What should I Know about Bacterial Identification?

Bacteria are identified by examining all aspects of the bacteria. For example: bacterial metabolism test for carbohydrates, indole test, starch hydrolysis and other tests.

Name: Identification of bacteria

category: Biochemical tests

Bacteria identification normal value

The normal flora of the gastrointestinal tract can be divided into aerobic bacteria, facultative anaerobic bacteria and anaerobic bacteria. The most dominant is anaerobic bacteria, accounting for 99% of the total flora, of which only 90% are Bacteroides and Bifidobacteria, while Lactobacillus and Bifidobacteria can be with us for life. The types and proportions of these normal flora are normal.

Clinical significance of bacteria identification

Some bacteria can break down tryptophan to produce indole, which can react with dimethylaminobenzaldehyde to produce red rose indole. Therefore, bacteria can be identified based on whether the bacteria can break down tryptophan to produce indole.

Abnormal results: (1) The internal environment of the intestine is not in dynamic equilibrium, and the proportion of normal bacteria is out of balance. Symptoms such as pain, stomach acid, bloating, diarrhea, abdominal pain, falling, and pus and bloody stools can also cause gastrointestinal bleeding, perforation, and canceration, such as gastric cancer and colon cancer. (2) Escherichia coli causes parenteral infections, especially urinary tract infections. Citrobacter genus causes primary or secondary citric acid pneumonia. Pathological changes are mainly manifested as bronchial pneumonia, alveolar wall destruction may form small abscesses and focal bleeding. Klebsiella caused clinical symptoms such as respiratory infections, sepsis, purulent meningitis, and urinary tract infections. There are also various abnormal symptoms caused by Salmonella and Proteus. (3) Some bacteria hydrolyze starch and use its hydrolysate to produce discomfort due to acid and gas production. People to be examined: Those who have symptoms of bacterial infection such as gastrointestinal bleeding, perforation, and canceration.

Identification of bacteria

Unsuitable people: temporarily unknown before inspection: keep good habits and rest, pay attention to normal eating habits. Examination requirements: actively cooperate with the doctor

Bacteria identification and inspection process

(1) Indole test method: inoculate a fresh slant culture of the bacteria to be tested in a Dunn's peptone solution and incubate at 37 ° C for 24-48 hours (can be extended for 4-5 days). Add 2-3ml of pentanol or xylene to the culture solution, shake well, and let stand for a while, then add 2ml of reagent along the wall of the test tube. The liquid that turns red under pentanol or xylene is a positive reaction. You can also put two drops of Orech's reagent on absorbent cotton with a large finger, and then add two drops of high-potassium sulfate (K2S2O4) saturated aqueous solution in the same place, and place it in the test tube containing the culture solution, about half from the liquid surface. Inch, until the water bath in the beaker is boiled, the red appears positive on the absorbent cotton. This method is slightly more complicated, but saves reagents and is accurate, because the indole and skatole are positive when the reagent is added to the liquid, but with this method, only the indole (which can volatilize) is positive. Alternatively, a filter paper sheet can be soaked in a 10% concentrated HCl solution of 1% dimethyl benzaldehyde, and then a ring agar pure culture is scraped with an inoculating ring and coated on the filter paper. Those with blue stains around the bacteria were positive, and those with no color change or pale yellow around the bacteria were negative. (2) Hydrolysis of starch Starch can be hydrolyzed under the catalysis of acid; the hydrolysis process of starch: firstly, a small molecular weight dextrin (a product of incomplete hydrolysis of starch) is generated, and the dextrin continues to hydrolyze to produce maltose, and the final hydrolysis product It's glucose. Counteragent: 2 g of potassium iodide, 300 ml of distilled water. Culture medium: inoculate the bacteria on a plate, and incubate in a 37 ° C incubator for 24 hours. Add Gram's iodine solution to the colonies. Observe the color changes. The blue ones are negative. No blue. Is positive. (3) -galactosidase test reagent: 0.75M ONPG solution: take 80mg dissolved in 15ml distilled water, add buffer solution (6.9g NaH2P04 dissolved in 45ml distilled water, adjust the pH to 7.0 with 30% NaOH, and then add water To 50ml) 5ml, store in 4 ° C refrigerator. Methods: Take pure colonies to make a concentrated bacteria suspension with sterile physiological saline, add 0.25ml ONPG solution, and place in a 35 ° C water bath for 20min to 3h, and observe the results. Result judgment: usually develop color within 20-30min. A yellow reaction is positive.

Identification of Bacteria Related Diseases

Erichliosis, Erichliosis, Nocardiosis, Clostridium wound infections, colon cancer, acute upper respiratory infections in children, athlete's foot, pasteurosis