Question

Plasmid mediated antibiotic resistances in bacteria are acquired by

• A. hydrolysis by β-lactamase (penicillin resistance).
• B. expression of aminoglycoside modifying enzyme (kanamycin resistance).
• C. mutation in DNA gyrase (quinolone resistance).
• D. overproduction of dihydrofolate reductase (trimethoprim resistance).

Hint:

Plasmids can carry antibiotic resistance genes, including those for β-lactamase, which can hydrolyze and inactivate β-lactam antibiotics.

Answer 1

The Correct Option is A, B

Step 1: Understanding plasmid-mediated resistance. 
Plasmids are extrachromosomal genetic elements that can carry genes for antibiotic resistance. These genes can be transferred between bacteria, conferring resistance to various antibiotics. 
 

Step 2: Analyzing the options. 
(A) Hydrolysis by β-lactamase (penicillin resistance): Correct — β-lactamase is an enzyme that hydrolyzes the β-lactam ring of penicillin and other β-lactam antibiotics, rendering them ineffective. 
(B) Expression of aminoglycoside modifying enzyme (kanamycin resistance): Correct — This is also a form of resistance. 
(C) Mutation in DNA gyrase (quinolone resistance): This is a mutation-based resistance mechanism, not plasmid-mediated. 
(D) Overproduction of dihydrofolate reductase (trimethoprim resistance): This is another type of resistance but not primarily plasmid-mediated. 
 

Step 3: Conclusion. 
The correct answer is 

(A) hydrolysis by β-lactamase (penicillin resistance)

(B) Expression of aminoglycoside modifying enzyme (kanamycin resistance)