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4/27/2015
Infectious Diseases Board Review
Session One
• James Myers MD
• Program Director Infectious Diseases
• Quillen College of Medicine
• 18 year old woman seen at JCIM with complaint of tender
periauricular lymph node
• Occasional fever
• Very tender lymph node approximately 6 cm in diameter
• Small, healed excoriations over right wrist
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KNOW THE DIFFERENTIAL DIAGNOSIS OF
CERVICAL LYMPHADENOPATHY
-malignancy
-TB, non-TB mycobacteria
-actinomycosis
-viral (EBV, CMV)
-bacterial/suppurative
-Bartonella infection
• Bartonella henselae
• 25,000 cases annually
• B. henselae recovered from the blood of healthy cats and
from cat fleas
• 90% of cases are typical: papule, ipsilateral
lymphadenopathy (>90%), fever (up to 60%), mild
leukocytosis
• nodes may be multiple, persist for 2-4 months
• Biopsies reveal nonspecific inflammation including
granulomata and stellate necrosis
• bacilli are seen by Warthin-Starry staining
• serologic testing is more sensitive than skin testing
• treatment controversial:
• Bass et al. (Pediatr Infect Dis J 1998;17:447) demonstrated a
more rapid resolution of LAD when treated with azithromycin
• however, outcome is almost always benign (Margileth et al.:
Pediatr Infect Dis J 1992;11:474)
• other drugs reported to be successful
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• 45 yo woman with RA presents with 12 hours of fever, nausea,
and abdominal pain
• Meds include prednisone 15 mg QD and methrotrexate
• Exam: temp 102.6, BP 90/62, RR 16, P 110; no rash,
abdomen mildly tender in mid-epigastrium; no HSM; joint
deformities c/w RA
• Urine culture negative, U/S RUQ negative
• Develops loose stools 12 h later
• Blood culture, stool culture: Campylobacter jejuni
KNOW THE DIFFERENTIAL DIAGNOSIS OF DYSENTERY
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Fever, tenesmus, bloody stools most common symptoms
Check fecal lactoferrin or WBC count and stool culture
Salmonella, Shigella, Campylobacter, Yersinia E. coli 0157:H7
Treatment:
• Shigella:bactrim DS or a fluoroquinolone X 3 d
• Campylobacter: erythromycin X 5 d
• E. coli 0157: DON’T treat, avoid antimotility agents
• Salmonella: only treat typhoidal disease or if severely ill or
immunocompromised; use a fluoroquinolone or ceftriaxone
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• 56 yo man underwent CABG two weeks ago
• Complicated by post-operative aspiration pneumonia
treated with ceftriaxone and clindamycin with
improvement
• HD#7 develops onset of fever, profuse loose stools,
leukocytosis to 28,000
• Exam with hypoactive bowel sounds, marked distention
• Abdominal flat plate reveals…
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• Onset after 3 d in hospital; associated fever, abdominal pain,
leukocytosis common
• Associated especially with cephalosporins, penicillins, and clindamycin;
can occur with chemotherapy
• New Tcd mutant/NAP1 strain: hypersecretor
• Diagnosis by stool PCR
• Could send stool for fecal lactoferrin (up to 75% will be +) or fecal
WBC (up to 40% +) or for C. diff toxin assay
• Treatment:
• metronidazole 250 mg Q6 or 500 mg Q8 X 10 d
• Stop the offending agent
• Oral vancomycin (NOT IV) MORE effective now and should be used in
all severe cases
• little data on combining the two
• 22 yo college student c/o watery diarrhea for 6 weeks
• Previously traveled to Belize
KNOW THE DIFFERENTIAL OF CHRONIC DIARRHEA
• Persistent diarrhea for > 7 days
• Send inflammatory screen and O&P
• Consider parasites:
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Giardia
Cryptosporidium
Cyclospora
Isospora belli
If HIV positive, add Microsporidia, Mycobacterium avium, and communityacquired pathogens
• Treatment based on findings
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Rice/Chinese food: Bacillus cereus
Poorly cooked beef: E. coli 0157:H7
Pork (especially Mexico): neurocystercercosis (Taenia solium)
Raw/unpasteurized dairy/cheese (esp. goat): Brucella,
Listeria, Mycobacteria bovis
• Strawberries/raspberries/sprouts: Isospora, cyclospora
• Mountain stream water: Giardia lamblia
• Seafood:
• Vibrio sp. (cirrhotics)
• Hepatitis A
• If freshwater….Aeromonas
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• 34 yo female with a benign PMH presents in August of 2000
with 3 days of worsening HA without decrease in mental status
• exam reveals temp of 39.1 C, nuchal rigidity, and photophobia;
no papilledema
• LP reveals 300 WBC, 95% lymphocytes; CSF protein 54, CSF
glucose 82
• gram stain negative
generally no decreased MS
fever 76-100%, nuchal rigidity 50%
HA uniform, often frontal
CSF pleocytosis is present, characteristically
lymphocytes or monocytes (100-1000 cells/mm3)
• CSF protein is usually minimally elevated and CSF
glucose minimally decreased
• etiology...
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• Enteroviral most common:
• echovirus
• coxsackievirus
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seasonal: late summer and fall
family outbreaks
may be associated with rash; LP ? therapeutic
diagnosis: immunoassays; PCR
treatment: supportive
• HIV!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
• Look for rash over upper chest
• Diagnose with HIV RNA by RT PCR
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Lyme disease/Borrelia burgdorferii
Ehrlichia/Anaplasma sp.
Cat-scratch disease
rabies
TB
syphilis
fungal
• Drugs
• NSAIDS
• sulfa agents
• autoimmune diseases
• RA, lupus
• Behcet’s
• sarcoidosis
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• 48 yo school teacher brought to ER by family after being
found sitting on the floor in her bedroom
• Further questioning: headache all day, “just can’t get my
words out”
• Exam: temp 99.4; no focal motor abnormalities; MMSE
18/30, poor short-term memory
• LP: 12 WBC, 700 RBC, prot 56, glu 65
• MRI...
KNOW THE DIFFERENTIAL DX OF ENCEPHALITIS
• =inflammation of the brain
• Viruses most common: HSV, WNV, arboviruses, rabies,
herpesviruses in general (EBV/CMV)
• Other causes
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Rickettsia
Syphilis
Lyme
Fungi
parasites
• Only HSV and Enteroviral encephalitis can be treated
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• Diagnosis:
• HSV PCR on CSF
• HSV culture from CSF VERY poor
• HSV serologies not useful
• Treatment:
• IV Acyclovir 10 mg/kg Q8 h
• Empiric treatment in all cases of encephalitis of unknown
etiology
• Only major side effect: reversible renal failure due
• 56 yo renal transplant on CSA/prednisone
• C/o 1 d of SOB, fever
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• ? Clinical clues:
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Severe clinical illness
Hyponatremia
Diarrhea
Multilobar involvement
Sputum with leukocytosis but gram stain, culture negative
Immunocompromised
Outbreaks: associated with air conditioning units, cooling towers,
whirlpools
• Diagnosis:
• Legionella urinary antigen (only L. pneumophila serotype 1)
• sputum DFA
• Treatment
• Fluoroquinolone
• azithromycin
• Birds
• Chlamydia psittaci=psittacosis (parrots, parakeets)
• Cryptococcus (bird feces)
• Dirt (often lung-skin and occasionally brain diseases)
• Histoplasmosis (Ohio River Valley)
• Cryptococcosis
• Blastomycosis
• Coccidiomycosis (San Juaquin Valley)
• 32 yo man with history of Hodgkin’s disease, cured X
10 years
• Presents with acute onset fever and prostration
• Denies fever, cough, nausea/vomiting, diarrhea
• Had “flu” 10 days ago, improved until this A.M.
• Exam: temp 103.2, BP 80/50, P 130, RR 24; lungs
with minimally decreased LLL breath sounds
• No sputum could be obtained
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KNOW WHAT INFECTIONS YOU GET WITH IMPAIRED SPLENIC OR HUMORAL FUNCTION
• Defects in antibody production=impaired opsonization
• Mortality high in this setting
• diseases with impaired antibody production
• Splenectomized patients
• CLL
• Sickle cell anemia
• Lymphomas
• Cirrhotics
• Hemodialysis patients
• Congenital and acquired immunoglobulin deficiencies
• Organisms
• Strep. Pneumoniae**************
• H. flu
• N. meningitidis
• Capnocytophagia=DF2
• babesiosis
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• 24 yo WF s/p heart transplant 5 weeks ago
• Meds include CSA, prednisone, mycophenolate
• C/o fatigue, nausea, fever, abdominal discomfort,
dysphagia
• Exam reveals temp 100.5; no rash
• Labs reveal AST 82, ALT 69, WBC 2.9
• Chest film WNL s/p transplant
KNOW WHAT INFECTIONS ARE SEEN IN THE SETTING OF T CELL IMPAIRMENT
• At risk: AIDS pts, transplant recipients, patients on
immunosuppressants (including RA, lupus, COPD, GN)
• Defective T cell immunity= INTRACELLULAR
PATHOGENS
• Viruses (esp. CMV, HSV, EBV, VZV)
• Fungi (esp. Candida sp., cryptococcus, pneumocystis)
• Bacteria (esp. mycobacteria species, listeria,toxoplasma)
A 35-year-old male office worker from Baltimore was feeling fatigued and had low grade fevers. He
went to his family physician, and is referred to you because his liver function tests are abnormal. He has
been previously healthy, but he has had multiple male and female sexual partners without condom use.
On physical examination, he is icteric, and has mild RUQ tenderness, but no other abnormality.
He denies any recent illness or travel, and drinks a “few” beers per week. He had an insurance physical
exam with blood tests one year ago and donated blood at a hospital two months ago. He was not
informed of any abnormality although he failed to reveal that he had many sexual partners.
Lab profile:
• ALT =1600 IU/L; AST = 1200 IU/L; Bili 4.2 mg/dl; Prothrombin time 12.0 seconds
• CBC: normal
• Hepatitis A antibody: positive (history of hep A immunization)
• Hepatitis C antibody: negative
• Hepatitis B: IgM antibody to HBc positive; IgG to HBc positive, HBs-antigen positive, HBs antibody
negative, e antigen
negative.
• Hepatitis D antibody negative
Which if the following tests would be most useful?
A. Hepatitis E antibody
B. RPR
C. Hepatitis B viral load
D. Hepatitis D viral load
E. Hepatitis C viral load
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A 27-year-old man is brought by ambulance to the emergency room. His mother came home at the end of her work day
and found him delirious on the living room couch. When she touched him he was “burning up,” and she called for
emergency service. In the emergency room his temperature is 103.4° F, his heart rate is 132, and his blood pressure is
88/56mmHg. He is not responsive to commands and mumbles incoherently. He has an abdominal scar that his mother
reports is due to a splenectomy, the result of trauma from a motorcycle accident when he was 19 years old. There is a
deep abrasion on his right lateral calf that was erythematous, but not purulent. His mother reports that he scraped his leg
5 days ago when he slipped and fell off a stone wall while helping her plant spring flowers. She says the family dog likes
to lick the wound. She thinks her son had “all his shots” as a child but is unclear about his tetanus immunization history.
His white blood cell count is 24,700 with 19% band forms.
The lab calls to say that they think they see little rod-shaped bacteria on the Wright-stained blood smear.
His illness is most likely due to which one of the following?
A. Streptococcus pneumoniae
B. Haemophilus influenzae
C. Vibrio vulnificus
D. Capnocytophaga canimorsus
E. Pasteurella canis
Correct Answer: D
Rationale:
“Dog bite septicemia” is a rare but highly lethal infection caused by
Capnocytophaga canimorsus or Capnocytophaga cynodegmi producing
overwhelming sepsis or meningitis. It occurs most often in asplenic or alcoholic
persons who are bitten by a dog or who have a wound licked by a dog.
There is high grade bacteremia and the gram-negative rod bacteria may be
seen on peripheral blood smears.
S. pneumoniae and H. influenzae may cause overwhelming sepsis
postsplenectomy,but the rods seen on peripheral smear are not consistent with
pneumococci.
H. influenzae bacteremia is quite rare in adults. Neither pneumococcus nor
Haemophilus is associated with wounds or dog contact. The epidemiology
here is not consistent with Vibrio infection (no water contact; no shellfish
ingestion).
Pasteurella canis is much less virulent than P. multocida and is often found as
part of complex flora in infected dog bite wounds, but rarely causes
bacteremia.
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• Which of the following would be
the mostly likely pathogen in this
rapidly expanding skin lesion in
a febrile neutropenic patient with
acute leukemia? The skin biopsy
with sutures is seen in the lesion.
• A. Fusarium solani
B. Streptococcus pyogenes
C. Borrelia burgdoferi
D. Pseudomonas aeruginosa
• This lesion is typical of early ecthyma gangrenosum,
typically presenting in neutropenic patients and usually
due to Pseudomonas aeruginosa..
• The sharp border and pale center comes from invasion
of blood vessels in the dermis.
• Lyme lesions (Borrelia burgdorferi) or streptococcal
cellulitis are sharply circumscribed but don’t have pale
centers.
• Fusariosis causes nodular, erythematous lesions which
often ulcerate with time.
•
This 25 year old woman from Guatemala had been
given antithymocyte globulin and cyclosporine for her
aplastic anemia but had as yet not responded and
remained profoundly aplastic when she was observed
to have over 24 hr to develop this swelling
underneath her chin. There no lesions visible in the
front of her mouth but she couldn’t open very wide
because that caused pain She took sips of fluid
without discomfort but was very nauseated and
drinking very little. The swelling was firm and not
apparently red or painful. She could speak softly
without obvious hoarseness.
•
The most likely source of this infection is which of
the following:
A. Herpetic stomatitis
B. Dental abscess
C. Oropharyngeal candidiasis
D. Vincent’s angina
E. Lemierre’s syndrome
•
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• This is Ludwig’s angina in a patient with poor dental hygiene. Ludwig’s is an infection
of the submandibular and sublingual space from streptococci or other oral bacteria
and originates from a dental abscess in the first molar or adjacent tooth. Infection
spreads below the mylohyoid line into the soft tissue below the mandible.
• The tongue protrudes upward and posteriorly, potentially obstructing the airway.
Tracheostomy may be necessary.
• The patient is febrile, toxic and has difficulty opening the mouth if infection has
spread into the pterygoid space Therapy with piperacillin-tazobactam, ampicillinsulbactam or any regimen that is active against both aerobic and anaerobic flora is
indicated.
• Surgical drainage of the dental abscess can wait until the patient has responded to
antibiotic therapy.
• Septic thrombosis of the internal jugular vein to cause Lemierre’s syndrome does not
cause symmetrical submandibular swelling and there is no indication of septic emboli
to the lung or positive blood culture in this patient. Vincent’s angina is severe
gingivitis, and like herpetic stomatitis and oropharyngeal candidiasis, does not
extend into the neck.
•
This man was referred from Puerto Rico for
management of his chronic myelogenous
leukemia, currently responding to imatinib
(Gleevec). He brought summaries from
recent hospitalizations which mentioned
courses of amphotericin B which were
apparently given empirically during periods
of neutropenia. He had indwelling vascular
catheters at the time but they had been
removed. He was currently feeling relatively
well and had a normal physical examination
and liver function tests. Because he had a
low grade persistent fever he had a CT
scan done.
•
The most likely source of the lesions is
which of the following:
A. Aspergillus
B. Hemangioma
C. Chronic myelogenous leukemia
D. Bartonella species
E. Candida species
•
• These multiple small rim-enhancing lesions are consistent with chronic disseminated
candidiasis, an infection which begins during neutropenia but is only appreciated in
the survivors, usually after recovery of neutrophils and treatment with antifungal
agents.
• These necrotic lesions may be seen in the liver or spleen as well. Aspergillus, Fusarium
and agents of mucormycosis rarely result in this imaging result.
• An erroneous diagnosis of aspergillosis is often made because pseudohyphae of
Candida may resemble a mold on liver biopsy and cultures may be negative
because of prior treatment.
• Metastatic cancer can give a similar image but not CML and usually without fever.
Bacillary peliosis hepatis, due to Bartonella henselae, is accompanied by fever and
can cause similar lesions on imaging (Abdom Imaging 2005;30:738-40) but this
infection is rarely noted in patients recovering from neutropenia, such as the one
above.
• Perhaps the antibacterial antibiotics given to febrile neutropenics account in part for
the rarity of Bartonella infections in this population. Hemangiomas in the liver are
common but have contrast enhancement located within the lesion, if at all, rather than
in the margin, and would not explain the fever.
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• This 34 year old female with AIDS
was brought to a Washington DC
emergency room by her husband
because of fever and somnolence.
There is no history of travel outside
the locality. Her only medications
had been naturopathic.
• Which of the following would
most likely be effective:
• A. azithromycin
B. metronidazole
C. quinine+clindamycin
D. pyrimethamine+clindamycin
• The location in the basal ganglia and the HIV-infected host
would be consistent with toxoplasmosis or lymphoma.
• Only one of the drug choices would treat toxoplasmosis and, of
course, none would treat lymphoma.
• The usual treatment of cerebral toxoplasmosis would be
sulfadiazine plus pyrimethamine but pyrimethamine plus
clindamycin gave comparable therapeutic results in one
randomized trial.
• Trimethoprim-sulfamethoxazole has been reported useful in a
few case reports.
• This 9 year old girl from a dairy
farm near Frederick, Maryland
had the sudden onset in July of
fever, severe headache, nausea,
vomiting and muscle aches. On the
fourth day she developed the rash
shown here on her palms and soles.
The drug of choice would be:
• A. cefotaxime
B. penicillin G
C. levofloxacin
D. doxycycline
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• Development of a petecchial rash on the fourth day is
very consistent with Rocky Mountain Spotted fever, as
is a severe headache, fever and myalgias.
• Treatment of this rickettsiosis is doxycycline despite her
age. Meningococcal sepsis can cause a similar rash
and severe headache but rash would have appeared
earlier after the onset of severe headache.
• This 32 year old male from a rural
area on the Eastern shore of
Maryland had a low grade fever
and expanding rash on his
abdomen, shown here.
• Which of the following would be
the most likely later complication
of this infection?
• A. transverse myelitis
B. sexual transmission
C. uveitis
D. arthritis
• The lesion is typical of erythema migrans due to Lyme disease,
Borrelia burgdorferi infection acquired from a deer tick bite in
an endemic area.
• Days to weeks after the skin lesion appears, cardiac or
neurologic complications occur. Arthritis begins in weeks or
months, with intermittent attacks of acute arthritis, usually large
joints, with each episode lasting from days to months.
• A few patients with acute arthritis develop chronic arthritis,
usually in the knee. Uveitis and transverse myelitis are not
associated with Lyme, though neuroretinitis and encephalitis can
occur.
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• This EKG from a 35 yr
old female Nantucket
shop owner was most
likely acquired by a bite
of a:
• A. mosquito
B. fly
C. tick
D. flea
• The EKG shows second degree heart block with a 3:1 capture
ratio. Heart block is one of the most common cardiac
complications of Lyme disease, starting from days to weeks
after a bite by an infected Ixodid (deer) tick.
• Heart block also occurs in acute rheumatic fever and chronic
Chagas’ disease. Chagas’ cardiomyopathy can be occur years
after the bite of a Triatome (reduviid) bug in South America but
is very rare in US residents.
• Heart failure usually accompanies cardiac conduction
abnormalities in Chagas’ cardiomyopathy. The other insect
vectors listed are not associated with diseases that cause AV
block.
• This is the modified acid fast smear of
sputum from a 34 year old woman with
pneumonia. She had systemic lupus
erythematosus and was receiving
prednisone 60 mg daily. When she had
been given sulfamethoxale trimethoprim
last year, she had developed severe
Stevens Johnson syndrome.
• Of the following antimicrobial agents,
which would be select for treatment of
her pneumonia:
• A. imipenem plus amikacin
B. intravenous azithromycin
C. clarithromycin and ethambutol
D. ceftriaxone
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• Presence of branching acid fast bacilli indicates nocardiosis,
one of the causes of pneumonia in immunosuppressed patients.
• Trimethoprim-sulfamethoxazole is the preferred drug but
reports of imipenem, with or without amikacin, have indicated
efficacy.
• Azithromycin does not appear to be effective. There are a few
reports of success with ceftriaxone but this may depend on the
Nocardia species.
• Susceptibility testing is not clearly reliable and speciation is
often not available at time of diagnosis, making ceftriaxone not
recommended.
• The following tongue lesion was
scraped: Wet mount with
Calcofluor stain for fungus and
Gram Stain for bacteria were
negative.
• The patient is asymptomatic and
has no notable symptoms related
to his tongue or mouth.
• Which of the following is linked
etiologically to this lesion:
• A. HSV
B. VZV
C. CMV
D. EBV
E. HHV-6
• The structures involved are: - Usually lateral tongue, but buccal
mucosa floor of mouth, palate may also be involved.
• OHL is EBV associated.
• No treatment is necessary although the lesions often regress
with acylcovir.
• These lesions often disappear on antiretroviral therapy
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• A 34 year old male with HIV (CD4
= 12 cells, VL = 800k) has not
been in care.
• He presents with visual blurring.
• His fundoscopic examination is
shown.
• The most likely cause of this
lesion is:
• A. Toxoplasmosis
B. Syphilis
C. CMV
D. HSV
E. VZV
• There is a long list of causes of retinitis in a highly
immune deficient patient with HIV.
• CMV is by far the most common, especially in a
patient with little anterior or posterior chamber
inflammation (the fundus can be clearly visualized
here) and with the combination of hemorrhages and
exudates.
• Infectious disease specialists should know the
differential diagnosis, and the basic findings of the
common syndromes of CMV, HSV, VZV, Toxoplasma,
and syphilis.
•
A previously healthy young female had
the onset of pain in her calf and a red,
tender rash on her calf. She was unaware
of preceding trauma. In the photo, the
bleeding was from an unsuccessful
needle aspirate. She was given
cephalexin 250 mg po qid but the
progressively excruciating pain increased
and came to the emergency room about
48 hours after onset. Her vital signs were
normal except for a temperature of 102.
There was no rash outside the calf, which
was red, tensely swollen and tender. A
soft tissue film showed no gas. WBC was
15,000 with 80% PMN and 5% bands.
•
The clinical picture is most consistent
with infection by which of the following
organisms:
•
A. Streptococcus pyogenes
B. Clostridum perfrigens
C. Staphylococcus aureus
D. Mixed infection with anaerobes and
aerobes
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• This patient should be considered to have streptococcal
necrotizing fasciitis and emergency surgical consultation
obtained.
• The location, normal host, severe pain and rapid progression
make Meleney’s gangrene with mixed anaerobes and aerobes
less likely. Clostridum perfringens, gas gangrene, usually follows
major trauma or occurs in poorly vascularized tissue and has
gas in the tissue.
• Staphylococcal pyomyositis is a rare cause of this clinical picture
in the calf and is most often mistaken for deep venous
thrombosis.
• But patients in the USA with Staphylococcal pyomyositis often
have comorbid conditions, pain is less intense or progression
slower. Imaging is often helpful in distinguishing causes in
patients like this.
• This lesion in the ocular
fundus is most
consistent with which
of the following:
• A. Miliary tuberculosis
B. Candidemia
C. Endocarditis
D. Systemic lupus
erythematosus
• A retinal hemorrhage with a pale center is called a Roth spot,
as occurs in endocarditis.
• Retinal lesions due to candidemia, miliary tb and SLE (cytoid
bodies) are pale with no surrounding hemorrhage.
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
A 56 year-old man is admitted with 3 days of fever, rash, confusion, and leg weakness in
August. He lives in Alabama.
 He is febrile to 104°F and is confused.
 He has a faint maculopapular rash in the trunk.
 His neurologic exam reveals mild tremors, a strength of 5/5 in the arms, 3/5 in the lower
extremities, normal deep tendon reflexes, and normal sensory exam.

CBC, chemistry tests, urinalysis, chest-X-ray and head CT without contrast are normal.
HIV is negative.
 A lumbar puncture reveals 1351 WBC, 70% polys, 30% lympho/monos, protein 81
mg/dL, glucose 92 mg/dL.

 Gram stains and Cryptococcal antigen are negative.

He is treated with vancomycin and ceftriaxone. Over the next three days the weakness
progresses to the point that he is paraplegic.


Which of the following is the most likely diagnosis?
A) Poliovirus

B) West Nile virus

C) Saint Louis encephalitis virus
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D) Acute HIV infection
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E) Guillain-Barre syndrome
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West Nile virus has an extensive distribution, it is seen in Africa, the Middle East, parts
of Europe and Asia, Australia, and in recent years has become endemic in the
continental United States. It has a seasonal incidence, with a peak in late summer or
early fall.
The virus is transmitted by the Culex mosquitoes, other less common mechanisms of
transmission are blood transfusion, organ transplantation, transplacental transmission
or breastfeeding, and occupational transmission in healthcare workers.
It is estimated that 80% of the infections are asymptomatic. West Nile fever is seen in
20%, and is characterized by nonspecific symptoms such as fever, headache,
malaise, back pain, myalgias, anorexia, or rash. Neuroinvasive disease is seen in 1
out of 150 individuals who are infected. The neurological manifestations include
encephalitis, meningoencephalitis, meningitis, poliomyelitis (acute flaccid paralysis). In
endemic areas, flaccid paralysis or weakness with or without encephalitis is very
suggestive of West Nile virus.
Lumbar puncture usually reveals meningitis, with elevated WBCs with either
lymphocytes or neutrophils. The diagnosis of neuroinvasive diseaseis based on
detection of IgM antibody in CSF. Viral cultures become negative too early to be useful
in previously normal patients; initial results can be negative so it is important to check
convalescent titers. Risk factors for severe disease are older age, diabetes, alcohol
abuse, and being immunocompromised.
Poliovirus has been eradicated from the United States.
Acute HIV infection can occasionally present with a Guillain-Barre-like syndrome
(GBS). GBS is an acute immune mediated polyneuropathy, with progressive
ascending weakness and albuminocytologic dissociation where the CSF protein is
very high and the cell count is not.
St. Louis encephalitis virus is one of etiologic agents of viral encephalitis in the
United States, and presents as encephalitis, not as poliomyelitis.
 Which one of the following is true about progressive
multifocal leukoencephalopathy?
 A) Anti-TNF-alpha therapy may predispose to
infection
B) Seizures are rare
C) Serodiagnosis is useful
D) Transmission is by sexual intercourse
E) Infection with this agent usually leads to disease
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 A number of cases of PML have been described in
patients receiving anti TNF alpha therapy and in
patients receiving other immunosuppressive monoclonal
antibodies, including rituximab.
 PML is rare in immunologically intact persons. Exposure
to JC is common and by the respiratory route.
Approximately 80% of the population has antibody to
JC virus and thus serum antibody testing is not useful.
 Which of the following antibiotics is active against
Mycoplasma pneumoniae?
 A) Ampicillin-sulbactam
 B) Azithromycin
 C) Imipenem
 D) Penicillin
 E) Vancomycin
 Mycoplasma species are unique among bacteria
because they do not have a cell wall and their cell
membrane contains sterols.
 The absence of the cell wall renders the mycoplasmas
resistant to antibiotics that interfere with synthesis of
the cell wall, such as penicillins (ampicillin-sulbactam,
penicillin), cephalosporins, carbapenems (imipenem),
and vancomycin.
 Azithromycin is a macrolide antibiotic that inhibits
bacterial growth by disrupting protein synthesis
23
4/27/2015

A 22-year-old male, previously in good
health, develops a low-grade fever and a
cough. On the third day of his illness, he
developed the skin rash (shown below) on
his trunk, extremities, palms, and soles, and
has mucosal erosions in his mouth and
genitals. He comes to your office for
evaluation.
Chest x-ray shows a patchy bilateral
bronchopneumonia. CT is shown below.
Oxygen saturation on room air: 98%
WBC = 6000 with a normal differential
The most likely cause of his skin lesions
A) Treponema pallidum

B) Streptococcus pneumoniae

C) Mycoplasma pneumoniae

D) Legionella bozemanii

E) Chlamydia pneumoniae





 While many infectious agents can be associated with erythema
multiforme, which is the skin and mucous membrane lesion shown
here. Up to 7% of patients with M. pneumoniae infection have
been reported to develop erythema multiforme or Stevens
Johnson syndrome. Other types of skin lesions also have been
reported.
 While this skin rash could be due to syphilis, the presence of a
respiratory infection makes M. pneumoniae a much more likely
cause. HSV is a common cause of erythema multiforme, but
many respiratory viruses and live attenuated vaccines can also
be associated. Since no respiratory viruses were listed as
possible answers, M. pneumoniae is the best answer.
 Which one of the following procedures would provide the most sensitive and
specific test for the diagnosis of Clostridium difficile diarrhea?
 A) Submit 1 stool specimen for cytotoxicity testingB
 B) Submit 1 stool specimen for enzyme immunoassay tests
 C) Submit 1 stool specimen for PCR test
 D) Submit 3 daily stool specimens for enzyme immunoassay tests
 E) Submit 1 stool for latex agglutination test
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4/27/2015
 The FDA approved PCR test for the C. difficile toxin B
gene is the most sensitive and specific test available.
Cytotoxicity testing was formerly the gold standard
for detection of toxins but is associated with some
false-negative and false-positive reactions.
 The EIA tests have been found to be both insensitive
and nonspecific. There is no evidence that more than
one test is required (in contrast to detection of enteric
parasites). The latex test for C. diffiicile LDH is
sensitive but not specific.
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