Board Review

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Board Review

• Paul OKeefe
• April 16, 2003

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Skin/Soft Tissue Infections

• Impetigo
• Cellulitis
• Fasciitis

3
Impetigo

• Group A streptococcus, Staphylococcus arueus
• Superficial blisters?honey colored crusts on
  erythematous base
• No systemic signs
• Mainly in children
• May be associated with glomerulonephritis
• Treat with penicillin/antistaphylococcal
  penicillin

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Cellulitis

• Deeper infection usually involving skin and
  subcutaneous tissue
• Erythema, pain and swelling often with distinct
  border (erysipelas)
• Fever and lymphangitis or adenitis common
• Gp A streptococcus, Staphylococcus aureus most
  common
• Treat with antistaphylococcal penicillin unless
  culture positive

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Necrotizing Fasciitis

• Streptococcal gangrene (Gp A strept)
• Deeper infection involving fascia and often
  muscle
• Extreme toxicity and rapid spread (flesh-eating
  virus)
• May have associated toxic shock
• Treatment surgical removal of necrotic tissue
  and antibiotics
• Penicillin and clinidamycin

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A three year old boy presents with an itchy rash
that is spreading. Afebrile with numerous
cursted lesions in erythematous base involving
left shoulder and upper chest and back with few
lesions in the right thigh. Culture growing gram
positive coccus, beta hemolytic on SBA, catalase
negative, inhibited by bacitracin disc. The
isolated agent is

• Staphylococcus aureus
• Coagulase negative staphylococcus
• Streptococcus pyogenes
• Sterptococcus pneumoniae
• Enterococcus faecalis

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• A 13 year old develops high fever and a severely
• painful red rash on the right arm beginning at
  the
• site of a minor laceration. He has high fever,
  hypo-
• tension and extreme toxicity. The arm is red,
  very
• swollen, firm and there are areas of black
  discolor-
• ation of the skin. The remainder of the skin has
  a
• red sunburned appearance. The extreme toxicity
• is thought to be caused by
• Streptolysin O
• Hyaluronidase
• M Protein
• Pyrogenic exotoxin
• Peptidoglycan

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Upper Respiratory Tract Infection

• Pharyngitis
• Sinusitis
• Otitis media

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Pharyngitis

• Viral
• Group A streptococcus (S. pyogenes)
• Corynebacterium diphtheriae
• Infectious mononucleosis

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Characteristics of Pharyngitis
Agent Exudate Lymph nodes Treatment
Gp A strept Submandibular Penicillin
Viral - None
C. Diphtheriae Membrane Bull neck Antitixon Erythromycin, Penicillin
Infectious mononucleosis Diffuse None
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Pharyngitis and Fatigue
A 15 year old presents with fever, sore throat
and extreme fatigue. Temperature is 103.2 and
there is a yellowish exudate covering both
enlarged tonsils. Submandibular, anterior
cer- vical, and posterior cervical lymph nodes
are enlarged on both sides. Which of the
following is most characteristic of
infectious mononucleosis?

• Atypical lymphocytosis
• Positive culture for Group A streptococcus
• Neutrophilia with left shift
• Low serum globulin
• Hematuria

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Sinusitis
A 15 yo woman presents with fever, facial pain
and severe nasal congestion. She has been
suffering with hay fever. CT showed opacification
of the R maxillary sinus and an air- fluid level
in the left. Gram stain of material obtained by
antral puncture disclosed gram negative
coccobacilli. Which of the following
characterizes the organism most likely
respon- sible for the infection?

• Requires neither X nor V factor for growth
• Requires X factor but not V factor
• Requires V factor but not X factor
• Requires both X and V factors
• Exuberant growth on sheep blood agar

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Otitis Media
A 9 month old child with fever and congestion is
diagnosed with right otitis media. Common causes
of this infection are?

• Gp A streptococcus and Gp B streptococcus
• Neisseria meningitidis and Streptococcus
  pneumoniae
• Streptococcus pneumoniae and Haemophilus
  influenzae
• Haemophilus parainfluenzae and Gp A streptococcus
• Staphylococcus aureus and Gp A streptococcus

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Community Acquired Pneumonia

• Streptococcus pneumoniae
• Mycoplasma pneumoniae
• Legionella pneumophila
• Haemophilus influenzae
• Chlamydia pneumoniae
• Tuberculosis

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Community acquired pneumonia
A 33 year old male presents with fever and cough
3 weeks after his 7 year old son was treated for
pneumonia. X-ray shows a patchy bronchopneumonia
involving the right middle and lower lung field.
Cold agglutinin test is positive What is the
likely cause?
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Features of Community Acquired pneumonia
S. pneumoniae Mycoplasma Legionella pneumophila
Onset Sudden Gradual Less sudden
X-ray Lobar Bronchopneu-monia Can be lobar
Other features Rusty sputum, blood cultures Cold agglutinins Diarrhea, negative culture
Treatment Penicillin, ceftriaxone, vancomycin Macrolides, tetracycline Macrolides, quinolones
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Communinty Acquired Pneumonia
A 26 year old woman complained of fever, night
sweats and cough for 2 months. She had
occasional hemoptysis and 15 pound weight loss.
Chest x-ray showed fibronodular infiltrates with
a cavity in the posterior segment of the right
upper lobe. Please answer the following What
type of isolation would you order?What
diagnostic tests would you order? Sputum smear
returned positive for AFB. What treatment would
you order? Why are multiple drugs necessary for
treatment of tuberculosis?
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Food Poisoning
Agent Mechanism Incubation Clinical
S. Aureus Enterotoxin 1-8 h Nausea, vomiting, diarrhea
B. Cereus Toxin 4 h Diarrhea
Clostridium perfirngens Sporulation toxin 8-16 h Diarrhea
Salmonella 12-48 h Fever, pain and diarrhea
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Infectious Diarrhea
Fever Fecal WBC Inoculum Other
Enterotoxin
E. Coli - - ? Lactose
V. cholerae - - 107 Comma, TCBS
Invasive
Salmonella 105 Non lactose
Shigella 102 Non lactose
C. jejuni 104 Seagull
E. coli O157H7 - ? Meat, HUS
Y. Enterocolitica 108 Pets, adenitis
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Cause of diarrhea 4 hours after eating fried rice

• B. cereus
• S. aureus
• Salmonella
• Shigella
• C. jejuni
• Yersinia enterocolitica
• Vibrio parahemolyticus

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Contaminated poultry is the most likely source of

• Salmonella
• Vibrio cholerae
• Shigella dysenteriae
• Campylobacter jejuni
• S. aureus

22
An important virulence factor of the organism
found on biopsy of the stomach in patients with
chornic epigastric pain is

• Enterotoxin
• Polysaccharide capsule
• Endotoxin
• Urease
• Beta-lactamase

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Urinary Tract Infection
A 23 year old woman presents with acute dysuria
one day after intercourse. Urinalysis discloses
15-20 WBCs /HPF. Gram stain discloses gram
negative rods. What is the recommended treatment?

• Penicillin V
• Erythromycin
• Trimethoprim/sulfamethosoxazole
• Gentamicin
• Clindamycin

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Which of the following strongly favors the
diagnosis of pyelonephritis?

• Burning on urination
• Hematuria
• Suprapubic tenderness
• Fever
• WBC casts on urinalysis

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Causes of Meningitis by Age
Neonate E. coli, Gp B streptococcus, Listeria
Child 3 months-5 years Haemophilus infulenzae (no longer), S. pneumoniae
Adolescents, Young adults (age 5-40) Neisseria meningitidis, Streptococcus pneumoniae
Older adults Streptococcus pneumoniae, Listeria
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Meningitis
A 6 year old boy presents with fever and
lethargy. He has nuchal rigidity on examination.
Lumbar puncture discloses many PMNs and Gram
positive cocci in pairs. Which of the following
characterizes this organism?

• Beta hemolytic on sheeps blood agar
• Inhibited by bacitracin dise
• Inhibited by optichin disc
• Beta-lactamase positive
• Growth on MacConkey agar

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Vaccines are available to prevent meningitis
caused by which organisms ?

• E. coli and Streptococcus pneumoniae
• Haemophilus influenzae and Listeria monocytogenes
• Group B streptococcus and E. coli
• Neisseria meningitidis and Haemophilus influenzae
• Streptococcus pneumoniae and Group B streptococcus

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Bone and Joint Infections
A 22 year-old woman with sickle cell disease
presents with fever and pain in the left upper
arm. X-ray of the humerus shows a lytic lesion.
Biopsy is growing gram negative Bacilli.
Which of the following best describes the
organism?

• Comma-shaped with single polar flagellum
• Motile and oxidase positive
• Nonmotile facultative anaerobe
• Motile and does not ferment lactose
• Coccobacilli that require X and V factors

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Sexually Transmitted Diseases
A 16 year old man presents with burning on
urination and a scant urethral discharge 3 days
after intercourse with a new partner. Gram stain
of discharge discloses many PMNs but no
bacteria. The organism most likely responsible
for the infection is

• Gram positive coccus, catalase positive
• Gram positive coccus, catalase negarive,
  beta-hemolytic
• Has infectious elementary body and intracellular
  reticulate body
• Gram negarive coccus, oxidase positive
• Gram negarive rod, ixidase negarive lactose
  fermenting

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Arthritis
A 29 yo female presents with fever, rash and
arthritis 5 days after onset of menses. She has
a new sex partner. Exam discloses about 25
papular lesions on distal extremities and
inflamed tendon sheaths of the wrists and ankles
with painful motion but no fluid in the
joints. Cultures of blood and endocervix are
growing

• Catalase positive, gram positive coccus
• Gram negative coccus that ferments glucose but
  not maltose
• Gram negative coccus that ferments glucose and
  maltose
• Gram negative coccus that requries X and V
  factors for growth
• Gram negative bacillus that ferments lactose

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Neisseria gonorrhoeae undergoes antigenic
variation by altering

• Antigenic structure of pilus or expression of
  outer membrane protein II
• Antigenic structure of OMP II or expression of
  OMP I
• Expression of polysaccharide capsule
• Antigenic structure of pilus and expression of
  OMP I
• Expression of cytochrome c (Oxidase)

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Lesion
A 32 yo homosexual man presents with a painless
lesion on the penis of one weeks duration. It
developed 3 weeks after unprotected sex with an
anonymous partner. The cause of the infection
is identified from a specimen obtained from the
lesion which shows.

• Gram negative coccobacilli
• Gram positive cocci in clusters
• Gram negative diplococci
• Gram negative bacilli
• Motile corkscrew-shaped organisms on darkfield
  microscopy

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Response to Treatment
A 20 yo asymptomatic woman in the 6th week of
pregnancy has a positive RPR of 116. FTA Abs is
positive. She is treated with 3 doses of
benzathine penicillin. Follow up testing after
treatment should demonstrate

• Progressive rise in RPR and reversion of FTA Abs
  to negative
• No fall in RPR and reversion of FTA to negative
• Progressive fall in RPR and reversion of FTA to
  negative
• Progressive fall in RPR while FTA remains
  positive
• No change in RPR while FTA remains positive

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Discharge
A 33 yo sexually active woman complains of
vaginal discharge. Examination of the greenish
frothy discharge discloses pH of 5.5 with
numerous WBCs and organisms with a jerking
motion on saline wet mount. Treatment is best
accomplished with

• Doxycycline for 5 days
• Metronidazole single dose
• Ciprofloxacin single dose
• Ceftriaxone intramuscular one dose
• Benzathine penicillin G IM one dose

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Fever and Abdominal Pain
An 18 yo woman presents with fever and lower
abdominal pain. She has recently had intercourse
with a new partner. Pelvic examination discloses
vaginal discharge, pain on motion of the cervix
and bilateral adnexal fullness. Causes of these
symptoms include?

• Neisseria gonorrhoeae
• Treponema pallidum
• Chlamydia trachomatis
• E. coli, Prevotella bivia, enterococcus
• Herpes simplex

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Vaginitis
A 35 year old woman complains of scant vaginal
discharge and itching. Exam discloses erythema
of the vaginal mucosa with patches of white
discharge. The pH is 4.3. What is appropriate
treatment for this condition?

• Metronidazole for 5 days
• Ciprofloxacin one dose
• Doxycycline for 5 days
• Topical acetic acid
• Topical miconazole

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Zoonoses
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Plague Yersinia pestis

• Highly virulent, encapsulated, small gram
  negative rod
• Endemic in wild rodents Europe and Western N.
  America
• Transmitted by flea
• Virulence endotoxin, exotoxin, proteins
• Spreads to nodes Buboes, severe sepsis
• Pneumonic plague droplet spread
• Diagnosis aspirate bubo, blood (careful in lab)
• Treatment Gentamicin, Streptomycin, tetracycline

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Pastuerella multocida

• Short, gram-negative rod
• Cellulitis or osteomyelitis following cat bite or
  dog bite
• Treatment penicillin

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Anthrax Bacillus anthracis

• Gram positive, spore-forming rod with capsule
  Box cars. Spores in soil, on animal productrs
• Enter through skin, alimentary, respiratory
  tracts
• Toxin Protective antigen, edema factor
  (cyclase), lethal factor
• Painless ulcer with marked local edema
• Pneumonia (mediastinitis) ?meningitis
• Necrotizing enteritis?meningitis
• Diagnosis-culture
• Treatment ciprofloxacinclindamycinrifampin,
  penicillin if susceptible

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Gram Stain - CSF
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Tularemia

• Francisella tularensis small gram negative rod,
  enzootic in wild animals (rabbit)
• Transmission ticks or contact with dead animal
• Clinical
• Ulceroglandular ulcer with swollen regional
  lymph nodes
• Typhoidal fever, adenopathy
• Pulmonary
• Diagnosis Culture dangerous in lab serology
  and direct fluorescence
• Treatment Gentamicin or tobramycin

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Brucellosis

• Small, slow growing gram negative rod
• B. melitensis (goats, sheep), B. abortus
  (cattle), B. suis (swine)
• Transmission Occupation, milk
• Small granulomas in lymph nodes, spleen, marrow
• Fever, weakness, fatigue
• Diagnosis cluture blood and tissue, serology
• Treatment tetracycline, gentamicin

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Rocky Mountain Spotted Fever

• Tick borne rash illness caused by Rickettsia
  rickettsii, a small gram negative rod. Obligate
  intracellular parasite. Eastern and Midwestern
  US
• Vasculitis organism in endothelium
• Fever, headache, weakness followed by rash, DiC
  and shock
• Diagnosis Clinical, serology, ElISA, Weil Felix
  (Culture dangerous)
• Treatment Doxycycline

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Q Fever

• Coxiella burnetti
• Transmission contact with infectious aerosol
  from cattle, sheep, goats. Parturient cats
• Fever, headache, cough frequent hepatitis,
  endocarditis
• Diagnosis serology
• Treatment Doxycycline

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Lyme Disease

• Borrelia burgdorferi spirochete transmitted by
  Ixodes ticks
• Reservoir field mice and deer
• Erythema migrans, meningitis, encephalitis
• Heart disease, arthritis
• Diagnosis Serology ELISA and Western blot
• Treatment Doxycycline, amoxicillin, ceftriaxone

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Fungi
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Histoplasmosis

• Dimorphic fungus mold in soil, yeast in tissue
• Ohio and Mississippi river valleys, disturbed
  soil with bird droppings, bat caves
• Small oval yeast in macrophages
• Clinical
• Pulmonary acute pneumonia, chronic like
  tuberculosis
• Disseminated in immunocompromised esp AIDS
• Diagnosis Culture, Serology, Antigen in urine
• Treatment Self limited, Itraconazole,
  Amphotericin b

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Blastomycosis

• Dimorphic fungus large refractile yeast with
  broad based budding
• Ohio, Mississippi, St. Lawrence river valleys,
  Great Lakes. Soil with decaying organic material
• Clinical
• Pulmonary, pneumonia (refractory)
• Dissemination to skin common
• Diagnosis culture, histology
• Treatment Itraconazole, Amphotericin b

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Coccidioidomycosis

• Dimorphic fungus mold in soil, spherule in
  tissue
• Southwestern US (CA, AZ, NM, TX), Mexico.
  Arthrospores carried by wind
• Clinical
• Valley fever flu, pneumonitis, erythema nodosum
• Chronic pulmonary thin-walled cavity, nodule
• Disseminated Filipinos, African Americans,
  Immunosuppressed, pregnant
• Skin, bone, joint. CNS common chronic
  meningitis
• Diagnosis Sperules in tissue, culture (DANGER),
  serology
• Treatment Amphotericin b, fluconazole,
  itraconazole

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Candida

• Oval yeast with single bud. Pseudohyphae in
  tissue. Many species. Germ tube distinguish C.
  albicans from others
• Impaired defenses
• Mucosal disease mouth, esophagus, vagina, skin
  (warm, moist areas)
• Greater immune compromise dissemination to many
  organs
• Diagnosis seen on KOH, Culture
• Treatment
• Topical nystatin, azoles
• Systemic fluconazole, amphotericin b,
  caspofungin

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Cryptococcus neoformans

• Oval, budding yeast with polysaccharide capsule
• Ubiquitous in soil containing bird droppings.
  Inhaled
• Compromised AIDS, diabetes, malignancy,
  transplant
• Lung infection
• Aymptomatic nodule
• Pneumonia
• Meningitis common
• Diagnosis India ink on CSF, Culture, antigen in
  CSF and serum (follow titer during treatment)
• Treatment Amphotericin b flucytosine,
  Fluconazole

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Aspergillus

• Mold (no yeast form), ubiquitous, several species
  (A. fumigatus most common), Airborne conidia
• Manifestations
• Hypersensitivity sinusitis, asthma-like illness
  (ABPA)
• Mycetoma fungus ball in pre-existing lung
  cavity
• Invasive Severely immunocompromised. sinus and
  lung
• Causes thrombosis and infarction
• Disseminated especially to CNS
• Diagnosis culture and histology
• Treatment Amphotericin b, Voriconazole,
  itraconazole

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Zygomycosis

• Mucor, Rhizopus, Absidia saprophytic molds
• Invade blood vessels in paranasal sinuses or lung
• Progressive destruction across tissue planes
• Diagnosis culture, histology
• Treatment
• Surgical debridement
• Amphotericin b, newer azoles

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Fever in Returning Traveler

• Malaria if exposed
• Africa falciparum
• India vivix
• Blood smear
• Chloroquine plus primaquine, Quinine plus
  doxycycline
• Typhoid fever. Fever, rash, splenomegaly
• Dengue fever and headache

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Scenarios

• Returned from Philippines and passed a worm?
• Young Mexican immigrant with headache and new
  seizure. CT Cysts in brain
• Sepsis and severe diarrhea in WWII veteran who
  has just finished chemotherapy for NHL.
  Eosinophilia and microscopic worm in sputum