Micro-Miscellaneous and Fastidious Gram-Negative Rods

Question 1

1. A visitor to South America who returned
   with diarrhea is suspected of being infected with
   V. cholerae. Select the best medium for recovery
   and identification of this organism.
   A. MacConkey agar
   B. Blood agar
   C. TCBS agar
   D. XLD agar

Answer 1

C. TCBS agar

Question 2

2. A curved gram-negative rod producing
   oxidase-positive colonies on blood agar was
   recovered from a stool culture. Given the
   following results, what is the most likely
   identification?
   Lysine decarboxylase = + Arginine decarboxylase = Neg
   Indole = +
   KIA = Alk/Acid
   VP = Neg
   Lactose = Neg
   Urease = ±
   String test = Neg
   TCBS agar = Green colonies
   A. Vibrio cholerae
   B. Vibrio parahaemolyticus
   C. Shigella spp.
   D. Salmonella spp

Answer 2

B. Vibrio parahaemolyticus

Question 3

3. A gram-negative S-shaped rod recovered from
   selective media for Campylobacter species gave
   the following results:
   Catalase = +
   Oxidase = +
   Motility = +
   Hippurate hydrolysis = +
   Growth at 42°C = + Nalidixic acid = Susceptible
   Pigment = Neg
   Grape odor = Neg Cephalothin = Resistant
   The most likely identification is:
   A. Pseudomonas aeruginosa
   B. Campylobacter jejuni
   C. Campylobacter fetus
   D. Pseudomonas putida

Answer 3

B. Campylobacter jejuni

Question 4

4.. Which atmospheric condition is needed to recover
Campylobacter spp. from specimens inoculated
onto a Campy-selective agar at 35°C–37°C
and 42°C?
A. 5% O2, 10% CO2, and 85% N2
B. 20% O2, 10% CO2, and 70% N2
C. 20% O2, 20% CO2, and 60% N2
D. 20% O2, 5% CO2, and 75% N2

Answer 4

A. 5% O2, 10% CO2, and 85% N2

Question 5

5. Which group of tests best differentiates
   Helicobacter pylori from C. jejuni?
   A. Catalase, oxidase, and Gram stain
   B. Catalase, oxidase, and nalidixic acid sensitivity
   C. Catalase, oxidase, and cephalothin sensitivity
   D. Urease, nitrate, and hippurate hydrolysis

Answer 5

D. Urease, nitrate, and hippurate hydrolysis

Question 6

6. Which of the following tests should be done first
   in order to differentiate Aeromonas spp. from the
   Enterobacteriaceae?
   A. Urease
   B. OF glucose
   C. Oxidase
   D. Catalase

Answer 6

C. Oxidase

Question 7

7. Which is the best rapid test to differentiate
   Plesiomonas shigelloides from a Shigella species on
   selective enteric agar?
   A. Oxidase
   B. Indole
   C. TSI
   D. Urease

Answer 7

A. Oxidase

Question 8

8. Which are the best two tests to differentiate
   A. hydrophilia from P. shigelloides?
   A. Oxidase and motility
   B. DNase and VP
   C. Indole and lysine decarboxylase
   D. Growth on MacConkey and blood agar

Answer 8

B. DNase and VP

Question 9

9. Which genus (in which most species are oxidase
   and catalase positive) of small gram-negative
   coccobacilli is associated mainly with animals but
   may cause endocarditis, bacteremia, as well as
   wound and dental infections in humans?
   A. Actinobacillus
   B. Pseudomonas
   C. Campylobacter
   D. Vibrio

Answer 9

A. Actinobacillus

Question 10

10. Which of the following tests may be used to
    differentiate Cardiobacterium hominis from
    Actinobacillus spp.?
    A. Gram stain
    B. Indole
    C. Anaerobic incubation
    D. Oxidase

Answer 10

B. Indole

Question 11

11. A mixture of slender gram-negative rods and
    coccobacilli with rounded ends was recovered from
    blood cultures following a patient’s root canal
    surgery. Given the following results after 48 hours,
    what is the most likely organism?
    Catalase = Neg
    Ornithine decarboxylase = +
    Urease = Neg Lysine decarboxylase = +
    Oxidase = + X and V requirement = Neg
    Indole = Neg
    Carbohydrates = Neg
    (no acid produced)
    Growth on blood and chocolate agar = + (with pitting
    of agar)
    Growth on MacConkey agar = Neg
    A. Eikenella corrodens
    B. Actinobacillus spp.
    C. Cardiobacterium hominis
    D. Proteus spp

Answer 11

A. Eikenella corrodens

Question 12

12. Kingella kingae can best be differentiated from
    Eikenella corrodens using which medium?
    A. Sheep blood agar
    B. Chocolate agar
    C. MacConkey agar
    D. XLD agar

Answer 12

A. Sheep blood agar

Question 13

13. Kingella kingae is usually associated with which
    type of infection?
    A. Middle ear
    B. Endocarditis
    C. Meningitis
    D. Urogenital

Answer 13

B. Endocarditis

Question 14

14. Cultures obtained from a dog bite wound
    produced yellow, tan, and slightly pink colonies
    on blood and chocolate agar with a margin of
    fingerlike projections appearing as a film around
    the colonies. Given the following results at
    24 hours, which is the most likely organism?
    Oxidase = +
    Catalase = +
    Growth on MacConkey agar = Neg
    Motility = Neg
    A. Actinobacillus spp.
    B. Eikenella spp.
    C. Capnocytophaga spp.
    D. Pseudomonas spp.

Answer 14

C. Capnocytophaga spp.

Question 15

15. Smooth gray colonies showing no hemolysis are
    recovered from an infected cat scratch on blood
    and chocolate agar but fail to grow on MacConkey
    agar. The organisms are gram-negative pleomorphic
    rods that are both catalase and oxidase positive
    and strongly indole positive. The most likely
    organism is:
    A. Capnocytophaga spp.
    B. Pasteurella spp.
    C. Proteus spp.
    D. Pseudomonas spp.

Answer 15

B. Pasteurella spp.

Question 16

16. Which media should be used to recover Bordetella
    pertussis from a nasopharyngeal specimen?
    A. Chocolate agar
    B. Blood agar
    C. MacConkey agar
    D. Bordet–Gengou agar

Answer 16

D. Bordet–Gengou agar

Question 17

17. Which medium is recommended for the recovery
    of Brucella spp. from blood and bone marrow
    specimens?
    A. Biphasic Castenada bottles with Brucella broth
    B. Blood culture bottles with Brucella broth
    C. Bordet–Gengou agar plates and THIO broth
    D. Blood culture bottles with THIO broth

Answer 17

A. Biphasic Castenada bottles with Brucella broth

Question 18

18. In addition to CO2 requirements and biochemical
    characteristics, Brucella melitensis and Brucella
    abortus are differentiated by growth on media
    containing which two dyes?
    A. Basic fuchsin and thionin
    B. Methylene blue and crystal violet
    C. Carbol fuchsin and iodine
    D. Safranin and methylene blue

Answer 18

A. Basic fuchsin and thionin

Question 19

19. Which of the following amino acids are required
    for growth of Francisella tularensis?
    A. Leucine and ornithine
    B. Arginine and lysine
    C. Cysteine and cystine
    D. Histidine and tryptophan

Answer 19

C. Cysteine and cystine

Question 20

20. Which medium is best for recovery of Legionella
    pneumophila from clinical specimens?
    A. Chocolate agar
    B. Bordet–Gengou agar
    C. New yeast extract agar
    D. Buffered charcoal–yeast extract (CYE) agar

Answer 20

D. Buffered charcoal–yeast extract (CYE) agar

Question 21

21. Haemophilus influenzae causes ocular infections
    (pinkeye) and requires X and V factors in the
    primary medium for growth. The subspecies
    Haemophilus influenza (biogroup) aegyptius can
    further be identified and differentiated by which
    two tests?
    A. Indole and xylose
    B. Glucose and urease
    C. Oxidase and catalase
    D. ALA test and oxidase

Answer 21

A. Indole and xylose

Question 22

22. Haemophilus species that require the V factor
    (NAD) are easily recovered on which primary
    agar plate?
    A. Blood agar made with sheep red cells
    B. Blood agar made with horse red cells
    C. Chocolate agar
    D. Xylose agar

Answer 22

C. Chocolate agar

Question 23

23. Which of the following products is responsible
    for satellite growth of Haemophilus spp. around
    colonies of Staphylococcus and Neisseria spp. on
    sheep blood agar?
    A. NAD
    B. Hemin
    C. Indole
    D. Oxidase

Answer 23

A. NAD

Question 24

24. Which of the following plates should be used in
    order to identify Haemophilus haemolyticus and
    Haemophilus parahaemolyticus?
    A. Sheep blood agar and chocolate agar
    B. Horse blood agar and Mueller–Hinton agar with
    X and V strips
    C. Brain–heart infusion agar with sheep red cells
    added
    D. Chocolate agar and Mueller–Hinton agar with X
    factor added

Answer 24

B. Horse blood agar and Mueller–Hinton agar with
X and V strips

Question 25

25. The majority of Haemophilus influenzae infections are caused by which of the following capsular serotypes? A. a B. b C. c D. d

Answer 25

B. b

Question 26

26. Which Haemophilus species is generally associated with endocarditis? A. H. influenzae B. H. ducreyi C. H. aphrophilus D. H. haemolyticus

Answer 26

C. H. aphrophilus

Question 27

27. Which Haemophilus species is difficult to isolate and recover from genital ulcers and swollen lymph nodes? A. H. aphrophilus B. H. ducreyi C. H. haemolyticus D. H. parahaemolyticus

Answer 27

B. H. ducreyi

Question 28

28. Which of the following is a characteristic of strains of Haemophilus influenzae that are resistant to ampicillin? A. Production of β-lactamase enzymes B. Hydrolysis of chloramphenicol C. Hydrolysis of urea D. All of these options

Answer 28

A. Production of β-lactamase enzymes

Question 29

29. A small, gram-negative coccobacillus recovered from the CSF of a 2-year-old child gave the following results: Indole = + Glucose = + (acid) X requirement = + V requirement = + Urease = + Lactose = Neg Sucrose = Neg Hemolysis = Neg Which is the most likely identification? A. Haemophilus parainfluenzae B. Haemophilus influenzae C. Haemophilus ducreyi D. Haemophilus aphrophilus

Answer 29

B. Haemophilus influenzae

Question 30

30. The δ-ALA test (for porphyrins) is a confirmatory procedure for which test used for identification of Haemophilus species? A. X factor requirement B. V factor requirement C. Urease production D. Indole production

Answer 30

A. X factor requirement

Question 31

31. An elderly woman who cared for several domestic cats was hospitalized with suspected cat-scratch disease (CSD). Blood cultures appeared negative, but a small, slightly curved pleomorphic gram-negative bacillus grew on BHI agar (brain, heart infusion agar with 5% horse or rabbit blood). What is the most likely identification? A. Bartonella spp. B. Brucella spp. C. Kingella spp. D. Haemophilus spp

Answer 31

A. Bartonella spp.

Question 32

32. A 5-year-old nonimmunized male with a persistent cough, fever, and flulike symptoms was admitted to the hospital. Nasopharyngeal swabs were cultured on 15% blood, chocolate, Bordet–Genjou, and Regan–Lowe (with 10% charcoal) agars. All media grew a gram-negative coccobacillus. Carbohydrate and biochemical tests were negative. What is the most likely identification? A. Haemophilus influenza B. Bordetella pertussis C. Haemophilus parainfluenzae D. Bordetella bronchiseptica

Answer 32

B. Bordetella pertussis

Question 33

33. A 29-year-old male who often hunted rabbits and spent a lot of time in the woods was admitted to the hospital with skin ulcers on his upper extremities. At 48 hours, a small coccobacillus was recovered from the aerobic blood culture bottle only. The organism stained poorly with Gram stain, but did stain with acridine orange. Cultures taken from the ulcers did not grow on primary media. What is the most likely identification? A. Pseudomonas aeruginosa B. Pseudomonas fluorescens C. Chryseobacterium spp. D. Francisella tularensis

Answer 33

D. Francisella tularensis

Question 34

34. A neonate was readmitted to the hospital with a diagnosis of meningitis. The CSF revealed gram-negative straight rods. At 24 hours, the organism grew on 5% sheep blood and chocolate agars displaying a yellow pigment. On MacConkey agar, it appeared as a non–lactose fermenter. Colonies were oxidase, DNase, and gelatinase positive, and oxidized glucose and mannitol. What is the most likely identification? A. Haemophilus influenza B. Chryseobacterium meningosepticum C. Stenotrophomonas maltophilia D. Acinetobacter baumannii

Answer 34

B. Chryseobacterium meningosepticum

Question 35

35. A 46-year-old dog warden was admitted to the hospital with several puncture bite wounds encountered while wrangling with a stray dog. Culture at 48 hours produced small yellow colonies on 5% sheep blood and chocolate agars in 10% CO2, but no growth on MacConkey agar. Gram stain showed gram-negative curved, fusiform rods. Colonies were oxidase and catalase positive. What is the most likely identification? A. Capnocytophaga canimorsus B. Francisella tularensis C. Legionella pneumophila D. Pseudomonas aeruginosa

Answer 35

A. Capnocytophaga canimorsus

Question 36

36. The HACEK group of organisms (Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella spp.) are all known for which type of infection? A. Urinary tract B. Endocarditis C. Pharyngitis D. Tonsillitis

Answer 36

B. Endocarditis

Question 37

37. A suspected case of Legionnaires’ disease was noted on the request form for a culture and sensitivity ordered on a sputum sample. The patient was a 70-year-old male who presented with a positive serological test for Legionella spp. What is the most efficient way to confirm the infection using the submitted sample? A. Culture the sputum on MacConkey agar B. Gram stain of the sputum C. Acid-fast staining D. Direct immunofluorescent microscopy

Answer 37

D. Direct immunofluorescent microscopy