Microbiology Flashcards
Antibiotic
Treat infections caused by bacteria
Antiseptic
A substance used to stop or slow down the growth of microorganisms
Disinfectant
A chemical liquid that destroys bacteria
Aseptic
Aiming at the complete exclusion of harmful microorganisms
Bactericidal
Agent that kills bacteria
BacterIOSTATIC
Agent that prevents growth of bacteria
incubation
Time it takes for an infection to develope after a person has been exposed to disease-causing organism.
Normal flora
Microorganisms living on a surface (living or not) that do not cause disease and can even help prevent it.
Nosocomial
Disease originating in a hospital
H.A.I.
Infections associated infections from devices used during medical procedures.
- Catheters
- Ventilators
- Central lines
Ubiquity of microorganisms
Microorganisms are ubiquitous in all kinds of micro- and macro-ecology environments on earth.
Enteric
Bacteria that live in the digestive system of animals
Aerobic
Bacteria that requires oxygen to grow
Anaerobic
Bacteria that can grow in the absence of oxygen
Pathogenic
Microorganisms that cause disease
No colonies visible on BAP means?
No bacteria present in sample, bacteria killed during plate streaking process.
- blood agar is nutrient rich, should be able to grow anything… i think.
Colonies grow on BAP. Media surrounding colonies still appears red. What does this mean?
- Microbe capable of using blood as a source of nutrition
- Incapable of damaging/lysis RBCs (gamma hemolysis/non hemolytic)
Colonies present and surrounded by a green zone.
- microbe capable of using blood as a source of nutrition
- Capable of apathy-hemolysis/ partially hemolytic
Colonies present and surrounded by a transparent, clear zone.
- microbe capable of using blood as a source of nutrition
- Capable of beat-hemolysis/complete hemolytic
What does it mean if no colonies grow on an MAC plate?
Bacteria cannot grow in the presence of crystal violet and bile salts.
- bacteria GM+ and or non-enteric.
What does it mean if bacteria grows on an MAC plate?
Bacteria is GM- and enteric
What does it mean if colonies appear white on a MAC plate?
Bacteria are lac- (unable to ferment lactose) and metabolize the peptone in the media instead, forming ammonia, increase pH.
- salmonella
- shigella
What does it mean id colonies appear pink/red on MAC plate?
Lac+, ferment lactose, producing acid, decreasing pH, activating neutral red dye.
- E. coli
- Klebsiella
Function of crystal violet during GM stain?
Stains peptidoglycan in the bacterial cell wall, especially the thick later found in GM + cells.
Function of Gram’s iodine during GM stain?
Involves application of a mordant, forms a insoluble complex with crystal violet, fixing the stain to the cell wall.
Function of acetone-alcohol during GM stain?
Dehydrates the cell trapping the crystal violet/iodine complex.
In Gm- cells, this dissolves that lipopolysaccharide in the outermost membrane, washing away excess stain from the surface of the Gm- cells.
Function of safranin during GM stains?
Stains the thinner peptidoglycan coat of Gm- cells pink.
What does permissive formulated agar mean?
What does restrictive/selective agar mean?
Has the intent of allowing the growths of wearer organisms are present.
Only allows the growths of specific organisms. Ex. Including lactose so only enteric microorganisms can grow
What do indicator plates do and how?
organisms are not selected on the basis of growth, but a compound in the agar is altered by the bacteria so as to change the colour of the colonies or the agar. Dyes can be used.
Blood agar plates (BAP)
- contain mammalian blood (usually sheep), typically at a concentration of 5–10%.
- enriched media, used to isolate organisms which may require more nutrients than are provided in a regular nutrient agar plate
- differential media, as it is also used to detect hemolytic activity
- This type of agar is useful for the identification and culture of Streptococcus and Staphylococcus bacteria.
MacConkey agar (MAC)
- culture medium designed to grow Gram-negative bacteria and stain them for lactose fermentation. (enteric bacteria)
- contains bile salts (to inhibit nonenteric bacteria), crystal violet dye (to inhibit Gram-positive bacteria), neutral red dye (which stains microbes fermenting lactose), lactose and peptone.
- Lac+ bacteria such as Escherichia coli and Klebsiella will produce acid, which lowers the pH of the agar below 6.8 and results in the appearance of red/pink colonies.
- Non-lactose fermenting bacteria such as Salmonella and Shigella cannot utilize lactose, and will use peptone instead. This forms ammonia, which raises the pH of the agar, and leads to the formation of white/colourless colonies.
What are the steps to making a Gram stain?
- Crystal violet (30 sec)
- Rinse w/ distilled water (30 sec)
- Grams iodine (60 sec)
- Decolourize w/ acetone-alcohol
- Rinse w/ distilled water (30 sec)
- Counterstain w/ safranin (30 sec)
- Decolourize w/ distilled water
- Blot w/ bibulous paper
