F1 Diagnostic Tests for Gram Negative Bacilli Flashcards | Knowt (2025)

1 / 54

Gram Negative Bacilli

A diverse group of bacteria found in soil, plant, gut, and other environments.

Oxidase Test

A test used to determine if a bacteria is oxidase positive or negative, with G(-) Bacilli generally being oxidase negative.

Nitrate Reduction Test

A test determining whether bacteria can reduce nitrate (NO3) to nitrite (NO2), with all G(-) Bacilli being nitrate positive.

TSI (Triple Sugar Iron) Test

A primary test for Gram negative bacteria that checks for glucose fermentation and produces three possible results: A/A, K/A, K/K.

Lysine Iron Agar (LIA)

A test medium used to diagnose bacteria based on L-lysine decarboxylation and deamination reactions.

Indole Test

A test that detects indole production by bacteria, using SIM medium and Kovac's reagent to produce a red ring when positive.

Methyl Red Test

A test measuring the ability of bacteria to carry out mixed acid fermentation of glucose. A positive result is indicated by a red color.

Voges-Proskauer Test

A test indicating the production of acetoin from glucose fermentation, with a positive result showing a cherry red color.

Citrate Utilization Test

A test that determines if bacteria can utilize citrate as a sole carbon source, positive result indicated by a blue color.

Urea Hydrolysis Test

A test that detects the ability of bacteria to hydrolyze urea; a positive result changes the medium color to fuchsia pink.

Esculin Hydrolysis Test

A test used to determine if bacteria can hydrolyze esculin, resulting in a black color when positive.

MUG Test

A specific test for detecting E.coli using 4-methylumbelliferyl-ß-D-glucuronide, which fluoresces yellow.

Gelatin Hydrolysis Test

A test assessing the ability of bacteria to hydrolyze gelatin, indicated by liquefaction of the medium.

Enterotoxigenic E. coli (ETEC)

A type of E. coli that causes traveler's diarrhea through the production of heat-labile enterotoxin.

Enteropathogenic E. coli (EPEC)

A type of E. coli responsible for infantile diarrhea characterized by pathogenicity islands.

Hemolytic Uremic Syndrome (HUS)

A severe infection caused by Enterohemorrhagic E. coli (EHEC), often leading to bloody diarrhea and kidney failure.

Klebsiella pneumoniae

A bacterium causing pneumonia and demonstrating a mucoid colony appearance on MacConkey agar.

Salmonella spp.

A genus of bacteria known for causing gastroenteritis and typhoid fever, identifiable by black colonies on certain media.

Shigella spp.

A genus of non-lactose fermenting bacteria known for causing dysentery and characterized by their red pigment prodigiosin.

Yersinia pestis

The causative agent of plague, identifiable by its bipolar bodies (safety pin appearance) under microscopy.

Vibrio cholerae

The bacteria responsible for cholera, producing rice watery stools and positive on the string test.

Campylobacter spp.

A group of bacteria characterized by curved shapes and darting motility, which are microaerophilic and grow at 42°C.

Lysine Iron Agar (LIA) Test Purpose

Differentiates bacteria based on lysine decarboxylation, deamination, and hydrogen sulfide production.

LIA Test Medium Composition

Contains lysine, peptones, glucose, ferric ammonium citrate, sodium thiosulfate, and bromocresol purple as a pH indicator.

LIA Test Result - Decarboxylation

Purple (alkaline) if positive; yellow (acidic) if negative.

LIA Test Result - Deamination

Red if positive; purple if negative.

LIA Test Result - Hydrogen Sulfide Production

Black precipitate if positive.

TSI Test Medium Composition

Contains glucose, lactose, sucrose, phenol red as a pH indicator, sodium thiosulfate, and ferrous sulfate.

TSI Test Result - Glucose Fermentation

Yellow if positive; red if negative.

TSI Test Result - Lactose/Sucrose Fermentation

Yellow if positive; red if negative.

TSI Test Result - Hydrogen Sulfide Production

Black precipitate if positive.

LIA Test Positive Organisms for Decarboxylation

Proteus spp., Enterobacter spp.

LIA Test Positive Organisms for Deamination

Pseudomonas spp.

LIA Test Positive Organisms for H2S Production

Salmonella spp., Shigella spp.

TSI Test Positive Organism for Glucose Fermentation

Escherichia coli.

TSI Test Positive Organisms for Lactose/Sucrose Fermentation

Klebsiella spp., Enterobacter spp.

TSI Test Positive Organisms for H2S Production

Proteus spp., Salmonella spp.

Non-Fermenters

Pseudomonas, Serratia, Salmonella, Shigella, Providencia, Morganella, Plesiomonas, Yersinia.

Lactose Fermenters

Klebsiella, Escherichia coli, Enterobacter, Citrobacter, Arizona, Hafnia.

Enteroinvasive E. coli (EIEC)

Serotypes 0124, 0143, 0164; causes dysentery-like diarrhea due to invasin, with stool that is bloody and mucoid.

Sereny Test

Virulence test for EIEC; a positive result indicates keratoconjunctivitis.

Enterohemorrhagic E. coli (EHEC) / Verotoxin E. coli (VTEC)

Causes hemolytic uremic syndrome (HUS) and hemorrhagic colitis, affecting kidneys and gastrointestinal tract.

Verotoxin

Major virulence factor for EHEC, similar to Shigella toxin.

E. coli O157:H7

Identified as sorbitol MacConkey negative and MUG negative; associated with severe infections.

Enteroaggregative E. coli (EAEC)

Causes acute and chronic diarrhea; characterized by aggregative adhesion fimbriae that create a stacked brick pattern.

Klebsiella pneumoniae

Also known as Friedlander's bacillus; encapsulated, non-motile, and string test positive.

Klebsiella pneumoniae TSI Test Result

A/A + gas, indicating fermentation with gas production.

Klebsiella pneumoniae LIA Test Result

K/K, positive control for lysine decarboxylation.

Klebsiella pneumoniae IMViC Results

(-) (-) (+) (+), indicating specific metabolic characteristics.

Klebsiella pneumoniae Causes

Can cause pneumonia and wound infections.

Positive Result for Potassium Cyanide Test

Turbidity in the broth indicates a positive result.

Negative Result for Potassium Cyanide Test

Clear broth indicates a negative result.

Positive Genera for Potassium Cyanide

Klebsiella spp., Enterobacter spp., Proteus spp., Providencia spp., Citrobacter spp.

Bacteria that Test Positive for Esculin Hydrolysis

Klebsiella pneumoniae, which shows a black color in the medium.

Bacteria that Test Negative for Esculin Hydrolysis

Shigella flexneri, which shows a yellow color in the medium.

Note

Note

Note

Note

Note

Note

Note

Note

Flashcard (27)

Flashcard (138)

Flashcard (26)

Flashcard (59)

Flashcard (86)

Flashcard (21)

Flashcard (83)

Flashcard (69)