Which media is similar to tsi

Purpose: Contains bile salts and crystal violet which selects for gram-negative enterics, differentiates lactose-fermenters from non-fermenters. Can include sugars other than lactose for further differentiation for example, to differentiate enterohemorrhagic E. Interpretation: Selects for non-fastidious gram-negatives; red colonies indicate fermentation of lactose, white indicates no fermentation of lactose.

MacConkey Agar - Escherichia coli Note: Red colonies and red precipitate due to acid production as a result of lactose fermentation. Colorless colonies, medium is slightly yellow due to the increased pH resulting from bacterial digestion of peptone in the medium.

Eosin Methylene Blue Agar - uninoculated. Type: Differential lactose and selective dye inhibition and precipitation at acid pH. Purpose: Differentiates lactose fermenters E. Eosin Methylene Blue Agar - Salmonella enteritidis Note: pink colonies indicative of non-lactose fermentation. Eosin Methylene Blue Agar - Escherichia coli Note: Green metallic sheen indicative of dye precipitation due to lactose fermentation.

Eosin Methylene Blue Agar - Klebsiella pneumoniae Note: Mucoid colonies with dark centers due to capsule production and lactose fermentation respectively. Hektoen Agar. Hektoen - uninoculated. Purpose: Detects lactose fermentation, H 2 S production, inhibits non-enterics.

Interpretation: Lactose fermenters yellow or salmon, non-fermenters colorless; H 2 S production produces black precipitate. Hektoen - Escherichia coli Note: Orange color indicates acid production as a result of lactose fermentation. Mannitol Salt Agar. When the H2S is produced in the slant, it get escaped but in the slant, it get trapped and react with Iron, resulting the black pigmentation.. If organism is fermenter, it will ferment at the butt also, if organism is non-fermenter, it will oxidize the peoptone and alkali condition will come.

So as per my knowledge and understanding such condition is unlikely to occur. I know E. Could it have been that there was not enough bacteria inoculated? Hello Alianis Hernandez, yellow slant and red butt reaction can not be justified in any circumstances, the reverse can happen in case of NLF and no change in both slant and butt can be seen in case non fermenter and in case of oxidative organisms, the slant become red but butt may not change.

I suggest you to repeat the inoculation of TSI again and incubate for hours and also please use known strain organism to check the TSI agar is giving actual result. Such type of result is unexpected.

Did you sub-culture the isolate in MacConkey Agar? What was the colony characteristics? What about Catalase and Oxidase test results? Please repeat the procedure following all the steps and precautions as mentioned with a single isolated colony; and observe the result within hours.

I know that Phenol red is a pH indicator which turns yellow below a pH of 6. Also air bubbles were observed inside all 3 Durham tubes. And the Kligler Iron Agar was completely yellow with one or two small bubbles at the bottom. Dear Olivia, thank you so much for your query. Based on the information you have provided here, the isolate can be one of them; Escherichia coli , Klebsiella spp pneumoniae or oxytoca , Enterobacter spp or Citrobacter spp.

These are the most common lactose fermenter. You need other information to identify the isolate such as production of Hydrogen sulphide gas, indole production, citrate utilization, urease production, motility etc. Sir I have a question in which mechanism bacteria that produce gas for example Proteus produce copious of carbon dioxide which causing gap at the but and separate at the slant I need to know the mechanism behind which leading the occurrence of that gaps.

Thanks Tankeshwar for your information i have understood TSI reaction basing on fermentation but i have a question how can you differentiate vibrio cholera on tsi. Dear Anderson, Thank you for inspiring comment. We wont be able to identify Vibrio cholerae only on the basis of TSI reaction results. Please find out in details about Vibrio in this post: Vibrio Cholerae laboratory diagnosis and confirmation.

Thanks Tankeshwar Acharya for directing me to the Lab diagnosis of vibrio i found out that there are other biochemical test for example oxidase test and others including TSI for identifying Vibrio and thats is clear. Dear Anderson koech, Thank you for your comment.

In our settings; we do not perform Cholera Red Reaction as a part of routine test to identify Vibrio cholerae. We perform simple test from Hanging drop for rice watery stool with mucus flecks , followed by plating in TCBS agar. Observation of colony morphology and performing other biochemical test is done after that.

Finally we perform serological test to differentiate the serotypes, O1 and Non O1. I have listed the tests we perform in our laboratory here:. The rationale is, MTB concentrate in the sputum at night and sensitivity increases if early morning sample is taken. Why is the organism positive for the agar and negative on the TSI? Sir I have a question. But on my MacConkey agar, it showed red colonies that indicates that it is a lactose fermenter.

Discard tubes showing a red or pink coloration, which is due to urea hydrolysis by Proteus or other organisms. Where there is no urea hydrolysis, examine the Triple Sugar Iron Agar tubes after 18 hours and 48 hours. The following are typical reactions:. The presumptive evidence so obtained may be confirmed serologically after sub-culturing the organism from the Triple Sugar Iron Agar slope in Nutrient Broth No. References 1.

Bulmash J. In the picture below the organism on the right Pseudomonas aeruginosa is oxidase positive. Coagulase is an enzyme that clots blood plasma. This test is performed on Gram-positive, catalase positive species to identify the coagulase positive Staphylococcus aureus. Coagulase is a virulence factor of S. The formation of clot around an infection caused by this bacteria likely protects it from phagocytosis. This test differentiates Staphylococcus aureus from other coagulase negative Staphylococcus species.

This is a differential test used to distinguish between organisms sensitive to the antibiotic bacitracin and those not. Bacitracin is a peptide antibiotic produced by Bacillus subtilis.

It inhibits cell wall synthesis and disrupts the cell membrane. This test is commonly used to distinguish between the b -hemolytic streptococci: Streptococcus agalactiae bacitracin resistant and Streptococcus pyogenes bacitracin sensitive. The plate below was streaked with Streptococcus pyogenes ; notice the large zone of inhibition surrounding the disk.

This is a differential test used to distinguish between organisms sensitive to the antibiotic optochin and those not. This test is used to distinguish Streptococcus pneumoniae optochin sensitive pictured on the right below from other a -hemolytic streptococci optochin resistant Streptococcus mitis is pictured on the left below. This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria.

The differential ingredient is lactose. Fermentation of this sugar results in an acidic pH and causes the pH indicator, neutral red, to turn a bright pinky-red color. Thus organisms capable of lactose fermentation such as Escherichia coli , form bright pinky-red colonies plate pictured on the left here.

MacConkey agar is commonly used to differentiate between the Enterobacteriaceae. Organism on left is positive for lactose fermentation and that on the right is negative. This is a defined medium used to determine if an organism can use citrate as its sole carbon source. It is often used to differentiate between members of Enterobacteriaceae. In organisms capable of utilizing citrate as a carbon source, the enzyme citrase hydrolyzes citrate into oxaoloacetic acid and acetic acid. The oxaloacetic acid is then hydrolyzed into pyruvic acid and CO 2.

If CO 2 is produced, it reacts with components of the medium to produce an alkaline compound e. The alkaline pH turns the pH indicator bromthymol blue from green to blue. This is a positive result the tube on the right is citrate positive. Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms. Escherichia coli and Shigella dysenteria e are citrate negative.

This agar is used to identify organisms that are capable of producing the enzyme lipase. This enzyme is secreted and hydrolyzes triglycerides to glycerol and three long chain fatty acids.

These compounds are small enough to pass through the bacterial cell wall. Glycerol can be converted into a glycolysis intermediate. Spirit blue agar contains an emulsion of olive oil and spirit blue dye. Bacteria that produce lipase will hydrolyze the olive oil and produce a halo around the bacterial growth.

The Gram-positive rod, Bacillus subtilis is lipase positive pictured on the right The plate pictured on the left is lipase negative. This test is used to identify bacteria that can hydrolyze starch amylose and amylopectin using the enzymes a -amylase and oligo-1,6-glucosidase. Often used to differentiate species from the genera Clostridium and Bacillus. Because of the large size of amylose and amylopectin molecules, these organisms can not pass through the bacterial cell wall.

In order to use these starches as a carbon source, bacteria must secrete a -amylase and oligo-1,6-glucosidase into the extracellular space. These enzymes break the starch molecules into smaller glucose subunits which can then enter directly into the glycolytic pathway.

In order to interpret the results of the starch hydrolysis test, iodine must be added to the agar. The iodine reacts with the starch to form a dark brown color. Thus, hydrolysis of the starch will create a clear zone around the bacterial growth. Bacillus subtilis is positive for starch hydrolysis pictured below on the left. The organism shown on the right is negative for starch hydrolysis. This test is used to determine which fermentation pathway is used to utilize glucose.

In the mixed acid fermentation pathway, glucose is fermented and produces several organic acids lactic, acetic, succinic, and formic acids.