Post on 19-Dec-2015
Microbiology
Gram-negative rods:Enterobacteriaceae
Part IIIKaren Honeycutt, M.Ed., MT(ASCP)SM
MT 418 Clinical Microbiology
Student Laboratory Session
Microbiology
Isolation • Growth on BAP at 24 hrs, ambient air,
CO2 or anaerobically (facultative anaerobe)
• In general colony morphology: large, gray, beta- or nonhemolytic(normally larger than Staph, Strep, & Enterococci)
GNR: Enterobacteriaceae
Microbiology
Biochemicals – ONPG Rapid Lactose “F” requires permease enzyme
ONPG similar to lactose, doesn’t require permease enzyme to enter the organism
ONPG + beta-galactosidease = yellow color
Slow lactose fermenter (appear as NLF on MAC, KIA, etc.) and
Rapid lactose fermenter (appear as LF on MAC & KIA are
POSITIVE
GNR: Enterobacteriaceae
Microbiology
Nitrate to Nitrite to Nitrogen GasInoculate to media with nitrateIncubate test 18-24 hrsAdd reagentReagent reacts with nitrite to
form red color.This reaction indicates:
What did the work?
GNR: Enterobacteriaceae
NO3 to NO2
Organism
Microbiology
Biochemicals – Nitrate After nitrate rgt addition:
Zinc will reduce nitrate to nitrite
Add zinc dust
What did the work?
GNR: Enterobacteriaceae
Zinc
Therefore, the organism is: Nitrate negative
Microbiology
Biochemicals – Nitrate After nitrate rgt addition:
Zinc will reduce nitrate to nitrite
Add zinc dust
What did the work?
GNR: Enterobacteriaceae
Organism reduced nitrate to nitrogen gas
Therefore, the organism is: Nitrate positive
Microbiology
Identification – CategoriesLactose “F”
Lysine, phenyalalanine or tryptophane deaminase positive?
Lactose NF & LDA/TDA/PDA negative
GNR: Enterobacteriaceae
Microbiology
Identification
GNR: Enterobacteriaceae
Motile
HEKIA LIA ODC
Indole
Salmonella sp.Identification =
Microbiology
Identification
GNR: Enterobacteriaceae
Indole CitrateLIA
Motile
ODCKIA
Escherichia coliIdentification =