Deck 42: Obligate Intracellular and Non-culturable Bacterial Agents

Question 1

The C.burnetii,an acute systemic infection,primarily affects the lungs and can exist in two antigenic states.The reference method that is both highly specific and sensitive and is recommended for identification is:

A)immunofluorescent antibody (IFA).
B)direct fluorescent antibody (DFA).
C)Western blot.
D)latex agglutination.

Answer 1

A
C.burnetii can exist in two antigenic states.When isolated from animals,C.burnetii is in a phase I (large-cell variant)form and is highly infectious.In its phase II form (small-cell variant),C.burnetii has been grown in cultured cell lines and is not infectious but acts like a spore assisting in extracellular survival of the organism.IFA is considered the reference method for both acute and chronic Q fever that is both highly specific and sensitive and is recommended for its reliability,cost effectiveness,and ease of performance.

Question 2

A prokaryote that differs from most other bacteria with respect to its very small size and obligates intracellular parasitism is:

A)Rickettsia.
B)Bartonella.
C)Calymmatobacterium.
D)Coxiella.

Answer 2

A
The organisms addressed in Chapter 43 are obligate intracellular bacteria or are considered either extremely difficult to culture or unable to be cultured.Organisms of the genera Chlamydia,Chlamydophila,Rickettsia,Orientia,Anaplasma,and Ehrlichia are prokaryotes that differ from most other bacteria with respect to their very small size and obligate intracellular parasitism.

Question 3

Of the following organisms,which can be described as a fastidious obligate intracellular parasite that multiplies by binary fission in the cytoplasm of host cells and infects humans as accidental hosts in most cases?

A)Rickettsia
B)Chlamydia
C)Calymmatobacterium
D)Coxiella

Answer 3

A
Rickettsiae are fastidious bacteria that are obligate intracellular parasites.These bacterial agents survive only briefly outside of a host (reservoir or vector)and multiply only intracellularly.The organisms are small (0.3 mm× 1.0 to 2.0 mm),pleomorphic,gram-negative bacilli that multiply by binary fission in the cytoplasm of the host cells.The release of mature Rickettsiae results in the lysis of the host cell.

Question 4

A Weil-Felix test was performed on serial dilutions from a patient bitten by a tick.The results obtained were positive for OX-19 and negative for OX-2 and OX-K.Based on these findings,the organism can be identified as:

A)R.rickettsii.
B)O.tsutsugamushi.
C)Rickettsia prowazekii.
D)Rickettsia typhi.

Question 5

Of the following organisms,which has a unique developmental life cycle including a replicative form,the reticulate body (RB),and an extracellular,metabolically inert,infective form,the elementary body (EB)?

A)Rickettsia
B)Chlamydia
C)Ehrlichia
D)Coxiella

Question 6

The drug of choice for the treatment of granuloma inguinale,which is a major cause of genital ulcers in India,New Guinea,and part of South America,is:

A)clindamycin.
B)doxycycline.
C)imipenem.
D)gentamycin.

Question 7

Which of the following vectors transmit scrub typhus?

A)Lice
B)Ticks
C)Fleas
D)Chiggers

Question 8

Binary fission within vacuoles divides which of the following forms of Chlamydia?

A)RB
B)EB
C)Replicate body
D)Initial body

Question 9

Tropheryma whipplei is characterized by the presence of periodic acid-Schiff (PAS)-staining macrophages,which indicates mucopolysaccharide or glycoprotein,in almost every organ system.Without treatment,this disease is uniformly fatal.Identification is achieved using:

A)enzyme-linked immunosorbent assay (ELISA).
B)IFA.
C)immunoblotting.
D)real-time polymerase chain reaction (PCR).

Question 10

The most common sexually transmitted bacterial pathogen and a major cause of pelvic inflammatory disease (PID)is:

A)Rickettsia rickettsii.
B)Chlamydia trachomatis.
C)Klebsiella granulomatis.
D)Coxiella burnetii.