Download - ISpatula

Microbiology- pharmacy –
lecture 10
of these microorganisms (bergey’s manual
is used for microorganisms, like
pharmacopeia is used for drugs)
In the classification of microorganisms we
have key elements that we use to identify
which type we’re dealing with;
Examples:
-spirochaete bacterium  Treponema
pallidum which causes syphilis disease
First we ask about Its Microscopic
morphology (shape , motility), but this
doesn’t give us enough information so as
to find out what type of microorganism it
is, so we start with biochemical properties
(gram reaction , aerobic or non-aerobic),
and then the molecular properties (PCR,
DNA hybridization)which give us the best
results, we can use phage typing, and
serological tests (antibody-antigen).
•
•
•
-Aerobic motile helical gram-negative
bacteria  Helicobacter (H.pylori) which
causes peptic ulcer, Campylobacter (both
bacteria related to GI disease)
- Gram-negative aerobic rods and cocci 
pseudomonas : burn infection, UTI
Pseudomonas doesn’t need a lot of
nutrition, it is non fastidious, its enzymes
are complex and it is able to synthesize
nutrients; that’s why its capable of living
in water even though water has little
amount of nutrients.
Most macroscopic organisms can
preliminarily
be
classified
according to observable structural
characteristics but many of the
bacteria have similar structures
(when it is found in a burn infection, it
forms a green color,,
Separating the bacteria according
to cell shape, size, and arrangement
does not produce a very useful
classification system Nor does the
presence of specific structures such
as flagella, endospores, or capsules
It can also be found in eye drops and eye
solutions if not handled carefully, which
might eventually cause eye infection and
might cause blindness). It is a very
important gram negative problematic
microorganism
the Gram stain, were among the
first
properties
other
than
morphology to be used to classify
bacteria . Other properties now in
use include features related to
growth, nutritional requirements,
physiology, biochemistry, genetics,
and molecular analysis. These
features include properties of DNA
and proteins
An example of Gram negative rods:
Escherichia coli which is the main cause if
UTI infections !! --> Escherichia coli is the
main causitive agent for UTI (urinary tract
infections)
- some types of E.coli are found in the GI
as part oof the normal flora. nevertheless it
could cause unirary tract infection
##REMEMBER## UTI infection  E.
coli.
Accordingly we have Bergey’s manual
which
lists
characteristics
of
microorganisms and disease and products
1
- Neisseria: Neisseria gonorrhoeae causes
STD gonorrhea
Irregular non spore forming gram positive
bacteria: dyfteria ‫مرض الخانوق‬, propioni
acne bacteria
- salmonella, shigella, and other types of
microorganisms, and anaerobic gram
negative rods “bacteroides” that is found in
the GI and can cause infection in different
sites of the body
- Mycobacteria is an acid fast bacteria
-Nocardia:
“Obligate intracellular microorganism”
(has to be inside a cell in order for it to
grow)  viruses : they are called obligate
intracellular parasites
by
(look at the table , memorize the ticked
lines )
Rickettsiae and Chlamydiae, are “Obligate
intracellular microorganism” and contain
rather unusual organisms that have
different Methods of reproduction other
than the conjugation and binary fission.
Chlamydia may be found in the form of an
elementary body and a reticulate body; a
reticulate body is highly involved in the
process of replication and growth of these
bacteria
Mycoplasma; it is a type of bacteria that
lack the cell wall. It contains steroids in its
cytoplasmic membrane; an important cause
of atypical pneumonia
cocci:
caused
Actinomyces and Streptomyces: they are
bacteria but they divide in more than one
plane, filamentous growth, we use it to
form over 500 antibiotics , they look like
fungus but they are not.
Aerobic gram negative bacteria may be
present in the GI tract and can cause
infections.
Gram positive
streptococcus
nocardioform,
staphylococcus,
-Endospore- forming
gram positive
bacteria : Bacillus that causes anthrax
- Anaerobes and endospores-forming:
clostridium (clostridium tetani, clostridium
perfringens)
-Regular non spore forming gram positive
bacteria: lysteria
2
*DNA:
- single-stranded
- double- stranded
* RNA:
- single-stranded:
(positive sense ssRNA, or negative
sense ssRNA )
-double-stranded RNA
(classification according to their
genetic material)
**Viruses **
General
viruses:
-
-
-
-
-
characteristics
of
Viruses are microorganisms ‫(بين‬
)‫الحياة والال حياة‬
They can replicate, or multiply,
only inside a living host cell
(obligate intracellular parasites)
They can’t be seen by light
microscopes , we need electron
microscopes to be able to see them
Some viruses cause infections to
humans
only,
some
cause
infections to animals only, and
some cause both, and these viruses
are transferred from animals to
humans and the other way around
as well,.
When they invade susceptible host
cells, viruses display some
properties of living organisms and
so appear to be on borderline
between living and nonliving
Viruses contain DNA or RNA but
never both
•
Some viruses are composed of only
the genetic material, surrounded
with a capsid
Other viruses have another layer
that surrounds the capsid; called
the
envelope
(additional
surrounding
lipid
bilayer
membrane)
Components of Viruses:



capsid: Surrounding protein coat
core: that contains the genetic
material which is either the DNA
or the RNA
Major groups of viruses are
distinguished first by their nucleic
acid content as either DNA or RNA
Because most eukaryotic cells do
not have the enzymes to copy viral
RNA molecules, the RNA viruses
must either carry the enzymes or
have the genes for those enzymes
as part of their genome. (VERY
IMPORTANT)
-
3
Naked viruses: are viruses with
a nucleocapsid and no envelope
Enveloped viruses: viruses with
additional envelope (they have
genes for forming an envelope)
(classification according to
their structure)

On the other hand, a naked virus
activates the immune system
because the body recognizes a
foreign object (from its outer
membrane),
nevertheless;
the
protein that surrounds naked
viruses is very tough and is very
resistant to chemicals, that’s why
they are found in the environment
in large numbers.
-Virion: A complete virus particle
(in a naked virus; the virion is the
genetic material with the capsid.
In an enveloped virus; a virion is
the genetic material with the capsid
and envelope)
 A capsid is composed of
polymers
of
capsomeres
(polymer of protein)
Protrusions called spikes are found
on an envelope (attachment site)
•
•
•
The enveloped viruses are very
sensitive
to
antimicrobial
treatments or to virusoid treatment
.
Viruses use their nucleic acids
(genome) to replicate themselves in
host cells
Capsids also play a key role in the
attachment of some-naked- viruses.
Each capsid is composed of protein
subunits
called
capsomeres.
(capsomeres have different shapes,
which means that viruses can be
classified according to the shape of
the capsid or the capsomere)
Enveloped viruses have a typical
bilayer membrane outside their
capsids and acquire their envelope
after they are assembled in a host
cell and “bud” through host’s
membrane (we mentioned in a
previous lecture that yeasts also
undergo “budding”)
*budding: the virus forms its
envelope though the process of
budding out of the host cell .
Which means that the outer
membrane is very similar to a
human cell membrane, that’s why
it is very difficult for the immune
system to recognize such a virus.
- It is very resistant to the
immune system because of the
budding process
Lets take “hepatitis A” for an
example; hepatitis A is transferred
by food, it is a naked virus, and
considered one of the most
resistant viruses to disinfectants
and antimicrobial agents because it
has a capsid.
HIV & hepatitis B are more
dangerous than hepatitis B because
they are enveloped;
Hepatitis B is more dangerous
because it causes chronic infection
and might cause cancer, while
hepatitis A causes acute infection.
Hepatitis B has little resistance to
antimicrobial agents, that’s why it
is considered fragile,
For an instance if we have blood
spillage containing hepatitis B and
we put an antimicrobial agent, it
will kill the virus, while if we had
hepatitis A in the blood, it would
be very hard to kill it using the
antimicrobial
agent.
(because
hepatitis A has a capsid, and
hepatitis B has an envelope)
4
NOTE: hepatitis A activates the
immune system more than hepatitis
B
-As seen in the graph, viruses fit
inside the bacteria which means
they are very small, some are even
as tiny as a ribosome
------------------------------------------•
Nucleocapsid comprises the viral
genome together with the capsid
•
Naked viruses: viruses with a
nucleocapsid and no envelope
•
Spikes: projections that extend
from the viral envelope that may
aid in attachment to the host cell
(made out of glycoproteins)
•
Glycoprotein:
these surface
projections serve to attach virions
to specific receptor sites on
susceptible host cell surfaces
•
Envelopes help the virus in evading
detection by the host’s immune
system
-The triangled structure is
capsomere (it is polyhedral)
a
-The structure that looks like a
spaceship is a bacteriophage which
is a virus that causes an infection to
bacteria, it has a core and tails
(resembles a spider), it ejects its
genetic material into the bacteria.
Virus shape:
•
Some viruses are variable in shape,
but most have a specific shape that
is determined by the capsomeres or
envelope (most envelopes are
spherical)
•
Helical capsid:
consists of a
ribbonlike protein that forms a
spiral around the nucleic acid
•
Polyhedral capsid:
many-sided,
and one of the most common
polyhedral capsid shapes is the
icosahedron (20 triangle faces)
•
Complex capsid: a combination
between helical and icosahedral
•
Some viruses have a bullet-shaped
capsid and some are spherical
Viral sizes and shapes
- They are too tiny and can’t be
seen by light microscope
- Variations in shapes and sizes of
viruses compared with a bacterial
cell, an animal cell, and a
eukaryotic ribosome
Classification of viruses:
Studying viruses is harder, because the
growth of viruses has to happen in a
tissue culture unlike bacteria which
could grow if we put it under optimum
temp optimum PH and optimum
nutrition.
5
Viruses need live cells in order to
grow and replicate, that’s why –
compared to bacteria- we have very
little information about viruses;
The classification of viruses is simpler
than that of bacteria (‫ )التقسيمات‬because
we don’t have enough knowledge to
use complicated classifications
•
•
Historically, virologists classified
viruses by the type of host/host
structures they infected (human
virus, animal virus, and plant
virus)/(skin virus)
Bacteriophages:
cells
In 1977 of the International
Committee on Taxonomy of
Viruses (ICTV) formed to establish
a single, universal taxonomic
scheme for viruses
•
They concluded that it is very
difficult to classify viruses
according to typical taxonomical
categories, it is not as easy as
classifying bacteria
•
Therefore:
-
-
infect bacterial
-
•
Plant viruses infect plant cells
•
Animal viruses are subgrouped by
the tissues they attack:
1. Dermotrophic:
skin
•
-
if they infect the
2. Neurotrophic: if they infect nerve
tissue
Discoveries into biochemical and
molecular allowed for viruses to be
classified based on:
1. Type and structure of their nucleic
acids
family
is
the
highest
taxonomical category by the
ICTV
Viral genera have been
established
Species is the common name of
the virus (English name)
Example: family: rhabdoviridae
Genus: Lyssavirus
, species: rabies (English name)
Family: Coronaviridae:
Coronavirus got their name
(corona, Latin for “crown”)
---------------------------------------------*single- stranded RNA are
major
*double- stranded RNA are less
* double- stranded DNA are
major
* single-stranded DNA are less
RNA viruses:
2. Method of replication
•
Many ssRNA viruses contain positive
(+) sense RNA, and during an
infection acts like mRNA and can be
translated by host’s ribosomes
•
Other ssRNA viruses have negative (-)
sense RNA and the RNA acts as a
3. Host range
4. Other physical
characteristics
and
chemical
6
template during transcription to make
a complementary (+) sense mRNA
•
enters through the mouth
(that’s why the vaccine is
given orally, since the form
of administration of this
virus is orally- ‫)المطعوم الثالثي‬
epidemic
polio
is
transferred by water and
food
 Rhino virus (common cold
virus)
and hepatitis A
belong to the same group :
positive sense RNA
 Togaviridae family: rubella:
German measles : ‫الحصبة‬
‫ األلمانية‬: naked virus: very
contagious because it is less
fragile
since
it
can
withstand
environmental
conditions
Negative (-) sense RNA must carry an
RNA polymerase within the virion
 positive sense ssRNA: act
as messenger RNA: undergoes
translation
by
ribosomes
forming proteins of the capsid
 Negative sense ssRNA :
does
not
undergo
translation: instead it forms
complementary
RNA
(positive
sense)
using
reverse transcriptase, the
positive
sense
RNA(messenger
RNA)
then undergoes translation
to proteins
 Example: -positive sense:
picornaviridae family:very
small, naked, polyhedral,
(+) sense RNA viruses,
include:
enteroviruses
(related to the GI tract,)
rhinoviruses
and
hepatoviruses (related to the
liver)
 As we said earlier: hepatitis
A is a naked virus, and
hepatitis B is enveloped;
and it causes cancer
(anything that causes cancer
has DNA as its genetic
material), therefore we
cannot say that hepatitis
A,B,&C belong to the same
family, since they are
completely different and
they differ in their genetic
material, and differ in being
enveloped or naked
 Poliovirus : enterovirus:
‫مسبب شلل األطفال‬:
 Retroviruses(retroviridi):
“retro= bacteria that have
reverse transcriptase”
They are enveloped viruses
that have two complete
copies of (+) sense RNA.
They also contain the
enzyme
reverse
transcriptase, which uses
the viral RNA to form a
complementary strand of
DNA, which is then
replicated to form a dsDNA
(such as HIV virus and
human
leukemia
virus(which is a type of
cancer:
cancer
means
abnormal growth of cells; it
can be caused by viruses
when a virus injects its
genetic material into a
human cell which leads to
abnormal growth,
7
in order for that to happen,
the genetic material of both
the virus and the human
should be the same : double
stranded DNA ))
vaccine contains antigens
from influenza A & B
viruses)
 **examples on double
stranded RNA viruses:
 Any virus that causes
cancer has to have double
stranded DNA
 Retroviruses
don’t
originally have dsDNA but
the presense of reverse
transcriptase
leads
to
forming dsDNA
dsRNA ; least number
(less than ssRNA)
 Reoviruses : cause upper
respiratory infections
DNA viruses: ( dsDNA more than
ssDNA)
 **Examples: - negative
sense RNA:
 Paramyxoviruses: myxo =
mucous membrane; like
measles (‫)الحصبة‬
 Rhabdoviruse : (-) sense
RNA virus group consists
of
medium-sized,
enveloped viruses.
The
capsid is helical and makes
the virus nearly rod or
bullet-shaped. Contain an
RNA-dependent
RNA
polymerase that uses the (-)
sense strand to form a (+)
sense strand that serves as a
mRNA and template for
synthesis of new viral RNA
‫ مسبب مرض الكأل‬rhabidis
 Orthomyxoviruses:
“myxo”
=
mucous
membrane, medium-sized,
enveloped, (-) sense that
vary in
shape
from
spherical to helical. Their
genome is segmented into
eight pieces (mutation to
influenza A and B happens
in these segments, the
*double stranded:
 adenoviridae : adenovirus,
which causes
human
respiratory infection
 Herpesviruses:
herpes
disease(oral & genital),
chickenpox(varicella)
and shingles(zoster)-( ‫الحزام‬
‫)الناري‬
,smallpox
and
cowpox
 Papovaviruses: Named for
three related viruses, the
papilloma, polyoma, and
vacuolating
viruses,
papillomaviruses
cause
both benign and malignant
warts in humans, 90% of
cervical cancer in females is
caused by papilloma virus
8, which has double
stranded DNA. A new
vaccine is being used in the
USA so as to prevent
females from being infected
with papillomavirus which
causes cancer and opposing
death. Papillomavirus is
considered
a
sexually
transmitted disease (STD)
8
 hepadnaviruses
:Their
name comes from the
infection of the liver—
hepatitis—by a DNA virus.
In humans, the hepatitisB
virus causes hepatitis B,
which can progress to liver
cancer
next lecture we will talk
about virus replication..
good luck all :)
done by: Lana Hammad
9