Microbiology 2420 Lab Practical Final Study Cards

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Epidemic

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sudden increase in a disease,affecting many persons at the same time, and spreading from person to person in a locality where the disease is not permanently prevalent

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Endemic

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always around, belonging exclusively or confined to a particular place

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Epidemiology

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the branch of medicine dealing with the incidence and prevalence of disease in large populations and with detection of the source and cause of epidemics of infectious disease

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Pandemic

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crosses borders, prevalent throughout an entire country, continent, or the whole world; epidemic over a large area

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prevalence

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the total number of existing cases of disease within a defined population.

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Incidence

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the number of new cases of a disease occurring among defined population within a specific period.

no. new cases within defined time period/ size of at-risk population times K (k is constant)

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common source epidemic

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when many people are infected through contact with a single source, such as a contaminated food item

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Propagated transmission epidemic

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disease is passed person to person

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Index case

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First person were it started

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Ultraviolet radiation effects on bacterial cells

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Lid is used as control, UV light doesn't penetrate surface

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Ultraviolet radiation effects on bacterial cells

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Lid is used as control, UV light doesn't penetrate surface

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pyrimidine dimer

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forms double bonds like cytosine-cytosine, thymine-thymine, or thymine-cytosine making replication and transcription difficult. if their is enough it can result in cell death

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light repair

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cells repair themselves with natural light

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E.coli and water sample contamination three reason

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fecal matter not in soil
not fastidious
green sheen on EMB plate

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Presumptive test

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tubes of lactose broth are inoculated with measured amount of water to see if the water contains any lactose fermenting bacteria that produces gas, if gas is seen after incubation it is presumed that coliforms are present in the sample

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MPN

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Most Probable Number of coliforms present per 100ml of water

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Coliforms

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gram negative, facilitative anaerobic, non-edospore forming rods that ferment lactose to produce acid and gas in 48 hours at 35 degrees celcius

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Confirmed

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EMB agar is inoculated, the presence of typical coliform colonies indicate that gas in presumptive tubes was do to coliforms, these colonies have a dark center and may have a greenish metallic sheen

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Completed

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two agars are inocluated one a lactose broth and the other a nutrient agar slant, if the slant is a gram negative, non spore forming rod and the broth produced gas the the completed test is positive

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E. aerogenes

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other possible outcome in contaminated water

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antibiotic

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chemicals produced and secreted by microorganisms that can inhibit or destroy the growth of pathogenic microorganisms

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Antisepsis

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chemicals able to inhibit in vivo sepsis (infection)

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disinfectant

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a chemical able to kill vegetative forms but not necessarily spore forms of bacteria

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zone of inhibition

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an area where the organism could not grow due to the chemical used

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susceptible

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Likely to be affected with a disease, infection, or condition. Especially sensitive; highly impressionable.

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Resistance

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The capacity of an organism, a tissue, or a cell to withstand the effects of a harmful physical or environmental agent

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Opportunistic bacteria

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organism that under usual circumstances are non pathogenic but in special situations cause disease

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resident microorganisms

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bacteria that normally reside on the skin or digestive tract

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PR tubes with glucose, sucrose and lactose

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to check if the organism can ferment glucose, sucrose, lactose

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Fermentation tubes

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contain a small Durham tube which has sucrose, glucose or lactose if it can be fermented acid will be produced causing the broth to change colors because of the PH indicator if it produces hydrogen you will get gas bubles

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Indole test

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produces indole from breaking down
tryptophan
Uses tryptone broth
Kovac’s reagent is introduced into the
medium after incubation
Red ring = pos = indole production

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Methyl red test

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Tests for use of the mixed acid
fermentation pathway in metabolism
Uses MR-VP medium
After incubation, 5-10 drops of methyl red
pH indicator is added
Red = positive = uses mixed acid
fermentation pathway

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Voges-Proskauer Test

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Tests for use of butanediol fermentation
pathway and acetoin production as an
intermediate in the fermentation process
Uses MR-VP
After incubation, Voges-Proskauer reagents A
and B are added to the medium
Voges-Proskauer reagent A – alpha-naphthol
solution
Voges-Proskauer reagent B – 40% KOH
Red color = positive = acetoin produced
(solution must stand for up to 1 hour to see
results)

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Simmons citrate

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Blue = pos. = can use citrate as sole
carbon source (citrase is present)
Contains
mineral medium with citrate as the sole carbon
source
bromthymol blue as pH indicator

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Sim’s Semi-Solid Medium

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Tests for the production of FeS and for
motility
Black = pos = FeS production (H2S reacts
with FeSO4 in medium to produce FeS)

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Urea test

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Tests for production of urease

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m-staphylococcus broth

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medium that contains 7.5% sodium chloride, making it highly selective for staphylococci.

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Blood agar

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contains sheep blood, allows for the detection of hemolysis, or the lysing of red blood cells by bacterial toxins.

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Mannitol salt agar

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This media is both selective and differential, inhibits most bacteria growth due to its high salt concentration, good for staph. S.aureus and S. saprophyticus produce acid changing the color due to the pH indicator

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Bacteria commonly found on skin or nose

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S.aureus, S. Epidermidis, S. Saprophyticus

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Organisms found in skin

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S.epidermidis, S. aureus, M.luteus, Propionibacterium acnes, Propionibacterium granulosum

TSY plate used

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glucose + bromcresol purple slant

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if organism can ferment glucose, the acid produced will turn the purple yellow.

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organism found in throat

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streptococcus, staphylococcus, yeast, corynabacterium, diphtheroids, Moraxella catarhalis

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Catalase test

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hydrogen peroxide is put on sample if it bubbles catalase is present

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Oxidase test

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paper saturated with oxidase reagent if pinkish purple color is produced then the cells are oxidase positive