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Microbiology Test 1

Microbiology test 1

TermDefinition
Communicable disease when an infected host can transmit the infectious agent to another host and establish infection in that host
contagious. Highly communicable diseases
Non-communicable infectious diseases do not arise through transmission from host to host.;occurs primarily when a compromised person is invaded by his or her own normal microflora;Can occur through direct contact with organism in natural, non-living reservoir
how many of nosocomial infections could be prevented. More than 1/3rd; 2 to 4 million cases/year in U.S. with approximately 90,000 deaths Most commonly involve urinary tract, respiratory tract, and surgical incisions Most common organisms involved: Gram-negative intestinal flora;E. coli, Pseudomonas, Staph
Hand sanitizer is a non-water-based hand hygiene agent. Active ingredient is usually isopropanol or ethanol Needs to contain at least 60% alcohol to be effective Added benefit of viral inactivation
Antibacterial soap most Triclosan-based (antibacterial compound) based: Many Triclosan resistant bacteria can be found in the environment Triclosan has no effect upon viruses Antimicrobial effects are concentration dependent High – biocide – multiple cytoplasmic and mem
emulsification. allows water to remove normally-insoluble matter
Soaps Anionic surfactants have both a hydrophilic end, which dissolves in water, as well as a hydrophobic end, which is able to dissolve nonpolar molecules like grease; emulsification
Joseph Lister father of antisepsis; cleaned using carbolic acid solution; stiches; sterile instruments could be left in patients; got idea from Pasteur,
Ignaz Semmelweis handwashing in Vienna General in 1846; puerperal fever in babies;
Normal microbiotia or normal flora More or less permanent residents of your body Actual numbers and types may vary over time Different people will have different distributions
Transient microbiota or transient flora Present only for days or weeks in/on the body Some of these are pathogens; i.e. bacteria that could colonize and cause an infection – resulting in disease
Oceans 1 billion of microbial cells per liter of sea water
Soil There are more microbes in a gram of soil than there are humans alive today. There are 10,000 different species found in one gram of soil
Humans There are 100 trillion (1014) microbial cells in the gut. Ten times the number of human cells in an adult body Over 1,000 different species; prevalence and type vary from individual to individual
Robert Hooke reported that living things were composed of little boxes or cells
Antonie van Leeuwenhoek construction of microscopes which could magnify up to 30 - 100X Described microorganisms that he observed in teeth scrapings & rain water “animalcules”
Germ Theory of disease The theory that proposes that microorganisms are the cause of many diseases.; Pasteur and Koch
Louis Pasteur Disproved theory of spontaneous generation
Robert Koch Developed postulates that validated the germ theory of disease
Spallanzani – 1700s Experiment effectively disproved spontaneous generation Previous experiments performed in this manner were refuted in that “the boiling kills the life force” How did Spallanzani disprove this? Critics then argued “air” was required for spontaneous gen
Why was Koch successful? Developed techniques for culturing microorganisms
Agar Not degradable by most microorganisms Liquefies at 100°C Solidifies at temps under 40°C Once solidified, can be incubated at temps up to 100°C
Streak plate Most common Determines the “what” is in the culture
Serial dilution and plating Determines the “how much” is in a culture Used in conjunction with spread plating Expressed in terms of cfu/ml Colony forming units per milliliter of culture
Pipetman Dual stop: should go down to 1st stop to take up sample and should go to 2nd stop to expel sample P-1000 100 – 1000 µl sample transfer P – 200 20-200 µl sample transfer P- 20 2-20 µL sample transfer
cfu/ml Colony counts are expressed from serial dilutions;Colony forming units/ml Each colony represents outgrowth from a single cell, but an individual colony is made up of millions of bacterial cells!
Spot plating: TNTC too numerous to count More than 30 colonies per spot
Spot plating: TFTC too few to count Less than 5 colonies per spot
Spread plating more sensitive than spot plating; more expensive as you need more plates
Spread plates: TNTC more than 250
Spread: TFTC less than 25
Spread plate Formula: #colonies x reciprocal of dilution x (1000/amt plated)This accounts for your µL to mL conversion
Spot Plate Formula: #colonies (average of the 3 spots)x reciprocal of dilution x (1000/amt plated)This accounts for your µL to mL conversion
UTIs only considered an active infection if plated cfu/mls exceed 105
Cfu/ml numbers can be used in the following: Estimate the amount of protein and or DNA based upon viable counts in a population for research purposes
most compound light microscopes have 3 or 4 objectives mounted on the nosepiece directly over the stage
longer the lens... greater the mag
Magnification is limited by resolution
Resolution Ability to see two objects as separate and distinct
resolution depends upon refraction (scattering) of light
Refraction can be limited by: Light wavelength Shorter wavelengths = better resolution most scopes employ a blue filter (short wavelenght) Numerical aperture (NA) of the lens The ability of the objective to capture scattered light Related to curvature of the lens
Glass and air different refractive indexes;- Some light is “lost” before it makes it to the objective
Glass and oil almost identical refractive indexes;-More light makes it to the objective = less refraction, therefore better resolution Use of oil immersion increases magnification approximately 2.5-fold
oil immersion lens only fine adjustment; should be able to see seal
As you switch from low to high power the field of view becomes darker.   To deal with this the iris diaphragm needs to be opened to allow more light into the condenser.
As you switch from low to high power the field of view becomes smaller.
Parfocal in focus with one lens – in focus with all (in theory) – higher magnifications may require slight adjustments
Brightfield microscopy Objects are dark and the “field” is light
Stains Are chromophores – charged ions Acidic (-) or basic (+)
Direct/simple stains organism; uses a basic stain
Negative/indirect stains field or background; uses an acidic stain Based upon the inherent properties of the negatively charged bacterial membrane and chromosome
What do we stain? smear
what do we need? clean slide
Why do you fix organism to slide? to increase adherence; to increase stain uptake; kill bacteria
Negative Staining Stains background not bacteria. Ionic Repulsion – like charges repel
Pros of Negative Staining: Bacteria less distorted- does not require heat fixation Can display cell morphology and size more clearly than other staining.
Primary stain Imparts color to all cells
Decolorizing agent May or may not remove the primary stain from the entire cell or certain cell structures
Counterstain Provides color contrast to primary stain
Gram positive peptidoglycan 90% of cell wall;
Gram negative peptidoglycan in 10% of cell wall; cells have outer lipolysaccharide layer (LPS)
Primary stain Crystal Violet (1˚) dissociates into CV+ and Cl- ions
Iodine (mordant) makes CV-I complexes
. Alcohol (decolorizing agent) washes away outer layer of Gram- along with CV-I. CV-I in gram+ cells stays in layer of peptidoglycan so stays PURPLE.
Safranin (2˚) gives gram- its PINK color.
Gram Positive characteristics thick layer cell wall peptidoglycan; low lipid (1-4%); quite susceptible to penicillin; complex for many species (pathogens); more resistant to physical disruption
Gram Negative characteristcs Think layer cell wall peptidoglycan; high lipid (11-22%); less susceptible to penicillin; simple; less resistant to physical disruption
Problems with gram staining Some bacteria will not Gram stain (Mycobacterium, Mycoplasma, Nocardia spp. to name a few examples) Accurate staining is often dependent upon culture age (18-24 hr cultures give best results) Some bacteria give variable results – (Gram – v) Stressed ba
some bacteria contain what which makes them impermeable to staining procedures mycolic acids
Acid fast bacteria Resist decolorization with acid alcohol Carbol fuschin contains phenol which solubilizes traditional cell walls Methylene blue serves as a counter stain
Steam heat is used to facilitate the uptake of the carbol fuchsin by the acid fast bacteria
go over slides in the powerpoints slides 24-28
Created by: KatelynnJoy