Microbiology Lab Exam 2

Question 1

bacteria

Answer 1

bacteria are prokaryotic, one-celled organisms. Individual bacterial cells are visible only with the aid of a high-powered microscope.

bacteria can be grown in a laboratory setting on sterile petri dishes containing a gelatin-like nutrient called agar.

bacteria reproduce by binary fission. Population of cells grow very rapidly (exponential growth).

Question 2

colony

Answer 2

when a population of bacteria has multiplied to a million or more cells, a colony can be seen on the surface of the agar plate with the naked eye.
- morphological characteristics of a bacterial colony, such as shape, margin, opacity, and color can be used to identify the species of bacteria in the colony.

Question 3

chemotherapeutic agents

Answer 3

chemicals used to treat disease

Question 4

antimicrobial drugs

Answer 4

antimicrobial drugs or disinfectants used to control bacterial growth are all ANTIMICROBIALS

Question 5

Alexander Fleming

Answer 5

In 1928, Alexander Fleming identified mold Penicillum notatum, excreting compound toxic to Staphylococcus aureus in culture.

Question 6

different categories of antimicrobial chemicals that are used to control bacterial growth

Answer 6

• antibiotics
• disinfectants
• antiseptics

Question 7

antibiotics

Answer 7

antimicrobial drugs naturally produced by microorganisms (be able to kill off and prevent infection, but uses a living thing to do it)

Question 8

disinfectants

Answer 8

any substance or process that is used primarily on non-living objects to kill germs, such as viruses, bacteria, and other microorganisms that can cause infection and disease (ex: alcohols, chlorine)

Question 9

antiseptics

Answer 9

antimicrobial substances that are non-damaging to living tissue/skin while reducing the possibility of infection, sepsis, or putrefaction (ex: mouthwash, alcohols, ethyl alcohol, rubbing alcohol, hydrogen peroxide)

Question 10

sterilant

Answer 10

destroy all microorganisms (heat- sensitive critical instruments)

Question 11

high-level disinfectants

Answer 11

destroy viruses, vegetative cells (do not reliably kill endospores; semi-critical instruments used)

Question 12

intermediate-level disinfectants

Answer 12

destroy vegetative bacteria, mycobacteria, fungi, and most viruses (disinfect non-critical instruments)

Question 13

low-level disinfectants

Answer 13

destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses (do not kill endospores, naked, viruses; disinfects furniture, floors, walls)

Question 14

bacterial susceptibility

Answer 14

“susceptible” means “weak to”- for example to certain disinfectants, antibiotics

a bacterial species can be susceptible to some specific antibiotic drugs, meaning it can’t grow in the drugs presence. The opposite of susceptible is resistant.

Question 15

Kirby- Bauer test

Answer 15

the Kirby- Bauer test, also called the disc diffusion test is a standard test to determine a bacterium’s susceptibility to antibiotics, disinfectants, or antiseptics

basics of the test:
1) the bacterium is swabbed on the agar and the antibiotic discs are placed on top
2) the antibiotic diffuses from the disc into the agar in decreasing amounts the further it is away from the disc
3) if the organism is killed or inhibited by the concentration of the antibiotic, there will be NO GROWTH in the immediate area around the disc: this is called the zone of inhibition (ZOI)

size of the disc= 7mm (if there is no zone at all)

Question 16

selective toxicity

Answer 16

cause greater harm to microbes (interfere with essential structures or properties common in microbes but not human cells: which will kill more effectively and which microbes it will target) **kill off bacteria without killing us

Question 17

bacteriostatic drugs

Answer 17

drugs that inhibit bacterial growth (patient’s defenses must still eliminate)

Question 18

bactericidal drugs

Answer 18

drugs that kill bacteria

Question 19

zone of inhibition (ZOI)

Answer 19

area of media where bacteria are unable to grow, due to prescence of a drug that impedes their growth

Question 20

antimicrobials

Answer 20

a substance that kills microorganisms such as bacteria or mold, or stops them from growing and causing disease

Question 21

antimicrobials

Answer 21

a substance that kills microorganisms such as bacteria or mold, or stops them from growing and causing disease

Question 22

innate or intrinsic resistance

Answer 22

the innate ability of a bacterial species to resist activity of a particular antimicrobial agent through its inherent structural or functional characteristics, which allow tolerance of a particular drug or antimicrobial class (something your born with, for ex: mycoplasma lack a cell wall, so they resist penicilin, or outer membrane of gram-negatives resist many drugs)

Question 23

acquired resistance

Answer 23

it is said to occur when a particular microorganism obtains the ability to resist the activity of a particular antimicrobial agent to which it was previously susceptible. (spontaneous mutations, horizontal gene transfer, bacteria conjugate)

** something that happens from generation to the next (mutations occurred, change in DNA sequence randomly)

Question 24

spontaneous mutation

Answer 24

occur during replication. happen at a low rate but can have a significant effect. Just a single-base pair change in gene encoding a ribosomal protein yields resistance to streptomycin.

combination therapy of multiple drugs is often used; unlikely cells will simultaneously develop resistance to all drugs

Question 25

broad- spectrum antimicrobials

Answer 25

affect a wide range. It is important for treating acute life-threatening diseases, especially when no time to culture for identification.
**kills off all bacteria, and kills off good bacteria which is not good (bacteria in gut)

Question 26

narrow- spectrum antimicrobials

Answer 26

affect limited range. Requires identification of pathogen, testing for sensitivity. Less disruptive to normal microbiota.

**more specific; sensitive to the antibiotic and dosage that will be effective.

Question 27

drug’s TARGET

Answer 27

bacterial cell structure or process upon which the drug acts