Medical Interventions 1.2 Quiz

How do antibiotics work to fight bacterial infections?

They target essential bacterial processes (cell-wall synthesis, protein synthesis, DNA replication, or metabolism), killing bacteria or stopping growth so the immune system can clear the infection.

What methods do bacteria use to share antibiotic-resistant genes?

They transfer genes by conjugation (plasmid through a pilus), transformation (uptake of naked DNA), and transduction (bacteriophage carries DNA).

What human actions contribute to antibiotic resistance?

Overprescribing, not finishing courses, using antibiotics for viruses, adding antibiotics to livestock feed, poor infection control, and improper disposal — all increase selection for resistant bacteria.

Identify and describe the structure of a bacterial cell

A bacterial cell has a capsule for protection, a cell wall for shape and strength, and a cell membrane that controls what enters and leaves. Inside are the cytoplasm, a nucleoid (genophore) with the main circular DNA, and plasmids that carry extra genes such as antibiotic resistance. Ribosomes make proteins, pili help bacteria attach or share DNA, and flagella help the cell move.

Describe and compare the structure of Gram-positive and Gram-negative cell walls

Gram-positive bacteria have a thick layer of peptidoglycan with teichoic acids and no outer membrane, which makes them stain purple in the Gram stain.
Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane that contains lipopolysaccharide (LPS), making them stain pink. The outer membrane also makes Gram-negative bacteria more resistant to many antibiotics.

Identify and explain the mechanism of action for different antibiotic classes

• β-lactam antibiotics (penicillins, cephalosporins) block formation of the cell wall, causing the bacteria to burst.

• Tetracyclines and chloramphenicol stop bacteria from making proteins, so they can’t grow or reproduce.

• Fluoroquinolones stop DNA replication, preventing bacteria from multiplying.

• Sulfonamides (sulfa drugs) and Co-trimoxazole block folate synthesis, which bacteria need to make DNA.

Identify and describe the technique of antibiotic sensitivity testing

Antibiotic sensitivity testing is a lab method used to find out which antibiotics can effectively kill or stop the growth of a specific bacterial infection. Bacteria from a patient are grown in a lab and then exposed to different antibiotics. The results show whether each antibiotic is effective (sensitive), partly effective (intermediate), or not effective (resistant). This helps doctors choose the right antibiotic to treat the infection.

Identify, describe, and explain mechanisms through which bacteria become resistant to antibiotics

Bacteria become resistant by:

• Producing enzymes that destroy or inactivate the antibiotic (like β-lactamase)

• Using efflux pumps to push the antibiotic out

• Mutating so the antibiotic no longer fits its target

• Blocking entry of the antibiotic through their membrane

• Gaining resistance genes from other bacteria

Identify, describe, and explain the pathways through which bacterial cells can transfer genes

• Conjugation: DNA (usually a plasmid) is passed through a pilus from one cell to another.

• Transformation: A bacterium takes in naked DNA from its environment.

• Transduction: A bacteriophage (virus) carries DNA from one bacterium to another.

Identify and describe the effects of taking or not taking antibiotics on a bacterial population

When antibiotics are taken properly, they kill the bacteria and prevent resistance from spreading. If antibiotics are stopped early or used incorrectly, some bacteria survive and multiply, leading to more resistant bacteria in the population.

Explain how the misuse of antibiotics affects a bacterial population

Overuse or misuse of antibiotics creates selective pressure, allowing only resistant bacteria to survive and reproduce. Over time, this leads to the rise of superbugs that are very hard to treat.

Antibiotic

A medicine that kills bacteria or stops them from growing.

β-lactam antibiotic

Antibiotics with a β-lactam ring that block bacterial cell-wall building, causing the cell to burst.

Capsule

A protective outer layer that helps bacteria avoid the immune system and stick to surfaces.

Cell envelope

All the layers surrounding a bacterial cell — includes the membrane, cell wall, and capsule if present.

Cell (plasma) membrane

A thin barrier that controls what goes in and out of the cell and contains important enzymes.

Cell wall

A rigid layer made of peptidoglycan that gives the cell shape and prevents bursting.

Cephalosporin

A type of β-lactam antibiotic that stops bacteria from forming a proper cell wall.

Co-Trimoxazole

A combination antibiotic (sulfamethoxazole + trimethoprim) that blocks steps in folate and DNA production.

Doxycycline

An antibiotic that prevents bacteria from making proteins they need to grow.

Endotoxin

A toxin found in the outer membrane of Gram-negative bacteria (part of LPS) that can cause strong immune reactions.

Flagella

Tail-like structures that spin to help bacteria move.

Fluoroquinolones

Antibiotics that stop bacteria from copying their DNA, preventing reproduction.

Genophore

The main circular chromosome in a bacterial cell that holds most of its genetic information.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane containing LPS; stain pink.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer and no outer membrane; stain purple.

Lipopolysaccharide (LPS)

A molecule in the outer membrane of Gram-negative bacteria that protects the cell and can act as an endotoxin.

Nucleoid

The region inside a bacterial cell where the main DNA (genophore) is located; not enclosed by a membrane.

Penicillins (β-lactam antibiotics)

A group of β-lactam antibiotics that stop cell-wall formation, causing the bacteria to burst.

Peptidoglycan

A strong, mesh-like material made of sugars and amino acids that makes up the bacterial cell wall.

Pili

Short, hair-like structures that help bacteria attach to surfaces or exchange DNA.

Plasmid

A small circular piece of DNA separate from the main chromosome that often carries antibiotic-resistance genes.

Ribosome

A structure that builds proteins by reading genetic instructions from RNA.

Sulfonamides (sulfa drugs)

Antibiotics that block folate production, stopping bacteria from making DNA and growing.

Tetracyclines

Antibiotics that stop bacteria from making proteins needed for growth and reproduction.

Antibiotic sensitivity test

A lab test used to find out which antibiotics a bacteria is sensitive or resistant to, helping doctors choose the right treatment.

Ampicillin

A broad-spectrum penicillin that stops bacteria from building cell walls.

Aminoglycoside

A type of antibiotic that interferes with bacterial protein production, stopping growth.

Chloramphenicol

An antibiotic that blocks bacterial protein production to stop growth.

Gentamycin

An aminoglycoside antibiotic used to treat serious infections by stopping bacteria from making proteins.

Streptomycin

An antibiotic that prevents bacteria from making proteins and was one of the first drugs to treat tuberculosis.

Zone of inhibition

The clear area around an antibiotic spot on a culture plate where bacteria didn’t grow; shows how effective the antibiotic is.

Antibiotic resistance

When bacteria develop the ability to survive and grow even when exposed to an antibiotic.

Bacteriophage

A virus that infects bacteria and can carry genes from one bacterium to another.

Conjugation

The process where one bacterium passes DNA (often a plasmid) directly to another through a pilus.

Destruction / Inactivation

A resistance mechanism where bacteria produce enzymes that destroy or change the antibiotic so it no longer works.

Efflux pump

A protein system that pushes antibiotics out of the bacterial cell to prevent them from working.

Mutation

A random change in a gene that can alter how a bacterium responds to an antibiotic.

Naked DNA

Free DNA fragments released by dead bacteria that other bacteria can take up through transformation.

Penicillin

A β-lactam antibiotic that weakens bacterial cell walls, leading to cell death.

Pilus

A thin, tube-like structure bacteria use to transfer DNA during conjugation.

Superbug

A bacterial strain resistant to many or all commonly used antibiotics.

Transduction

When a bacteriophage (virus) accidentally transfers DNA from one bacterium to another.

Transformation

When a bacterium takes in free DNA from its environment and adds it to its own DNA.

Natural selection

When bacteria with resistance genes survive antibiotic use and reproduce, passing those traits on.

Evolution

The gradual change in a population’s genes over time, such as bacteria becoming resistant to antibiotics.