Epsilometer测试（e测试） - 原理，程序，结果，优势

Introduction

Epsilometer test (E- test) is defined as the “exponential gradient” method that determines the antimicrobial resistance of the microorganism. It is a cost-effective tool that has been developed to provide a direct quantification of antimicrobial susceptibility of microorganisms. It is a quantitative method that applies both the dilution of antibiotics and the diffusion of antibiotics into the medium. More precisely, the test combines a disk diffusion pattern with the determination of Minimum Inhibitory Concentration (MIC) which is considered as the lowest concentration of an antimicrobial that inhibits the visible growth of a microorganism. The E-test uses rectangular plastic strips with the predefined, continuous and exponential gradient of antibiotic concentration (one side of the strip contains the antimicrobial agent concentration gradient and the other side of the strip contains a numeric scale that indicates the drug concentration).

目标

1. 确定尖锐，生长缓慢或营养缺乏的微生物的MIC。
2. 检测和确认特异性抗微生物表型抗性的低抗性。
3. 确定并证明给定抗生素的MIC值给给定微生物。

Principle of E test

当细菌悬浮液的培养物上进行时穆勒亨顿琼脂（MHA）using the sterile cotton swab. The e test strip is then placed on to an inoculated agar plate. After placing the strip on the agar surface, there is an immediate release of antibiotics from the plastic carrier surface into the agar surface. After incubation, bacterial growth becomes visible on the plate, and symmetrical inhibition ellipse along the strip is seen. The MIC value is read from the scale in terms of µg/ml where the ellipse edge intersects the strip as seen on the plate.

程序

1. Inoculum Preparation
   1. 在需要之前至少30分钟从冰箱（-20°C）中取出电子测试包。
   2. Emulsify 3 or 4 individual test strain colonies and transfer to a tube of saline.
   3. Compare turbidity to that in the 0.5 McFarland standards. Adjust turbidity of inoculum in order to match the standard.
2. 在Muller hinton琼脂中接种
   1. 无菌棉签蘸培养液和rO.tate the swab against the inside of the tube above the fluid level to remove excess liquid before swabbing.
   2. 通过大约60旋转板条在琼脂平板的整个表面上旋转拭子^O.。
   3. Complete inoculation by running the swab around the rim of the agar.
   4. 将板琼脂的盖子留下5分钟，以允许任何过量的水分在施用条带之前被吸收。
3. 电子试验条的应用：
   1. Open the E-test package and take a strip out using sterile forceps.
   2. 使用镊子将条带施加到琼脂表面。
   3. 将条带放在板边缘的“e末端”，并用刻度可见（即向上）。
   4. 在37℃下孵育18-24小时。

Result and Interpretation

Image Source:ETEST® TelavancinandRapid Test Methods Ltd

• After the incubation, the tests are read by viewing the strips from the top of the plate, a symmetrical inhibition ellipse is produced and seen on the plate.
• 用试管读取椭圆形生长抑制区域的下部的麦克风。如果麦克风值在双重稀释率之间，请始终舍入到最高值。
• Read the MIC value at complete inhibition of all growth.
• 通过将每种抗生素的断点值与推荐的标准和由CLSI指南给出的标准进行比较，应解释细菌的麦克风值。

Precautions

1. 在处理细菌标本时，应使用无菌手术和免疫学危害的预防措施。
2. 应严格使用根据所描述的程序严格使用e-test。
3. One should be very careful while placing the E strip on the plate containing the bacterial suspension to not touching the edge of the plate.
4. Read results only if a good inhibition ellipse is visible.
5. While doing or placing multiple strips on a single plate, the strips shouldn’t touch one another that would make the difference in the result interpretation of the given antibiotic.

E测试的优点

1. 它很容易执行，需要最少的测试性能培训，易于执行。
2. 可以容易地识别污染。
3. 它是少耗时，非常方便地确定最小抑制浓度（MIC）并适用于各种药物和微生物。
4. 检测一些表型抗性是有用的。
5. It is an adequate method to detect potentially resistant strains to Amphotericin B.
6. 它有助于确认或检测低级或新的电阻机制。
7. 它可用于研究组合疗法的任何协同潜力。

e测试的限制

1. E-test is not suitable forCryptococcus neoformans.。
2. 对于每次使用多种抗生素的使用，必须彼此的互动，难以知道它们是否具有添加剂，协同或拮抗作用。

References

1. Tille P.M（2014）。Bailey和斯科特的诊断微生物学。十三个版本。Mosby，Inc。是elsevier Inc.3251 Riverport Lane的联盟。圣路易斯。密苏里63043
2. Biomerieux
3. Joyce LF，拖欠J，Stockman K，Andrew Jh（1992）。五种方法的比较，包括PDM肺炎仪测试（E试验），用于假单胞菌铜绿假单胞菌的抗菌易感性试验。J Clar Microbiol.。30（10）：2709-2713。
4. https://www.jove.com/science-education/10512/antibiotic-suscepity-testing-epsilometer-tests-to-determine-mic.
5. Sader HS, Pignatari ACC (1994). E Test: a novel technique for antimicrobial susceptibility testing. Sao Paulo Med. J. vol.112 no.4. Retrieved from:http://www.scielo.br/scielo.php?script=sci_arttext& pid=s1516-31801994000400003.

互联网资源

• 13％ - https://microbreononline.com/e-test-epsilometer-test-princifle-purpose-procedure-results-and-interprations/
• 9％ - https://microbiologynotes.com/e-epsilometer-test-princifle-purport-procedure-result-interpretation-with-precaution -Advantares-and-disAdvantages/
• 3% – https://pinardsflorist.com/epsilometer-test-94/
• 2％ - https://www.ncbi.nlm.nih.gov/pubmed/11420333
• 2% – http://legacy.bd.com/ds/technicalCenter/inserts/L007393(11)(0706).pdf
• 1% – https://www.ncbi.nlm.nih.gov/pubmed/1324301
• 1% – https://www.dermnetnz.org/topics/laboratory-tests-for-bacterial-infections/
• 1％ - https://www.biomerieux-diagnostics.com/testr
• 1％ - https://file.scirp.org/pdf/aim_2013053114403142.pdf
• 1％ - https://fas.org/irop/doddir/army/fm8-9.pdf
• <1% – http://www.chem.ucla.edu/~bacher/General/30BL/tips/TLC1.html