医学微生物英语试题

Part 1 Single Best Choice Questions （401 point=40 pts）

Instruction： （1) Mark the letter that corresponds to the right answer in the formatted ANSWER SHEET with 2B PENCIL. Since the

marks are read by computer， answers in this question sheet will not be collected。 (2） For one question， only one letter is permitted

to be darkened， otherwise， it will be recognize as wrong by the computer。 (3） Do not forget to mark your student ID number and

write in your name。

1. Bacteria that lack cell walls and do not synthesize the precursors of

peptidoglycan are called

A. Spirochetes

B。 Chlamydiae

C。 Mycoplasmas

D. L forms

E. Bacilli

2。 Each of the following is a typical property of obligate anaerobe EXCEPT

A. They generate energy by using the cytochrome system

B. They grow best in the absence of air

C。 They lack superoxide dismutase

D。 They lack catalase

E。 Tetanus is caused by a typical obligate anaerobe

3。 . Which one of the following agents lacks nucleic acid?

A. Bacteria

B。 Viruses

C。 Viroids D。 Prions

E. Protozoa

4. Which one of the following most correctly describes vaccines containing live,

attenuated （weaken) pathogens？

A。 Pathogen does not multiply in human hosts

B。 They provide extended， sometimes life—long immunity

C. There is no possibility for reversion to pathogenic form

D。 They provide little cell—mediated immunity

E。 They are administered by injection

5。 Each of the following statements concerning the killing of bacteria is correct

EXCEPT

A。 A 70％ solution of ethanol kills more effectively than absolute （100%)

ethanol

B. An autoclave uses steam under pressure to reach the killing temperature of

121 oC

C. The pasteurization of milk kills pathogens but allows many organisms and

spores to survive

D。 Iodine kills by causing the formation of thymine dimers in the bacterial DNA

E. Ultraviolet is widely used to disinfect the air of a room

6。 A patient presents with severe colitis associated with an overgrowth of

Clostridium difficile （艰难梭菌） in the lower bowel。 The most likely cause

of this condition is

A. botulinum food poisoning

B。 a stomach ulcer

C. a compromised immune system

D. abtibiotic therapy

E。 mechanical blockage of the large intestine

7。 The growth rate of bacteria during the exponential phase of growth is

A。 Zero

B. Increasing

C。 Constant

D。 Decreasing

E。 Negative

8。 A principal criterion for the diagnosis of meningococcal meningitis is

observation of bacteria in a sample of

A。 urine

B。 spinal fluid

C。 saliva

D。 throat swab

E. sputum 9. Each of the following statements concerning peptidoglycan is correct

EXCEPT

A. It has a backbone composed of alternating units of muramic acid and

acetylglucosamine

B。 Cross—links between the tetrapeptides involve D-alanine

C。 It is thinner in gram-positive than in gram-negative cells

D。 It can be degraded by lysozyme

E。 It can be degraded by penicillin

10。 Each of the following is a typical property of obligate anaerobe EXCEPT

A。 They generate energy by using the cytochrome system

B. They grow best in the absence of air

C。 They lack superoxide dismutase

D。 They lack catalase

E。 Tetanus is caused by a typical obligate anaerobe

11。 The effects of antibody on bacteria include each of the following EXCEPT

A。 Lysis of gram—negative bacteria in conjunction with complement

B。 Augmentation of phagocytosis

C。 Increase in the frequency of lysogeny

D。 Inhibition of adherence of bacteria to mucosal surfaces

E。 Neutralize exotoxins

12。 Each of the following statements concerning exotoxins is correct EXCEPT

A. Exotoxins are polypeptides

B. Exotoxins are more easily inactivated by heat than are endotoxins C。 Exotoxins are less toxic than the same amount of endotoxins

D。 Exotoxins can be converted to toxoids

E. Exotoxins are usually composed of two subunits including binding subunit

and active subunit

13。 Each of the following statements concerning the killing of bacteria is

correct EXCEPT

A。 A 70% solution of ethanol kills more effectively than absolute （100％）

ethanol

B. An autoclave uses steam under pressure to reach the killing temperature of

121 oC

C。 The pasteurization of milk kills pathogens but allows many organisms and

spores to survive

D。 Iodine kills by causing the formation of thymine dimers in the bacterial

DNA

E. Ultraviolet is widely used to disinfect the air of a room

14。 Each of the following statements concerning the normal flora is correct

EXCEPT

A。 The normal flora of the colon consists predominantly of anaerobic bacteria

B. The presence of the normal flora prevents certain pathogens from colonizing

the upper respiratory tract

C。 Fungi， eg, yeasts, are not members of the normal flora