BACTERIOLOGY
BACTERIOLOGY
7. The organism MOST resistant to
1. Bacteria are simple genetic units with thermal inactivation is
all of the following properties EXCEPT A. Bacterial spores
A. They are diploid B. Virus
C. Spirochete
B. Their genetic material is organized into a
D. Streptococcus mutans
single chromosome
C. Their DNA has intervening sequences Ans: A
(Introns) in almost all genes Ref: Ananthanarayan and Panicker’s
D. They use the same genetic code as all Text Book of Microbiology, 8/E, p. 31
the eukaryotes Explanation
• Therefore spores are used as sterilization
Ans : C
control.
2. Coating of bacteria particles with host 8. Which of the following structures, found
proteins to facilitate phagocytosis is external to the bacterial cell wall, are
known as involved in bacterial attachment to cell
A. Chemotaxis surfaces
B. Chemokine A. Capsule
C. Opsonization B. Flagella
D. Membrane attack complex C. Pili
D. Mesosomes
Ans: C. Opsonization
Ref: Wintrobe's Clinical Hematology, Ans: C
Volume 1, John p. Greer, 12/E, p. 283 Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 21
3. ASO (Antistreptolysin O) test is used Explanataion
for the diagnosis of • They are organs of adhesion originating
A. Rheumatoid arthritis from cell membranes, e.g.
B. Typhoid fever Escherichia, Klebsiella.
C. Rheumatic fever • They are detected by hemagglutination
D. Rickettesial fever
Ans: C
Ref: Ananthanarayan and Panicker’s 9. Monotrichous, Lophotrichous,
Textbook of Microbiology, 8/E, p. 208 Amphitrichous
and Peritrichous. These are all
4. Bacteria that grow best at temperatures types of ______ in anatomy of a bacterial
below 20º C are called cell.
A. Mesophilic A. Flagella
B. Psychrophilic B. Ribosomes
C. Thermophilic C. Mesosomes
D. Microaerophilic D. None of the above
Ans: B Ans: A. Flagella
Ref: Ananthanarayan and Panicker’s Ref: Textbook of microbiology,
Text Book of Microbiology, 8/E, p. 27 Ananthnarayan and Panicker, 8/E, p. 20
Explanation
• Mesophilic: 25–40°C
• Psychrophilic: < 20°C 10. Which of the following fulfill all the
• Thermophilic: 55–80°C criterias of Koch's postulates?
A. Treponema pallidum
B. Mycobacterium leprae
5. Negative staining is used to demonstrate C. N Gonorrhoeae
A. Bacterial spore D. None of the above
B. Bacterial flagella
C. Bacterial capsule Ans: D. None of the above
D. Bacterial fimbriae Ref: Textbook of microbiology,
35. Ans: C Ananthnarayan and Panicker, 8/E, p. 6
Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 19
11. Which of the following statement is
6. Bacteria acquire characteristics by all true in the case of Endotoxins?
the following except A. Highly antigenic
A. Through plasmids B. Proteins in nature
B. Incorporating part of host DNA C. Heat stable
C. Through bacteriophages D. Action is often enzymatic
D. Through configuration
Ans: C. Heat stable
Ans: B
Ref: Textbook of microbiology,
Ref: Ananthanarayan and Panicker’s
Ananthnarayan and Panicker, 8/E,
Text Book of Microbiology, 8/E, p. 19
p. 643
, BACTERIOLOGY
12. Black pigmented anaerobes include all Ans: C
the above except Ref: Ananthanarayan and Panicker’s
A. Tannerella Text Book of Microbiology, 8/E, p. 18
B. Porphyromonas Explanation
C. Bacteroides • The lipopolysaccharide present on the
D. Prevotella cell walls of gram negative bacteria
consists of 3 regions
Ans: D. Prevotella 1. Region I – polysaccharide portion
Ref: Koneman’s Color Atlas and determining antigen specificity
Textbook of Diagnostic Microbiology, 2. Region II – core polysaccharide
Elmer W. Koneman, 6/E, p. 921 3. Region III – glycolipid portion
responsible for endotoxins
13. Ipratropium bromide is used for activities
A. Renal colic
B. Organophosphorus poisioning 18. Plasmid is transmitted to other bacteria
C. Bronchial asthma in
D. Miosis A. Transformation
B. Transduction
Ans: D C. Conjugation
Ref: Ananthanarayan and Panicker’s D. All of the above
Text, Book of Microbiology, 8/E, p. 24
Ans: C
14. The process of attenuation can be Ref: Ananthanarayan and Panicker’s
achieved by all EXCEPT Text Book of Microbiology, 8/E, p. 60
A. Growing bacteria in adverse Explanation
environment • Plasmids are circular DNA molecules
B. Growing bacteria in unconventional present in the cytoplasm of bacteria,
host capable of autonomous replication
C. Serial passage in an experimental • By their ability to transfer genes from
host one cell to anther by conjugation, they
D. Repeated cultures in artificial media have become important vectors in
genetic engineering
Ans: C
Ref: Ananthanarayan and Panicker’s 19. Which of the following is NOT a
Text Book of Microbiology, 8/E, p. 78 characteristic of exotoxins?
Explanation A. Produced in minute amounts
Reduction of virulence is known as B. Released from bacterial cell wall
attenuation. This can be achieved by: C. Destroyed by proteolytic enzymes
• Passage through unfavourable hosts D. Weakly antigenic
• Repeated cultures in artificial media
• Growth in high temperature Ans: D
• In the presence of weak antiseptic Ref: Ananthanarayan and Panicker’s
• Prolonged storage in culture Text Book of Microbiology, 8/E, p. 78
Explanation
15. Botryomycosis is a ............. disease
A. Fungal
B. Bacterial
C. Viral
D. Parasitic
Ans: B
Ref: Ananthanarayan and Panicker’s
Text, Book of Microbiology, 8/E, p. 393
Explanation
Botryomycosis is caused by Staphylococcus.
16. Endotoxin is released from
A. C. albicans
B. S. Sanguis
C. Gram negative bacteria
D. Actinomyces viscosus
Ans: C
Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 82
17. Which component of the cell wall is
responsible for endotoxic activity
A. Region I
B. Region II
C. Region III
D. Bovine antigen
, BACTERIOLOGY
20. The number of bacteria in the oral cavity is Ans:- (a) and (c) Mitochondria always
greater: absent and Divide by binary fission
A. In the morning Ref:- Ananthnarayan 8/e, p 12, 17
B. After meals Explanation:-
C. At night
D. After brushing Only bacteria having sterol in its cell
Ans:B. After Meals membrane: Mycoplasma
Bacteria can be seen by:
21. Microorganisms which grow in the
- Optical or light microscopy
presence or
absence of oxygen? - Phage contrast microscopy
A. Microaerophilic - Dark field or dark ground
B. Facultative anaerobic microscopy
C. Obligate aerobic - Electron microscopy
D. Anaerobic -
Ans:B. Facultative anaerobic
25. A diabetic patient developed cellulitis
Ref: Burton’s Microbiology for the Health
due to S.aureus, which was found to be
Sciences,
9/E, p. 63 methicillin resistant on the antibiotic
Explanation sensitivity testing. All the following
Classification of Bacteria Based on Oxygen antibiotics will be appropriate except:
Requirement A. Vancomycin
• Strict or Obligate Anaerobes: Cannot tolerate B. Imipenem
oxygen. E.g.: Clostridium tetani
C. Teicloplanin
• Strict or Obligate Aerobes: Requires oxygen,
lack of D. Linezolid
oxygen kills organism. E.g.: Pseudomonas
• Facultative Anaerobes: Can live with or Ans:- B Imipenem
without Ref:- Harrison 18/e p 1168
oxygen. E.g.: Staphylococcus , E. coli Explanation:-
• Aero Tolerant: Do not use oxygen, but oxygen
doesn’t harm them. E.g.: Lactobacillus Imipenem is not effective against
• Microaerophiles: Requires very low oxygen Enterococcus faecium, MRSA, clostridium
concentration and higher CO2 concentration. difficle, Burkholderia cepacia as they
E.g.: produce metallobetalactamases. Though it is
Campylobacter. effective against methicillin sensitive
staph.aureus.
22. A 12 year old boy developed sore throat
grayish pseudomembrance covering Treatment of MRSA
tonsils and pharynx. The causative agent Drug of choice Alternative Investigator
is? y
A. Gram positive bacillus Vancomycin TMP-SMX Oritavancin
Minocycline Tigecycline
B. Gram negative baccilus
C. Single standard positive sense rna Ciprofloxacin Ceftobipirol
e, e
viruses
Levofloxacin
D. A gram negative catalase positive coccus Quinupristin/
arranged in cluster dalfopristin
Ans: A Linezolid
Daptomycin
23. A patient present with frontal abscess.
Antibiotic resistance
Foul smelling pus is aspirated. Pus Agent Mechanism Site
shows red fluorescence on ultraviolet of resistance
examination. The most likely organism Penicillins Β-lactamase Plasmid
causing the frontal abscess is Methicilin Altered Chromosom
A. Bacteroides binding e
B. Peptostreptococcus Cephalosporin protein
C. Pseudomonas Chlorampheni Acetyl Plasmid
D. Acanthamoeba col transferase
Erythromycin Methylation Plasmid
Ans: A
of ribosome
Streptomycin Altered Chromosom
24. True about bacteria
ribosomal e
A. Mitochondria always absent protein
B. Sterols always present in cell wall Vancomycin Van A gene Chromosom
C. Divide by binary fission e
D. Can be seen only under electron Quinolones Mutation in
microscope topoisomera
se IV
, BACTERIOLOGY
Note : Mechanism of vancomycin resistance - Hospital strains mostly form type A
involves the replacement of the last D- penicillinase.
alanine residue of peptidoglycan precursors - Same plasmid carry genes for
with D-lactate or D-serine resulting resistance to tetracycline,
respectively in high level and low level erythrocmycin, aminoglycoside too.
resistance. Altered penicillin binding protein
26. Staphylococcus aureus differs from - Due to production of novel penicillin
staphylococcus epidermidis by binding protein PBP2a, this protein
A. Is coagulase positive is synthesized by mecAgene.
B. Forms white colonies - Chromosomally mediated, expressed
C. A common cause of UTI more at 30◦C than at 37◦C.
D. Causes endocarditis of prosthetic valve - Responsible for resistance against
penicillinase resistant penicillin such
Ans:- A Is coagulase positive as methicilin, cloxacillin. Strains are
Ref:- Ananthanarayan 8/e p 202 called MRSA (Methicillin resistant
Explanation:- staph. Aureus)
- MRSA escape methicillin by
Property Staphylococc Staphylococc synthesizing an extra PBP called
us aureus us
PBP-2A which carries out function of
epidermidis
Coagulase Positive Negative those PBPs that are inactivated by
Mannitol Ferments Not ferment methicillin.
Pathogenicit Pathogenic Less Tolerance to penicillin
y pathogenic - Bacteria only inhibited not killed.
Colony Golden White B. Vancomycin
Hemolysis Show Not show - Intermediate susceptible strain: Also
Cause In normal In prosthetic known as VISA (vancomycin-
endocarditis native valve valve intermediate S.aureus). for these
VISA strain MIC (minimal inhibitory
27. Which of the following statement is concentration) of vancomycin is 4-8
most correct regarding resistance to µg/ml. the mechanism of resistance
methicillin in MRSA is increased cell wall synthesis and
A. Resistance is produced as a result of alteration in the cell wall.
alteration in penicillin binding protein - Resistant strain: Also known as
B. Resistance is produced by production of VRSA (vancomycin resistant strain):
β lactamase This is due to presence of van A gene
C. Resistance is mediated by plasmids C. Others
D. Expression of resistance is enhanced by - Plasmid mediated resistance to
incubating at 38◦C during susceptibility tetracycline, erythromycin,
testing aminoslycosides.
Ans:- A Resistance is produced as a 28. A patient in an ICCU is on CVP line. His
result of alteration in penicillin binding blood culture shows growth of Gram-
protein positive cocci which are catalase positive
Ref:- Katzung 10/e p 727 and coagulase negative. The most likely
Explanation:- etiological agent is
Production of novel penicillin binding protein A. Staph.aureus
(PBP 2 α or 2) is responsible for methicillin B. Staph.epidermidis
resistance”. Protein in synthesized by mec A C. Streptococcus pyogenes
gene which is part of a large mobile genetic D. Enterococcus faecalis
element called SCC mec.
Ans:-B Staph.epidermidis
It is hypothesized that the genetic material Ref:- Harrison 17/e p 873
was acquired via horizontal transfer from a Explanation:-
related species, S. sciuri.
Gram +ve, catalase +ve, coagulase –ve
Drug resistance in staphylococcus bacteria is coagulase-negative staph.
A. Penicillin resistance S. epidermidis is uniquely adapted to
Production of β latamase colonize prothestic devicese due to its
- Plasmid mediated inducible enzyme capacity to elaborate the extracellular
which is transmitted by transduction polysaccharide (glycocalyx or slime) that
(more commonly) or conjugation. facilitates formation of protective biofilm on
Now only <5% of strains of staph are the device surface. This slime production
sensitivity to penicillin. also protect the bacteria against antibiotics.
BACTERIOLOGY
7. The organism MOST resistant to
1. Bacteria are simple genetic units with thermal inactivation is
all of the following properties EXCEPT A. Bacterial spores
A. They are diploid B. Virus
C. Spirochete
B. Their genetic material is organized into a
D. Streptococcus mutans
single chromosome
C. Their DNA has intervening sequences Ans: A
(Introns) in almost all genes Ref: Ananthanarayan and Panicker’s
D. They use the same genetic code as all Text Book of Microbiology, 8/E, p. 31
the eukaryotes Explanation
• Therefore spores are used as sterilization
Ans : C
control.
2. Coating of bacteria particles with host 8. Which of the following structures, found
proteins to facilitate phagocytosis is external to the bacterial cell wall, are
known as involved in bacterial attachment to cell
A. Chemotaxis surfaces
B. Chemokine A. Capsule
C. Opsonization B. Flagella
D. Membrane attack complex C. Pili
D. Mesosomes
Ans: C. Opsonization
Ref: Wintrobe's Clinical Hematology, Ans: C
Volume 1, John p. Greer, 12/E, p. 283 Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 21
3. ASO (Antistreptolysin O) test is used Explanataion
for the diagnosis of • They are organs of adhesion originating
A. Rheumatoid arthritis from cell membranes, e.g.
B. Typhoid fever Escherichia, Klebsiella.
C. Rheumatic fever • They are detected by hemagglutination
D. Rickettesial fever
Ans: C
Ref: Ananthanarayan and Panicker’s 9. Monotrichous, Lophotrichous,
Textbook of Microbiology, 8/E, p. 208 Amphitrichous
and Peritrichous. These are all
4. Bacteria that grow best at temperatures types of ______ in anatomy of a bacterial
below 20º C are called cell.
A. Mesophilic A. Flagella
B. Psychrophilic B. Ribosomes
C. Thermophilic C. Mesosomes
D. Microaerophilic D. None of the above
Ans: B Ans: A. Flagella
Ref: Ananthanarayan and Panicker’s Ref: Textbook of microbiology,
Text Book of Microbiology, 8/E, p. 27 Ananthnarayan and Panicker, 8/E, p. 20
Explanation
• Mesophilic: 25–40°C
• Psychrophilic: < 20°C 10. Which of the following fulfill all the
• Thermophilic: 55–80°C criterias of Koch's postulates?
A. Treponema pallidum
B. Mycobacterium leprae
5. Negative staining is used to demonstrate C. N Gonorrhoeae
A. Bacterial spore D. None of the above
B. Bacterial flagella
C. Bacterial capsule Ans: D. None of the above
D. Bacterial fimbriae Ref: Textbook of microbiology,
35. Ans: C Ananthnarayan and Panicker, 8/E, p. 6
Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 19
11. Which of the following statement is
6. Bacteria acquire characteristics by all true in the case of Endotoxins?
the following except A. Highly antigenic
A. Through plasmids B. Proteins in nature
B. Incorporating part of host DNA C. Heat stable
C. Through bacteriophages D. Action is often enzymatic
D. Through configuration
Ans: C. Heat stable
Ans: B
Ref: Textbook of microbiology,
Ref: Ananthanarayan and Panicker’s
Ananthnarayan and Panicker, 8/E,
Text Book of Microbiology, 8/E, p. 19
p. 643
, BACTERIOLOGY
12. Black pigmented anaerobes include all Ans: C
the above except Ref: Ananthanarayan and Panicker’s
A. Tannerella Text Book of Microbiology, 8/E, p. 18
B. Porphyromonas Explanation
C. Bacteroides • The lipopolysaccharide present on the
D. Prevotella cell walls of gram negative bacteria
consists of 3 regions
Ans: D. Prevotella 1. Region I – polysaccharide portion
Ref: Koneman’s Color Atlas and determining antigen specificity
Textbook of Diagnostic Microbiology, 2. Region II – core polysaccharide
Elmer W. Koneman, 6/E, p. 921 3. Region III – glycolipid portion
responsible for endotoxins
13. Ipratropium bromide is used for activities
A. Renal colic
B. Organophosphorus poisioning 18. Plasmid is transmitted to other bacteria
C. Bronchial asthma in
D. Miosis A. Transformation
B. Transduction
Ans: D C. Conjugation
Ref: Ananthanarayan and Panicker’s D. All of the above
Text, Book of Microbiology, 8/E, p. 24
Ans: C
14. The process of attenuation can be Ref: Ananthanarayan and Panicker’s
achieved by all EXCEPT Text Book of Microbiology, 8/E, p. 60
A. Growing bacteria in adverse Explanation
environment • Plasmids are circular DNA molecules
B. Growing bacteria in unconventional present in the cytoplasm of bacteria,
host capable of autonomous replication
C. Serial passage in an experimental • By their ability to transfer genes from
host one cell to anther by conjugation, they
D. Repeated cultures in artificial media have become important vectors in
genetic engineering
Ans: C
Ref: Ananthanarayan and Panicker’s 19. Which of the following is NOT a
Text Book of Microbiology, 8/E, p. 78 characteristic of exotoxins?
Explanation A. Produced in minute amounts
Reduction of virulence is known as B. Released from bacterial cell wall
attenuation. This can be achieved by: C. Destroyed by proteolytic enzymes
• Passage through unfavourable hosts D. Weakly antigenic
• Repeated cultures in artificial media
• Growth in high temperature Ans: D
• In the presence of weak antiseptic Ref: Ananthanarayan and Panicker’s
• Prolonged storage in culture Text Book of Microbiology, 8/E, p. 78
Explanation
15. Botryomycosis is a ............. disease
A. Fungal
B. Bacterial
C. Viral
D. Parasitic
Ans: B
Ref: Ananthanarayan and Panicker’s
Text, Book of Microbiology, 8/E, p. 393
Explanation
Botryomycosis is caused by Staphylococcus.
16. Endotoxin is released from
A. C. albicans
B. S. Sanguis
C. Gram negative bacteria
D. Actinomyces viscosus
Ans: C
Ref: Ananthanarayan and Panicker’s
Text Book of Microbiology, 8/E, p. 82
17. Which component of the cell wall is
responsible for endotoxic activity
A. Region I
B. Region II
C. Region III
D. Bovine antigen
, BACTERIOLOGY
20. The number of bacteria in the oral cavity is Ans:- (a) and (c) Mitochondria always
greater: absent and Divide by binary fission
A. In the morning Ref:- Ananthnarayan 8/e, p 12, 17
B. After meals Explanation:-
C. At night
D. After brushing Only bacteria having sterol in its cell
Ans:B. After Meals membrane: Mycoplasma
Bacteria can be seen by:
21. Microorganisms which grow in the
- Optical or light microscopy
presence or
absence of oxygen? - Phage contrast microscopy
A. Microaerophilic - Dark field or dark ground
B. Facultative anaerobic microscopy
C. Obligate aerobic - Electron microscopy
D. Anaerobic -
Ans:B. Facultative anaerobic
25. A diabetic patient developed cellulitis
Ref: Burton’s Microbiology for the Health
due to S.aureus, which was found to be
Sciences,
9/E, p. 63 methicillin resistant on the antibiotic
Explanation sensitivity testing. All the following
Classification of Bacteria Based on Oxygen antibiotics will be appropriate except:
Requirement A. Vancomycin
• Strict or Obligate Anaerobes: Cannot tolerate B. Imipenem
oxygen. E.g.: Clostridium tetani
C. Teicloplanin
• Strict or Obligate Aerobes: Requires oxygen,
lack of D. Linezolid
oxygen kills organism. E.g.: Pseudomonas
• Facultative Anaerobes: Can live with or Ans:- B Imipenem
without Ref:- Harrison 18/e p 1168
oxygen. E.g.: Staphylococcus , E. coli Explanation:-
• Aero Tolerant: Do not use oxygen, but oxygen
doesn’t harm them. E.g.: Lactobacillus Imipenem is not effective against
• Microaerophiles: Requires very low oxygen Enterococcus faecium, MRSA, clostridium
concentration and higher CO2 concentration. difficle, Burkholderia cepacia as they
E.g.: produce metallobetalactamases. Though it is
Campylobacter. effective against methicillin sensitive
staph.aureus.
22. A 12 year old boy developed sore throat
grayish pseudomembrance covering Treatment of MRSA
tonsils and pharynx. The causative agent Drug of choice Alternative Investigator
is? y
A. Gram positive bacillus Vancomycin TMP-SMX Oritavancin
Minocycline Tigecycline
B. Gram negative baccilus
C. Single standard positive sense rna Ciprofloxacin Ceftobipirol
e, e
viruses
Levofloxacin
D. A gram negative catalase positive coccus Quinupristin/
arranged in cluster dalfopristin
Ans: A Linezolid
Daptomycin
23. A patient present with frontal abscess.
Antibiotic resistance
Foul smelling pus is aspirated. Pus Agent Mechanism Site
shows red fluorescence on ultraviolet of resistance
examination. The most likely organism Penicillins Β-lactamase Plasmid
causing the frontal abscess is Methicilin Altered Chromosom
A. Bacteroides binding e
B. Peptostreptococcus Cephalosporin protein
C. Pseudomonas Chlorampheni Acetyl Plasmid
D. Acanthamoeba col transferase
Erythromycin Methylation Plasmid
Ans: A
of ribosome
Streptomycin Altered Chromosom
24. True about bacteria
ribosomal e
A. Mitochondria always absent protein
B. Sterols always present in cell wall Vancomycin Van A gene Chromosom
C. Divide by binary fission e
D. Can be seen only under electron Quinolones Mutation in
microscope topoisomera
se IV
, BACTERIOLOGY
Note : Mechanism of vancomycin resistance - Hospital strains mostly form type A
involves the replacement of the last D- penicillinase.
alanine residue of peptidoglycan precursors - Same plasmid carry genes for
with D-lactate or D-serine resulting resistance to tetracycline,
respectively in high level and low level erythrocmycin, aminoglycoside too.
resistance. Altered penicillin binding protein
26. Staphylococcus aureus differs from - Due to production of novel penicillin
staphylococcus epidermidis by binding protein PBP2a, this protein
A. Is coagulase positive is synthesized by mecAgene.
B. Forms white colonies - Chromosomally mediated, expressed
C. A common cause of UTI more at 30◦C than at 37◦C.
D. Causes endocarditis of prosthetic valve - Responsible for resistance against
penicillinase resistant penicillin such
Ans:- A Is coagulase positive as methicilin, cloxacillin. Strains are
Ref:- Ananthanarayan 8/e p 202 called MRSA (Methicillin resistant
Explanation:- staph. Aureus)
- MRSA escape methicillin by
Property Staphylococc Staphylococc synthesizing an extra PBP called
us aureus us
PBP-2A which carries out function of
epidermidis
Coagulase Positive Negative those PBPs that are inactivated by
Mannitol Ferments Not ferment methicillin.
Pathogenicit Pathogenic Less Tolerance to penicillin
y pathogenic - Bacteria only inhibited not killed.
Colony Golden White B. Vancomycin
Hemolysis Show Not show - Intermediate susceptible strain: Also
Cause In normal In prosthetic known as VISA (vancomycin-
endocarditis native valve valve intermediate S.aureus). for these
VISA strain MIC (minimal inhibitory
27. Which of the following statement is concentration) of vancomycin is 4-8
most correct regarding resistance to µg/ml. the mechanism of resistance
methicillin in MRSA is increased cell wall synthesis and
A. Resistance is produced as a result of alteration in the cell wall.
alteration in penicillin binding protein - Resistant strain: Also known as
B. Resistance is produced by production of VRSA (vancomycin resistant strain):
β lactamase This is due to presence of van A gene
C. Resistance is mediated by plasmids C. Others
D. Expression of resistance is enhanced by - Plasmid mediated resistance to
incubating at 38◦C during susceptibility tetracycline, erythromycin,
testing aminoslycosides.
Ans:- A Resistance is produced as a 28. A patient in an ICCU is on CVP line. His
result of alteration in penicillin binding blood culture shows growth of Gram-
protein positive cocci which are catalase positive
Ref:- Katzung 10/e p 727 and coagulase negative. The most likely
Explanation:- etiological agent is
Production of novel penicillin binding protein A. Staph.aureus
(PBP 2 α or 2) is responsible for methicillin B. Staph.epidermidis
resistance”. Protein in synthesized by mec A C. Streptococcus pyogenes
gene which is part of a large mobile genetic D. Enterococcus faecalis
element called SCC mec.
Ans:-B Staph.epidermidis
It is hypothesized that the genetic material Ref:- Harrison 17/e p 873
was acquired via horizontal transfer from a Explanation:-
related species, S. sciuri.
Gram +ve, catalase +ve, coagulase –ve
Drug resistance in staphylococcus bacteria is coagulase-negative staph.
A. Penicillin resistance S. epidermidis is uniquely adapted to
Production of β latamase colonize prothestic devicese due to its
- Plasmid mediated inducible enzyme capacity to elaborate the extracellular
which is transmitted by transduction polysaccharide (glycocalyx or slime) that
(more commonly) or conjugation. facilitates formation of protective biofilm on
Now only <5% of strains of staph are the device surface. This slime production
sensitivity to penicillin. also protect the bacteria against antibiotics.
