Lecture 2: Microbiology

Question 1

What is microbiology?

Answer 1

The study of microorganisms

Question 2

What kind of organisms are bacteria?

Answer 2

Prokaryotic organisms

Question 3

What is virulence?

Answer 3

The severity or harmfulness of a disease

Question 4

What is a flagella?

Answer 4

A long whip like tail used for locomotion

Question 5

What are pilli?

Answer 5

Short filaments that help the bacteria attach to surfaces

Question 6

Septic

Answer 6

The presence of microorganisms

Question 7

Aseptic

Answer 7

The absence of microorganisms

Question 8

What is the aseptic technique and what does it prevent?

Answer 8

Aseptic technique is a series of steps to prevent the contamination of microbiological cultures (maintain integrity of a specimen as presented to the lab) and prevent the transmission of organisms from specimens to personnel, (standard/ universal precautions)

Question 9

Sterile/ to sterilize

Answer 9

NO viable microorganisms present. Several methods: some examples include in interaction, autoclaving, ethylene oxide, etc.

Question 10

Disinfect/ Disinfectant

Answer 10

To decrease the # of organisms present (not sterile!). Usually refers to inanimate objects (ex. Lysol)

Question 11

Antiseptic

Answer 11

An agent that decreases the # of organisms present, but usually in reference to body surfaces. Examples: mouthwash, soaps, etc.

Question 12

Pasteurization

Answer 12

A method to decrease the # of organisms present. Usually used in the food/ dairy industry

Question 13

Basal media

Answer 13

General type of nutritive media “supplies the basics,” useful for most organisms. Ex. Nutrient agar, Trypticase Soy Agar (TSA)

Question 14

Enriched media

Answer 14

Contains one or more substances to increase the growth of fastidious organisms. Ex. Blood Agar

Question 15

Selective media

Answer 15

Contain dies or antibiotics that inhibit certain bacteria. These media “select“ for bacteria able to survive in these conditions.

Question 16

Differential media

Answer 16

Contains certain nutrients, energy, sources, and color indicators. This provides a means “differentiating“ colonies from one another based on biochemical differences.

Question 17

MacConkey Agar (MAC)

Answer 17

This is an example of a selective and differential medium. The bile salts and crystal violet inhibit most gram-positive organisms and selects for gram-negative bacilli. MAC differentiates organisms that can use lactose from those that can’t use lactose (when the organisms use the sugar, acid end products are produced. This causes a pH change in the medium that is detected by the pH indicator and yield a color change. Lactose positive colonies, turn pink.)

Question 18

Colistin Nalidixic Acid Agar (CNA)

Answer 18

The medium contains basic nutrients and agar, 5% sheep’s blood (enrichment) and Colistin and nalidixic acid (inhibitors). This is an example of a selective and enriched medium. It is enriched because of the addition of the blood. It is selective because the colistin and nalidixic acid inhibit gram-negative organisms and allow the gram-positive organisms to grow.

Question 19

Inoculation

Answer 19

Transfer of organisms from one site to another. Requires aseptic technique and sterilization techniques. On solid media, requires “streaking“: dilution of the specimen on the surface of the media to isolate individual organisms. Eventually yields well, isolated colonies that arise from the individual organisms.

Question 20

What temperature do most bacteria like to grow at?

Answer 20

35–37°C

Question 21

Aerobic

Answer 21

Requires oxygen

Question 22

Anaerobic

Answer 22

Requires the absence of oxygen

Question 23

Capnophilic

Answer 23

Requires an increase in CO2

Question 24

Simple stain

Answer 24

One stain, all organisms, one color. Example methylene blue.

Question 25

Differential stain

Answer 25

More complex process, categorizes organisms on their ability to retain a particular stain or react to a specific treatment. Example Gram’s stain, acid fast stain

Question 26

Special stain

Answer 26

Stains a particular part or feature of the bacteria. Example spore stain, flagella stain

Question 27

Gram-positive bacteria

Answer 27

Bacteria that stain purple or blue as a result of retention of the crystal violet iodine complex. Grandpa cells have a thick peptidoglycan layer.

Question 28

Gram-negative bacteria

Answer 28

Bacteria that stain, red or pink from the counterstain safranin are termed gram-negative. Gram-negative cells have a thinner peptidoglycan layer with an additional outer membrane similar to the inner cell membrane.