Method

The gram stain

Lesson 14

1. Read the words and put down their Russian equivalents:

differential

characterization

depolarization

rainbow

trout

emulsify

iodine

anticoagulants

2. Master the active vocabulary:

flood – заливать

slide - предметное стекло (микроскопа)

vein - вена; кровеносный сосуд

counterstain - контрастное окрашивание

kidney – почка

anesthesia - anaesthesia анестезия, обезболивание

3. Read the text and define the meaning of new words.

Translate the text.

This is a differential staining method and is the first characterization test applied to all bacterial isolates. It demonstrates bacteria of different types: Gram positive - those which resist depolarization - stain blue/purple.

Gram negative - those which are decolourised - stain red/pink.

The difference in colour reaction is due to the different chemical composition of the cell wall and membrane. This stain will also reveal the general shape of the bacteria.

It can be useful in the diagnosis of Bacterial Kidney Disease (BKD) and rainbow trout fry syndrome (RTFS) using kidney material taken directly from the fish.

1. Take a clean slide and using a sterile loop, emulsify a small amount of material in a drop of sterile saline or distilled water.

2. Allow the slide to air dry, then heat fix it by passing it through a flame three times. Allow slide to cool.

3. Flood the slide with crystal violet for one minute.

4. Holding the slide at a steep angle, wash off the stain with Grams iodine and allow to sit for one minute.

5. Tip off the iodine and pour the alcohol/acetone mixture over the slide from the upper end, so as to cover its whole surface. Repeat until no more colour runs off, then wash gently in water.

6. After shaking off the excess water, flood the slide with the safranin counterstain and leave for approximately two minutes.

7. Wash the slide in water and dry.

8. Examine under X40 objective, then under oil immersion with X100 objective.

4. Read the micro text and define the main idea of the text.

Fish blood may be sampled for disease monitoring or health status analyses in the following areas:

1) haematology (examination of blood cells and blood cell indices), e.g. red blood cell count, haematocrit

2) blood biochemistry e.g. hormones, enzymes, etc.

3) plasma parameters e.g. plasma chlorides (for salt water challenge tests in salmon)

4) serology for pathogen antibodies i.e. salmon pancreas disease virus antibody screening

5) virology and bacteriology: some micro-organisms can be screened for using frank blood.

For biochemistry and hematology an anticoagulant should be used in the blood collection tube and this is normally heparin (heparinised tubes can be purchased), however, the laboratory where samples are being submitted should be consulted for their normal requirements. For serology, bacteriology and virology blood should be taken without anticoagulants. Where fish are large enough, blood samples can be taken under anesthesia i.e. nonlethal sampling. The normal sampling site is from the tail vein and the easiest approach is ventrally at midline towards the vertebral column.

a) Sciences researching blood

b) Blood sampling

c)Blood

5. Give Russian equivalents for the following words and word combinations:

heparin, chloride, the vertebral column, iodine, stain, rainbow trout fry syndrome, sterile loop, cell indices, blood collection tube, normal sampling site, crystal violet, requirement.

6. Give English equivalents for the following words and word combinations:

сафранин, масляная иммерсия, гематокрит, серология, антикоагулянт (вещество, задерживающее свертывание крови), брюшной, патогенные антитела, болезнь, химический состав.

7. Open the brackets using the correct tense form.

1. For virological sampling the fish organs and transport medium/conditions (to determine) by the virus suspected.

2. The laboratory where samples (to submit) should be contacted prior to sampling.

3. It (to demonstrate) bacteria of different types.

4. (To wash) the slide in water and (to dry).

5. The stain (to reveal) the general shape of the bacteria.

6. Blood biochemistry (to examine) hormones.

Дата добавления: 2014-12-26