MicroBio Lab - Final Exam Review

What do Antibiotics target?

Antibiotics target bacteria inside the body

What do Antiseptics target?

antiseptics are used on living tissue

What do Disinfectants target?

disinfectants are used on non-living surfaces

What method is commonly used to evaluate antimicrobial effectiveness?

Filter disk (Kirby-Bauer) method

What is a zone of inhibition?

The clear area around a disk where bacteria do not grow

How do you measure a zone of inhibition?

Measure the diameter in millimeters (mm)

How is bacterial sensitivity determined?

By comparing zone size to an interpretive chart

What is the purpose of an interpretive chart?

To classify bacteria as sensitive, intermediate, or resistant.

What is a lawn technique?

Evenly spreading bacteria across agar to create uniform growth

What are satellite colonies?

Small colonies growing within a zone of inhibition

What is a synergistic effect?

When two antibiotics work better together than alone.

What is bactericidal vs. bacteriostatic?

A: Cidal = kills bacteria; static = inhibits growth.

What are 4 modes of action of antibiotics?

Inhibit cell wall, protein synthesis, nucleic acids, or membrane function

What does penicillin target?

Cell wall synthesis

What does tetracycline target?

Protein synthesis; inhibit tRNA attachment

What does polymyxin target?

Cell membrane

What is antibiotic resistance?

Bacteria evolving to survive antibiotic exposure

How does antibiotic resistance develop?

Mutation and gene transfer, often worsened by misuse of antibiotics

What should you consider when controlling microbes?

Proper agent, dose, time, and resistance risk

What is the purpose of metabolism tests?

To identify organisms based on metabolic activity

What are endoenzymes?

Enzymes that function inside the cell

What are exoenzymes?

Enzymes secreted outside the cell

What do fermentation tubes test?

Ability to ferment sugars (glucose, lactose, sucrose)

What indicates a positive fermentation test?

Color change (acid) and possible gas production

What does starch hydrolysis test for?

Amylase enzyme

What indicates a positive starch test?

Clear zone after iodine

What does casein hydrolysis test for?

Protease

What indicates a positive casein test?

Clearing around growth

What does lipid hydrolysis test for?

Lipase

What indicates a positive lipid test?

Oily or iridescent sheen

What does gelatin hydrolysis test for?

Gelatinase

What indicates a positive gelatin test?

Liquid after refrigeration.

What does litmus milk test for?

Fermentation, reduction, protein digestion, & curd formation

What does the SIM test measure?

Sulfur reduction, indole production, motility

What do OF tubes test for?

Oxidation vs. fermentation of glucose

What does the indole test detect?

Tryptophan breakdown

What indicates a positive indole test?

Red layer after reagent

What does the nitrate test detect?

Reduction of nitrate to nitrite or nitrogen gas

What does the MR test detect?

Mixed acid fermentation

What does the VP test detect?

Acetoin production

What does the citrate test detect?

Ability to use citrate as carbon source

What does the catalase test detect?

Breakdown of hydrogen peroxide

What indicates a positive catalase test?

Bubbling

What is the first step in identifying unknown bacteria?

Staining (Gram stain)

What does a Gram stain differentiate?

Gram-positive vs. Gram-negative

What is a negative stain used for?

Observing cell size and shape

What is the 3% KOH test used for?

Confirm Gram reaction (string = Gram-negative)

What are colony characteristics?

Shape, size, color, texture, elevation, margin

What is used as the final identification reference?

Bergey's Manual of Systematic Bacteriology

What does the Staphslide latex test detect?

Coagulase enzyme

What organism is primarily identified with the Staphslide latex test?

Staphylococcus aureus

What happens in a positive latex test?

Agglutination (clumping)

What causes agglutination in this test?

Antigen-antibody binding

What do latex particles contain?

Antibodies against coagulase

What does coagulase indicate?

Virulence (pathogenicity)

Which cells produce antibodies?

Plasma cells

What is immunity?

The body’s ability to resist infection

How are antibodies formed?

Produced by plasma cells in response to antigens