Multiple drug resistance refers to bacteria carrying genes for resistance to multiple antibiotics

Steps:

• Recall that multiple drug resistance (MDR) occurs when a single bacterial strain acquires genes conferring resistance to several antibiotics via plasmids or mutations.
• Evaluate options: A describes one bacterium with genes for multiple antibiotics, matching MDR definition.
• Eliminate B and D, which focus on different species resisting one antibiotic, not multiple.
• Eliminate C, which implies population immunity rather than genetic resistance in individuals.

Why A is correct:

• MDR is defined as a bacterium's genome containing multiple resistance genes, allowing survival against various antibiotics, per microbiology standards like those from WHO.

Why the others are wrong:

• B: Describes interspecies resistance to one antibiotic, not multiple-drug resistance in a single bacterium.
• C: Refers to population-level immunity, not genetic resistance to multiple drugs in bacteria.
• D: Involves many species resisting one antibiotic, ignoring multiple-drug aspect in one organism.

Final answer: A