(Harr) III. Nonfermentative Bacilli Flashcards
(25 cards)
What are the most appropriate screening tests
to presumptively differentiate and identify the
nonfermentative gram-negative bacilli (NFB)
from the Enterobacteriaceae?
A. Catalase, decarboxylation of arginine, growth on blood agar
B. Motility, urease, morphology on blood agar
C. Oxidase, TSI, nitrate reduction, growth on MacConkey agar
D. Oxidase, indole, and growth on blood agar
C. Oxidase, TSI, nitrate reduction, growth on MacConkey agar
NFB will grow on the slant of TSI or KIA but they do
not acidify the butt (glucose fermentation), as do the
Enterobacteriaceae. NFB can be cytochrome oxidase
positive or negative, but all the Enterobacteriaceae are
oxidase negative. The Enterobacteriaceae grow well
on MacConkey agar and reduce nitrate to nitrite, but
the NFB grow poorly or not at all and most do not
reduce nitrate. Nearly 70% of the NFB recovered from
clinical specimens are:
Strains of Psuedomonas aeruginosa
Acinetobacter baumannii
Stenotrophomonas maltophilia
Presumptive tests used for identification of the Pseudomonas spp. are:
A. Oxidase, oxidation–fermentation (OF) glucose (open), OF glucose (sealed), motility, pigment production
B. Growth on blood agar plate (BAP) and eosin–methylene blue (EMB) agars, lysine decarboxylation, catalase
C. Growth on MacConkey, EMB, and XLD agars and motility
D. Growth on mannitol salt agar and flagellar stain
A. Oxidase, oxidation–fermentation (OF) glucose (open), OF glucose (sealed), motility, pigment production
The use of OF tubes helps to determine the
presumption of a nonfermentative bacillus (glucose
oxidation positive and glucose fermentation
negative). The positive cytochrome oxidase test
and pigment production indicate a possible
Pseudomonas species. Several NFB produce pigments
that aid in species identification: P. aeruginosa
produces yellow pyoverdins (fluorescein) and/or
pyocyanin (blue aqua pigment). The characteristic
grapelike odor of aminoacetophenone as well as
growth at 42°C are characteristics of P. aeruginosa
Which tests are most appropriate to differentiate between Pseudomonas aeruginosa and Pseudomonas putida?
A. Oxidase, motility, pyoverdin
B. Oxidase, motility, lactose
C. Oxidase, ONPG, DNase
D. Mannitol, nitrate reduction, growth at 42°C
D. Mannitol, nitrate reduction, growth at 42°C
Both organisms are oxidase positive, motile, and produce pyoverdin. Both are negative for ONPG and DNase. The differentiating tests are:
Test P. aeruginosa P. putida
Mannitol + Neg
Reduce NO3 + Neg
to NO2
42°C growth + Neg
Which test group best differentiates Acinetobacter baumannii from P. aeruginosa?
A. Oxidase, motility, NO3 reduction
B. MacConkey growth, 37°C growth, catalase
C. Blood agar growth, oxidase, catalase
D. Oxidase, TSI, MacConkey growth
A. Oxidase, motility, NO3 reduction
Acinetobacter spp. are nonmotile rods that appear as
coccobacillary forms from clinical specimens. All are
oxidase negative and catalase positive. P. aeruginosa
reduces NO3 to NO2, while A. baumannii does not.
In addition to motility, which test best differentiates Acinetobacter spp. and Alcaligenes spp.?
A. TSI
B. Oxidase
C. Catalase
D. Flagellar stain
B. Oxidase
The two genera, Acinetobacter and Alcaligenes, are
very similar. Both use oxidation for the metabolism
of carbohydrate, with some strains being
nonsaccharolytic. Both grow well on MacConkey
agar. However, Acinetobacter is nonmotile and
oxidase negative. Alcaligenes is motile by peritrichous
flagella and oxidase positive.
The most noted differences between P. aeruginosa and Stenotrophomonas maltophilia are:
A. Oxidase, catalase, and TSI
B. Oxidase, catalase, and ONPG
C. Oxidase, 42°C growth, and polar tuft of flagella
D. Catalase, TSI, and pigment
C. Oxidase, 42°C growth, and polar tuft of flagella
The two genera, Pseudomonas and Stenotrophomonas,
are motile and grow well on MacConkey agar.
However, P. aeruginosa is oxidase positive and grows
at 42°C but is motile only by polar monotrichous
flagella. S. maltophilia is oxidase negative, does not
grow at 42°C, and is motile by a polar tuft of flagella.
Which Pseudomonas is usually associated with a
lung infection related to cystic fibrosis?
A. P. fluorescens
B. P. aeruginosa
C. P. putida
D. Burkholderia pseudomallei
B. P. aeruginosa
P. aeruginosa is often recovered from the respiratory
secretions of cystic fibrosis patients. If the patient is
chronically infected with the mucoid strain of
P. aeruginosa, the biochemical identification is very
difficult. The mucoid strain results from production
of large amounts of alginate, a polysaccharide that
surrounds the cell.
A nonfermenter recovered from an eye wound is oxidase positive, motile with polar monotrichous flagella, and grows at 42°C. Colonies are dry, wrinkled or smooth, buff to light brown in color, and are difficult to remove from the agar. In which DNA homology group should this organism be placed?
A. Pseudomonas stutzeri
B. Pseudomonas fluorescens
C. Pseudomonas alcaligenes
D. Pseudomonas diminuta
A. Pseudomonas stutzeri
P. stutzeri produces dry, wrinkled colonies that are
tough and adhere to the media as well as smooth
colonies. B. pseudomallei produces similar colony
types but is distinguished by biochemical tests and
susceptibility to the polymyxins. The colonies of
P. stutzeri are buff to light brown because of the
relatively high concentration of cytochromes.
Which organism is associated with immunodeficiency syndromes and melioidosis (a glanders-like disease in Southeast Asia and northern Australia)?
A. Pseudomonas aeruginosa
B. Pseudomonas stutzeri
C. Pseudomonas putida
D. Burkholderia pseudomallei
D. Burkholderia pseudomallei
B. pseudomallei produces wrinkled colonies resembling
P. stutzeri. Infections are usually asymptomatic and
can be diagnosed only by serological methods.
The organism exists in soil and water in an area of
latitude 20° north and south of the equator (mainly in
Thailand and Vietnam). Thousands of U.S. military
personnel were infected with these bacteria during
the 1960s and 1970s. The disease may reactivate
many years after exposure and has been called the
“Vietnamese time bomb.”
Which biochemical tests are needed to differentiate Burkholderia cepacia from S. maltophilia?
A. Pigment on blood agar, oxidase, DNase
B. Pigment on MacConkey agar, flagellar stain,
motility
C. Glucose, maltose, lysine decarboxylase
D. TSI, motility, oxidase
A. Pigment on blood agar, oxidase, DNase
Both organisms produce yellowish pigment and have polar tuft flagella, but the oxidase and DNase tests are differential.
Test B. cepacia S. maltophilia
Pigment on BAP Green-yellow Lavender-green
Oxidase + Neg
DNase Neg +
Motility + +
Glucose OF + +
(open)
Maltose OF + +
(open)
Lysine + +
decarboxylase
The following results were obtained from a pure
culture of gram-negative rods recovered from the pulmonary secretions of a 10-year-old cystic fibrosis patient with pneumonia:
Oxidase = +
Motility = +
Glucose OF (op en) = +
Gelatin hydrolysis = +
Pigment = Red Arginine
dihydrolase = + (nonfluorescent)
Growth at 42°C = +
Flagella = + (polar, monotrichous)
Which is the most likely organism?
A. Burkholderia pseudomallei
B. Pseudomonas stutzeri
C. Burkholderia cepacia
D. Pseudomonas aeruginosa
D. Pseudomonas aeruginosa
The oxidase test and red pigment (pyorubin), as well
as growth at 42°C, distinguish P. aeruginosa from the
other pseudomonads listed, particularly B. cepacia,
which is also associated with cystic fibrosis.
Alcaligenes faecalis (formerly A. odorans) is distinguished from Bordetella bronchiseptica with which test?
A. Urease (rapid)
B. Oxidase
C. Growth on MacConkey agar
D. Motility
A. Urease (rapid)
Alcaligenes and Bordetella are genera belonging to
the Alcaligenaceae family. The two organisms are
very similar biochemically, but B. bronchiseptica is
urease positive. Both organisms are oxidase positive,
grow on MacConkey agar, and are motile by
peritrichous flagella. B. bronchiseptica grows well on
MacConkey agar but other species of Bordetella are
fastidious gram-negative rods.
Chryseobacterium spp. are easily distinguished from Acinetobacter spp. by which of the following two tests?
A. Oxidase, growth on MacConkey agar
B. Oxidase and OF (glucose)
C. TSI and urea hydrolysis
D. TSI and VP
A. Oxidase, growth on MacConkey agar
Chryseobacterium spp. and Acinetobacter spp. often
produce a yellow pigment on blood or chocolate
agar and are nonmotile. Acinetobacter spp. are
oxidase negative, grow on MacConkey agar, and are
coccobacillary on the Gram stain smear. In contrast,
Chryseobacterium spp. are oxidase positive, do not
grow on MacConkey agar, and are typically rod
shaped. Chryseobacterium meningosepticum is highly
pathogenic for premature infants.
A gram-negative coccobacillus was recovered on chocolate agar from the CSF of an immunosuppressed patient. The organism was nonmotile and positive for indophenol oxidase but failed to grow on MacConkey agar. The organism was highly susceptible to penicillin. The most probable identification is:
A. Acinetobacter spp.
B. Pseudomonas aeruginosa
C. Pseudomonas stutzeri
D. Moraxella lacunata
D. Moraxella lacunata
A specimen from a 15-year-old female burn patient was cultured after débridement, and the following results were obtained:
Oxidase = +
Lysine decarboxylase = Neg
Catalase = +
Motility = +
Ornithine decarboxylase = Neg
Glucose = + for oxidation (open tube)
Arginine dihydrolase = +
Maltose = Neg for oxidation (open tube)
Penicillin = Resistant
Aminoglycosides =Susceptible
Colistin (Polymixin B) = Susceptible
These results indicate which of the following
organisms?
A. Acinetobacter baumannii
B. Moraxella lacunata
C. Pseudomonas aeruginosa
D. Acinetobacter lwoffii
D. Acinetobacter lwoffii
Cetrimide agar is used as a selective isolation agar for which organism?
A. Acinetobacter spp.
B. Pseudomonas aeruginosa
C. Moraxella spp.
D. Stenotrophomonas maltophilia
B. Pseudomonas aeruginosa
A yellow pigment–producing organism that is
oxidase positive, nonmotile, and does not grow on MacConkey agar is:
A. Acinetobacter baumannii
B. Acinetobacter lwoffii
C. Burkholderia cepacia
D. Chryseobacterium meningosepticum
D. Chryseobacterium meningosepticum
Which reagent(s) is (are) used to develop the red color indicative of a positive reaction in the nitrate reduction test?
A. Sulfanilic acid and α-naphthylamine
B. Ehrlich’s and Kovac’s reagents
C. o-Nitrophenyl-β-D-galactopyranoside
D. Kovac’s reagent
A. Sulfanilic acid and α-naphthylamine
A culture from an intra-abdominal abscess
produced orange-tan colonies on blood agar that gave the following results:
Oxidase = +
Nitrate reduction = +
KIA = Alk/Alk (H2S)+
Motility = + (single polar flagellum)
DNase = +
Ornithine decarboxylase = +
Growth at 42°C = Neg
The most likely identification is:
A. Shewanella putrefaciens
B. Acinetobacter spp.
C. Pseudomonas aeruginosa
D. Chryseobacterium spp.
A. Shewanella putrefaciens
Chryseobacterium spp. and B. cepacia are easily
differentiated by which test?
A. Motility
B. OF glucose
C. Oxidase
D. Cetrimide agar
A. Motility
A 15-year-old female complained of a severe eye irritation after removing her soft-contact lenses. A swab of the infected right eye was obtained by an ophthalmologist, who ordered a culture and sensitivity test. The culture was plated on blood agar and MacConkey agar. At 24 hours, growth of a gram-negative rod that tested positive for cytochrome oxidase was noted. The Mueller–Hinton sensitivity plate showed a bluish-green “lawn” of growth that proved highly resistant to most of the antibiotics tested except amikacin, tobramycin, and ciprofloxacin.
What is the most likely identification?
A. Burkholderia cepacia
B. Pseudomonas aeruginosa
C. Stenotrophomonas maltophilia
D. Acinetobacter baumannii
B. Pseudomonas aeruginosa
Which of the listed Pseudomonas spp. is associated with the following virulence factors: exotoxin A, endotoxins, proteolytic enzymes, antimicrobial resistance, and production of alginate?
A. P. fluorescens
B. P. putida
C. P. stutzeri
D. P. aeruginosa
D. P. aeruginosa
A 20-year-old horse groomer exhibited a “glanders-like” infection. His history indicated he had suffered several open wounds on his hands 2 weeks before the swelling of his lymph nodes. A gram-negative rod was recovered from a blood culture that grew well on blood and MacConkey agars. Most of the biochemical tests were negative, including the cytochrome oxidase test. What is the most likely identification?
A. Burkholderia mallei
B. Pseudomonas aeruginosa
C. Pseudomonas stutzeri
D. Burkholderia pseudomallei
A. Burkholderia mallei
A Vietnam War veteran presented with a “glanders-like” infection (melioidosis). Several blood cultures produced gram-negative rods that were positive for cytochrome oxidase, oxidized glucose and xylose, and grew at 42°C. What is the most likely organism?
A. Stenotrophomonas maltophilia
B. Burkholderia pseudomallei
C. Pseudomonas aeruginosa
D. Acinetobacter spp.
B. Burkholderia pseudomallei
