Deck 30: Haemophilus

Question 1

Among Haemophilus influenzae strains,group designations (e.g. ,type b)are based on:

A)flagellar antigens.
B)capsular characteristics.
C)cell wall antigens.
D)infectious capabilities.

Answer 1

B
Among H.influenzae strains,two broad categories exist: typeable and nontypeable.Strains are typed on the basis of capsular characteristics.The capsule is made up of a sugar-alcohol phosphate (e.g. ,polyribitol phosphate)complex.Differences in this complex are the basis for separating encapsulated strains into one of six groups: type a,b,c,d,e,or f.

Question 2

To increase the sensitivity of direct Gram-stain examination of body fluid specimens,the specimens are usually:

A)incubated for 18 to 24 hours before staining.
B)centrifuged before staining.
C)examined for at least 1 hour.
D)stained for an additional 5 minutes.

Answer 2

B
To increase the sensitivity of direct Gram-stain examination of body fluid specimens,especially CSF,the specimens are usually centrifuged (2000 rpm for 10 minutes),and the smear is prepared from the resulting pellet.This concentration step can increase the sensitivity of direct microscopic examination by fivefold to tenfold.

Question 3

Isolates from cerebrospinal fluid (CSF)or respiratory tract specimens that are gram-negative coccobacilli grow on chocolate agar in CO₂ but not on blood agar,and are porphyrin-negative and nonhemolytic on rabbit or horse blood may be identified as:

A)H.parainfluenzae.
B)Haemophilus parahaemolyticus.
C)H.haemolyticus.
D)H.influenzae.

Answer 3

D
All characteristics listed are those that describe H.influenzae.

Question 4

A 6-year-old boy was diagnosed with purulent conjunctivitis caused by a species of Haemophilus.What would the biochemical profile of the organism be?

A)Growth requirements require both X and V factors;the organism is hemolytic on rabbit blood.
B)Growth requirements require both X and V factors;the organism is nonhemolytic on rabbit blood.
C)Growth requirements require V factor;the organism is hemolytic on rabbit blood.
D)Growth requirements require X factor;the organism is nonhemolytic on rabbit blood.

Question 5

Of the following media,which provides the NAD necessary for the growth of Haemophilus spp.?

A)5% sheep blood agar
B)Brain-heart infusion agar
C)Chocolate agar
D)Nutrient agar

Question 6

The virulence of this organism,which causes chancroid,is most likely attributed to:

A)proteases.
B)capsular factors.
C)hemolysins.
D)catalase.

Question 7

H.influenzae can be distinguished from H.aegyptius by its _____ test for _____.

A)negative;sucrose fermentation
B)negative;lactose fermentation
C)positive;catalase
D)positive;xylose fermentation

Question 8

Isolates from an ear swab that are gram-negative coccobacilli grow on chocolate agar in CO₂ but not blood agar,require both X and V factors for growth,and are nonhemolytic on rabbit or horse blood may be identified as:

A)H.parainfluenzae.
B)H.ducreyi.
C)H.aphrophilus.
D)H.influenzae.

Question 9

The sputum of a 75-year-old man with chronic lung infections yields the following:
·Many gram-negative coccobacilli in Gram stain
·X and V factors required for growth
·Nonhemolytic on rabbit blood agar
The organism can be identified as:

A)Haemophilus aegyptius.
B)H.parainfluenzae.
C)Haemophilus haemolyticus.
D)H.influenzae.

Question 10

Isolates from CSF that are gram-negative coccobacilli,grow on chocolate agar in CO₂ but not blood agar,require factor V but not X,and are nonhemolytic on rabbit or horse blood may be identified as:

A)H.parainfluenzae.
B)H.influenzae.
C)H.aphrophilus.
D)H.ducreyi.

Question 11

Performance of the "factor requirement test" for Haemophilus involves the:

A)inoculation of unsupplemented media with a light suspension of the organism and placement of X and V factor disks on the agar surface.
B)inoculation of liquid media,unsupplemented and supplemented with X and V factors.
C)detection of the presence of enzymes that convert d-aminolevulinic acid (ALA)into porphyrins.
D)growth of the organism in the presence of bacterial species that produce X and V factors as metabolic byproducts.

Question 12

Which of the following media provides the factors necessary for the growth of Haemophilus spp.?

A)5% sheep blood agar
B)Brain-heart infusion agar
C)Chocolate agar
D)Nutrient agar

Question 13

In a phenomenon known as satelliting,tiny colonies of Haemophilus spp.may be observed growing on sheep blood agar close to colonies of:

A)Streptococcus pyogenes.
B)Staphylococcus aureus.
C)Micrococcus spp.
D)other Haemophilus spp.

Question 14

With one exception,species of the genus Haemophilus require which of the following media ingredients for in vitro growth?

A)Vitamin K and hemin
B)Hemin and nicotine adenine dinucleotide (NAD)
C)Vitamin K and NAD
D)Hemin and cysteine

Question 15

In a phenomenon known as satelliting,tiny colonies of Haemophilus spp.may be observed growing on sheep blood agar close to colonies of bacteria that can produce:

A)hemin.
B)NAD.
C)vitamin K.
D)cystine.

Question 16

Although a useful test in the past,the particle agglutination assay for the detection of H.influenzae,type b,capsular polysaccharide antigen is no longer reliable because of:

A)insufficiently high concentration of the organisms in clinical infections.
B)a lack of sensitivity and specificity of the test procedure.
C)the frequent use of antimicrobial therapy before collecting the specimen.
D)the increased use of H.influenzae,type b,vaccination.

Question 17

Which of the following opportunistic organisms is associated with slowly progressive subacute bacterial endocarditis?

A)H.ducreyi
B)H.influenzae
C)Aggregatibacter aphrophilus
D)H.parahaemolyticus

Question 18

Growth of most Haemophilus species in culture is enhanced by:

A)incubation at 33°C to 35°C.
B)high humidity.
C)5% to 10% carbon dioxide (CO₂).
D)enriched special media.

Question 19

Chancroid is the sexually transmitted disease caused by:

A)H.influenzae.
B)Haemophilus ducreyi.
C)H.aphrophilus.
D)Haemophilus parainfluenzae.

Question 20

H.ducreyi requires what special media to grow?

A)Heart infusion-based agar,supplemented with 10% IsoVitaleX and vancomycin
B)Mueller-Hinton-based chocolate agar,supplemented with 1% IsoVitaleX and vancomycin
C)Heart infusion-based chocolate agar,supplemented with 10% fetal bovine serum and vancomycin
D)Mueller-Hinton-based agar,supplemented with 10% IsoVitaleX and vancomycin