Deck 20: Fastidious Gram-Negative Rods

Question 1

An organism, observed on direct Gram stain from a clinical specimen, does not grow on blood or chocolate agars incubated at 35°C in CO₂. This can be explained by all of following statements except

A) the organism is an anaerobe.
B) the organism is dead due to previous antibiotic therapy.
C) the organism requires nicotinamide adenine dinucleotide for growth.
D) the organism is fastidious and is not being provided the growth factor it needs.

Answer 1

the organism requires nicotinamide adenine dinucleotide for growth.

Question 2

The laboratory should be notified in advance when the physician suspects Francisella tularensis because the organism is

A) fastidious and requires special medium.
B) infectious for laboratory personnel.
C) not culturable.
D) a and b.
E) b and c.

Answer 2

a and b.

Question 3

The HACEK organisms share all of the following characteristics except

A) gram-negative coccobacilli that are oxidase and catalase positive.
B) slow growing and stimulated by carbon dioxide.
C) part of the normal oral flora.
D) causative agents of bacterial endocarditis.

Answer 3

gram-negative coccobacilli that are oxidase and catalase positive.

Question 4

Legionella pneumophila and Francisella tularensis share the characteristic of

A) being easily identified by biochemical testing.
B) a requirement for cysteine to grow in culture.
C) the necessity for the use of Gimenez stain rather than Gram stain to visualize.
D) having an animal reservoir.

Question 5

Legionella pneumophila and Francisella tularensis share all of the following characteristics except

A) poor Gram staining properties.
B) ability to cause pneumonia.
C) ability to diagnose infection with detection of serum antibodies.
D) fluorescence of colonies.

Question 6

A blood culture isolate that stains as pleomorphic gram-negative coccobacillus and

A) identified using the ALA test.
B) identified using the ALA and horse blood agar tests.
C) presumptively identified under BSL 2 conditions.
D) identified using X and V factor disks and horse blood agar.

Question 7

Which of the following organisms requires factor X only on initial isolation but loses the requirement on subculture?

A) Aggregatibacter actinomycetemcomitans
B) Eikenella corrodens
C) Francisella tularensis
D) Aggregatibacter aphrophilus

Question 8

Haemophilus ducreyi is unique among the genus because it requires

A) factors X and V.
B) no factors.
C) heme only.
D) NAD only.

Question 9

Streptobacillus moniliformis is most easily isolated from blood cultures because it requires _____ for growth.

A) heme
B) serum
C) cysteine
D) 1% ?-ketoglutarate

Question 10

A 57-year-old male farmer sees his physician complaining of fever, night sweats, and lethargy that come and go over the past three months. The patient's history reveals that he raises sheep for wool and meat and goats for milk. The physician suspects undulant fever. What is the optimal specimen(s) for culture of this suspected organism?

A) Blood
B) Bone marrow
C) Lymph node biopsy
D) All of the above
E) B and C

Question 11

A microbiologist processes a specimen for culture using a buffered charcoal yeast extract agar plate. What was the original specimen used for inoculation of this agar plate?

A) Blood
B) Lower respiratory specimen
C) Nasopharyngeal
D) Urine

Question 12

A nasopharyngeal swab containing ciliated epithelial cells is the best specimen for the recovery of the organism that causes

A) whooping cough.
B) undulant fever.
C) rat bite fever.
D) legionnaire's disease.

Question 13

What is the clinical significance of ALA-positive, gram-negative coccobacilli in a sputum culture?

A) Normal flora
B) Potential pathogen
C) Significant if it is hemolytic on horse blood agar
D) Further testing is needed to assess significance

Question 14

A small, slender, gram-negative rod was recovered from the blood cultures of a patient following root canal surgery. At 48 hours, the following results were
Observed:
BAP and CHOC agars: small gray colonies that tend to pit the agar
MAC agar: no growth
Odor upon opening the agar plates: bleach-like
This organism will also be

A) catalase and oxidase positive.
B) catalase positive and oxidase negative.
C) catalase and oxidase negative.
D) catalase negative and oxidase positive.

Question 15

A pleomorphic gram-negative coccobacillus is isolated from the blood cultures of 58-year-old male who had recent dental surgery. His history is significant for rheumatic fever as a child. The organism only grows on chocolate agar. It should be tested using

A) ALA.
B) X and V factor disks.
C) ALA and horse blood agar.
D) X and V factors and horse blood agar.

Question 16

The virulence of Bordetella pertussis is related to its

A) toxin's ability to paralyze ciliated epithelial cells.
B) ability to hide in the reticuloendothelial system.
C) easy dissemination.
D) ability to live inside white blood cells.

Question 17

Infection due to Brucella spp. is often slow to develop, long term, and displaying periodicity. This can be explained by the organism's ability to

A) colonize the upper respiratory tract prior to infection.
B) travel and hide in the reticuloendothelial system.
C) cause infection as the vaccine wanes in adults.
D) change its surface antigens.

Question 18

A 10-year-old male gave mouth-to-mouth resuscitation to his pet guinea pig, which proceeded to bite him on the lip. The guinea pig did not survive. Two days after the guinea pig's funeral, the boy became ill with fever, chills, joint pain, and a rash. What organism should the physician suspect based on the patient's history?

A) Brucella spp.
B) Francisella tularensis
C) Streptobacillus moniliformis
D) Eikenella corrodens

Question 19

You and your best friend get into a fist fight. Your knuckles are torn and bleeding afterwards. What organism are you likely to isolate if your wounds become infected?

A) Kingella kingae
B) Eikenella corrdens
C) Aggregatibacter aphrophilus
D) Cardiobacterium hominis

Question 20

Epiglottitis, a severe life-threatening infection occurring in non-vaccinated infants and children, is most commonly caused by

A) a pleomorphic gram-negative coccobacillus that is ALA positive and horse blood agar positive.
B) a gram-negative coccobacillus that is identified by direct fluorescent antibody and slide agglutination tests.
C) a gram-negative coccobacillus that is best identified by a rise in antibody titer in serum samples drawn two weeks apart.
D) a pleomorphic gram-negative coccobacillus that requires X and V factors and is horse blood agar negative.

Question 21

An organism isolated from the swab of purulent eye drainage shows no fluorescence on the ALA test. The horse blood agar displays no hemolysis. This organism should be reported as

A) Haemophilus influenzae.
B) H. aegyptius.
C) H. influenzae or H. aegyptius, biochemically similar.
D) H. parainfluenzae.

Question 22

Because of the nature of the profession, a veterinarian is at increased risk of acquiring
1) Brucella spp.
2) Aggregatibacter actinomycetemcomitans
3) Francisella tularensis
4) Streptobacillus moniliformis
5) Eikenella corrodens

A) 1, 2, 4, and 5
B) 1, 3, and 4
C) 2, 3, and 5
D) 3 and 4