exclude immunocompromised and neutropenic

Categories throughout the Ages
  • Infections
  • Malignancies
  • Collagen-vascular diseases (i.e. vasculitis,
    rheumatoid arthritis)

Taking a History of a FUO
  • Travel
  • Nocturia could suggest prostatitis
  • Jaw Claudication giant cell arteritis
  • Changes in behavior granulomatous meningitis
  • Fever Curve
  • Antipyretics

Taking a History of a FUO
  • Tick Exposure
  • Mosquito bits
  • Pets

Diagnostic Testing for a FUO
  • Lab Tests
  • Chem 10 and LFTs
  • CBC w/ diff
  • Hepatitis serology if LFTs abnormal
  • Urinalysis and Urine culture
  • CXR
  • HIV screening
  • ESR, LD
  • PPD
  • RF, ANA

Diagnostic Testing for a FUO
  • CT scan of Abdomen even if no localizing symptoms
    (this has replaced ex-lap which use to be done
  • Temporal artery biopsy (age 65)

Consider Biopsy in FUO
  • Bone marrow for malignancy or miliary TB
  • Liver for miliary TB, granulomatous hepatitis,
  • Lymph node for malignancy, infection
  • Temporal Artery
  • Pleural or pericardial for extrapulmonary TB
  • But whatever you do . . . . . . . .

Try NOT to treat empirically!!!
  • (Unless unstable)

The Phrase to Remember
  • It is more common to have a rare presentation of
    a common disease than a rare disease!

  • What is the most common infectious cause of
  • Fever of Unknown Origin in the United States?

Tuberculosis w/ only 50 of PPDs being positive
Most Common Infections
  • Tuberculosis
  • Abscesses usually pelvic or abdominal followed
    by pyogenic liver abscesses
  • Osteomyelitis vertebral often does not have
    localizing symptoms
  • Endocarditis 2-5 never have positive blood
    cultures more if the pt got abx

Most Common Malignancies
  • Lymphoma Non Hodgkins
  • Leukemia
  • Renal Cell Carcinoma (20 of cases present w/
  • Hepatocellular Carcinoma
  • Atrial Myxoma (rare but 30 present w/ fever
    also can have arthralgias and chills)

Collagen Vascular Disease
  • Juvenille Rheumatoid Arthritis in the young
  • Giant Cell Arteritis in older patients (usually
  • Polyarteritis Nodosa
  • Takayasus arteritis (Japanese)
  • Wegners granuloma
  • Mixed Cryoglobulinemia
  • Adult Onset JRA

Drug Fever
  • Antimicrobials (sulfonamides, penicillins,
    nitrofuratoin, antimalarials)
  • H1 and H2 blocking antihistamines
  • Antiepileptic drugs (barbiturates and phenytoin)
  • Iodides
  • Nonsteroidal antiinflammatory drugs (including

Drug Fever
  •  Antihypertensive drugs (hydralazine)
  •  Antiarrhythmic drugs (quinidine, procainamide
  • Antithyroid drugs

Outcomes of FUO
  • Depends heavily on the underlying diagnosis
  • Of 199 pts admitted for FUO 61 were d/cd w/o a
    diagnosis (i.e. real fuo)
  • 12 were eventually given a diagnosis
  • 31 became symptom free w/o sequelae during
    hospitalization or shortly there after
  • 18 had months to years of recurrent fever, ten of
    whom were eventually cured
  • 4 were treated w/ corticosteroids
  • 6 required NSAIDS intermittently
  • 6 died but only 2 were thought to have been
    secondary to their FUO

Bacterial Meningitis Physical Findings
  • Suspect in patient w/ fever, headache, altered
    mental status, meningismus
  • Brudzinskis Sign
  • Flexion of the hips and knees w/ passive flexion
    of the neck can be a sign of meningeal
  • Kernigs Sign
  • Pain and increased resistance to extending the
    knee when bilateral suggests meningeal irritation

Common Causes of Bacterial Meningitis
  • Most Common
  • Strep pneumoniae
  • 2nd most common
  • Neisseria meningitidis
  • Group B (B for Bad) is the main culprit
  • Vaccines for Groups A, C, Y and W-135
  • 3rd Most Common
  • Listeria monocytogenes (esp in neonates and 60
    years old)

  • Always treat empirically if either waiting for
    CSF results or if LP not immediate
  • 3rd Generation Cefphalosporin (Ceftriaxone/Cefotax
    ime) Vancomycin Dexamethasone (add ampicillin
    if 60 yrs)

Ques IV-49
  • A 19 y.o. college student is brought to the ED by
    friends from his dorm for confusion and altered
    mental status. They state that many colleagues
    have URIs. He does not use EtOH or illicit
    drugs. His physical is notable for confusion,
    fever and rigid neck. CSF exam reveals a white
    blood cell count of 1800 cells/uL w/ 98
    neutrohils, glucose of 35 mg/DL and protein of
    100 mg/dL.

Ques IV-49
  • Which of the following antibiotic regimens is
    most appropriate as initial therapy?
  • Ampicillin Vancomycin
  • Ampicilling gentamycin
  • Ceazolin doxycycline
  • Cefotaxime Doxycycline
  • Cefotaxime Vancomycin

Ques IV-50
  • In addition to antibiotics, which of the
    following adjunctive therapies should be
    administered to improve the chance of a favorable
    neurologic outcome?
  • A. Dexamethasone
  • B. Dilantin
  • C. Gabapentin
  • D. L-Dopa
  • E. Parenteral nutrition

Antibiotics in Bacterial Meningitis
Ques IV 48
  • A 24 yo college student is brought to the ED by
    friends from his dorm for altered mental status.
    They state that he recently returned from a trip
    to South America and that many colleagues have
    URI. His physical is notable for confusion,
    fever and rigid neck. CSF exam reveals a WBC
    1800 cells/uL w/ 98 neutrophils, glucose o 35
    mg/dL and protein of 100 mg/dL. He is placed on
    empirical treatmetn for meningitis.

Ques IV 48
  • Which of the following statements about the CSF
    exam is true
  • A neg latex agglutination test for staph
    pneumoniae r/o this organism as a cause of the
  • A negative latex agglutination test for neisseria
    meningitidis r/o this organism as a cause of the
  • Meningeal enhancement on MRI is diagnostic of
  • A positive limulus amebocyte lysate assay is
    diagnostic of protozoal meningitis
  • A positive latex agglutination test for s.
    pnaumoniae is diagnostic of S. pneumoniae

Answer IV-48
  • E The sensitivity of the latex agglutination
    (LA) test for the S. pneumoniae is 70-100. The
    LA test for N. meningitides is substantially
    lower at 33-70. Thus, a negative test does not
    r/o disease. The specificity of these tests is
    95-100, and so a positive test is virtually
    diagnostic. MRI will be abnormal in most
    patients w/ bacterial meningitis, but the
    findings of cerebral edema, ischemia and diffuse
    meningeal enhancement are not diagnostic.
    Meningeal enhancement occurs in any disease
    process that increases permeability of the
    blood-brain barrier. The limulus amebocyte
    lysate assay tests for endotoxin and a positive
    test suggests gram negative meningitis.

  • Humoral Immunity Deficiency
  • Cellular Immunity Deficiency
  • Complement Defeciency

Humoral Deficiencies
  • AIDS
  • Multiple Myeloma
  • Asplenia
  • ALL
  • CLL

Humoral Def Infections
  • Encapsulated organisms
  • Pneumococcus
  • Meningococcus
  • Haemophilus influenza
  • Malaria
  • Babesiosis
  • Giardia

Cellular Immunity Deiciency(T-cell Def)
  • AIDS
  • Hodgkin lymphoma if T cell derived
  • T cell variant of ALL
  • Corticosteroids or alkylating agents
  • Post organ transplant

Cellular Immunity Deiciency Infections
  • Fungi (PCP)
  • Listeria monocytogenes
  • Nocardia
  • Mycobacteria
  • CMV
  • HSV
  • Protozoa (Toxoplasma)
  • Helminths (Strongyloides)

Complement Deficiency
  • C2
  • Most common in US
  • Assoc w/ early onset SLE
  • C3
  • Severe bacterial infections
  • C5-9 (late complement def)
  • Encapsulated organisms
  • Esp meningococcemia
  • Check for terminal complement def in pt w/
    meningococcemia b/c 15 will have positive CH50
    or CH100

Quest IV-91
  • A 33 yo man w/ altered mental status is brought
    to the ED by his wife. She tells you he has a
    h.o sickle cell disease and that he has been well
    controlled on hydroxyurea. Two days ago he
    developed upper respiratory symptoms and fever
    that was treated w/ OTC medications. Today he
    became confused andlethargic. His physical is
    notable for BP 75/45 w/ HR 130 and T 40. His
    extremities are warm.

Ques IV-91
  • Blood cultures are most likely to grow which of
    the following organisms?
  • A. Candida albicans
  • B. Pseudomonas aeruginosa
  • C. Staphylococcus aureus
  • D. Streptococcus pneumoniae
  • E. Salmonella typhi

Answer IV-91
  • D Pts w/ SS sickle cell disease are considered
    functionally asplenic by middle childhood. Thus,
    they are at risk for serious infections from
    encapsulated bacteria. 90 of cases of
    overwhelming infections in this pt population are
    due to S. pneumoniae, usually from a pulmonary
    source. Pneumonia in this population may have a
    mortality as high as 45

Ques IV-71
  • A 35 yo IVDA w/ HIV infection is being managed w/
    combination antiretroviral therapy. The patient
    was doing well on his current medical regimen,
    which consists of lamivudine and saquinavir as
    well as methadone, trimethoprim-sulfamethoxazole,
    and fluconazole. Although he has been stable
    clinically of late, efavirenz recently was added
    to his medical regimen in an attempt to decrease
    a rising viral load. After approx 1 week of
    therapy w/ efavirenz, the patient develops
    abdominal cramps, malaise, sweats and anxiety.

Ques IV-71
  • The most likely reason for the patients symptoms
  • Primary efavirenz toxicity
  • Increased fluconazole levels
  • Infection w/ Pneumocystis as a result of
    decreased TMP/SMZ levels
  • Lamivudine toxicity secondary to decreased
    albumin binding
  • Reduced plasma methadone concentration

Answer IV-71
  • E The increase in plasma HIV RNA load is oten
    considered and indication to change therapy , as
    is a failure to achieve an improvement in the CD4
    counts. It is very important to consider
    drug-drug interactions in patients taking
    complicated medical regimens that include
    antiretroviral drugs in addition to prophylactic
    abx and other meds. There are numerous such
    interactions among the the antiretroviral drugs.
    Second both efavirenz and nevirapine can reduce
    plasma methadone conc by approx 50.

Ques IV-55
  • A 27 yo man is brought to the ED w/ fever,
    confusion and difficulty breathing. Five days
    ago he was evaluated for a sore throat and was
    found to have an exudate on the right tonsil. No
    abx were prescribed. He works in an office, is
    in a monogamous sexual relationship, denies
    tobacco, illicit drugs or any medications. On
    the day of admission he complained o worsening
    sore throat, right neck pain, dysphagia and
    rigors. Exam is notable for T 39.2 BP 85/55 HR
    125 and swelling, redness and pain over right
    lateral neck and CXR shows multiple round
    opacities, some w/ air-fluid levels.

Ques IV-55
  • Which of the following organisms is most likely
    to grow on blood culture
  • Bacteroides ragilis
  • Fusobacterium necrophorum
  • Rhizopus oryzae
  • Staphylococcus aureus
  • Neisseria gonorrhea

Answer IV-55
  • B THis pt has Lemierres disease, jugular vein
    suppurative thrombophlebitis or postanginal
    septicemia. First described by Lemierre in 1936,
    in this disease young adults develop septic
    thrombophilebitis 3-10 days after a sore throat,
    exudative tonsillitis or peritonsillar abscess.
    Infection of the deep pharyngeal tissues extends
    to the lateral pharyngeal space that includes the
    jugular vein and carotid artery. Bacteremia may
    lead to septic pulmonary and systemic emboli.
    The infection classicall is due to Fusobacterium
    necrophorum. In the presence of poor dentition
    or malnutrition, Bacteroides would be considered.
    IVDA would make staph more likely. Rhizupus is
    in poorly controlled diabetics. Gonococcal
    pharyngitis my disseminate to joints but rarely
    causes sepsis

Ques IV-21
  • A 30 yo female complains of a week o bloody
    diarrhea, nausea, vomiting and fever. She
    rapidly develops weakness in her lower
    extremities, beginning in the lower legs and
    ascending to the thighs. A diagnosis of
    Guillian-Barre syndrome is made.

Ques IV-21
  • Which infectious agent is most strongly
    associated w/ development of Guillain-Barre
  • Campylobacter jejuni
  • E. coli O157H7
  • Norwalk virus
  • Shigella
  • Yersinia enterocolitica

Answer IV-21
  • A Campylobacter species are motile, non
    sporeforming curved gram negative rods. They are
    found in GI tracts of many animals. In most
    cases they are transmitted to humans in
    undercooked meats. Clinical manifestations
    include diarrhea, abdominal pain and fever.
    Enteritis is usually self-limited and rarely may
    be complicated by bacteremia. 1/1000 cases are
    complicated by GBS. 20-40 of all GBS cases are
    triggered by Campylobacter infection. E.coli
    O157H7, Shigella and Yersinia are in the diff
    dx for bloody diarrhea but not GBS

Ques IV-23
  • 35 yo man presents to ED in late summer w/ acute
    onset of fevers and severe pleuritic chest pain.
    He reports he felt well until the day before
    presentation when he initially developed
    paroxysms of knifelike pleuritic chest pain.
    This was followed by a fever to 39.4. On exam
    the pt appears in marked distress, writhing in
    pain w/ rapid shallow breathing. His T 38.8, RR
    32, HR 120 BP 112/68. HEENT exam is
    unremarkable. CV exam shows tachycardia. Pulm
    examreveals no accessory muscle use w/ shallow
    respirations. A focal pleural friction rub is
    heard posteriorly at right lung base. There are
    no crackles. The rest of the exam in normal
    including, skin, joints and abdomen. Hgb 13.1
    WBC 9.1 and CXR is normal.

Ques IV-23
  • What is the most likely cause of the patients
  • SLE
  • Pneumocystis pneumonia
  • Coxsackie B virus infection
  • Echovirus inection
  • Familial Mediterranean fever

Answer IV-23
  • C This pt is suffering from pleurodynia, which
    is also known by the eponym Bornholm disease.
    Pleurodynia is most commonly caused by coxsackie
    B viral infection. An RNA virus, coxsackie B
    virus is a member of the enterovirus family. In
    temperate areas, these viruses most commonly
    cause symptoms in late summer and early fall. In
    tropical areas they cause disease year round.
    Paroxysms of knifelike pleuritic chest pain in
    adults or abdominal pain in chlidren lastint
    15-10 minutes are followed by fevers w/
    diaphoresis and tachycardia. The WBC count and
    CXR are nml and the disease is self limited.
    Treatment is symptomatic w/ high dose NSAIDS for