Week 3

Question 1

Epidemiology

Answer 1

the study of how a specific agent survives and spreads through a community

Question 2

Disease Transmission

Answer 2

the actual way the infectious agent spreads

Question 3

Examples of Disease Transmission

Answer 3

• handshake
• kiss
• cough
• biological vectors (ex: mosquito)

Question 4

Portal of Entry

Answer 4

Entrance-way through which a specific microbe is able to invade a host

Question 5

Examples of Portals of Entry

Answer 5

• Gastrointestinal tract
• Respiratory tract
• Conjunctiva
• Skin
• Urogenital Tract (STD)
• Pregnancy and birth

Question 6

Reservoir of Infection

Answer 6

Any object, living or non-living, that allows a microbe to grow, reproduce, and maintain its ability to remain infective
ex: makeup, nose-drops, eye-drops

Question 7

Fomites

Answer 7

a non-living object capable of allowing a microbe to survive but not reproduce

• an inanimate object that can serve as a vehicle for the spread of disease
• proper and consistent hand washing controls fomite transmission

Question 8

Examples of Fomites

Answer 8

• test tubes
• books
• pens
• cell phones
• stethoscope
• syringes
• call buttons
• bed linens
• toilet seats
• door knobs
• diner plate
• forks, spoons, knives

Question 9

Hand Washing

Answer 9

the single most important method of controlling microbes in a clinical setting
-every person alive is a host to about 100 trillion bacterial cells
>outnumber human cells

Question 10

Isolation Streak Plate

Answer 10

Utilized to separate individual bacteria from mixtures

• most widely used method of obtaining a pure culture
• samples from patients and the environment are mixtures of different bacteria

Question 11

Goal of The Isolation Streak Plate

Answer 11

Goal of a streak plate is to thin out the number of bacteria on a plate to get isolated colonies

• all members of the colony are genetically identical and arose from a single bacterial cell
• isolated colonies are needed for all tests and procedures

Question 12

Pure Cultures are needed to:

Answer 12

• carry out biochemical testing for identification purposes
• determine antibiotic sensitivity
• determining nutritional and growth requirements
• study the organism and the disease it causes
• develop vaccines

Question 13

Spread-plate method

Answer 13

• sample is pipetted onto surface of agar plate
• sample is spread evenly over surface of agar using sterile glass spreader
• Incubation
• Typical spread-plate results (surface colonies)

Question 14

Pour-plate method

Answer 14

• sample is pipetted into sterile plate
• sterile medium is added and mixed well with inoculum
• Incubation
• Typical pour-plate results (subsurface colonies, surface colonies)

Question 15

Robert Koch

Answer 15

He and his team developed many of the techniques used to isolate bacteria in pure cultures

Question 16

Agar

Answer 16

substance derived from seaweed

• melts at 100 Degrees Celsius
• remains liquid above 45 Degrees Celsius
• solidifies completely at 40 Degrees Celsius

-Agar provides a solid surface to grow bacteria–> isolated colonies

Question 17

Colony

Answer 17

clump of bacteria growing on a solid surface

• every cell in the colony arose from a single cell
• every cell in the colony is genetically identical

Question 18

Media

Answer 18

-Synthetic growth media is used in laboratories to culture (grow) bacteria
Media must provide the nutrients an organism needs to grow:
-a nitrogen source (peptones or amino acids)
-Carbohydrates
-minerals (sulfur, phosphorous)
-buffers to maintain pH
-vitamins may also be added

Question 19

Forms of Media

Answer 19

• Agar Plate
• Agar Deep Tube
• Broth
• Agar Slant

Question 20

Tryptic Soy Media

Answer 20

Contains:
-Dextrose (carbohydrate)
-Tryptone (milk casein)
-Soybean Protein
-Salt
Media is available in both broth and agar forms

Question 21

Making Media

Answer 21

• Powdered media dissolved in distilled water
• Media is dispensed into tubes or bottles
• Autoclave to sterilize

Question 22

Making Media: Autoclave

Answer 22

Used to Sterilize

• Temperature: 121 Degrees Celsius
• 15 lbs of pressure per square inch
• 15 minutes- kills vegetative bacteria, fungi, viruses and endospores (spores)

Question 23

Tools + Equipment: Incubator

Answer 23

holds a constant temperature, used to grow bacterial cultures

Question 24

Tools + Equipment: Incinerator

Answer 24

device used to sterilize inoculating tools (needle, loop)

Question 25

Transferring Bacterial Cultures

Answer 25

Follow aseptic techniques when handling bacteria: - never put caps or inoculating tools on the bench top - flame the tops of the tubes before and after each transfer - flame the inoculating tools in the incinerator at the start and end of every transfer

Question 26

Aseptic Technique

Answer 26

method of handling microbes and materials in a way that minimizes conatmination

Question 27

Inoculation

Answer 27

the process of transferring a microbe from one medium to the next -we transfer microorganisms from one medium to another for further study or to maintain cultures

Question 28

Inoculum

Answer 28

sample being transferred

Question 29

Tools + Equipment: Inoculating loop, needle

Answer 29

tools used to transfer bacteria from a culture to sterile media (used to transfer an inoculum) -Loop: used for most of the transfer procedures done in class -Needle: used for techniques that require stabbing into the agar such as is done with the triple sugar iron (TSI) slant

Question 30

Turbidity

Answer 30

tubes uniformly cloudy

Question 31

Flocculent

Answer 31

flecks or chunks of bacterial growth scattered throughout the tube

Question 32

Sediment

Answer 32

growth settled onto the bottom of the tube

Question 33

Pellicle

Answer 33

film of bacteria covering the surface

Question 34

Ring

Answer 34

growth only around the edge

Question 35

Successful Isolation Streak Plate

Answer 35

- First Streak Area- shows heavy confluent growth - Second Streak Area- can see that the growth is starting to thin out and some individual colonies are staring to appear - Third Streak Area- thinner growth, and isolated colonies appear

Question 36

Salmonella Gastroenteritis Symptoms

Answer 36

- diarrhea (three or more loose bowel movements during a 24-hour period) - abdominal cramping - fever - muscle aches - bloody stools

Question 37

Normal Biota

Answer 37

Microbes ex: Micrococcus luteus, Staphylococcus epidermidis, Staphylococcus aureus, Corynebacterium, Propionibacterium acnes - harmless and some are beneficial - usually difficult to remove from skin

Question 38

Transient Organisms

Answer 38

found on skin for short periods of time but do not grow there (temporary) - acquired by contact with contaminated surfaces and are usually easily removed - some cause disease

Question 39

Opportunistic Pathogens

Answer 39

an infectious microorganism that does not harm its host but can cause disease when the hosts resistance is low