virus observation (lab diagnosis ).

1. virus observation (Laboratory diagnosis )
By
Assist Lecturer
Mawahb Hatem mons
Virology Lab 3
3th class

2. There are four methods to diagnosis of viral infection:
1- Direct detection of virus/physical method
2- Indirect detection / biological method (virus isolation)
3- Immunology (detection of antibody)
4- Detection of viral nucleic acid (molecular techniques)

3. 1. physical methods (microscope).
• 1- Electron microscopy (EM)
• is a technique used for obtaining high resolution images of biological And
non-biological specimens up to two million times than light microscope.
 observation of viruses by microscope.
Two types of microscopes used for observation of viruses:
a. directly by electron microscope
b. indirectly by inverted microscope.

4.  The high resolution of EM images results from the use of two
things:
1. electrons beams (as the source of illuminating radiation) which have very short
wavelengths; 100,000 times shorter than that of visible light photons.
2. magnetic lenses.
 The Electron microscopes are used in
biomedical research to investigate the detailed
structure
of
tissues,
cells,
macromolecular
organelles and
complexes (e.g.
and
proteins, nucleic acid, lipids
carbs).

5.  Types of electron microscope
1. Transmission Electron Microscope (TEM)
In a transmission electron microscope or TEM, a beam of electrons hits a very thin
sample (usually less than 100 nm thick). The electrons are transmitted through the sample
(Figure below). After the sample, the electrons hit a fluorescent screen that forms an image
with the electrons that were transmitte
d.
Transmission Electron Microscope. A beam of electrons is focused on a sample. The electrons
pass through the sample to form an image on a fluorescent screen.

6. The image above was captured with a transmission electron microscope. you can see the
spikes on the surface of the virus (which gives the coronavirus its name, meaning 'crown').

7. 2. Scanning Electron Microscope (SEM)
In a scanning electron microscope or SEM, a beam of electrons scans the surface of a
sample (Figure below). The electrons interact with the material in a way that triggers the
emission of secondary electrons. These secondary electrons are captured by a detector,
which forms an image of the surface of the sample.
A Scanning Electron Microscope focuses a beam of electrons on the surface of a sample. Secondary electrons are
emitted from the sample surface. A detector is used to form an image from the secondary electrons.

8. What you're seeing above is a scanning electron microscope image in false color, showing the
COVID-19 virus from a patient in the US; the viral particles are colored yellow as it emerges from the
surface of a cell, which is colored blue and pink.

9. 3. scanning transmission electron microscope (STEM)
A scanning transmission electron microscope or STEM combines the capabilities of
both an SEM and a TEM. The electron beam is transmitted across the sample to create
an image (TEM) while it also scans a small region on the sample (SEM).
Generally, the image resolution of an SEM
is lower than that of a TEM. …why?
because the SEM images the surface of a sample rather
than its interior. This reduces the need for extensive
sample preparation to thin the specimen to electron
transparency as in TEM

11. Fig 3 viral (bacteriophage)
under electron microscope
Figure 4 immunoflorecent electron
microscope
Figure 5 immuno electron
microscope

12. 2- Indirect detection / biological method (virus isolation)
* virus isolation: There are three methods are used for isolation of viruses: -
a. Animals inoculation. b. Chick embryo.

13. c. Cell culture.

14. 3-Immunological techniques: (detection of antibody)
Immunological techniques are used to diagnose virus diseases. This is done by
demonstrating an antigen-antibody reaction of virus infection. There are several
serological and immunological methods and these methods include:
-ELISA
-Complement fixation (CF)
-Latex Agglutination
- Haemagglutination Assay (HA) and Haemagglutination Inhibition (HI)
-Virus neutralization
-Immunofluorescence techniques (IF)
-Agar Gel diffusion and Agar Gel Precipitation

15. The principles of these assays are fundamentally the same, they
depend upon antibody-antigen interactions and consist of a known
virus or viral protein, a patient sample (usually serum), and an
indicator. If antibodies are present in the patient’s serum, they will
bind to the virus. If no antibodies are present, no binding will occur.
The indicator is observed to determine whether the sample is
positive or negative for antibodies.

16. Rapid test

17. 4- Molecular Methods
Molecular methods do not rely on the presence of a live virus like
virus isolation procedures. These methods detect a piece of the viral
genome, making them more sensitive for the detection of viruses. The
technique that has probably had the greatest impact on the field of
a- Polymerase chain reaction (PCR, identification of DNA)
b- Reverse transcriptase polymerase chain reaction (RT-PCR,
identification of RNA)virology are