Week 3 Flashcards
Chapter 2,3 and 26
Epidemiology
the study of how a specific agent survives and spreads through a community
Disease Transmission
the actual way the infectious agent spreads
Examples of Disease Transmission
- handshake
- kiss
- cough
- biological vectors (ex: mosquito)
Portal of Entry
Entrance-way through which a specific microbe is able to invade a host
Examples of Portals of Entry
- Gastrointestinal tract
- Respiratory tract
- Conjunctiva
- Skin
- Urogenital Tract (STD)
- Pregnancy and birth
Reservoir of Infection
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
Fomites
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
Examples of Fomites
- test tubes
- books
- pens
- cell phones
- stethoscope
- syringes
- call buttons
- bed linens
- toilet seats
- door knobs
- diner plate
- forks, spoons, knives
Hand Washing
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
Isolation Streak Plate
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
Goal of The Isolation Streak Plate
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
Pure Cultures are needed to:
- 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
Spread-plate method
- 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)
Pour-plate method
- sample is pipetted into sterile plate
- sterile medium is added and mixed well with inoculum
- Incubation
- Typical pour-plate results (subsurface colonies, surface colonies)
Robert Koch
He and his team developed many of the techniques used to isolate bacteria in pure cultures
Agar
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
Colony
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
Media
-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
Forms of Media
- Agar Plate
- Agar Deep Tube
- Broth
- Agar Slant
Tryptic Soy Media
Contains: -Dextrose (carbohydrate) -Tryptone (milk casein) -Soybean Protein -Salt Media is available in both broth and agar forms
Making Media
- Powdered media dissolved in distilled water
- Media is dispensed into tubes or bottles
- Autoclave to sterilize
Making Media: Autoclave
Used to Sterilize
- Temperature: 121 Degrees Celsius
- 15 lbs of pressure per square inch
- 15 minutes- kills vegetative bacteria, fungi, viruses and endospores (spores)
Tools + Equipment: Incubator
holds a constant temperature, used to grow bacterial cultures
Tools + Equipment: Incinerator
device used to sterilize inoculating tools (needle, loop)
Transferring Bacterial Cultures
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
Aseptic Technique
method of handling microbes and materials in a way that minimizes conatmination
Inoculation
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
Inoculum
sample being transferred
Tools + Equipment: Inoculating loop, needle
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
Turbidity
tubes uniformly cloudy
Flocculent
flecks or chunks of bacterial growth scattered throughout the tube
Sediment
growth settled onto the bottom of the tube
Pellicle
film of bacteria covering the surface
Ring
growth only around the edge
Successful Isolation Streak Plate
- 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
Salmonella Gastroenteritis Symptoms
- diarrhea (three or more loose bowel movements during a 24-hour period)
- abdominal cramping
- fever
- muscle aches
- bloody stools
Normal Biota
Microbes
ex: Micrococcus luteus, Staphylococcus epidermidis, Staphylococcus aureus, Corynebacterium, Propionibacterium acnes
- harmless and some are beneficial
- usually difficult to remove from skin
Transient Organisms
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
Opportunistic Pathogens
an infectious microorganism that does not harm its host but can cause disease when the hosts resistance is low
