MDS PREP
Selective medium for streptococcus mutans?
1 mac conkey medium
2 mitis salivarius bacitracin agar
3 neutrient agar
4 tellurite medium
Microbiology
Answer: 2
Colonies of E. coli serotype O157:H7 appear on Mac Conkey Sorbitol Agar as colourless colonies non-sorbitol fermenter. Others E. coli, sorbitol fermenters, give red colonies and gram-negative non-sorbitol fermenters appear translucent.
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.
Which of the following is a characteristic of endotoxins that makes them distinct from exotoxins?
1) They are heat labile
2) They are actively secreted by bacterial cells
3) They are proteins
4) They are part of the bacterial cell wall
General Microbiology Answer: 4
Endotoxins are components of the outer membrane of Gram-negative bacteria and are released when the bacteria die or divide. This structural characteristic differentiates them from exotoxins, which are secreted by living bacteria.
Which of the following statements about the fermentation of sugars by Anthracoid bacilli is true?
1) Anthracoid bacilli ferment glucose, maltose, lactose, and sucrose, producing acid and gas.
2) Anthracoid bacilli do not ferment glucose but ferment maltose, lactose, and sucrose.
3) Anthracoid bacilli only ferment glucose.
4) Anthracoid bacilli ferment glucose, maltose, and lactose, but not sucrose.
Anthracoid bacilli ferment glucose, maltose, lactose, and sucrose, producing acid and gas.
What is a key characteristic of the colonies formed by Streptococcus pneumoniae?
1) Dome-shaped
2) Initially dome-shaped, later draughtsman colonies
3) Granular turbidity with a powdery deposit
4) Not typically seen in culture
Streptococcus pneumoniae colonies are initially dome-shaped and later develop draughtsman colonies.
What is the typical microscopic finding in amoebic dysentery?
1) Numerous pus cells
2) Abundant Charcot-Leyden crystals
3) Many motile bacteria
4) Abundant pyknotic bodies
The typical microscopic finding in amoebic dysentery includes numerous pus cells and abundant Charcot-Leyden crystals.
Which of the following hepatitis viruses has a single-stranded RNA genome?
1) Hepatitis A
2) Hepatitis B
3) Hepatitis C
4) Hepatitis D
General Microbiology Answer: 1Hepatitis C virus (HCV) is known for its single-stranded RNA genome. This characteristic is crucial for its classification and understanding its replication cycle, which involves RNA-dependent RNA polymerase.
Which of the following describes the colony morphology of Bacillus anthracis on an agar plate?
1) Smooth and shiny
2) Irregularly round with a frosted glass appearance
3) Small and translucent
4) Large and mucoid
Bacillus anthracis colonies on an agar plate typically appear irregularly round with a frosted glass appearance.