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Lecture 7
Questions
Pathogen
A microorganism is a pathogen if it is capable of causing disease; however,
some organisms are highly pathogenic (i.e., they often cause disease),
whereas others cause disease rarely. Opportunistic pathogens are those
that rarely, if ever, cause disease in immunocompetent people but can
cause serious infection in immunocompromised patients.
Virulence
Virulence is a quantitative measure of pathogenicity and is measured by the
number of organisms required to cause disease.
Overpowering the host
If the number of organisims are high even though the virulence is low it can
affect and if the no. of org are low but virulence is high then also it can
affect
Asymtomatic infections
Lecture 7 1
, In many instances, a person acquires an organism, but no infectious
disease occurs because the host defenses were successful. Such
asymptomatic infections are very common and are typically recognized by
detecting antibody against the organism in the patient’s serum
Bacteria disease mechanism
Bacteria cause disease by two major mechanisms: (1) toxin
production and (2) invasion and inflammation
Toxins fall in 2 categories exotoxins and endotoxins
Exotoxins(only in gram neg) are polypeptides released by the cell, whereas
endotoxins are lipopolysaccharides (LPS), which form an integral part of
the cell wall
Stages of Infection
(1) Transmission from an external source into the portal of entry.
(2) Evasion of primary host defenses such as skin or stomach acid.
(3) Adherence to mucous membranes, usually by bacterial pili.
(4) Colonization by growth of the bacteria at the site of adherence.
(5) Disease symptoms caused by toxin production or invasion accompanied
by inflammation.
(6) Host responses, both nonspecific and specific (immunity), during steps
3, 4, and 5.
(7) Progression or resolution of the disease.
Formites
. Fomites are inanimate objects, such as towels, that serve as a source of
microorganisms that can cause infectious diseases
Vertical transmission
Bacteria, viruses, and other microbes can also be transmitted from mother
to offspring, a process called vertical transmission. The three modes by
which organisms are transmitted vertically are across the placenta, within
the birth canal during birth, and via breast milk
Reservoir , Vector
Animals are also an important source of organisms that infect humans.
They can be either the source (reservoir) or the mode of transmission
Lecture 7 2
Lecture 7
Questions
Pathogen
A microorganism is a pathogen if it is capable of causing disease; however,
some organisms are highly pathogenic (i.e., they often cause disease),
whereas others cause disease rarely. Opportunistic pathogens are those
that rarely, if ever, cause disease in immunocompetent people but can
cause serious infection in immunocompromised patients.
Virulence
Virulence is a quantitative measure of pathogenicity and is measured by the
number of organisms required to cause disease.
Overpowering the host
If the number of organisims are high even though the virulence is low it can
affect and if the no. of org are low but virulence is high then also it can
affect
Asymtomatic infections
Lecture 7 1
, In many instances, a person acquires an organism, but no infectious
disease occurs because the host defenses were successful. Such
asymptomatic infections are very common and are typically recognized by
detecting antibody against the organism in the patient’s serum
Bacteria disease mechanism
Bacteria cause disease by two major mechanisms: (1) toxin
production and (2) invasion and inflammation
Toxins fall in 2 categories exotoxins and endotoxins
Exotoxins(only in gram neg) are polypeptides released by the cell, whereas
endotoxins are lipopolysaccharides (LPS), which form an integral part of
the cell wall
Stages of Infection
(1) Transmission from an external source into the portal of entry.
(2) Evasion of primary host defenses such as skin or stomach acid.
(3) Adherence to mucous membranes, usually by bacterial pili.
(4) Colonization by growth of the bacteria at the site of adherence.
(5) Disease symptoms caused by toxin production or invasion accompanied
by inflammation.
(6) Host responses, both nonspecific and specific (immunity), during steps
3, 4, and 5.
(7) Progression or resolution of the disease.
Formites
. Fomites are inanimate objects, such as towels, that serve as a source of
microorganisms that can cause infectious diseases
Vertical transmission
Bacteria, viruses, and other microbes can also be transmitted from mother
to offspring, a process called vertical transmission. The three modes by
which organisms are transmitted vertically are across the placenta, within
the birth canal during birth, and via breast milk
Reservoir , Vector
Animals are also an important source of organisms that infect humans.
They can be either the source (reservoir) or the mode of transmission
Lecture 7 2
