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      常用培養基的菌落圖片、原理和作用

      發布時間:

      2022-12-24

      作者:

      一次性成品培養基


      微生物檢測人員天天都在培養和鑒定各種細菌真菌,培養和鑒定過程中肯定都會用到各種各樣的培養基,尤其是一些選擇性和鑒定性的培養基。我們每天都在用的這些培養基,你知道它們的原理嗎?今天小編就挑選幾種常用的培養基給大家科普一下。
      伊紅美藍瓊脂培養基,簡稱EMB,常用于大腸埃希氏菌的檢測,其主要原理是培養基中存在的伊紅和美藍這兩種染色劑,其中伊紅為酸性染料,美藍為堿性染料。大腸埃希氏菌在伊紅美藍上的典型狀態為具黑色中心有光澤或者無光澤。當大腸埃希氏菌分解乳糖產酸時細菌就會帶正電荷被伊紅染成紅色,再與美藍結合形成紫黑色菌落并帶有金屬光澤;不分解乳糖產酸的細菌就不著色,伊紅和美藍就不能結合,因此沙門氏菌等為無色或琥珀色半透明菌落。
       
      Baird-Parker瓊脂主要用于金黃色葡萄球菌的選擇性分離培養,其主要原理是培養基中含有的丙酮酸鈉、甘氨酸、氯化鋰、亞碲酸鉀等。金黃色葡萄球菌在Baird-Parker平板上的典型狀態為黑色,且周圍有一渾濁帶,在外側有一透明環,呈現“雙環”現象。其原理為:丙酮酸鈉和甘氨酸刺激葡萄球菌的生長,氯化鋰和亞碲酸鉀抑制非葡萄球菌,含有卵磷脂酶的葡萄球菌降解卵黃是菌落產生透明圈,而脂酶作用產生不透明的沉淀環,凝固酶陽性的葡萄球菌還能還原亞碲酸鉀產生黑色菌落。一般應該注意,典型的金黃色葡萄球菌是具有“雙環”的,即一渾濁帶之外還有一圈透明環,只具有單環渾濁帶的一般是變形桿菌。
       
      HE瓊脂常用于腸道致病菌的檢測,比如沙門氏菌的分離性選擇就會用到。沙門氏菌在HE瓊脂上的典型狀態為藍綠色或藍色,多數菌落中心黑色或者幾乎全黑色;部分菌株為黃色,中心黑色或幾乎全黑色。其原理主要是非目標菌會分解乳糖、蔗糖和水楊素產酸,而pH指示劑溴麝香草酚藍和酸性復紅會使產酸菌呈紅色,而沙門氏菌等不發酵產酸的菌或呈藍綠色。同時膽鹽、去氧膽酸鈉以及兩種指示劑可以抑制革蘭氏陽性菌,硫代硫酸鈉和檸檬酸鐵銨會檢測硫化氫的產生使菌落中心呈黑色。
       
      TCBS瓊脂
      TCBS瓊脂又叫硫代硫酸鹽檸檬酸鹽膽鹽蔗糖瓊脂培養基,用于致病性弧菌的選擇性分離。例如副溶血性弧菌。典型的副溶血性弧菌在TCBS上呈圓形、半透明、表面光滑的綠色菌落。培養基中的氯化鈉可刺激弧菌的生長;蔗糖是可發酵的糖類;膽酸鈉、牛膽汁粉、硫代硫酸鈉和檸檬酸鈉及較高的pH可抑制革蘭氏陽性菌和大腸菌群;霍亂弧菌對酸性環境比較敏感,因此該pH值可增強其生長;硫代硫酸鈉與檸檬酸鐵反應作為檢測硫化氫產生的指示劑;溴麝香草酚藍和麝香草酚藍是pH指示劑。

      Images, principles and functions of colonies in common medium
      Microorganism inspectors are training and identifying various kinds of bacteria and fungi every day. In the process of culture and identification, all kinds of medium are used, especially some selective and identification medium. Do you know the principles of these media that we use every day? Today Xiaobian selects several commonly used media to give you popular science.
      Eosin Blue Agar
      The eosin blue agar medium, called EMB, is commonly used for the detection of Escherichia coli. The main principle is the two kinds of dyestuffs, eosin and methylene blue, of which eosin is acid dye and methylene blue as alkaline dye. Escherichia coli is typically black, glossy or glossy on eosin methylene blue. When Escherichia coli decomposes lactose to produce acid, bacteria will be dyed red with eosin and then combine with methylene blue to form purple black colonies and metallic luster; bacteria that do not decompose lactose and acid are not coloured, eosin and methylene blue can not be combined, so Salmonella is a colorless or amber color semitransparent colony. Typical Escherichia coli on eosin methylene blue medium is shown in Fig.
      eosin methylene blue medium
      Baird-Parker agar
      Baird-Parker agar is mainly used for selective isolation and culture of Staphylococcus aureus. The main principle is the sodium pyruvate, glycine, lithium chloride and potassium tellurite in the medium. The typical state of Staphylococcus aureus on the Baird-Parker plate is black, and there is a turbid zone around it. There is a transparent ring on the outside of the Staphylococcus aureus, showing a "double ring" phenomenon. The principle is: sodium pyruvate and glycine stimulate the growth of Staphylococcus, lithium chloride and potassium tellurite inhibit non Staphylococcus, and the staphylococcal degradation of yolk with lecithin produces transparent rings, and lipase produces opaque precipitation rings, coagulase positive Staphylococcus can also reduce potassium tellurite to produce black. Chromatic colonies. In general, it should be noted that the typical Staphylococcus aureus is a "double ring", that is, there is a circle of transparent rings outside the turbidity zone, and only the turbid band of the mono ring is usually proteus. The typical colonies of Staphylococcus aureus on the Baird-Parker plate are as follows:
      Baird-Parker agar
      HE agar
      HE agar is often used for the detection of enteric pathogens, such as Salmonella isolates. The typical state of Salmonella on HE agar is bluish green or blue, most of the colonies are black or almost completely black; some are yellow, black or almost completely black. The principal principle is that the non target bacteria decompose lactose, sucrose and salicylic acid, while the pH indicator bromothymol blue and acid reddish will make acid producing bacteria red, while Salmonella and other bacteria that do not ferment acid are blue green. At the same time, bile salts, sodium deoxycholate, and two indicators can inhibit Gram-positive bacteria. Sodium thiosulfate and ammonium citrate will detect the production of hydrogen sulfide to make the center of the colony black. The typical colonies of Salmonella on HE agar plate are as follows:
      HE agar
      TCBS agar
      TCBS agar is also called thiosulfate citrate bile salt sucrose agar medium, which is used for selective isolation of pathogenic Vibrio. Vibrio parahaemolyticus, for example. The typical Vibrio parahaemolyticus on TCBS is a round, translucent, smooth green colony. Sodium chloride in the medium can stimulate the growth of Vibrio; sucrose is fermentable sugar; sodium cholate, bovine bile powder, sodium thiosulfate and sodium citrate and high pH can inhibit Gram-positive and coliform bacteria; Vibrio cholerae is more sensitive to acid environment, so the pH value can enhance its growth; sodium thiosulfate and lemon Acid iron reaction is used as an indicator for the detection of hydrogen sulfide; bromothymol blue and thymol blue are pH indicators. Typical colonies of Vibrio parahaemolyticus on the TCBS plate are shown below.

       

      TCBS agar

       

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