[식품미생물학실험 레포트] S. aureus의 gram staining과 coagulase, catalase test

본 내용은 " [식품미생물학실험 레포트] S. aureus의 gram staining과 coagulase, catalase test " 의 원문 자료에서 일부 인용된 것입니다. 2023.08.09

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• 1. Gram staining

  Gram staining은 세균을 그람 양성균과 그람 음성균으로 구분하는 방법이다. 그람 양성균은 두꺼운 peptidoglycan 층으로 인해 crystal violet-iodine 복합체가 빠져나가지 못해 보라색으로 염색되고, 그람 음성균은 얇은 peptidoglycan 층으로 인해 복합체가 빠져나가 대조 염색약인 safranin에 의해 붉은색으로 염색된다. 실험 결과 S. aureus는 그람 양성균으로 확인되었다. 다만 일부 균체가 붉은색을 띠는 이유는 오랜 에탄올 처리로 인해 복합체가 빠져나갔기 때문으로 보인다.

• 2. Catalase test

  Catalase test는 세균이 과산화수소를 물과 산소로 분해하는 능력을 확인하는 것이다. 호기성 및 통성 혐기성 세균은 catalase를 가지고 있어 과산화수소를 분해할 수 있지만, 혐기성 세균은 catalase가 없어 분해하지 못한다. 실험 결과 S. aureus는 catalase 양성으로 확인되어 통성 혐기성 세균임을 알 수 있었다.

• 3. Coagulase test

  Coagulase test는 S. aureus가 가진 coagulase 효소를 확인하는 것이다. Coagulase는 혈장의 fibrinogen을 fibrin으로 응고시키는 능력이 있어 S. aureus의 병원성 인자로 작용한다. 실험에서는 fibrinogen이 포함된 시약과 대조군 시약을 사용했는데, 균 배양액에 fibrinogen 시약을 넣었을 때 약간의 응고가 관찰되어 S. aureus가 coagulase 양성임을 확인할 수 있었다.

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• 1. Gram staining

  Gram staining is a widely used technique in microbiology to classify bacteria based on their cell wall structure. It is a simple, rapid, and cost-effective method that provides valuable information about the morphology and Gram reaction of bacterial cells. The Gram stain divides bacteria into two main groups: Gram-positive and Gram-negative. Gram-positive bacteria retain the crystal violet dye during the staining process, appearing purple, while Gram-negative bacteria lose the crystal violet and appear pink or red after the counterstaining with safranin. This distinction is crucial for the identification and characterization of bacteria, as Gram-positive and Gram-negative bacteria often have different cell wall compositions, susceptibilities to antibiotics, and pathogenic properties. The Gram staining technique is an essential tool in clinical microbiology, allowing for the rapid presumptive identification of bacteria and guiding the selection of appropriate antimicrobial therapies. It is also widely used in research, food microbiology, and environmental microbiology to study the diversity and distribution of bacterial communities. Overall, Gram staining remains a fundamental and indispensable technique in the field of microbiology.

• 2. Catalase test

  The catalase test is a simple and widely used biochemical test in microbiology to identify the presence of the enzyme catalase in bacterial cells. Catalase is an enzyme that catalyzes the breakdown of hydrogen peroxide (H2O2) into water and oxygen. The test is performed by adding a drop of hydrogen peroxide solution to a bacterial colony or a suspension of bacterial cells. If the bacteria possess catalase, the rapid production of oxygen bubbles is observed, indicating a positive catalase test. This test is particularly useful for the differentiation of Gram-positive bacteria, as most Gram-positive cocci (e.g., Staphylococcus) are catalase-positive, while Gram-positive rods (e.g., Bacillus) are catalase-positive. The catalase test is also helpful in distinguishing between aerobic and anaerobic bacteria, as aerobic bacteria typically possess catalase to protect themselves from the toxic effects of hydrogen peroxide, a byproduct of aerobic respiration. The catalase test is a simple, rapid, and inexpensive diagnostic tool that provides valuable information about the metabolic and physiological characteristics of bacteria, aiding in their identification and classification. It is routinely used in clinical microbiology laboratories, food microbiology, and environmental microbiology studies.

• 3. Coagulase test

  The coagulase test is a crucial diagnostic tool in microbiology, primarily used to identify the presence of the enzyme coagulase in Staphylococcus bacteria. Coagulase is an enzyme produced by certain Staphylococcus species, particularly Staphylococcus aureus, that has the ability to clot plasma. The coagulase test is performed by mixing a bacterial suspension with human or rabbit plasma, and observing whether the plasma coagulates or remains in a liquid state. A positive coagulase test, indicated by the formation of a clot, is a strong indicator of the presence of Staphylococcus aureus, which is a significant human pathogen responsible for a wide range of infections, from mild skin and soft tissue infections to life-threatening conditions like sepsis and endocarditis. The coagulase test is an essential tool in clinical microbiology laboratories, as it helps to differentiate Staphylococcus aureus from other Staphylococcus species, which have important implications for diagnosis, treatment, and infection control measures. Additionally, the coagulase test is used in food microbiology to detect the presence of Staphylococcus aureus, a common foodborne pathogen. Overall, the coagulase test is a simple, rapid, and reliable method that provides crucial information for the identification and characterization of Staphylococcus species, particularly in the context of clinical and food safety applications.