Antibiotic sensitivity and resistance of micro organisms is determined by
**Core Concept**
The sensitivity and resistance of microorganisms to antibiotics are primarily determined by their genetic makeup, specifically the presence or absence of target enzymes, efflux pumps, and membrane modifications that affect drug penetration and interaction.
**Why the Correct Answer is Right**
The correct answer involves the process of horizontal gene transfer, where bacteria acquire antibiotic resistance genes from other bacteria through plasmids, transposons, or other mobile genetic elements. This allows resistant bacteria to spread their resistance genes to other bacteria, making them resistant to antibiotics. Additionally, mutations in target enzymes, such as beta-lactamases, can also confer resistance to antibiotics.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it oversimplifies the complex process of antibiotic resistance, which involves multiple genetic and molecular mechanisms.
* **Option B:** This option is incorrect because it implies that antibiotic resistance is solely determined by the host's immune system, which is not the primary factor.
* **Option C:** This option is incorrect because it suggests that antibiotic resistance is solely determined by the type of antibiotic used, which is not the primary factor.
**Clinical Pearl / High-Yield Fact**
The spread of antibiotic resistance is facilitated by the use of broad-spectrum antibiotics, which can select for resistant bacteria and drive the evolution of new resistance mechanisms.
**Correct Answer: B. The host's immune system plays a role but is not the primary determinant of antibiotic resistance.**