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Micro Lab Exam


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copy deck
specimen is stained, so its image appears dark against a brigter background
brightfield microscopy
equal to the magnification of the objective multiplied by that of the ocular
total magnification
gathers light rays and focuses these on the object to be illuminated
an opaque disk with an adjustable aperture that by adjusting it one may improve on contrast of the image
iris diaphragm
light beams are deflected by different thicknesses of the object
phase-contrast microscopy
useful for direct observation of specimens that are not stained ex: protozoa
phase-contrast microscopy
specimen appears luminous against a background of little or no light
dark-field microscopy
used primarily to view spirochetes, which do not stain well and are too narrow to be observed by any other methods
dark-field microscopy
uses dyes known as fluorochromes that absorb ligh in the ultraviolet range, fluoresce, and then emit visible light of a greater wavelength
fluorescent microscopy
select and limit the wavelength of the transmitted light
excitation filters
transmits excited wavelengths to the objective
dichromatic splitter
longer wavelengths that are emitted pass through the ______ and the image fluoresces
beam splitter
a method to ensure the light microscope used is setup in such a way so as to provide the best sample illumination
kohler illumination
gram stain reagents
1) crystal violet
2) gram's iodine mordant
3) acetone/alcohol mixture
4) safranin
gram stain primary stain
crystal violet
gram stain mordant
gram's iodine
gram stain decolorizer
acetone/alchol mixture
gram stain counterstain
acid fast staining
acid fast reagents
1) carbolfuschsin
2) acid-alcohol mixture
3) methylene blue
acid fast primary stain
acid fast decolorizer
acid-alcohol mixture
acid fast counterstain
methylene blue
acid-fast bacilli appear as...
red aggregations against a blue background
partial acid-fast staining
In partial acid-fast staining what is used instead of heat to allow penetration of the stain into the cell wall?
Kinyoun stain is used in detecting?
Partial acid-fast reagents
1) carbolfuchsin
2) acid-alcohol mixture
3) methylene blue
endospore staining reagents
1) malachite green
2) safranin
In endospore staining, endospores will appear ______ in color and vegetative cells will appear ______
green; red
culture media constructed completely from chemically defined components
defined or synthetic media
media may contain constituents like peptones and yeast extract whose precise composition is unknown
complex media
media that supports the growth of many non-fastidious microorganisms
general purpose (nutrient media)
media that supports and encourages the growth of fastidious bacteria
enriched/fortified media
media that favors the growth of particular microorganisms, while specifically inhibiting the growth of others
selective media
media that distinguish between different groups of bacteria and even permit tentative identification of microorganisms based on their biological characteristics
differential media
wide spread media used in isolation and identification of bacteria, combines the characteristics of both selective and differential media
selective/differential media
agar/broth used for cultivating Brucella and other fastidious microorganisms
tryptose agar/broth
used with blood in isolating, cultivating and determining the hemolytics reactions of fastidious microorganisms
tryptose blood agar base
the reduction of hemoglobin to methemoglobin in the medium surrounding the colony
alpha/incomplete hemolysis
causes a greenish discolorization of the medium
alpha/incomplete hemolysis
lysis of red blood cells resulting in a clear zone surrounding the colony
beta/complete hemolysis
no destruction of red blood cells occurs and there is no change in the medium
gamma/no hemolysis
a small zone of complete hemolysis that is surrounded by an area of partial lysis produced by staph aureus and clostridium perfringens
alpha-prime/double zone hemolysis
a selective and differential medium used for the isolation and differentiation of gram-positive microorganisms from clinical and nonclinical materials, supplemented with 5% sheep blood
Columbia CNA agar with 5% sheep blood
a medium consisting of colistin and nalidixic acid
Columbia CNA agar
Columbia CNA agar cultural response
gram-positive bacteria: typical hemolytics colonial morphology
gram-negative bacteria: no growth to trace growth
selective isolation of staphylococci from clinical and nonclinical materials
mannitol salt agar
mannitol salt agar selective chemical
sodium chloride
mannitol salt agar differential chemical
mannitol salt agar pH indicator
phenol red
concentration of sodium chloride in mannitol salt agar
bacteria that that utilize mannitol in mannitol salt agar ______ the pH turning the phenol red ______
decrease; yellow
bacteria that do not use mannitol in mannitol salt agar _____ the ph turning the phenol red _______
increase; bright pink
used to differentiate Enterococci and Streptococcus bovis group from other Streptococci
Bile Esculin Agar
indicator of esculin hydrolysis and resulting esculetin formation
ferric citrate
used to inhibit gram-positive bacteria other than enterococci
oxgall (bile salt)
macconkey agar selective chemicals
bile salts and crystal violet
macconkey agar substrate
macconkey agar pH indicator
neutral red
used for isolating and differentiating lactosefermenting from lactose nonfermenting gram-negative enteric bacilli
macconkey agar
macconkey agar expected results
lactose fermenting oraganisms gros as pink to brick-red colonies with or without a zone of precipitated bile
lactose-nonfermenting organisms grow as colorless or clear colonies
higly selective/differential medium for the isolation of gram-negative enteric bacteria
Eosin Methylene Blue (EMB) agar
EMB agar selective chemicals
Eosin Y and methylene blue dyes
EMB agar pH indicators
eosin y and methylene blue
EMB agar differential substrate
EMB agar expected results
lactose-fermenter bacteria will form blu-black colonies with dark centers. E. coli will appear as dark purple colonies with green metallic sheen
non-lactose-fermenter bacteria will appear colorless to translucent
highly selective/differential medium for the isolation of pathogenic enteric bacilli, especially those belonging to the genus Salmonella
Salmonella Shigella (SS) agar
SS agar selective chemical
bile salts and brilliant green dye
SS agar differential substrate
SS agar pH indicator
neutral red
SS agar sulfur source for H2S production
sodium thiosulfate
H2S indicator
ferric citrate
SS agar expected results
lactose-fermenter bacteria will form pink to red colonies
non-lactose-fermenter bacteria will form colorless colonies
H2S-producing bacteria will have black centered colonies of ferric sulfide
small group of bacteria killed by normal atmospheric levels of oxygen, but yet require traces of oxygen to grow
terminal electron acceptor in aerobic respiration
terminal electron acceptor in anaerobic respiration
NO3, SO4, CO2 or fumarate
terminal electron acceptor in fermentation
organic compound
bacterial cells with a single flagellum
single flagellum at one end of a rod-shaped cell
polar flagellum
bacteria with a single tuft of flagella
bacteria with tufts of flagella at both ends of the cell
bacteria that are covered all over in flagella
special dye added to motility test medium to make the radiating growth more visible as the reddish diffuse area
tetrazolium salt (TTC)
determines the atmospheric requirement of a bacterium, whether a bacterium is oxidatively or fermentatively using glucose
O/F glucose media
O/F glucose media contains how much glucose
O/F glucose media pH indicator
bromothymol blue
Bromothymol blue is what color at low pH
bromothymol blue is what color at high pH
O/F glucose media interpretation
both tubes ar acidic (yellow): the organism is faculative anaerobe (fermentative)
only open tube is acidic: the organism is an obligate aerobe (oxidative)
no color change in both tubes: the organism is asaccharolytic
used to identify bacteria containing the respiratory enzyme cytochrome oxidase
Oxidase test
Enterobacteriaceae is oxidase...
Pseudomonadaceae is oxidase...
Oxidase test interpretation
Oxidase positive: smear will turn purple within 20-30 sec
Oxidase negative: smear will not turn purple within 20-30 sec
test the presence of the enzyme catalase
catlase test
Catalase test reagent
hydrogen peroxide
catalase test interpretation
if the bacteria in question produce catalase, gas bubbles form and this is indicative of a positive test
determines the ability of an organism to ferment a specific carbohydrate incoporated in a basal medium and produce acid or acid with visible gas
carbohydrate fermentation tests
All enterobacteriacae are or are not glucose fermenters
carbohydrate fermentation test pH indicator
phenol red
carbohydrate test interpretation
positive carbohydrate reaction: acid by products lead to decreased pH causing the phenol red to change from pink to yellow, inverted Durham tube in glucose broth is used to collect any gas produced
negative carbohydrate reaction: the utilization of proteins in the medium increases pH causing the phenol red to change to a darker red color
determines the ability of an organism to attack specific carbohydrates incorporated in a basal growth medium with or without the production of gas along with the determination of possible H2S production
Triple Sugar Iron (TSI) agar tests
concentrations of the carbohydrate in TSI
glucose: 0.1%
lactose: 1.0%
sucrose: 1.0%
TSI interpretation
Red/Yellow[alkaline/acid]K/A: bacterium is facultative anaerobe, saccharolytic and utilizes glucose only
Yellow/Yellow[acid/acid]A/A or A/A+G: bacterium is facultative anaerob, saccharolytics, and utilizes glucose, lactose and/or sucrose, the presence of bubbles or cracking is indicative of gas production
black precipitation: if an organism can produce H2S gas the gas will react with the iron to from iron sulfide which apppears as a black precipitate
Red/No change[alkaline/alkaline] K/N: organism failed to ferment glucose and is strictly aerobic
broth which contains .5% glucose and pH indicator
MR/VP medium
tests the ability of an organism to produce and maintain stable acid end products from glucose fermentation and to overcome the buffering capacity of the system
methyl red test
What does IMViC stand for?
Indole, Methyl Red, Voges-Proskauer, Citrate
when glucose is fermented through mixed acid pathways the pH is lowered below _____ and produces a positive methyl red test
methyl red test interpretation
MR positive: the culture is sufficiently acid to allow the methyl red reagent to remain a distinct, stable, bright red color at the surface of the medium
MR negative: yellow culture at the surface of the medium
Delayed reaction: reddish orange color indicates organisms produce less acid from test substrate
determines the ability of some organisms to produce a neutral end product, acetylmethylcarbinol (AMC, acetoin) from glucose fermentation
Voges-Proskauer (VP) test
VP-I reagent
alpha naphthol + KOH
VP-II reagent
determines if an organism is capable of utilizing citrate as the sole source of carbon for the metabolism growth
citrate test
citrate substrate
sodium citrate
citrate source of nitrogen
ammonium salts
citrate pH indicator
bromothymol blue
citrate test interpretation
Positive reaction: growth with an intense blue color
Negative: no growth and no change in color (green)
determines the ability of an organism to split indole from tryptophan
indole test
indole substrate
indole product
indole reagent
Kovac's reagent
indole test interpretation
positive reaction: bacteria produce a red layer following addition of Kovac's reagent
negative reaction: bacteria fail to produce a red layer following addition of Kovacs' reagent
detection of lysine decarboxylase (LDC), lysine deaminase (LDA), and/or hydrogen sulfide production for the identification of Enterobacteriaceae
Lysine iron agar
LIA substrate
the amino acid lysine and a small amount of glucose
LIA pH indicator
bromocresol purple
LIA source of sulfur
sodium thiosulfate
LIA H2S indicator
ferric ammonium citrate
LIA interpretation
purple slant/purple butt: LDA negative, LDC positive
purple slant/yellow butt: LDA negative, LDC negative, decrease in pH
port wine slant/ yellow butt: LDA positive decrease in pH, LDC negative decrease in pH
black precipitation: hyrdogen sulfide production
determines the ability of an organism to reduce nitrate to nitrites or free nitrogen gas
nitrate reductase test
nitrate substrate
potassium nitrate
nitrate product
nitrite salts
nitrate reagents
nitrate a: sulfanilic acid
nitrate b: alpha-naphthylamine
novobiocin sensitivity interpretation
all staph species except staph saprophyticus are susceptible
optochin sensitivity test
differentiates between strep pneumonia and other alpha hemolytic strep
bacitracin sensitivity test
differentiates between strep pyogenes and other beta hemolytic strep
What is the biochemistry involved with bacitracin?
Inhibits bacterial cell wall synthesis
Determines an organism's ability to produce and elaborate the CAMP factor
CAMP test
CAMP test
differentiates and presumptively identifies human or animal strains of group B Streptococcus agalactiae from other Streptococcus spp.
gram negative rods that do not produce spores
Family enterobacteriaceae
Family entero are oxidase positive or negative
family entero have what kind of flagella
what species in family entero are non motile
klebsiella and shigella
primary pathogens of the family entero
shigella, salmonella, yersinia, e. coli, klebsiella pneumoniae
opportunistic pathogens of entero
e. coli, klebsiella pneumoniae, proteus, serratia, enterobacter, morganella, providencia
Who devised the orginal classification system for entero
Edwards and Ewing
antigen binding sites found ont he antibodies
capsule antigen
K antigen
flagella antigen
H antigen
polysaccharide side chain of endotoxin of LPS
O or somatic antigen
enterohemorrhagic e. coli
somatic(O), Flagellar(H), and/or capsular(K)
enteroinvasive e. coli
O, H, K
enteropathogenic e. coli
O, H, K
enterotoxigenic e. coli
Salmonella pathotypes
O, H, Virulence(Vi)
agar used for Kirby-Bauer Disk-diffusion method
mueller-hinton or mueller-hinton blood
ph 7.2-7.4
what is used to standardize the inoculum density

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