Studied by 8 people
Looks like no one added any tags here yet for you.
when writing the name of an organism ALWAYS make sure it is
in italics
how to shorten name of organism
first letter of first word, period, full second word. (all in italics)
ex E. coli
total magnification equation
(Objective magnification) X (Ocular magnification) = Total magnification
ocular magnification is usally 10x
objective magnification can be 4x, 10x, 100x, etc
gram stain for a gram-negative species will appear
pink
gram stain for a gram-positve species will appear
purple
what are the 7 gram-negative tests we used
Indole
Methyl Red
Voges Proskauer
Simmons Citrate
Oxidase
EMB (Eosin methylene blue fermentation patterns)
TSI
what medium is used for indole tests
tripticase soy broth
indole tests test for
Tests for presence of tryptophanase enzyme (breaks
down tryptophan into indole)
positive indole test
has pink/red layer on top
negative indole test
no color change (appears just yellow)
methyl red tests for
Tests for “mixed acid” vs “butanediol” fermentation
pathway usage (break down glucose)
Mixed acid pathway ends in
acidic end-products
Butanediol pathway ends in
neutral end-products
positive meythl red result (and what it means)
red color stays, meaning mixed acid pathway was used
negative meythl red result
copper color forms, meaning mixed acid pathway was NOT used. yellowish
Voges-Proskauer tests for
tests for positive presence of butanediol pathway (used to ferment glucose)
general rule for MR-VP testing
for a given organism, only one test will be positive!
VP positve results
color change to red
VP negative results
no color change (will stay pale yellow color)
Simmon’s Citrate agar contains
citrate as sole sugar source and bromothymol blue pH indicator
simmons citrate tests for
Testing for whether the organism can utilize citrate ALONE as a sugar source
positve citrate result
color change to blue
negative citrate result
no color change. stays green.
oxidase tests for
Testing for presence of cytochrome c oxidase enzyme
how long to wait for oxidase results
30 seconds (dont walk away! they will all change to purple if left long enough. waiting too long could lead to false positves)
positve oxidase result
color change to purple
negative oxidase result
no color change (stays white)
is EMB selective or differential?
both!
how to EMB plates work
dyes inhibit G(+)s, act as pH indicators for sucrose and lactose fermentation
(wealky selective. sometime G+ can grow)
if an organism is a Vigorous lactose/sucrose fermenters it will appear ______ on an EMB plate
black/purple (green if its E.coli)
if an organism is a slow lactose/sucrose fermenters it will appear ______ on an EMB plate
pink
if an organism does not ferment lactose/sucrose (not coliform) it will appear ______ on an EMB plate
clear
EMB tests for
lactose/sucrose fermentation
4 tests for gram-postive bacteria we used
Bile Esculin
Catalase
Blood agar hemolysis patterns
Mannitol salt agar fermentation patterns
Selective means
selects for certain bacteria, kills others
ex only G+ can grow on MSA
Differential means
differentiates between similar species
ex S. aureus turns yellow on MSA; S. epidermidis does not
is nutrient agar selective or differential?
neither!
is Mannitol Salt Agar (MSA) selective or differential
both
How does MSA work
High salt content SELECTS for G(+) species
Phenol red (pink color) turns yellow when mannitol sugar is digested, DIFFERENTIATING species
positve MSA result
yellow! indicates mannitol sugar digestion
negative MSA result
no color change. stays pink. no mannitol sugar digested
are blood agar plates (BAP) selective or differential
differential. DIFFERENTIATES species based on how the blood is/isn’t broken down
hard to grow organims can usually be grown on
BAP because bacteria love blood
BAP alpha hemolysis
partial breakdown. looks brown.
BAP beta hemolysis
total breakdown. looks yellow and has a clearish halo around it
BAP gamma hemolysis
no breakdown. just growth on top of plate; appears white/regualr color.
are Bile Esculin Slants (BES) selective or differential
both
how do BES work
SELECTS for G(+) species with bile salts
DIFFERENTIATES species by +/- esculin hydrolysis esculin by-products react with ferric citrate, turn media black
black BES means
esculin hydrolysis occured
Catalase Test determines
Determines if a species produces the enzyme catalase
positve catalse test
bubbles when hydrogen peroxide is added
negative catalse test
no bubbles
cell
A single, independent living unit
colony
A visible grouping of cells on a solid medium, all descended from a single original cell, creating a clone population.
culture
The practice of growing cells in a controlled environment, often referring to a population of cells derived from a single colony
aseptic technique encompasses
Methods of working free of microbial contamination
purpose of aseptic technique
Prevent culture/specimen contamination
Prevent contamination of yourself/others/environmen
examples of aseptic tenchique
Safely dispensing culture media
Flame-sterilizing instruments
Proper labeling, handling, and storing
Practicing correct hand hygiene and workspace disinfection
simple stains
coloring cells to see shape
gram stains
differentially coloring cells to see shape and determine Gram class
endospore stains
differentially coloring to see if the species makes spores
kirby bauer test is used to idenfity
an organisms antibiotic resistence proflie
how to interpret kirby bauer results
measure diamter and compare it to a suscetpibility table
Susceptible—zone of inhibition falls in the susceptible range
▪ Resistant—zone of inhibition falls in the resistant range
▪ Intermediate—borderline response
Collected data and present in an antibiogram
Obligate aerobe:
needs O2 to live, breaks down sugars using it
Obligate anaerobe:
dies in presence of O2 (doesn't use it, can't detoxify it!)
Facultative anaerobe:
prefers O2 (more energy!), but can do anaerobic respiration and detoxify O2 when needed
Microaerophile:
can only stand O2 in low concentrations (uses it a little in metabolism, can only detoxify a little)
Aerotolerant:
doesn’t use O2 , but doesn’t die when exposed to it (can detoxify!)
