Page 25 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART I Basic Bacteriology
14
3. In the process of studying how bacteria cause disease, it was
found that a rare mutant of a pathogenic strain failed to form
often produce extracellular substances that allow them to stick
a capsule. Which one of the following statements is the most
firmly to medical devices, such as intravenous catheters. Which
one of the following is the name of this extracellular substance?
accurate in regard to this unencapsulated mutant strain?
(A) It was nonpathogenic primarily because it was easily
(A) Axial filament
phagocytized.
(B) Endotoxin
(C) Flagella
(B) It was nonpathogenic primarily because it could not invade
tissue.
(D) Glycocalyx
(C) It was nonpathogenic primarily because it could only grow
(E) Porin
anaerobically. 9. Lysozyme in tears is an effective mechanism for preventing bac-
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terial conjunctivitis. Which one of the following bacterial struc-
(D) It was highly pathogenic because it could secrete larger
amounts of exotoxin.
tures does lysozyme degrade?
(E) It was highly pathogenic because it could secrete larger
(A) Endotoxin
amounts of endotoxin.
(B) Nucleoid DNA
4. Mycobacterium tuberculosis stains well with the acid-fast stain,
(C) Peptidoglycan
but not with the Gram stain. Which one of the following is the
(D) Pilus
most likely reason for this observation?
(E) Plasmid DNA
(A) It has a large number of pili that absorb the purple dye.
(B) It has a large amount of lipid that prevents entry of the purple
gens. Which one of the following is the most accurate statement
dye.
about bacterial spores?
(C) It has a very thin cell wall that does not retain the purple
dye.
(B) They are produced primarily by gram-negative cocci.
(D) It is too thin to be seen in the Gram stain.
(C) They are formed primarily when the bacterium is exposed to
(E) It has histones that are highly negatively charged. (A) They are killed by boiling for 15 minutes.
antibiotics.
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5. Of the following bacterial components, which one exhibits the
(D) They are produced by anaerobes only in the presence of oxygen.
most antigenic variation?
(E) They are metabolically inactive yet can survive for years in
(A) Capsule
that inactive state.
(B) Lipid A of endotoxin
(C) Peptidoglycan
ANSWERS
(D) Ribosome
(E) Spore
(1) (D)
6. β-Lactamases are an important cause of antibiotic resistance.
(2) (C)
Which one of the following is the most common site where
(3) (A)
β-lactamases are located?
(A) Attached to DNA in the nucleoid
(5) (A)
(B) Attached to pili on the bacterial surface
(C) Free in the cytoplasm
(D) Within the capsule (4) (B)
(7) (A)
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(E) Within the periplasmic space
(8) (D)
7. Which one of the following is the most accurate description of
(9) (C)
the structural differences between gram-positive bacteria and
(10) (E)
gram-negative bacteria?
(A) Gram-positive bacteria have a thick peptidoglycan layer,
whereas gram-negative bacteria have a thin layer.
(B) Gram-positive bacteria have an outer lipid-rich membrane,
COURSE EXAMINATIONS
whereas gram-negative bacteria do not.
(C) Gram-positive bacteria form a sex pilus that mediates conju-
Questions on the topics discussed in this chapter can be found
gation, whereas gram-negative bacteria do not.
(D) Gram-positive bacteria have plasmids, whereas gram-negative
Board) Practice Questions starting on page 709. Also see Part
bacteria do not.
XIV: USMLE (National Board) Practice Examination starting
(E) Gram-positive bacteria have capsules, whereas gram-negative
on page 751.
bacteria do not. in the Basic Bacteriology section of Part XIII: USMLE (National
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