Triple Sugar Iron

(TSI)

- Used to differentiate Enterobacteriaceae 

- Differentiates them from other Gram-negative rods such as Pseudomonas

Urease Tests

- Distinguishes Proteus pathogens from other Enterobacteriaceae

- Differentiates organisms based on their ability to hydrolyze urea with enzyme urease

Positive (+) = all pink within 24 hrs; rapid urea hydrolysis;strong urease production

Weak Positive (w+) = orange or yellow (24 hrs); partially pink (24 hrs - 6 days); slow urea hydrolysis; weak urease

Negative (--) = orange or yellow at 24 hrs and 24 hrs - 6 days;No urea hydrolysis;urease absent

Voges-Proskauer Test

- Component of IMViC

- Identifies organisms able to produce acetoin from the degredation of glucose

- Used to distinguish between Enterobacteriaceae

- Differentiates them from other Gram-negative rods

 Positive = Red

 Negative= No color/copper color 

Phenylalanine Deaminase Test

- Differentiates Morganella, Proteus, Providencia (pheny. deaminase positive)

from other Enterobacteriaceae that are phenylalanine deaminase negative

Positve = green; presence of phenylpyruvic acid

Negative = yellow

Oxidation-Fermentation (O-F) Test

- Used to differentiate bacteria based on their ability to oxidize or ferment specific sugars

-Allows separation of fermentative Enterobacteriaceae from oxidative Pseudomonas and Bordetella, and the assachralytic Alcaligenes and Moraxella

ONPG Test

- used to differentiate late lactose fermenters from lactose nonfermenters in the Enterobacteriaceae family

Positive = yellow

Negative = No change

Nitrate Reduction Test

- Differentiates Enterobacteriaceae from Gram-negative rods that do not reduce nitrate or reduce it beyond nitrate to N2 

- Zinc is added to catalyze reaction

Negative = red color AFTER zinc; nitrate was not reduced by organism

Positive = no color change AFTER zinc; organism reduced nitrate to nitrite

Motility Test

- Used to detect bacterial motility

-Motility is a differential characteristic of Enterobacteriaceae

Motile = diffuse growth radiating from central stab line

Methyl Red Test

- Component of IMViC tests

- used to differentiate Enterobacteriaceae

- identifies bacterial ability to produce acid end products by means of a mixed-acid fermentation of glucose

Positive = Red

Negative/Inconclusive = orange or yellow

Lysine Iron Agar

(LIA)

- Used to differentiate Enterics based on their ability to decarboxylate or deaminate lysine & produce hydrogen sulfide (H2S)

- Used in combination with Triple Sugar Iron to identify members of Salmonella and Shigella

Kligler's Iron Agar

(KIA)

- Used to differentiate Enterobacteriaceae and distinguishes them from other Gram-negative bacilli such as Pseudomonas or Alcaligenes

-Differentiates bacteria on basis of glucose fermentation, lactose fermentation & sulfur reduction

Indole Test 

(SIM Medium)

-Used to differentiate Enterics

Identifies bacteria capable of producing indole using the enzyme tryptophanase

Indole rapid test = pink = positive

Kovac's reagent - added to tube, forming a liquid layer 

Positive = formation of red color

Indole - Negative = no color

Decarboxylation Test

- Used to differentiate organisms in the Enterobacteriaceae family & distinguish them from other Gram-negative rods

Positive = purle

Negative = all other colors

Citrate Utilization Test

- used to determine the ability of an organism to use citrate as its sole source of carbon

- Distinguishes between enteric members and differentiates from other Gram-negative rods

Positive = green to blue

Negative = no color change or growth on slant

β-Lactamase Test

- Rapid test used to identify if patient isolates are resistant to penicillins & cephalosporins

-β-lactam ring in structure kill bacteria by interfering with cell wall synthesis

Resistant = disk will turn pink

Susceptible = disk will not change colors

Gram Stain

-Distinguishes between Gram-positive and Gram-negative bacteria

Gram-positive = purple cells

Gram-negative = reddish-pink cells

Bacitracin Susceptibility Test

-Differentiate & identify a Beta-hemolytic group A Streptococci

-Staphylococcus are resistant

-Micrococcus are susceptible

-S. pyogenes is susceptible

Bile Esculin Test

Used for identification of Enterococci and Streptococcus bovis group members

- both have a positive result

CAMP Test

- used to differentiate Group B Streptococcus agalactiae from other Streptococcus species which are negative

- S. agalactiae is positive

Catalase Test

- used to differentiate catalase-positive Staphylococcus from catalase-negative Streptooccus

Positive = formation of bubble

Negative = no bubble formation

Coagulase Test

- used to differentiate Staphylococcus aureus from other Gram-positive cocci

-Tube test detects either bound or free coagulase

-Slide test detects only bound coagulase

Optochin Susceptibility Test

(P-Disk)

- differentiates Streptococcus pneumoniae from other alpha-hemolytic streptococci

Oxidase Test

Useful in differentiating:

Oxidase-negative Enterobacteriaceae

Oxidase-positive Pseudomonadaceae

Positive = color change within seconds

Negative = no color change

PYR Test

Used to identify Group A Streptococci (S. pyogenes) and Enterococci

Positive = deep red color

Negative = yellow or orange color

Sulfamethoxazole-Trimethoprim

(SXT) Susceptibility Test

Used to differentiate Groups A and B Streptococci which are SXT resistant from other beta-hemolytic streptococci that are SXT susceptible

Quad Plates

A petri dish divided into 4 sections used to identify Haemophilus species

Contents of the 4 quadrants are as follows:

Quadrant I - supplemented with hemin (X Factor)

Quadrant II - supplemented with NAD (V Factor)

Quadrant III - supplemented with BOTH Hemin (X) and NAD (V)

Quadrant IV - supplemented with NAD and horse blood; horse blood provides hemin and is used to determine if the organism is hemolytic

Quad Plates

Interpretation of Results

Quadrant I         Quadrant II          Quadrant III       Quadrant IV                         Interpretation

No Growth               Growth                    Growth            Growth, No Hemolysis          H. parainfluenzae

No Growth               Growth                    Growth            Growth, β-hemolysis        H. parahaemolyticus

Growth                     Growth                    Growth            Growth, No Hemolysis           H. aphrophilus

No Growth               No Growth               Growth            Growth, No hemolysis            H. influenzaie

Oxidase-Fermentation Glucose Test Reactions

* Organism is an oxidizer of glucose; it can catabolize (break down) glucose oxidatively, but not fermentatively.

Open tube = Yellow                                       Closed Tube = Green

* Organism is a fermenter of glucose; it can catabolize (break down) glucose in both the presence and absence of oxygen

Open Tube = Yellow                                       Closed Tube = Yellow

* Organism is a nonoxidizer/nonutilizer (Assacharolytic) of glucose; it cannot catabolize (break down) glucose

Open tube = Green                                         Closed Tube = Green