Friday, December 19, 2014

More Questions - Somewhat Rarely Isolated Organisms

1. A 10 year-old boy spent the summer with his uncle in Mexico who lives on a dairy farm.  He is complains of fever, hip pain and fatigue.  He drank unpasteurized cow milk.  The most likely organism causing his infection:

a. Francisella tularensis
b. Brucella abortus
c. Brucella melitensis
d. Bacillus cereus
e. Pasteurella multocida

2. Blood cultures were collected from the patient in Question #1.  What would be expected to grow from this culture:

a. Small gram negative rod which took 5 days to grow in aerobic blood culture bottle
b. Large gram negative rod that grew in 24 hours in anaerobe bottle
c. Small gram negative rod that grew only after addition of cysteine to the blood culture bottle
d. Sea gull shaped gram negative rod that grew in 3 days in the aerobic bottle
e. This organism will not grow in routine blood culture bottles

3. A culture is received in the microbiology laboratory from a patient who was bit by his dog.  The cultured organism has the reactions:  small gram negative rod, grey pinpoint colony pitting the agar surface, oxidase positive, catalase negative, bleach type odor.  The organism is most likely:

a. Pasteurella multocida
b. Eikinella corrodens
c. Erysipelothrix rhusiopathiae
d. Cardiobacterium hominis
e. Haemophilus parainfluenzae

4. Positive patient blood culture grow an organism gram stain shows a gram negative cocco-bacilli, beta hemolytic colony on blood agar plate after 72 hours of incubation at 35*C and growing best on plates incubated in 5% C02 atmosphere, oxidase positive, catalase negative:  

a. Haemophilus parainfluenza
b. Actinobacillus actinomycomitans
c. Kingella kingae
d. Cardiobacterium hominis
e. Eikinella corodens

5. An organism isolated from a positive blood culture from a patient in the intensive care unit.  The organism isolated grows well on a Blood agar plate incubated at 35*C in room air, grey non-hemolytic colony, gram positive rod (diphtheroid like), non-motile, catalase positive, urease negative, resistant to most antibiotics but susceptible to vancomycin.  

a. Erysipelothrix rhusiopathiae
b. Corynebacterium jeikeium
c. Listeria monocytogenes
d. Corynebacterium urealyticusm
e. Bacillus cereus

6. A positive blood culture at 36 hours grows an organism on Gram stain shows gram positive cocci in pairs and chains.  Initial subculture onto Blood agar plate incubated at 35*C in 5% CO2 shows “no growth”.  However, the organism has satellite growth as pinpoint colonies around a streak of Staphylococcus aureus on a blood agar plate.  The organism is most consistent with:

a. Streptococcus anginosus
b. Streptococcus agalactiae
c. Abiotrophia species
d. Gemella species
e. Rothia species

7. A positive blood culture is gram stained and shows a gram negative diplococcius, grows on Blood agar and Chocolate agar media incubated at    35 *C in 5% CO2., oxidase positive, utilize the carbohydrates glucose and maltose, but cannot utilize sucrose or lactose.  This organism is most likely:

a. Neisseria lactamica
b. Kingella kingae
c. Neisseria meningitidis
d. Moraxella catarrhalis
e. Neisseria gonorrnoeae

8. A wound culture is submitted to microbiology which grows gram positive cocci in clusters, white non-hemolytic colony on blood agar plate, coagulase negative, catalase positive, PYR positive.  Identification is most likely:

a. Staphylococcus saprophyticus
b. Staphylococcus haemolyticus
c. Enterococcus faecalis
d. Enterococcus faecium
e. Staphylococcus ludgeninsis

9. A positive blood culture is gram stained and shows a short gram positive rod, alpha hemolytic colony on blood agar plate, catalase negative, non-motile, non-spore producer, H2S produced on a triple sugar iron agar slant:

a. Erysipelothrix rhusiopathiae
b. Listeria monocytogenes
c. Corynebacterium urealyticus
d. Corynebacterium jeikeium
e. Bacillus cereus

10. A culture was performed from a lymph node aspirate, gram stain shows a  gram negative rod that has bipolar staining (like a safety pin), grows on a blood agar plate incubated at 35*C in 5% CO2, oxidase negative, catalase positive.  The person had been on an extended hike in the Southwest and reported some insect bites.

a. Francisella tularensis
b. Cardiobacterium hominis
c. Yersinia pestis
d. Haemophilus parainfluenza
e. Brucella canis

Key:  1.B  2.A   3.B   4.C   5.B   6.C   7.C   8.E   9.A   10.C

Tuesday, December 16, 2014

Dr. Morgan’s Microbes Questions #2 – Antibacterial Agents

1. Antibiotic choice for pneumonia due to Legionella pneumophila:

a. Penicillin
b. Macrolide antibiotic/Erythromycin
c. Trimethoprim/Sulfamethoxazole
d. Imipenem
e. Vancomycin

2. Antibiotic choice for Enterococcus faecalis endocarditis:

a. Cefotaxime
b. Erythromycin plus Gentamicin
c. Tetracycline
d. Ampicillin plus Gentamicin
e. Trimethoprim/Sulfamethoxazole

3. Antibiotic choice for complicated pneumonia caused by Streptococcus pneumoniae with a Penicillin MIC = 4 mcg/ml and susceptible to other antibiotics tested.

a. Penicillin
b. Cefotaxime
c. Vancomycin
d. Imipenem
e. Ertapenem

4. Antibiotic choice for bacteremia caused by a Staphylococcus aureus strain detected to have a mecA gene:

a. Ampicillin
b. Vancomycin
c. Cefotaxime
d. Cefazolin
e. Imipenem

5. Antibiotic choice for a urinary tract infection caused by Klebsiella pneumoniae detected to have carbapenamase enzyme:

a. Ampicillin
b. Ceftriaxone
c. Gentamicin
d. Colistin
e. Imipenem

6. Antibiotic  choice to treat bacteremia caused by Escherichia coli with a CTX-M type enzyme:

a. Imipenem
b. Cefotaxime
c. Ampicillin
d. Cefazolin
e. Ceftriaxone

7. A Staphylococcus aureus isolate was determined to be “D” test positive – this eliminates the ability to use which antibiotic  to treat a patient with soft tissue infection:

a. Ampicillin
b. Vancomycin
c. Clindamycin
d. Erythromycin
e. Cefazolin

8. An immune suppressed cancer patient was diagnosed with Listeria monocytogenes bacteremia.  The best choice for therapy would be:

a. Cefazolin
b. Ampicillin
c. Gentamicin
d. Ceftriazone
e. Cefotazime

9. An elderly adult is diagnosed with Haemophilus influenza meningitis.  The H. influenza is found to produce a beta-lactamase enzyme by the cefinase test.   The positive reaction eliminates the ability to use which antibiotic:

a. Cefotaxime
b. Ceftriaxone
c. Ampicillin
d. Vancomyin
e. Erythromycin

10. A 35 year old male was diagnosed with diarrhea caused by Shigella flexneri and required antibiotic  therapy.  The best choice for therapy would be:

a. Tetracycline
b. Ciprofloxacin
c. Erythromycin
d. Vancomycin
e. Clindamycin

Keys to the questions:  1.b  2.d  3.b  4.b  5.d  6.a  7.c  8.b  9.c  10.b

Monday, December 15, 2014

Dr. Morgan’s Microbes Questions – Short Case Histories

1. A 65 year old man is diagnosed with peritonitis due to a perforated colon. Anaerobic culture was performed with the following results:  Gamma hemolytic gray colony on anaerobic blood agar, black pigmented colony on bile esculin agar, resistant to kanamycin, colistin and vancomycin.  What is the most likely organism?

a. Escherichia coli
b. Bacteroides fragilis
c.  Prevotella melaninogenica
d. Clostridium perfringens
e. Porphyromonas gingivalis

2. A 35 year old male visits the Emergency Department with problems breathing over 2 weeks after recovering from a bout of diarrhea and vomiting.  Physical exam:  ascending muscle weakness began with his toes.  A stool culture from two weeks prior grew a small grey colony on Skirrow’s blood agar plate that Gram stained a “sea gull” shaped negative rod.  What is the most likely diagnosis of this patient?

a. Clostridium botulinum, botulism
b. Poliovirus, poliomyelitis
c.  Campylobacter jejuni, Guillain-Barre syndrome
d. JC virus, progressive multifocal leukoencephalopathy

3. A patient in the intensive care unit developed severe watery diarrhea and pseudomembranous colitis after 5 days of antibiotics.  The disease occurred as a result of which of the following?

a. Lecithinase
b. Hyaluronidase
c.  Shiga toxin
d. Collagenase
e. Toxins A and B

4. A patient in the intensive care unit grows Gram positive cocci in pairs and chains from a blood culture.  The organism is PYR positive, bile esculin positive, and 6.5% salt tolerant.  This organism is most likely:

a. Streptococcus pneumonia
b. Streptococcus pyogenes
c.  Streptococcus bovis
d. Streptococcus anginosis group
e. Enterococcus faecium

5. An 85 year old female arrives in the Emergency Department and is diagnosed with bacterial meningitis.  The Cerebrospinal fluid Gram stain has numerous PMNs and a Gram positive lancet shaped cocci in pairs and short chains.  The organism is most likely:

a. Listeria monocytogenes
b. Viridans group Streptococcus
c.  Streptococcus agalactiae
d. Streptococcus pneumonia
e. Streptococcus anginosis group

6. A 4 year old girl arrives at the Emergency Department in renal failure.  She had bloody diarrhea and severe hematological abnormalities.  She loved to eat chicken pieces, hamburgers and French fries from a local restaurant.  The most likely organism to cause this disease is:

a. Salmonella typhi
b. Campylobacter jejuni
c.  Yersinia enterocolitica
d. Shiga toxin producing Escherichia coli
e. Vibrio vulnificus

7.  A 50 year old male presents to his doctor with a history of vomiting blood.  He is thought to have a peptic ulcer.  He is sent for endoscopy to obtain an antral biopsy specimen.  A rapid test is performed on the antral biopsy to diagnose the presence of Helicobacter pylori.  This rapid test would most likely be:

a. Gram stain for curved Gram negative rods
b. Oxidase production
c.  Catalase reaction
d. Urease production
e. Occult blood reaction

8.  An elderly woman arrives in the Emergency Department with a headache, fever, and nuchal rigidity.  The Gram stain of the CSF shows numerous polys and small gram negative rods.  The organism did not grow on blood agar plate, but grew on chocolate agar when incubated in the Co2 incubator. The organism required X and V growth factors.  This patient most likely has:

a. Eikinella corrodens
b. Haemophilus influenza
c.  Haemophilus parainfluenza
d. Kingella kingae
e. Acinetobacter baumannii

9.  A 45 year old homeless man arrives in the Emergency Department complaining of difficulty breathing and spitting up bloody sputum that could be described as “currant jelly” like.  The organism most likely causing this infection is:

a. Escherichia coli
b. Klebsiella pneumonia
c.  Pseudomonas aeruginosa
d. Streptococcus pneumonia
e. Serratia marcescens

10.  A pregnant female has flu-like illness with possible sepsis.  Blood cultures are collected and become positive after 24 hours of incubation.  The organism isolated from the blood culture is a Gram positive cocci to short rod which is catalase positive, bile esculin positive and exhibits tumbling motility.  This organism is most likely:

a. Enterococcus faecalis
b. Streptococcus agalactiae
c.  Corynebacterium species
d. Listeria monogytogenes
e. Gemella species

Questions key:
1.b  2.c  3.e  4.e  5.d  6.b 7.d  8.b  9.b  10.d