Upload
sandeep-patil
View
727
Download
5
Tags:
Embed Size (px)
DESCRIPTION
differential media
Citation preview
• Labs #6 (whitewhite) and #7 (green)• Overall scheme: Lab #6 (whitewhite) , last page
Biochemical Tests and Diagnostic Media
SIM medium: Motility test
POSITIVE:Organism moves away from stab
NEGATIVE:Organism does NOT move away from stab
SIM medium: Sulfur test
H2S-POSITIVE:black precipitate
formed
H2S-NEGATIVE:no black
precipitate formed
Simmon’s citrate agar slant
positivenegative
Diagnostic Media
• Mannitol salt agar• Eosin methylene blue (EMB) agar• Brilliant green agar
Selective medium
Selects for the GROWTH of some organisms and inhibits the growth of
other organisms.
i.e. Some organisms grow on a selective medium whereas others do not grow (or do not grow well) on that
same medium.
Differential medium
Differentiates between one type of organism and another type of organism.
Different types of organism look different from each other when grown on differential media.
Mannitol salt agar
Selective mediumHigh salt (NaCl) concentration in medium favors organisms that tolerate high salt concentration, e.g. Staphylococcus.
Staphylococcus aureusgrows
Serratia marcescens
does not grow
Mannitol salt agar
Differential medium
Differentiates among staphylococci
Mannitol salt agar
Differential medium
Differentiates among staphylococci
Mannitol salt agar
Differential medium Differentiates among staphylococci:• pathogenic Staphylococcus species ferment mannitol to produce acid (yellow medium)(yellow medium)
Staphylococcus ferments mannitol(yellow)(yellow)
Mannitol salt agar
Differential medium Differentiates among staphylococci:• pathogenic Staphylococcus species ferment mannitol to produce acid (yellow medium)(yellow medium)• less pathogenic Micrococcus (a staphylococcus) do not ferment mannitol (red/pink medium)
Staphylococcus ferments mannitol(yellow)(yellow)
Micrococcus does not ferment mannitol
(pink)
Levine Eosin-Methylene Blue (EMB) Agar
Gram negatives (growth)
Gram positive(growth inhibited)
SELECTIVE MEDIUM
Levine Eosin-Methylene Blue (EMB) Agar
Nonlactose fermenters
Lactose fermenter
DIFFERENTIAL MEDIUM
High acid producers on EMBe.g. E. coli
blue-black colonies or metallic sheen
Levine Eosin-Methylene Blue (EMB) Agar
Lactose fermenter (low acid producer:
pink colonies)
Non-lactose fermenter Lactose fermenter (high acid producer:
black colonies)
Gram positive(growth inhibited)
Brilliant Green Agar
SELECTIVE
DIFFERENTIAL
• Growth of all gram positive and many gram negative bacteria inhibited
• Growth of many Salmonella species occurs
Brilliant Green AgarDIFFERENTIAL
Differentiates lactose fermenters lactose fermenters from nonlactose fermenters
Brilliant Green AgarNon-lactose fermenter Lactose fermenter
SalmonellaE. coliE. coli
Catalase Test
Many bacteria produce the enzyme catalase.
H2O2 H2O + O2catalase
hydrogenperoxide
oxygen (gas)
Catalase Test
bubbles (gas)
Catalase positive organism