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Section | III Microbiology 321
SHORT NOTE
Q. 1. Define bacteraemia, septicaemia and pyaemia. 2. Septicaemia is the condition where bacteria circulate
and multiply in the blood and form toxic products caus-
Ans.
ing high swing type of fever.
1. The circulation of bacteria in the blood is known as 3. Pyaemia is a condition where pyogenic bacteria pro-
bacteraemia. The bacteraemia of greater severity and duce septicaemia with multiple abscesses in the internal
longer duration is seen during generalized infections organs such as the spleen, liver and kidney.
like typhoid fever.
Part III
Medical Virology
Topic 27
General Properties of Viruses
SHORT ESSAYS
Q. 1. Classification of viruses
Ans. The classification of major virus groups based on the
type of nucleic acid they possess and the genera included
under each group are as follows:
1. DNA Viruses 2. RNA Viruses
a. Pox viridae family a. Picorna viridae family: Three genera
i. Several genera i. Entero virus—polio, coxsackie, echo, etc.
b. Herpes viridae family: Only one genus ii. Rhinovirus—of human, bovine and equine.
i. Herpesvirus iii. Hepato virus—hepatitis A virus
c. Adeno viridae family has two genera b. Orthomyxo viridae family
i. Mastadenovirus (mammalian adenoviruses) i. only one genus Influenzavirus
ii. Aviadenovirus (adenoviruses of birds) c. Paramyxo viridae family: Three genera
d. Papova viridae family: Two genera i. paramyxovirus—Newcastle disease virus, mumps virus
i. Papilloma virus and parainfluenza viruses of humans, other mammals
ii. Polyoma virus and birds
e. Parvo viridae family: Three genera ii. Morbilli virus—measles, canine distemper, rinderpest
i. Parvo virus and related viruses.
ii. Adenosatello virus iii. Pneumovirus—respiratory syncytial virus of humans
iii. Denso virus and related viruses
f. Hepadna viridae family d. Toga viridae family: Three genera (Alpha, Rubi and Pesti
i. Human hepatitis type B virus and related virus)
viruses of animals and birds e. Flavi viridae family
f. Bunya viridae family
g. Arena viridae family: Only one genus Arena virus
h. Rhabdo viridae family: Two genera
i. Vesiculo virus
ii. Lyssa virus—rabies and related viruses
i. Rheo viridae family
j. Retro viridae family
k. Corona viridae family
l. Calici viridae family
m. Filo viridae family
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322 Quick Review Series: BDS 2nd Year
Q. 2. Cultivation of virus Organ culture
Ans. Viruses are obligate intracellular parasites. They can- l Small bits of organs can be maintained in vitro for days
not be grown on any inanimate culture medium. and weeks preserving their original architecture and
function.
They can be cultivated by l It is indicated mainly for highly specialized parasites of
a. inoculation into animals, certain organs.
b. embryonated eggs or Example: The tracheal ring organ culture for isolation of
c. tissue cultures. corona virus a respiratory pathogen.
ANIMAL INOCULATION
Explant culture
l Animal inoculation is used for primary isolation of cer-
l Fragments of minced tissue can be grown as explants
tain viruses and for studies of the pathogenesis, epide-
embedded in plasma clots.
miology, immune response and oncogenesis.
l They may also be cultivated in suspensions. This was
l Disadvantages of animal inoculation are that immunity
originally known as tissue culture.
may interfere with the viral growth and that animal
l This method is now rarely used.
often harbours latent viruses.
Example: Adenoid tissue explant cultures were used for
isolation of adenoviruses.
INOCULATION INTO EMBRYONATED
EGGS
Cell culture
Goodpasture (1931) was first to use the embryonated hen’s
l This is the culture routinely employed nowadays for
egg for cultivation of viruses.
growing viruses.
The embryonated eggs offer several sites for cultivation
l Tissues are dissociated into the component cells by the
of viruses as follows:
action of proteolytic enzymes such as trypsin and me-
Inoculation on the Chorioallantoic Membrane chanical shaking.
(CAM) of Chick Embryo l The cells are washed, counted and suspended in a
growth medium.
Produces visible lesions (pocks). Pocks produced by differ-
l The essential constituents of growth medium for tissue
ent viruses have different morphology. A single virion can
culture are basically physiological amounts of essential
produce one pock. Thus number of pocks indicates number
amino acids and vitamins, salts, glucose, and a buffering
of viruses present in the inoculum.
system generally consisting of bicarbonate in equilib-
Pock counting can be used for the assay of pock form-
rium with atmosphere containing 5% CO2.
ing viruses such as variola or vaccinia.
This is supplemented with up to 5% calf or fetal calf serum.
Inoculation into Allantoic Cavity Antibiotics are added to prevent the growth of bacterial
Inoculation into the allantoic cavity provides rich yield of contaminants and phenol red as indicator. Such media will
influenza virus. enable most of the cell types to multiply with a division
The allantoic inoculation is mainly used for growing influ- time of 24–48 h.
enza virus for vaccine production. The yellow fever and rabies
l This cell suspension is dispensed in bottles, tubes or
vaccines are other chick embryo vaccines in routine use.
Petri dishes. The cells adhere to the glass surface and on
Inoculation into the Amniotic Sac incubation, divide to form a confluent monolayer sheet
of cells covering the surface within 1 week.
It is mainly employed for primary isolation of influenza virus.
l Cell culture tubes are incubated in a sloped horizontal
Yolk Sac Inoculation position either as stationary culture or rolled in special
roller drums to produce better aeration. Some fastidious
It is inoculated for cultivation of some viruses and some
viruses grow only in such roller cultures.
bacteria like chlamydiae and rickettsiae.
l Based on their origin, chromosomal characters and the
number of generation through which they can be main-
TISSUE CULTURES tained.
There are three types of tissue culture as follows: The cell cultures are classified into three types as follows:
1. Organ culture 1. Primary cells cultures
2. Explant culture 2. Diploid cell strains
3. Cell culture 3. Continuous cell lines
Section | III Microbiology 321
SHORT NOTE
Q. 1. Define bacteraemia, septicaemia and pyaemia. 2. Septicaemia is the condition where bacteria circulate
and multiply in the blood and form toxic products caus-
Ans.
ing high swing type of fever.
1. The circulation of bacteria in the blood is known as 3. Pyaemia is a condition where pyogenic bacteria pro-
bacteraemia. The bacteraemia of greater severity and duce septicaemia with multiple abscesses in the internal
longer duration is seen during generalized infections organs such as the spleen, liver and kidney.
like typhoid fever.
Part III
Medical Virology
Topic 27
General Properties of Viruses
SHORT ESSAYS
Q. 1. Classification of viruses
Ans. The classification of major virus groups based on the
type of nucleic acid they possess and the genera included
under each group are as follows:
1. DNA Viruses 2. RNA Viruses
a. Pox viridae family a. Picorna viridae family: Three genera
i. Several genera i. Entero virus—polio, coxsackie, echo, etc.
b. Herpes viridae family: Only one genus ii. Rhinovirus—of human, bovine and equine.
i. Herpesvirus iii. Hepato virus—hepatitis A virus
c. Adeno viridae family has two genera b. Orthomyxo viridae family
i. Mastadenovirus (mammalian adenoviruses) i. only one genus Influenzavirus
ii. Aviadenovirus (adenoviruses of birds) c. Paramyxo viridae family: Three genera
d. Papova viridae family: Two genera i. paramyxovirus—Newcastle disease virus, mumps virus
i. Papilloma virus and parainfluenza viruses of humans, other mammals
ii. Polyoma virus and birds
e. Parvo viridae family: Three genera ii. Morbilli virus—measles, canine distemper, rinderpest
i. Parvo virus and related viruses.
ii. Adenosatello virus iii. Pneumovirus—respiratory syncytial virus of humans
iii. Denso virus and related viruses
f. Hepadna viridae family d. Toga viridae family: Three genera (Alpha, Rubi and Pesti
i. Human hepatitis type B virus and related virus)
viruses of animals and birds e. Flavi viridae family
f. Bunya viridae family
g. Arena viridae family: Only one genus Arena virus
h. Rhabdo viridae family: Two genera
i. Vesiculo virus
ii. Lyssa virus—rabies and related viruses
i. Rheo viridae family
j. Retro viridae family
k. Corona viridae family
l. Calici viridae family
m. Filo viridae family
, Click here to Visit - www.thedentalhub.org.in
322 Quick Review Series: BDS 2nd Year
Q. 2. Cultivation of virus Organ culture
Ans. Viruses are obligate intracellular parasites. They can- l Small bits of organs can be maintained in vitro for days
not be grown on any inanimate culture medium. and weeks preserving their original architecture and
function.
They can be cultivated by l It is indicated mainly for highly specialized parasites of
a. inoculation into animals, certain organs.
b. embryonated eggs or Example: The tracheal ring organ culture for isolation of
c. tissue cultures. corona virus a respiratory pathogen.
ANIMAL INOCULATION
Explant culture
l Animal inoculation is used for primary isolation of cer-
l Fragments of minced tissue can be grown as explants
tain viruses and for studies of the pathogenesis, epide-
embedded in plasma clots.
miology, immune response and oncogenesis.
l They may also be cultivated in suspensions. This was
l Disadvantages of animal inoculation are that immunity
originally known as tissue culture.
may interfere with the viral growth and that animal
l This method is now rarely used.
often harbours latent viruses.
Example: Adenoid tissue explant cultures were used for
isolation of adenoviruses.
INOCULATION INTO EMBRYONATED
EGGS
Cell culture
Goodpasture (1931) was first to use the embryonated hen’s
l This is the culture routinely employed nowadays for
egg for cultivation of viruses.
growing viruses.
The embryonated eggs offer several sites for cultivation
l Tissues are dissociated into the component cells by the
of viruses as follows:
action of proteolytic enzymes such as trypsin and me-
Inoculation on the Chorioallantoic Membrane chanical shaking.
(CAM) of Chick Embryo l The cells are washed, counted and suspended in a
growth medium.
Produces visible lesions (pocks). Pocks produced by differ-
l The essential constituents of growth medium for tissue
ent viruses have different morphology. A single virion can
culture are basically physiological amounts of essential
produce one pock. Thus number of pocks indicates number
amino acids and vitamins, salts, glucose, and a buffering
of viruses present in the inoculum.
system generally consisting of bicarbonate in equilib-
Pock counting can be used for the assay of pock form-
rium with atmosphere containing 5% CO2.
ing viruses such as variola or vaccinia.
This is supplemented with up to 5% calf or fetal calf serum.
Inoculation into Allantoic Cavity Antibiotics are added to prevent the growth of bacterial
Inoculation into the allantoic cavity provides rich yield of contaminants and phenol red as indicator. Such media will
influenza virus. enable most of the cell types to multiply with a division
The allantoic inoculation is mainly used for growing influ- time of 24–48 h.
enza virus for vaccine production. The yellow fever and rabies
l This cell suspension is dispensed in bottles, tubes or
vaccines are other chick embryo vaccines in routine use.
Petri dishes. The cells adhere to the glass surface and on
Inoculation into the Amniotic Sac incubation, divide to form a confluent monolayer sheet
of cells covering the surface within 1 week.
It is mainly employed for primary isolation of influenza virus.
l Cell culture tubes are incubated in a sloped horizontal
Yolk Sac Inoculation position either as stationary culture or rolled in special
roller drums to produce better aeration. Some fastidious
It is inoculated for cultivation of some viruses and some
viruses grow only in such roller cultures.
bacteria like chlamydiae and rickettsiae.
l Based on their origin, chromosomal characters and the
number of generation through which they can be main-
TISSUE CULTURES tained.
There are three types of tissue culture as follows: The cell cultures are classified into three types as follows:
1. Organ culture 1. Primary cells cultures
2. Explant culture 2. Diploid cell strains
3. Cell culture 3. Continuous cell lines
