Microbiology - General Microbiology
(55 MCQ) Questions And Answers|
Update 26| Verified Set 2026
Question 1 :
Which of the following is an important disinfectant on account of effectively
destroying gram-positive and gram negative bacteria, viruses and even
spores at low pH levels
a) Phenol
b) Alcohol
c) Chlorine
d) Hexachlorophene - c) Chlorine
Question 2 :
Conjugation does not involve
a) Bacteriophages
b) HFr
c) Fr
d) Plasmids - a) Bacteriophages
Question 3 :
All are sporonticidal except
a) Lysol
b) Glutaraldehyde
c) Ethylene dioxide
d) Formaldehyde - a) Lysol
Question 4 :
,Phenol Co-efficient indicates
a) Efficacy of a disifectant
b) Dilution of a disinfectant
c) Quantity of a disinfectant
d) Purity of a disinfectant - a) Efficacy of a disifectant
Question 5 :
All are true regarding disinfectants except
a) Glutaraldehyde is sporicidal
b) Hypochlorites are virucidal
c) Ethylene oxide is intermediate disinfectant
d) Phenol usually requires organic matter to act - d) Phenol usually requires
organic matter to act
Two phenol derivatives commonly found as constituents of hospital
disinfectants are ortho-phenylphenol and ortho-benzyl-para-chlorophenol.
Residual disinfectant can irritate tissue
Mode of Action:
In high concentrations, phenol acts as a gross protoplasmic poison,
penetrating and disrupting the cell wall and precipitating the cell proteins.
Low concentrations of phenol and higher molecular-weight phenol
derivatives cause bacterial death by inactivation of essential enzyme
systems and leakage of essential metabolites from the cell wall
Commercial phenolics are not sporicidal but are tuberculocidal, fungicidal,
virucidal, and bactericidal at their recommended use-dilution
Many phenolic germicides are EPA-registered as disinfectants for use on
## environmental surfaces (e.g., bedside tables, bedrails, and laboratory
surfaces) and noncritical medical devices.
Phenolics are not FDA-cleared as high-level disinfectants for use with
semicritical items but could be used to preclean or decontaminate critical
, and semicritical devices before terminal sterilization or high-level
disinfection.
The use of phenolics in nurseries has been questioned because of ##
hyperbilirubinemia in infants placed in bassinets where phenolic detergents
were used.
Phenolics (and other disinfectants) should not be used to clean infant
bassinets and incubators while occupied.
Phenolic compounds used as antiseptics or disinfectants include pure
phenol and substitution products with halogens and alkyl groups. They act
to denature proteins and are general protoplasmic poisons.
Phenol (carbolic acid) is bacteriostatic at concentrations of 0.1-1% and is
bactericidal/fungicidal at 1-2%.
A 5% solution kills anthrax spores in 48 hr.
The bactericidal activity is enhanced by ethylenediamine tetraac
Question 6 :
Which of the following toxins acts by inhibiting protein synthesis
a) Cholera toxin
b) Shiga toxin
c) Pertussis toxin
d) LT of enterotoxigenic E-coli - b) Shiga toxin
Question 7 :
All the following pathogenic bacteria fulfill Koch's postulates, except
a) Treponema pallidum
b) Yersinia pestis
c) Bacillus anthracis
d) Heliobacter pylori - a) Treponema pallidum
(55 MCQ) Questions And Answers|
Update 26| Verified Set 2026
Question 1 :
Which of the following is an important disinfectant on account of effectively
destroying gram-positive and gram negative bacteria, viruses and even
spores at low pH levels
a) Phenol
b) Alcohol
c) Chlorine
d) Hexachlorophene - c) Chlorine
Question 2 :
Conjugation does not involve
a) Bacteriophages
b) HFr
c) Fr
d) Plasmids - a) Bacteriophages
Question 3 :
All are sporonticidal except
a) Lysol
b) Glutaraldehyde
c) Ethylene dioxide
d) Formaldehyde - a) Lysol
Question 4 :
,Phenol Co-efficient indicates
a) Efficacy of a disifectant
b) Dilution of a disinfectant
c) Quantity of a disinfectant
d) Purity of a disinfectant - a) Efficacy of a disifectant
Question 5 :
All are true regarding disinfectants except
a) Glutaraldehyde is sporicidal
b) Hypochlorites are virucidal
c) Ethylene oxide is intermediate disinfectant
d) Phenol usually requires organic matter to act - d) Phenol usually requires
organic matter to act
Two phenol derivatives commonly found as constituents of hospital
disinfectants are ortho-phenylphenol and ortho-benzyl-para-chlorophenol.
Residual disinfectant can irritate tissue
Mode of Action:
In high concentrations, phenol acts as a gross protoplasmic poison,
penetrating and disrupting the cell wall and precipitating the cell proteins.
Low concentrations of phenol and higher molecular-weight phenol
derivatives cause bacterial death by inactivation of essential enzyme
systems and leakage of essential metabolites from the cell wall
Commercial phenolics are not sporicidal but are tuberculocidal, fungicidal,
virucidal, and bactericidal at their recommended use-dilution
Many phenolic germicides are EPA-registered as disinfectants for use on
## environmental surfaces (e.g., bedside tables, bedrails, and laboratory
surfaces) and noncritical medical devices.
Phenolics are not FDA-cleared as high-level disinfectants for use with
semicritical items but could be used to preclean or decontaminate critical
, and semicritical devices before terminal sterilization or high-level
disinfection.
The use of phenolics in nurseries has been questioned because of ##
hyperbilirubinemia in infants placed in bassinets where phenolic detergents
were used.
Phenolics (and other disinfectants) should not be used to clean infant
bassinets and incubators while occupied.
Phenolic compounds used as antiseptics or disinfectants include pure
phenol and substitution products with halogens and alkyl groups. They act
to denature proteins and are general protoplasmic poisons.
Phenol (carbolic acid) is bacteriostatic at concentrations of 0.1-1% and is
bactericidal/fungicidal at 1-2%.
A 5% solution kills anthrax spores in 48 hr.
The bactericidal activity is enhanced by ethylenediamine tetraac
Question 6 :
Which of the following toxins acts by inhibiting protein synthesis
a) Cholera toxin
b) Shiga toxin
c) Pertussis toxin
d) LT of enterotoxigenic E-coli - b) Shiga toxin
Question 7 :
All the following pathogenic bacteria fulfill Koch's postulates, except
a) Treponema pallidum
b) Yersinia pestis
c) Bacillus anthracis
d) Heliobacter pylori - a) Treponema pallidum
