Question

List four ways in which a microorganism can be resistant to an antimicrobial agent and explain why they can or can't be transferred to other microorganisms.

Answer 1

Following are the four ways through which a microbe can be resistant to an antimicrobial agent-

1. A microbe can produce an enzyme that is capable of inactivating the antimicrobial agent.
2. A microbe can alter the target site receptor, which will reduce or block the binding of antimicrobial agent to microbial DNA.
3. A microbe can prevent the entry of the antimicrobial agent in its cell or use an efflux pump to transport the antimicrobial out of its cell.
4. A microbe can modulate/regulate gene expression to produce more of the microbial enzyme altered or blocked by the antimicrobial agent.

Antimicrobial resistance that are coded by genes can be transferred from one microbe to another through horizontal gene transfer as a result of transformation, transduction, and conjugation or by acquiring large DNA sequences from one microbe to another in a single transfer. Horizontal gene transfer enables microorganisms to respond and adapt to their environment much more rapidly than mutation acquired by single large DNA sequence transfer.

There are also other resistances that microbes aquire against an antimicrobial agent and become tolerant to it. In this case the microbe stops growing in the presence of antimicrobial agent but does not get killed. Antimicrobial tolerance generally does not get transferred among the microorganisms.