Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
|
MPN procedure allows one to calculate |
1) TOTAL coliform counts in a water sample 2) E. coli count in a water sample |
|
|
after 48 hr incubation, _____ broths in MPN procedure are examined for |
LTB broth
growth presence of gas |
|
|
positive LTB's in MPN procedure are used to inoculate 2 media: |
BGLB EC |
|
|
BGLB media |
for MPN
Brilliant Green Lactose Bile Broth (selective for confirming presence of coliforms)
Lactose - sugar coliforms can ferment Durham tube - gas produced from lactose ferm? Bile - inhibits non-coliforms |
|
|
EC media |
E. coli broth (selective for E. coli when grown at 45C)
Lactose - sugar coliforms can ferment Durham tube - gas produced? bile - inhibits non-coliforms |
|
|
formula for MPN? |
MPN/100 ML = 100P /√VnVa
P = TOTAL # positive results Vn = combined vol. of sample that produced negative results Va = combined vol. of sample in ALL tubes |
|
|
selective media ___ some bac. to grow, ___ others
also called ________ |
prevent, allow
inhibitors |
|
|
selective media/inhibitors work by 4 methods:
GEM D |
DNA synthesis Gene expression Enzymatic activity Membrane permeability
GEM D |
|
|
selective media vs. _____ media
media can be both!!
components?
|
differential
1) substrate - chem that only one species can utilize in a reaction 2) indicator |
|
|
presumtive identification |
identification of organisms present in a culture through data from biochemical information |
|
|
coliform |
bacteria that reside in the guts of birds and all mammals |
|
|
4 characteristics of coliforms |
1) gram negative rods 2) Non-Spore forming 3) Aerobes/facultative anaerobes 4) can FERMENT LACTOSE
neg, NON-spore, aerobes, FERM LAC |
|
|
MacConkey Agar |
selective and differential - to identify coliforms
Bile Salts - S Crystal Violet Dye - S Natural Red Dye - D (can ferm. lactose?) Lactose - D (can ferment lactose?)
[Salt CV, Dye Red Lactose] |
|
|
only gram _____ organisms will grown on MacConkey Agar |
gram negative - like coliforms! |
|
|
no growth on MacConkey, EMB or Hektoen Enteric indicates gram _____ |
positive |
|
|
MacConkey
colorless growth
red/pink growth |
colorless = gram neg, NO ferm, NO acid = not coliform
red/pink = gram neg, ferm, acid = probable coliform |
|
|
EMB (Eosin Methylene Blue) Agar |
selective and differential for coliforms
Eosin Y Dye - S + D Methylene Blue Dye - S + D Sucrose - D Lactose - D
|
|
|
only gram _____ organisms grow on EMB agar |
negative - like coliforms |
|
|
EMB agar
colorless growth pink mucoidy growth purple, green, metallic
|
colorless - no ferm, no acid pink mucoid - SLOW LACTOSE ferm, SOME acid purple, green, metallic - LAC/SUC form, high acid |
|
|
Hektoen Enteric Agar |
selective and differential - isolate/distinguish between Salmonelle and Shiaella spp.
Bile salts - S Sucrose, Lactose - D Salicin, Ferric ammonium citrate - D Bromothymol Blue Dye, Acid Fuchin Dye - D Sodium thiosulfate - sulfur source |
|
|
Hektoen Enteric Agar
Orange/Yellow Blue/Green Blue/Green + black precipitate
|
orange/yellow = fermentation! high acid (low pH) NOT salmonella or shiaella
blue/green = NO fermentation, PROTEIN degradation (increase pH) POSSIBLY salmonella or shiaella
black precipitate = sulfur reduction PROBABLY Salmonella |
|
|
Triple Sugar Iron Agar (TSIA) functions |
1) determine ability to ferm. 3 different sugars 2) ability to reduce sulfide 3) differentiate b/w enteric bacteria such as Salmonella, Shiaelle and E. coli |
|
|
in fermentation, glucose is _____ the only carbohydrate that can be used in _________ |
NOT, glycolysis |
|
|
end products of fermentation = |
acidic compounds, sometimes gas |
|
|
most enteric bacteria are _______ ________ and can grow in anaerobic environments |
facultative anaerobes |
|
|
sometimes in anaerobic conditions, the TEA is sulfur, and sometimes thiosulfate. In ________ conditions, the enzyme ______ ________ produces _____ and _____ |
acidic conditions enzyme thiosulfate reducatase
produces sulfite and hydrogen sulfide (H2S) gas |
|
|
H2S |
reducing agent
can react with ferrous sulfate to form ferrous sulfide (a black insoluble metallic compound)
H2S = product of thiosulfate reductase |
|
|
Triple Sugar Iron Agar (TSIA) components |
Glucose - low conc. Lactose, Sucrose - high conc. Sodium thiosulfate - sulfar source Ferrous sulfate - H2S indicator Phenol Red - pH indicator (red at neutral pH)
|
|
|
TSIA is always prepared as a ______ |
slant
slant = aerobic butt = anaerobic |
|
|
what is reversion and when does it occurs? |
akaline produce (from breakdown of amino acids to ammonia) raises the pH and media returns to red color
TSIA |
|
|
TSIA - red slant, yellow butt |
red slant = basic yellow butt = acidic
glucose only fermentation
cracks/lifting in media = gas production |
|
|
TSIA - yellow slant, yellow slant |
acidic and acidic!
Glucose AND Lactose and/or Sucrose ferm
H2S/Black Precipitate = sulfur reduction |
|
|
TSIA
red slant red butt |
basic + basic!
NO FERM Amino Acidic Degradation |
|
|
Blood agar = ____ + ____
useful when culturing ______ organisms
DIFFERENTIAL - differentiates organisms based on their _______ characteristics (i.e. ability to destroy RBC's) |
TSA + Sheep's Blood
fastidious organisms (microbes that require strict physiological conditions)
differential - differentiate organisms based on their hemolytic characteristics
|
|
|
Blood Agar
Greenish zone |
a - Hemolysis
H2O2 oxidizes RBC Methmoglobin produced
|
|
|
Blood Agar
Colorless Zone |
B - Hemolysis
RBC's lysed! |
|
|
Blood Agar
No Zone |
y- Hemolysis
no RBC lysis |
|
|
Columbia CNA Agar with 5% sheep's blood |
selective and differential for Gram positive
Digested Casein/Animal Tissues Beef, Yeast Extract Corn Starch, Sheep Blood Collistin - S (antibiotic against G -ive organisms, causes bacterial lysis of outer membrane) Nalidixic Acid - S (antibiotic agaisnt G-ive organisms, disrupts enzymes involved in DNA replication/synthesis)
|
|
|
Columbia CNA Agar
Greenish zone |
a - Hemolysis
H2O2 oxidizes RBC Methmoglobin produced Gram + organism
partial destruction |
|
|
Columbia CNA Agar
Colorless zone |
B - Hemolysis
RBC's lysed
complete destruction of RBC's AND hemoglobin |
|
|
Columbia CNA Agar
no zone |
y - Hemolysis
no RBC lysis
no destruction of RBC' |
|
|
Mannitol Salts Agar (MSA) |
to identify pathogenic Staphylococcus species from non-pathogenic
7.6% salt - S Mannitol (carb) - D Phenol Red (pH indicator) - D |
|
|
MSA Agar
no growth |
NO staphylococcus |
|
|
MSA Agar
Yellow growth OR halo |
Mannitol Ferm Acid (decrease pH)
possibly Staphylococcus aureus |
|
|
is staphylococcus aureus pathogenic? |
yes? **** |
|
|
MSA Agar
red growth/ no color |
NO Mannitol fermentation No Acid (= pH)
non-pathogenic Staphylococcus species |
