MDS PREP
Dry heat sterilization of paper points without incineration is accomplished at
1. 160�C for 2hours
2. 120�C for l hour
3. 100�C for 2 hours
4. 200�C for 1 hour
Microbiology
Answer: 1
Dry heat sterilization of paper points without incineration is accomplished at 160�C for 2hours
What is the name of the live oral vaccine for typhoid fever and what is its mechanism of action?
1) Typhoral, a Gal E mutant of S. typhi that "self-destructs" after a few cell divisions
2) CholeraVax, a killed whole-cell vaccine
3) Salmonellosis vaccine, a live attenuated strain of S. paratyphi
4) Shigellosis vaccine, a bacteriophage preparation
General Microbiology Answer: 1the live oral vaccine for typhoid fever is Typhoralx, which is a Gal E mutant of S. typhi. The mechanism of action involves the attenuated bacteria colonizing the intestinal mucosa and inducing an immune response that protects against subsequent infection with the pathogenic strain.
Which of the following is a characteristic of amoebic dysentery?
1) More than 10 motions a day
2) Small, odorless stools
3) Dark red, copious stools
4) Presence of Charcot-Leyden crystals
Amoebic dysentery is characterized by more than 10 motions a day and the presence of Charcot-Leyden crystals.
The most pronounced effect on the oral microflora of a reduction in rate of salivary flow is a
1. significant increase in number of oral bacteria
2. shift towards a more acidogenic microflora
3 significant decrease in number of oral bacteria
4 shift towards a more aerobic micro flora
Microbiology
Answer: 2
The most pronounced effect on the oral microflora of a reduction in rate of salivary flow is a shift towards a more acidogenic microflora
What is the role of the Vi antigen in the pathogenesis of typhoid fever?
1) It aids in colonization of the intestinal mucosa.
2) It confers resistance to antibiotics.
3) It is involved in the production of toxins.
4) It allows the bacteria to evade the host's immune response by inhibiting phagocytosis.
General Microbiology Answer: 4The role of the Vi antigen in the pathogenesis of typhoid fever is it allows the bacteria to evade the hosts immune response by inhibiting phagocytosis: The Vi antigen is a polysaccharide capsule found in some strains of S. typhi that helps the bacteria avoid phagocytosis by host immune cells. This contributes to the bacterias ability to survive and proliferate within the human body.
Which of the following statements is true about the colony morphology and cultural characteristics of Anthrax bacilli?
1) Anthrax bacilli are motile and produce a turbidity in broth.
2) The Medusa head appearance is seen in non-virulent strains of anthrax bacilli.
3) Virulent capsulated strains form smooth colonies.
4) The inverted fir tree appearance is characteristic of Anthracoid bacilli.
The Medusa head appearance is characteristic of virulent strains of anthrax bacilli, not non-virulent strains.
What is the typical biochemical profile of E. coli on the IMViC test series?
1) Indole positive, Methyl red positive, Voges-Proskauer positive, Citrate positive
2) Indole positive, Methyl red positive, Voges-Proskauer negative, Citrate positive
3) Indole positive, Methyl red negative, Voges-Proskauer positive, Citrate negative
4) Indole positive, Methyl red negative, Voges-Proskauer negative, Citrate positive
General Microbiology Answer: 3
The IMViC test series is used to differentiate members of the Enterobacteriaceae family, including E. coli. E. coli typically has an indole positive (indole is produced when tryptophan is metabolized), methyl red positive (indicating the ability to ferment glucose and produce acid), Voges-Proskauer positive (produces acetoin from glucose), and citrate negative (does not utilize citrate as a sole carbon source) biochemical profile. This profile helps distinguish it from other related bacteria like Proteus and Klebsiella species.
What is the principle behind the oxidase test used to identify bacteria?
1) The presence of specific antigens
2) The activity of certain bacterial oxidases
3) The growth of bacteria on selective media
4) The presence of enzymes that hydrolyze certain sugars
General Microbiology Answer: 2
The oxidase test is based on the presence of cytochrome c oxidase in bacteria. This enzyme catalyzes the oxidation of certain substrates, leading to a color change in the test medium, which indicates a positive result for oxidase activity.