Clinical Microbiology

Question 1

Binary Fission

Answer 1

form of asexual reproduction and cell division

used by most bacteria

Question 2

Generation time

Answer 2

length of time required for a single bacterial cell to yield two
daughter cells

Question 3

Lag phase

Answer 3

active metabolism of the cells as they acquire various essential constituents prior to
division

Question 4

Log Phase

Answer 4

Binary fission of the young cells results in an exponential increase in numbers

Question 5

Stationary Phase

Answer 5

growth ceases as
nutrients are depleted and toxic metabolites accumulate in the medium.

No net increase in bacterial number.

Question 6

Decline Phase

Answer 6

Old cells die rapidly followed by younger

resulting rate of
cell death is exponential

involution forms can be seen

Question 7

involution forms

Answer 7

abnormally shaped cells

Question 8

Direct physical measurement of cell mass

Answer 8

dry weight, wet weight, or volume of cells after centrifugation

Question 9

Direct chemical measurement of cell mass

Answer 9

some chemical component of the cells such as total protein, or total DNA content

Question 10

Indirect measurement of chemical activity

Answer 10

rate of O2 production or consumption, CO2 production or consumption, etc

Question 11

Turbidity measurements of cell mass

Answer 11

amount of light scattered by a suspension of cells

Question 12

Counting cells using a Direct smear (Breed’s method)

Answer 12

Microscopic counting of cells on a fixed and stained smear prepared from a defined volume of fluid

Question 13

Counting cells using a counting chamber

Answer 13

Microscopic counting on a fixed volume of bacterial suspension using a calibrated slide

Question 14

Real-Time PCR method for cell counting

Answer 14

number of bacterial cells in a sample is quantified based on detection of DNA concentration

For detection of total viable cells

Question 15

chemoheterotrophs

Answer 15

bacteria that use organice chemicals as sources of energy production

Question 16

fermentation

Answer 16

metabolic process that:

1) releases energy from a sugar or other organic molecules
2) does not require oxygen or an electron transport system
2a. uses an organic molecule as the final electron acceptor

Question 17

Peptones

Answer 17

short chains of amino acid monomers linked by peptide (amide) bonds

Question 18

Phosphates

Answer 18

essential for production of nucleic acids and molecules containing energy-rich bonds

Question 19

Sulfates

Answer 19

are required for synthesis of sulfur-containing amino acids

Question 20

Trace Elements

Answer 20

dietary element needed in very minute quantities for proper growth, development, and physiology

Question 21

Growth factors

Answer 21

essential substances required in small amounts to fulfill specific roles in biosynthesis

Question 22

Purines and pyrimidines (growth factors) required for…

Answer 22

synthesis of nucleic acids

Question 23

Amino Acids (growth factors) required for…

Answer 23

synthesis of proteins

Question 24

Vitamins (growth factor) needed as…..

Answer 24

coenzymes and functional groups of enzymes

Question 25

General Purpose Medium

Answer 25

provides enough nutrients to allow for a wide variety of microorganisms to grow

Question 26

Bile Salts

Answer 26

inhibit most gram-positive bacteria

Question 27

Crystal Violet Dye

Answer 27

inhibits certain gram-positive bacteria

Question 28

Neutral Red Dye

Answer 28

stains microbes fermenting lactose

Question 29

Mesophils

Answer 29

Organisms with an optimum growth temperature near 37 degrees Celsius (body temperature of warm-blooded animals)

Question 30

Thermophils

Answer 30

organisms with an optimal growth temperature between 45 and 70 degrees Celsius

Question 31

Hyperthermophiles / extreme thermophils

Answer 31

optimum growth temperature between 80 and 115 degrees Celsius

Question 32

psychrophiles

Answer 32

cold loving organisms | ability to grow at 0 degrees Celsius 10-15 optimum

Question 33

psychrotrophs

Answer 33

optimum temperature near room temp but can grow at 0 degrees Celsus

Question 34

acidophiles

Answer 34

grow at an optimum pH well below neutrality (7.0)

Question 35

neutrophiles

Answer 35

grow best at a neutral pH

Question 36

alkaliphiles

Answer 36

grow best under alkaline conditions

Question 37

Buffers (in medium)

Answer 37

used to maintain pH of medium at optimal for growth despite bacterial waste products accumulating

Question 38

Protoplast

Answer 38

bacteria whose cell wall has been completely or partially removed using either mechanical or enzymatic means

Question 39

obligate aerobes

Answer 39

require oxygen for growth

Question 40

Obligate anaerobes

Answer 40

do not need or use oxygen as it is toxic to them

Question 41

Facultative anaerobes

Answer 41

can switch between aerobic and anaerobic types of metabolism

Question 42

Aerotolerant anaerobes

Answer 42

exclusively anaerobic but are insensitive to oxygen

Question 43

Capnophiles

Answer 43

grow best in carbon dioxide

Question 44

Substrate level phosphorylation (SLP)

Answer 44

ATP synthesized during the conversion of an organic molecule from one form to another

Question 45

Electron Transport Phosphorylation (ETP)

Answer 45

ATP synthesized by dumbing electrons down transport chain

Question 46

Main nutritional requirements for bacteria

Answer 46

Organic Compounds: C, O, N, H, P Growth Factors: Purines & Pyrimidines - for nucleic acids Amino Acids - for protein synthesis Vitamins - as coenzymes and functional groups

Question 47

___________ is a general purpose medium used for a wide range of applications including; culture storage, enumeration (counting), isolation of pure cultures or simply general culture

Answer 47

Trypticase soy agar (TSA)

Question 48

____________ is a general purpose enriched medium often used to: - grow fastidious organisms - identify hemolytic bacteria

Answer 48

Blood Agar

Question 49

_______________ is designed to grow Gram-negative bacteria and differentiate lactose fermenters from non-fermenters.

Answer 49

MacConkey agar

Question 50

Presence of a red/pink color in MacConkey agar indicate what has happened?

Answer 50

Lactose has been fermented producing acid that lowers pH of medium to produce red/ pink colored colonies

Question 51

What does MacConkey agar contain and why is it used?

Answer 51

bile salts and crystal violet dye - to inhibit most Gram-positive bacteria crystal violet dye neutral red dye - stains microbes fermenting lactose lactose and peptone as food source

Question 52

Describe the 4 basic steps in gram staining.

Answer 52

1) Primary stain (crystal violet) - stains gram + and - cells 2) Mordant (Gram's Iodine) - forms complexes with primary stain and fixes it to cells 3) Decolorizer (alcohol or acetone) - destroys gram negative membrane and washes away primary stain - large peptidoglycan layer of gram positive keeps primary stain in 4) Counterstaining - safranin or basic fuchsin stains gram negative only

Question 53

Environmental factors that influence bacterial growth.

Answer 53

``` – Temperature – pH (H+ concentration) – Moisture – Atmospheric composition – Osmotic pressure ```

Question 54

Testing for antibiotic sensitivity is often done by the _____________, where mall wafers containing antibiotics are placed onto a plate upon which bacteria are growing. If the bacteria are sensitive to the antibiotic, a clear ring, or zone of inhibition, is seen around the wafer indicating poor growth.

Answer 54

Kirby-Bauer method

Question 55

Minimum Inhibitory Concentration (MICs) can be determined by _________ or ____________, usually following the guidelines of a reference.

Answer 55

agar dilution | broth microdilution

Question 56

minimum inhibitory concentration (MIC)

Answer 56

the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation