Bacterial Pathogenesis Transfer of nuclear material by transduction through Movement of DNA from one bacteria to another connection tube or pilus is called:

1. Bacterial Pathogenesis
Bacterial Pathogenesis Multiple Choice
Question And Answers
Bacterial Genetics
Question 1. Jumping gene is:
1. Transposon
2. Episome
3. Cosmid
4. Plasmid
Answer. (1) (Transposon)
Question 2. Function of CRISPR is:
1. Bacterial genome editing to protect against infecting viruses
2. Bacterial genome editing to protect against human immune system
3. Mechanisms used by viruses to produce reassortants
4. Genotypic mixing seen in viruses for genetic reactivation
Answer. (2) (Bacterial genome…)
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CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats):
⚫ The sequences contain snippets of DNA from viruses that have attacked the
bacterium.
⚫ These snippets are used by the bacterium to detect and destroy DNA from
similar viruses during subsequent attacks.
⚫ In short, this is a prokaryotic immune system that confers the bacteria
resistance to foreign genetic elements such as those present within plasmids
and phages.
Question 3. Transfer of nuclear material by transduction through:

2. Bacterial Pathogenesis
1. Transposons
2. Plasmids
3. Bacteriophage
4. Insertion sequences
Answer. (3) (Bacteriophage)
⚫ Transduction refers to transfer of genetic material from one bacterium to other
by mean of bacteriophage.
Question 4. Bacteria used in Griffith experiment is:
1. Streptococcus pyogenes
2. Capsulated Streptococcus pneumoniae
3. Staphylococcus aureus
4. MRSA
5. Non-capsulated Streptococcus pneumoniae
Answer. (2, 5) (Capsulated S. pneumoniae, Non-capsulated S. pneumoniae)
Capsulated dead S. pneumoniae + non-capsulated live S. pneumoniae →
Transformation of gene coding capsule from dead to live pneumococci → Results in
capsulated live pneumococci
Question 5. Pick the true statement regarding Plasmids:
1. Nonself-replicative
2. Acts as Messenger RNA
3. Involved in conjugational transfer between strains
4. Involved in transformation
Answer. (3) (Involved in Conjugational…)
Plasmids are self-replicative extra-chromosomal elements frequently transferred by
conjugation.
Question 6. Nontoxigenic C. diphtheriae changes to toxigenicC. diphtheriae by the
help of bacteriophage… by which method this conversion occur?
1. Transfection
2. Transduction
3. Conjugation
4. Recombinant technology
Answer. (2) (Transduction)

3. Bacterial Pathogenesis
⚫ Transduction is the transfer of bacterial genes from one bacteria to other by
bacteriophage
⚫ Lysogenic Conversion would have been a better answer here. It is the process by
which the phage DNA is integrated to bacterial DNA and remains as lysogenic
phage. In such case, certain phage gene (e.g. gene coding for diphtheria toxin)
imparts toxigenicity to the bacteria.
Question 7. Movement of DNA from one bacteria to another connection tube or
pilus is called:
1. Transformation
2. Transduction
3. Conjugation
4. Lysogenic conversion
Answer. (3) (Conjugation)
Question 8. Mechanism of direct transfer of free DNA:
1. Transformation
2. Conjugation
3. Transduction
4. None
Answer. (1) (Transformation)
⚫ Transformation is the process of the transfer of free DNA itself from one
bacterium to another.
Question 9. Horizontal transmission of ‘R’ factor is by:
1. Transduction
2. Transformation
3. Conjugation
4. Fusion
Answer. (3) (Conjugation)
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Conjugation is the process where there is transfer of genetic elements from one
bacterium (male) to another (female) along sex pilus or conjugation tube—
Horizontal genetic transfer.

4. Bacterial Pathogenesis
⚫ Antimicrobial Resistance
Question 10. New Delhi metallo-Beta-Lactamase enzyme confers resistance to
which antibiotic?
1. Colistin
2. Amoxicillin
3. Carbapenems
4. Vancomycin
Answer. (3) (Carbapenems)
⚫ New Delhi metallo-Beta-Lactamase enzyme confers resistance to carbapenems.
Question 11. All the following are bacteriostatic except?
1. Vancomycin
2. Clindamycin
3. Tetracycline
4. Linezolid
Answer. (1) (Vancomycin)
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Vancomycin is a cell-wall-acting antibiotic, it is primarily bactericidal.
Primarily bacteriostatic antibiotic include: Clindamycin, Tetracycline, Linezolid,
Sulfonamide, Macrolide, Chloramphenicol
Question 12. The mechanism of action of vancomycin is inhibition/alteration of:
1. Cell wall synthesis
2. mRNA synthesis
3. Cell membrane integrity
4. Protein synthesis via 50s ribosomal subunit
Answer. (1) (Cell wall synthesis)

5. Bacterial Pathogenesis
Vancomycin acts by inhibition of cell wall synthesis by binding to D-Ala-D-Ala of
tetrapeptide side chain of peptidoglycan.
Question 13. Most common method of bacteria responsible for drug resistance:
1. Conjugation
2. Transduction
3. Transformation
4. Enzyme inactivation
5. Mutation
Answer. (1, 4) (Conjugation, Enzyme inactivation)
Transferrable resistance by conjugation is the most common method of transfer of
bacterial-resistant genes. Enzyme inactivation is the most common mechanisms of
bacteria drug resistance.
Question 14. Not true about bacterial drug resistance mechanism:
1. Most common mechanism is production of neutralizing enzymes
2. If resistance is plasmid mediated, it is always transferred vertically
3. Alteration of target seen in pneumococcal resistance
4. Complete removal of target is cause of resistance to Vancomycin
Answer. (2) (If resistance is plasmid mediated, it is always transferred vertically)
⚫ If resistance is chromosomally mediated, it is usually transferred vertically from
parent to daughter bacteria.
⚫ If resistance is plasmid mediated, it is usually transferred by horizontal route
mainly by conjugation.
About Other Options
⚫ Clinically, enzymatic drug inactivation is the most common mechanism for
acquired microbial resistance by bacteria.
Most common mechanism of bacterial drug resistance:
⚫ Pneumococcal resistance: is mainly due to Alteration of target, i.e. Penicillin-
binding protein (PBP)
⚫ Resistance to Vancomycin is due to complete removal of target D alanyl-D
alanine present the bacterial cell wall is the target site for Vancomycin, which
binds there and inhibits it and thus inhibits the cell wall synthesis.
Question 15. Multiple drug resistance is spread by:
1. Transformation
2. Transduction
3. Mutation
4. Conjugation

6. Bacterial Pathogenesis
Answer. (4) (Conjugation)
⚫ Resistance (R) factors are extrachromosomal plasmids responsible for spread of
multiple drug resistance among bacteria.
⚫ They are circular double-stranded DNA carry genes for variety of enzymes that
can destroy antibiotics.
⚫ R factor consists of 2 components: Resistance transfer factor (RTF) and resistant
determinant (r).
⚫ The resistance transfer factor is responsible for conjugational transfer while
each r determinant carries resistance for one of the several antibiotics.
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Question 16. A patient is on ceftriaxone and amikacin, ESBL Klebsiella has grown
from culture. What will you do next?
1. Continue with same antibiotic but in higher dose
2. Change ceftriaxone and add ceftazidime
3. Start imipenem in place of ceftriaxone
4. Remove Amikacin
Answer. (3) (Start Imipenem in place of ceftriaxone)
⚫ ESBL (Extended-spectrum beta-lactamases) are resistant to all Penicillin and
1st/2nd/3rd cephalosporin and monobactam
⚫ Which can be overcome by addition of β lactamase inhibitor like clavulinic acid
⚫ Other alternate which can be given are:
⚫ Carbapenems like Imipenem and meropenem
⚫ Cephamycins (like cefoxitin and cefotetan )
⚫ Different class of antibiotics like aminoglycoside
Question 17. Drug against ESBL-producing Pseudomonas:
1. Ceftriaxone + Piperacillin
2. Ceftriaxone + Tazobactam
3. Piperacillin + Tazobactam
4. Ceftriaxone + Piperacillin + Tazobactam
Answer. (3) (Piperacillin + Taz…)

7. Bacterial Pathogenesis
Extended Spectrum-β-Lactamases (ESBL) producing Pseudomonas can be treated
with an antipseudomonal β lactam (e.g. piperacillin) plus β lactamase inhibitor such
as tazobactam combination therapy.
Question 18. MIC (minimum inhibitory concentration) can be calculated by all of
the following antibiotic sensitivity methods except:
1. E test
2. Agar dilution method
3. Kirby-Bauer’s disk diffusion method
4. Broth dilution method
Answer. (3) (Kirby-Bauer’s disk diffusion method)
⚫ Kirby-Bauer’s disk diffusion method is used to know the zone of inhibition of the
streaked organism surrounding the disk by which we can know whether the
organism is sensitive or resistant to the antibiotic disk. However, we cannot
know the MIC.
⚫ MIC (Minimal inhibitory concentration) of the antibiotic is defined as the lowest
concentration of an antimicrobial agent that will inhibit the visible growth of a
microorganism.
⚫ MIC is calculated by: (1) Agar dilution method, (3) Broth dilution method and (3)
Epsilometer (E test)
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Question 19. For antibiotic sensitivity test, the organism broth prepared should
match with:
1. McFarland standard 0.5
2. McFarland standard 1
3. McFarland standard 2
4. McFarland standard 3
Answer. (1) (McFarland standard 0.5)
⚫ In microbiology, McFarland standards are used as a reference to adjust the
turbidity of bacterial suspensions so that the number of bacteria will be within a
given range.

8. Bacterial Pathogenesis
⚫ A 0.5 McFarland standard is prepared by mixing 0.05 mL of barium chloride
dihydrate with 9.95 mL of 1% sulfuric acid and its equivalent to 150 million no.
of bacteria/mL in a broth.
⚫ For antibiotic sensitivity test, the organism broth prepared should match with-
0.5 McFarland standard.
Question 20. Beta-lactamase is produced by:
1. E. coli
2. Gonococcus
3. Staphylococcus aureus
4. All of the above
Answer. (4) (All of the above)
Beta-lactamase enzymes are plasmid coded, produced by both gram positive and
gram-negative organisms.
Question 21. Which of the following disease(s) is/are not toxin mediated?
1. Diphtheria
2. Tetanus
3. Pertussis
4. Anthrax
5. Syphilis
Answer. (5) (Syphilis)
Syphilis is caused by T. pallidum. Refer chapter review.
Question 22. A strain of E. coli isolated from urine is resistant to third-generation
cephalosporins.
The mechanism of development of resistance is:
1. Extended-spectrum Beta-Lactamases
2. Decreased permeability
3. Active efflux of Beta-Lactam agents
4. Alteration of PBP
Answer. (1) (Extended spectrum Beta-Lactamases)
Out of several mechanisms of beta-lactam resistance in E. coli, Beta-Lactamase
production is the MOST COMMON; particularly Extended spectrum Beta-Lactamases
(ESBL).