Miscellaneous and Fastidious Gram-Negative Rods

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

C. TCBS agar

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. Shigellaspp.
D. Salmonellaspp.

B. Vibrio parahaemolyticus

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

B. Campylobacter jejuni

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

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

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

D. Urease, nitrate, and hippurate hydrolysis

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

C. Oxidase

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

A. Oxidase

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

B. DNase and VP

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

A. Actinobacillus

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

B. Indole

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. Actinobacillusspp.
C. Cardiobacterium hominis
D. Proteusspp.

A. Eikenella corrodens

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

A. Sheep blood agar

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

B. Endocarditis

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. Pseudomonasspp.

C. Capnocytophaga spp.

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.

B. Pasteurella spp.

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

D. Bordet-Gengou agar

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

A. Biphasic Castenada bottles with Brucellabroth

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

A. Basic fuchsin and thionin

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

C. Cysteine and cystine

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

D. Buffered charcoal-yeast extract (CYE) agar

Haemophilus influenzae causes ocular infections (pinkeye) and requires X and V factors in the primary medium for growth. The subspecies Haemophilus influenza (biogroup) aegyptiuscan 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

A. Indole and xylose

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

C. Chocolate agar

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

A. NAD

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

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

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

B. b

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

C. H. aphrophilus

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

B. H. ducreyi

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

A. Production of β-lactamase enzymes

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

B. Haemophilus influenzae

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

A. X factor requirement

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.

A. Bartonella spp.

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

B. Bordetella pertussis

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

D. Francisella tularensis

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

B. Chryseobacterium meningosepticum

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

A. Capnocytophaga canimorsus

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

B. Endocarditis

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

D. Direct immunofluorescent microscopy