Board Review
Paul O’Keefe
April 16, 2003
Skin/Soft Tissue Infections
• Impetigo
• Cellulitis
• Fasciitis
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
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
Necrotizing Fasciitis
• Streptococcal gangrene (Gp A strept)
• Deeper infection involving fascia and often
muscle
• Extreme toxicity and rapid spread (“flesheating virus”)
• May have associated toxic shock
• Treatment – surgical removal of necrotic
tissue and antibiotics
– Penicillin and clinidamycin
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
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, hypotension and extreme toxicity. The arm is red, very
swollen, firm and there are areas of black discoloration of the skin. The remainder of the skin has a
red sunburned appearance. The extreme toxicity
is thought to be caused by
A.
B.
C.
D.
E.
Streptolysin O
Hyaluronidase
M Protein
Pyrogenic exotoxin
Peptidoglycan
Upper Respiratory Tract Infection
• Pharyngitis
• Sinusitis
• Otitis media
Pharyngitis
•
•
•
•
Viral
Group A streptococcus (S. pyogenes)
Corynebacterium diphtheriae
Infectious mononucleosis
Characteristics of Pharyngitis
Agent
Exudate
Lymph
nodes
Treatment
Penicillin
Gp A strept
+
Submandibular
Viral
-
+
C. Diphtheriae
Membrane
Infectious
mononucleosis
+
None
“Bull neck”
Antitixon
Erythromycin,
Penicillin
Diffuse
None
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 cervical, and posterior cervical lymph nodes are enlarged on both
sides. Which of the following is most characteristic of infectious
mononucleosis?
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•
•
•
•
Atypical lymphocytosis
Positive culture for Group A streptococcus
Neutrophilia with left shift
Low serum globulin
Hematuria
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 airfluid 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 responsible 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
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
Community Acquired Pneumonia
•
•
•
•
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Streptococcus pneumoniae
Mycoplasma pneumoniae
Legionella pneumophila
Haemophilus influenzae
Chlamydia pneumoniae
Tuberculosis
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?
Features of Community Acquired
pneumonia
S. pneumoniae Mycoplasma
Legionella
pneumophila
Onset
Sudden
Gradual
Less sudden
X-ray
Lobar
Bronchopneumonia
Can be lobar
Other features
Rusty sputum,
+blood
cultures
Cold
agglutinins
Diarrhea,
negative
culture
Treatment
Penicillin,
ceftriaxone,
vancomycin
Macrolides,
tetracycline
Macrolides,
quinolones
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?
Food Poisoning
Agent
Mechanism
Incubation
Clinical
S. Aureus
Enterotoxin
1-8 h
Nausea,
vomiting,
diarrhea
B. Cereus
Toxin
4h
Diarrhea
Clostridium
perfirngens
Sporulation
toxin
8-16 h
Diarrhea
12-48 h
Fever, pain and
diarrhea
Salmonella
Infectious Diarrhea
Fever
Fecal WBC
Inoculum
Other
E. Coli
-
-
?
Lactose +
V. cholerae
-
-
107
Comma,
TCBS
Salmonella
+
+
105
Non lactose
Shigella
+
+
102
Non lactose
C. jejuni
+
+
104
Seagull
E. coli
O157:H7
+
-
?
Meat, HUS
+
108
Pets,
adenitis
Enterotoxin
Invasive
Y.
+
Enterocolitic
a
Cause of diarrhea 4 hours after eating fried rice
•
•
•
•
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•
B. cereus
S. aureus
Salmonella
Shigella
C. jejuni
Yersinia enterocolitica
Vibrio parahemolyticus
Contaminated poultry is the most likely
source of
•
•
•
•
•
Salmonella
Vibrio cholerae
Shigella dysenteriae
Campylobacter jejuni
S. aureus
An important virulence factor of the
organism found on biopsy of the
stomach in patients with chornic
epigastric pain is
•
•
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Enterotoxin
Polysaccharide capsule
Endotoxin
Urease
Beta-lactamase
Urinary Tract Infection
A 23 year old woman presents with acute dysuria one
day after intercourse. Urinalysis discloses 15-20 WBC’s
/HPF. Gram stain discloses gram negative rods.
What is the recommended treatment?
•
•
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Penicillin V
Erythromycin
Trimethoprim/sulfamethosoxazole
Gentamicin
Clindamycin
Which of the following strongly favors the diagnosis of
pyelonephritis?
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Burning on urination
Hematuria
Suprapubic tenderness
Fever
WBC casts on urinalysis
Causes of Meningitis by Age
Neonate
E. coli, Gp B streptococcus,
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
Listeria
Meningitis
A 6 year old boy presents with fever and lethargy. He has
nuchal rigidity on examination. Lumbar puncture discloses
many PMN’s and Gram positive cocci in pairs.
Which of the following characterizes this organism?
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Beta hemolytic on sheep’s blood agar
Inhibited by bacitracin dise
Inhibited by optichin disc
Beta-lactamase positive
Growth on MacConkey agar
Vaccines are available to prevent meningitis caused by
which organisms ?
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•
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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
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
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 PMN’s but
no bacteria.
The organism most likely responsible for the infection is
• Gram positive coccus, catalase positive
• Gram positive coccus, catalase negarive, betahemolytic
• Has infectious elementary body and intracellular
reticulate body
• Gram negarive coccus, oxidase positive
• Gram negarive rod, ixidase negarive lactose
fermenting
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
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)
Lesion
A 32 yo homosexual man presents with a painless lesion on
the penis of one week’s 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.
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•
•
•
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Gram negative coccobacilli
Gram positive cocci in clusters
Gram negative diplococci
Gram negative bacilli
Motile corkscrew-shaped organisms on darkfield
microscopy
Response to Treatment
A 20 yo asymptomatic woman in the 6th week of pregnancy has
a positive RPR of 1:16. 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
Discharge
A 33 yo sexually active woman complains of vaginal discharge.
Examination of the greenish frothy discharge discloses pH of
5.5 with numerous WBC’s and organisms with a jerking motion
on saline wet mount.
Treatment is best accomplished with
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•
•
•
•
Doxycycline for 5 days
Metronidazole – single dose
Ciprofloxacin – single dose
Ceftriaxone intramuscular – one dose
Benzathine penicillin G IM – one dose
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
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
Zoonoses
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
Pastuerella multocida
• Short, gram-negative rod
• Cellulitis or osteomyelitis following cat bite or dog
bite
• Treatment penicillin
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: ciprofloxacin+clindamycin+rifampin,
penicillin if susceptible
Gram Stain - CSF
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
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
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
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
Lyme Disease
• Borrelia burgdorferi – spirochete transmitted by
Ixodes ticks
– Reservoir – field mice and deer
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•
•
•
Erythema migrans, meningitis, encephalitis
Heart disease, arthritis
Diagnosis – Serology ELISA and Western blot
Treatment – Doxycycline, amoxicillin, ceftriaxone
Fungi
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
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
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
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
Cryptococcus neoformans
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•
•
•
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
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
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
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
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