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Microbiology Lab

Final exam study guide

general lab rules: no food/drinks, hand washing, disposal
gram stain procedure & times: crystal violet stain for 1 minute, gram iodine for 1 minute, decolorizer for 10-20 seconds, safranin stain for 1 minute
methods for manipulating cultured organisms while preventing contamination are called _______. aseptic techniques
why is aseptic technique important? to develop and maintain pure cultures, techniques for transferring growing organisms from a pure culture to a sterile medium without contaminants are essential
examples of aseptic techniques flaming a wired loop, hand washing, wearing gloves
antibiotics are chemical compounds that selectively inhibit or kill microorganisms while causing little or no damage to animal cells antibiotic susceptibility
composed of G(+) cocci, arranged in irregular "grape-like" clusters, important part of body's normal flora on skin, mucosal surfaces, and in the upper respiratory tract, some of the most disease causing organisms staphylococcus
composed of G(+) cocci, arranged in chains, found in normal flora and upper respiratory tract, common in throat streptococcus
importance of transport to urine cultures urine often becomes contaminated as it passes out of the body, culturing should begin soon after collection before contaminants can multiply and distort results
caused by organisms that enter and multiply in the intestine food infections
ingestion of preformed toxins food intoxications
ex: E. coli, salmonella food infections
ex: Staphylococcus aureus food intoxications
actively growing or vegetative stage trophozoite
dormant stage in the life cycle cyst stage
where is S. aureus found at? normal flora, usually in nostrils
where is S. epidermidis found at? normal flora, skin and mucous membranes
what are the different types of hemolysis? beta, alpha, and gamma
no hemolysis; results in NO change in blood agar gamma hemolysis
hemolysins cause partial lysis of red blood cells; result is a green zone around colonies alpha hemolysis
hemolysins cause complete lysis of red blood cells; result is a clear zone around colonies beta hemolysis
why must skin around the wound be disinfected? wounds can become infected with skin flora and it is important to be able to distinguish between organisms causing infection and normal flora
infection where pathogens are limited to a small area of the body (boils, abscenses) local infection
an infection throughout the body (HIV, measles) systemic infection
when a local infection spreads to another site in the body focal infection
one of the most common sexually transmitted diseases Neisseria gonorrhoeae
is neisseria gonorrhoeae gram negative or gram positive? gram negative
neisseria gonorrhoeae is a common cause of what type of cancer? cervical cancer
can neisseria gonorrhoeae live outside the human body? no; it must be transmitted from one human to another to survive
N. gonorrhoeae can infect what? any of the mucus membranes
pasteurization is named after who? Louis Pasteur
relies on heating to reduce the number of organisms present in milk in order to make a safer product pasteurization
today, pasteurization is used more for... increasing the shelf-life of the product, than for preventing the spread of disease
at the time that pasteurization was developed, ______ were prone to infections of the _______ which could be transmitted to humans. cattle; udder
method commonly used by public health facilities colilert method
method rapid to set up and can easily distinguish E. coli from other enterics? colilert method
what color appears when E. coli is present in colilert method? bright yellow
in the colilert method, what does the yellow color indicate? that lactose fermenters are present
in filtration method, the bacteria are grown on what? eosin methylene blue agar (EMB)
is EMB selective or differential? both
why is EMB selective? it selects for enteric organisms because it contains bile salts
why is EMB differential? it contains sugar lactose
in filtration method, colonies that can ferment lactose appear what color? pink
colonies of E. coli have ________ when grown on EMB a green sheen
filtering apparatus to collect the bacteria from 100ml of drinking water filtration method
are yeasts or molds eukaryotes? both
yeasts or molds are single cells? yeasts
yeasts or molds are multicellular filamentous organisms? molds
yeasts grow in a similar manner to ________, producing a creamy colony on agar media bacteria
yeasts or molds grow as large filamentous colonies? molds
is Candida albicans a type of yeast or mold? yeast
are Aspergillus niger and Penicillum notatum yeasts or molds? molds
purpose of crystal violet? to stain the cell walls of both gram negative and gram positive organisms
purpose of gram's iodine? acts as a mordant and causes crystal violet to form large crystals within the cell wall
purpose of decolorizer for gram-positive cells? disolves crystal violet and dehydrates the thick cell wall of gram-positive cells (makes it hard for stain to leave cell wall so gram-positive stays purple)
purpose of decolorizer for gram-negative cells? dissolves lipid in the outer membrane and washes crystal violet out of the thin peptidoglycan layer; gram-negative bacteria becomes colorless.
purpose of safranin? stains all cells pink, but gram-positive cells remain strong purple color
the presence of bacteria in voided urine bacteriuria
if an organism is resistant to an antibiotic that inhibits other flora, the drug can be added to the growth medium to select for the growth of the organism of interest selective medium
contains a substance(s) that if used by the organism causes a visible change in the medium differential medium
good ex. of differential/selective mediums; contains mannitol and pH indicator that changes color when mannitol is fermented and thus acid is produced mannitol salt agar (MSA)
agar that contains substances that inhibit the growth of gram-positive organisms Eosin Methylene Blue (EMB)
an example of a differential media that is not selective blood agar
chemical compounds that selectively inhibit or kill organisms while causing little or no damage to animal cells antibiotics
one of the oldest methods for evaluating the effectiveness of a particular antibiotic against a specific type of bacteria Kirby- brauer method
steps of kirby-brauer method: mueller-hinton agar is inoculated with pure culture of an organism, filter paper disks w/ antibiotic are placed on agar surface, antibiotic diffuses thru the medium, after incubation the plates are inspected
a type of exotoxin enterotoxins
conditions most commonly due to a sudden decrease in the normal intestinal flora following treatment with a broad-spectrum antibiotic superinfection
cavities dental carriers
the amount of oxygen microorganisms use when they metabolize the organic material in water or milk is called Biological Oxygen Demand (BOD)
fungi that display both morphologies depending on environmental conditions dimorphic fungi
causes the illness popularly referred to as the "24 hour flu" Norwalk virus
bacteria in the blood bacteremia
blood poisoning, growth of bacteria in the blood septicemia
enzyme used to distinguish between streptococci and staphylococci catalase
the removal of oxygen can be followed using what? methylene blue
what does CFU mean? colony forming unit
Created by: yulissalira



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