كل ماهو معروف عن Oxidase Test و O.F Test
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Oxidase Test & O.F Test
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Oxidase Test & O.F Test
الا الحبيــــــــــب يا عبـــــاد الصليـــــب
اللهم صلي وسلم وبارك على سيدنا محمد وعلى آله وصحبه ومن تبعه باحسان الى يوم الدين.
قال ( ص ) :- كلمتان خفيفتان على اللسان ... ثقيلتان في الميزان ... حبيبتان الى الرحمن ...
" سبحان الله وبحمده ... سبحان الله العظيم "الكلمات الدلالية (Tags): لا يوجد
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Oxidase test
Oxidase Test
The oxidase test is based on the production of the enzyme indophenol oxidase by organisms containing cytochrome C. Indophenol oxidase, in the presence of
atmospheric oxygen, oxidizes a redox dye (N,N,N_,N_-tetramethyl-p-phenylene diamine dihydrochloride) to form a dark-purple indophenol compound.
Filter paper impregnated with the reagent is allowed to dry completely; smear of a loopful of bacteria from a nonselective plate is placed onto the paper with an
inoculating loop and examined for development of a violet or purple color (positive reaction). No color change indicates a negative result.
Wire loops containing iron may give a false-positive reaction and reactions from weak oxidase-positive organisms may be inaccurate. Colonies growing on
selective media or differential media containing glucose cannot be used for oxidase determination because fermentation inhibits indophenol oxidase activity resulting in false negative results (Koneman et al., 1997; Becton Dickinson, 2003).
Principles
Oxidase enzymes play an important role in the operation
of the electron transport system during aerobic respiration.
Cytochrome oxidase (aa3 type) uses O2 as an
electron acceptor during the oxidation of reduced cytochrome
c to form water and oxidized cytochrome c.
The ability of bacteria to produce cytochrome oxidase
can be determined by the addition of the oxidase
test reagent or test strip (tetramethyl-p-phenylenediamine
dihydrochloride or an Oxidase Disk, p-aminodimethylaniline)
to colonies that have grown on a
plate medium. Or, using a wooden applicator stick, a
bacterial sample can either be rubbed on a Dry Slide
Oxidase reaction area, on a KEY test strip, or filter
paper moistened with the oxidase reagent. The light
pink oxidase test reagent (Disk, strip, or Slide) serves
as an artificial substrate, donating electrons to cytochrome
oxidase and in the process becoming oxidized
to a purple and then dark purple (figure 30.1)
compound in the presence of free O2 and the oxidase.
The presence of this dark purple coloration represents
a positive test. No color change or a light pink coloration
on the colonies indicates the absence of oxidase
and is a negative test.
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O/F
OF Glucose Medium
Bacteria can utilize glucose and other carbohydrates by using various metabolic cascades. Some are fermentative routes; others are oxidative. Oxidationfermentation
(OF) medium permits classification of organisms by a simple method that differentiates aerobic and anaerobic degradation of carbohydrates. The low protein to carbohydrate ratio in the medium prevents neutralization of acids by the alkaline products of protein metabolism, thus allowing small quantities of weak
acids to be detected. Acid production results in a pH shift that changes the color of the bromthymol blue indicator from green to yellow.
Using an inoculating needle, 2 tubes of OF glucose medium are stab-inoculated halfway to the bottom of the tubes. The content of one tube is overlaid with 1 mL of sterile mineral oil. Both tubes are incubated at 35◦C in non-CO2, and examine daily for 72 h or longer for slow-growing organisms. Yellow color indicates the production of acid. Acid production in the tube without oil overlay is considered
oxidative reaction. Acid production in both tubes is considered fermentative. No acid production in either tube is considered nonsaccharolytic. Nonsaccharolytic organisms produce slight alkalinity (blue-green color) in the tube without oil overlay, but the tube with oil will not exhibit a color change and will remain green (BD Microbiology Systems, 1992).
OF Sugars
OF basal medium, when supplemented with an appropriate carbohydrate, is used to determine an organism’s ability to utilize sugars such as lactose, xylose, sucrose, maltose, and mannitol. The low protein to carbohydrate ratio in OF basal
medium prevents the neutralization of small quantities of weak acids by the alkaline products of protein metabolism, which makes this medium ideal for determining
carbohydrate utilization. Acid production from carbohydrate metabolism results in a pH shift that changes the color of the bromthymol blue indicator from green
to yellow. Yellow color indicates carbohydrate metabolism.
Using an inoculating needle, touch the center of one colony and stab-inoculate the OF medium with the appropriate carbohydrate once halfway to the bottom of the tube. Cap the tubes loosely and Incubate at 35◦C in non-CO2, and examine daily for 72 h or longer for slow-growing organisms. A yellow color indicates carbohydrate utilization and no color change (green) or blue color indicates no
carbohydrate utilization. The acid reaction produced by oxidative organisms is detected first at the surface and gradually extends throughout the medium. When
oxidation is weak or slow, it is common to observe an initial alkaline reaction at the surface of the tube that may persist for several days. This must not be mistaken for
a negative test. If the organism is unable to grow in the OF medium, add either 2% serum or 0.1% yeast extract prior to inoculation (BD Microbiology Systems, 1992).
http://www.bd.com/ds/technicalCenter...sal_Medium.pdf
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السلام عليكم
الله يعطيك العافية أخي Lifeالتعديل الأخير تم بواسطة DelloCocci; الساعة 31-05-2008, 08:34 PM.الا الحبيــــــــــب يا عبـــــاد الصليـــــب
اللهم صلي وسلم وبارك على سيدنا محمد وعلى آله وصحبه ومن تبعه باحسان الى يوم الدين.
قال ( ص ) :- كلمتان خفيفتان على اللسان ... ثقيلتان في الميزان ... حبيبتان الى الرحمن ...
" سبحان الله وبحمده ... سبحان الله العظيم "
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توضيح
السلام عليكم ورحمة الله وبركاته
اخي الفاضل ابو البراء
اولا اعتذار
اعتذر منك لاني جلبت المعلومات باللغة الانكليزية والتي قد تصعب احيانا على البعض فاذا كان في مشكلة فانا مستعدة ان شاء الله الخصها بالعربي ولو اني انصح بالتعود على الترجمة ولو كنا نلاقي صعوبة في البداية لكن بالنهاية انت المستفيد
ثانيا:نصيحة
انصحك يا اخي بزيارة قسم الكتب والمراجع الطبية في المنتدى هناك كتب قيمة تغنيك عن السؤال خاصة في مكتبة المايكروبايولوجي مثل كتاب
Advanced Techniques in
Diagnostic Microbiology
Yi-Wei Tang
Charles W. Stratton
C 2006 Springer Science+Business Media, LLC.
وكتاب المايكرو العملي المفيد جدا والذي قد تجد فيه معظم الاختبارات:
lab_exerc microbiology
prescott
laboratory exsercise in microbiology fifth edition 2002
والله الموفق
تعليق
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life science
مشكوووووووورة أختيالتعديل الأخير تم بواسطة أبو البراء; الساعة 01-06-2008, 06:03 AM.الا الحبيــــــــــب يا عبـــــاد الصليـــــب
اللهم صلي وسلم وبارك على سيدنا محمد وعلى آله وصحبه ومن تبعه باحسان الى يوم الدين.
قال ( ص ) :- كلمتان خفيفتان على اللسان ... ثقيلتان في الميزان ... حبيبتان الى الرحمن ...
" سبحان الله وبحمده ... سبحان الله العظيم "
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