What bacteria are lactose fermenting Gram-negative rods?
E. coli are facultative anaerobic, Gram-negative bacilli that will ferment lactose to produce hydrogen sulfide.
Which Gram-negative bacteria are indole positive?
Indole-Positive Bacteria penneri), Plesiomonas shigelloides, Pasteurella multocida, Pasteurella pneumotropica, Enterococcus faecalis, Vibrio sp., and Lactobacillus reuteri.
Do Gram-negative bacteria ferment lactose?
The only fermentable source of carbohydrate is lactose. The media also contains the pH indicator, neutral red. Therefore Gram negative bacteria that ferment lactose turn pink.
Is lactose fermentation positive or negative?
Lactose (Lac) positive (pink colonies): Lactose fermenting species will grow pink colonies. Lactose fermentation will produce acidic byproducts that lower the pH, and this turns the pH indicator to pink. Example of Lac positive species: Escherichia coli, Enterobacteria, Klebsiella.
Does Enterobacter aerogenes ferment lactose?
These bacteria ferment lactose, are motile, and form mucoid colonies. Enterobacter strains commonly arise from the endogenous intestinal flora of hospitalized patients but can occur in common source outbreaks or are spread from patient to patient.
What does it mean if a bacteria can ferment lactose?
Bacteria that can produce the enzyme lactase can ferment the lactose and will produce an acid waste, which will lower the pH of the media. A pH indicator, neutral red, turns bright fuchsia in color, due to the lowered pH when lactose is fermented.
What are examples of gram-positive rods?
There are five medically important genera of gram-positive rods: Bacillus, Clostridium, Corynebacterium, Listeria, and Gardnerella. Bacillus and Clostridium form spores, whereas Corynebacterium, Listeria, and Gardnerella do not.
Is Bacillus indole positive?
It was found that the bacteria are Gram positive spore chain Bacillus. The bacteria could only ferment glucose for acid production, but could not utilize lactose and maltose. The VP test for this bacteria was positive, while indole and methyl red tests were negative.
What is ferment lactose?
With the help of bacteria, lactose fermentation — the breaking down of the sugar lactose into an acid — is used to make fermented dairy foods and to test for food poisoning. Lactose fermentation also occurs in your body if you are lactose-intolerant.
What gram-negative rods do not grow on MacConkey agar?
Long, thin, slowly growing, oxidase-positive, catalase-positive gram-negative rods that do not grow on MacConkey agar should suggest DF-2. Although testing of antimicrobial susceptibility is problematic, DF-2 has been found to be resistant to aminoglycosides.
What does a positive lactose fermentation test mean?
yellow color
Positive: The development of a yellow color in the medium is indicative of a positive carbohydrate fermentation reaction. Negative: Lack of yellow color development is indicative of a negative carbohydrate fermentation reaction. Gas formation is indicated by the appearance of gas bubbles in the Durham tube.
Does Staphylococcus aureus ferment lactose?
aureus isolates showed positive results in gelatin, urea and galactose hydrolysis test, 50% isolates were positive in starch hydrolysis test, 35% in protein hydrolysis test, 100% isolates in lactose fermenting test, but no isolate was positive in sucrose fermenting test.
What is Enterobacteriaceae Gram negative rod?
Enteric Gram Negative Rods. Lactose Fermentation: Enterobacteriaceae are often sub-classified by their capacity to ferment lactose which can be visualized rapidly on EMB medium by the development of pigmented colonies when fermentation is positive. Consequently, organisms can be categorized as lactose fermenters and lactose non-fermenters Indole…
Are Enterobacteriaceae indole positive or indole negative?
Indole Production: Enterobacteriaceae are often sub-classified by their capacity to produce indole from tryptophan leading to categorization as indole positive and indole negative organisms.
Are Enterobacteriaceae lactose fermenters or non fermenters?
Lactose Fermentation: Enterobacteriaceae are often sub-classified by their capacity to ferment lactose which can be visualized rapidly on EMB medium by the development of pigmented colonies when fermentation is positive. Consequently, organisms can be categorized as lactose fermenters and lactose non-fermenters
What is the best media for the growth of Enterobacteriaceae?
Selective Media: All enterobacteriaceae usually grow well on MacConkey Agar which inhibits growth of gram positive bacteria Lactose Fermentation: Enterobacteriaceae are often sub-classified by their capacity to ferment lactose which can be visualized rapidly on EMB medium by the development of pigmented colonies when fermentation is positive.