Microbiology Gram-negative rods: Enterobacteriaceae Part III Karen Honeycutt, M.Ed., MT(ASCP)SM MT 418 Clinical Microbiology Student Laboratory Session.

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

Characteristics Utilization of glucose (OF Glucose):

GNR: Enterobacteriaceae

Microbiology

Characteristics

Oxidase reaction:

GNR: Enterobacteriaceae

Microbiology

Characteristics

GNR: Enterobacteriaceae

Growth on MAC: Yes

Microbiology

Characteristics

GNR: Enterobacteriaceae

Nitrate reduction: NO3 to NO2

Microbiology

Characteristics

GNR: Enterobacteriaceae

Flagellar arrangement:peritrichous

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 =

Microbiology

Identification

GNR: Enterobacteriaceae

Indole ODC

MacConkey

KIA LIA Urea

Proteus vulgarisIdentification =