Lecture 2: Microbiology Flashcards
What is microbiology?
The study of microorganisms
What kind of organisms are bacteria?
Prokaryotic organisms
What is virulence?
The severity or harmfulness of a disease
What is a flagella?
A long whip like tail used for locomotion
What are pilli?
Short filaments that help the bacteria attach to surfaces
Septic
The presence of microorganisms
Aseptic
The absence of microorganisms
What is the aseptic technique and what does it prevent?
Aseptic technique is a series of steps to prevent the contamination of microbiological cultures (maintain integrity of a specimen as presented to the lab) and prevent the transmission of organisms from specimens to personnel, (standard/ universal precautions)
Sterile/ to sterilize
NO viable microorganisms present. Several methods: some examples include in interaction, autoclaving, ethylene oxide, etc.
Disinfect/ Disinfectant
To decrease the # of organisms present (not sterile!). Usually refers to inanimate objects (ex. Lysol)
Antiseptic
An agent that decreases the # of organisms present, but usually in reference to body surfaces. Examples: mouthwash, soaps, etc.
Pasteurization
A method to decrease the # of organisms present. Usually used in the food/ dairy industry
Basal media
General type of nutritive media “supplies the basics,” useful for most organisms. Ex. Nutrient agar, Trypticase Soy Agar (TSA)
Enriched media
Contains one or more substances to increase the growth of fastidious organisms. Ex. Blood Agar
Selective media
Contain dies or antibiotics that inhibit certain bacteria. These media “select“ for bacteria able to survive in these conditions.
Differential media
Contains certain nutrients, energy, sources, and color indicators. This provides a means “differentiating“ colonies from one another based on biochemical differences.
MacConkey Agar (MAC)
This is an example of a selective and differential medium. The bile salts and crystal violet inhibit most gram-positive organisms and selects for gram-negative bacilli. MAC differentiates organisms that can use lactose from those that can’t use lactose (when the organisms use the sugar, acid end products are produced. This causes a pH change in the medium that is detected by the pH indicator and yield a color change. Lactose positive colonies, turn pink.)
Colistin Nalidixic Acid Agar (CNA)
The medium contains basic nutrients and agar, 5% sheep’s blood (enrichment) and Colistin and nalidixic acid (inhibitors). This is an example of a selective and enriched medium. It is enriched because of the addition of the blood. It is selective because the colistin and nalidixic acid inhibit gram-negative organisms and allow the gram-positive organisms to grow.
Inoculation
Transfer of organisms from one site to another. Requires aseptic technique and sterilization techniques. On solid media, requires “streaking“: dilution of the specimen on the surface of the media to isolate individual organisms. Eventually yields well, isolated colonies that arise from the individual organisms.
What temperature do most bacteria like to grow at?
35–37°C
Aerobic
Requires oxygen
Anaerobic
Requires the absence of oxygen
Capnophilic
Requires an increase in CO2
Simple stain
One stain, all organisms, one color. Example methylene blue.
Differential stain
More complex process, categorizes organisms on their ability to retain a particular stain or react to a specific treatment. Example Gram’s stain, acid fast stain
Special stain
Stains a particular part or feature of the bacteria. Example spore stain, flagella stain
Gram-positive bacteria
Bacteria that stain purple or blue as a result of retention of the crystal violet iodine complex. Grandpa cells have a thick peptidoglycan layer.
Gram-negative bacteria
Bacteria that stain, red or pink from the counterstain safranin are termed gram-negative. Gram-negative cells have a thinner peptidoglycan layer with an additional outer membrane similar to the inner cell membrane.
