Chpt 14 Flashcards
Chapter 14
PATHOGENESIS OF INFECTIOUS DISEASES
means the ability to cause
disease.
Pathogenicity
refers to the steps or
mechanisms involved in the development of a
disease.
Pathogenesis
disease caused by a microbe,
and the microbes that cause infectious diseases are
collectively referred to as pathogens.
infectious disease
synonym for infectious disease
mean colonization by a pathogen
Infection
T or F
A person can be infected with a pathogen, and have an infectious disease.
False
A person can be infected with a pathogen, but not have an infectious disease.
Four Periods or Phases in the Course of an
Infectious Disease
• The incubation period
• The prodromal period
• The period of illness
• The convalescent period
Once an infectious process is initiated, the disease
may remain localized or it may spread; examples are pimples, boils and abscesses
Localized Infection
When the infection spreads throughout the body
Systemic Infections
disease is one that has a rapid onset, and is
usually followed by a relatively rapid recovery
acute disease
examples of acute diseases
measles, mumps, and influenza.
slow onset and lasts a long time
chronic disease
Examples of chronic disease
tuberculosis, leprosy, and syphilis
one that comes on more suddenly
than a chronic disease but less suddenly than an acute disease
subacute disease
Examples of subacute disease
bacterial endocarditis
defined as some evidence of a
disease that is experienced by the patient; something that is subjective
symptom of a disease
the patient is experiencing
symptoms
symptomatic disease
the patient
is not experiencing any symptoms.
asymptomatic disease
defined as some type of objective
evidence of a disease
sign of a disease
are
infectious diseases that go
from being symptomatic to
asymptomatic, and then,
later, go back to being
symptomatic.
Latent infections
Examples of latent infection
syphilis and herpes virus
infections such as cold
sores, genital herpes,
and shingles.
sequence of steps in the pathogenesis of
infectious diseases
- Entry of the pathogen into the body.
- Attachment of the pathogen to some tissue(s) within the body
- Multiplication of the pathogen.
- Invasion or spread of the pathogen.
- Evasion of host defenses.
- Damage to host tissue(s).
sometimes used as a synonym for
pathogenic.
virulent
capable of causing disease
– Virulent strains
are not capable of causing disease
avirulent strains
used to express the measure of pathogenicity
virulence
attributes that enable pathogens to
attach, escape destruction, and cause disease
Virulence factors
special molecules on the surface
of pathogens – are considered to be virulence factors because they enable pathogens to recognize and bind to particular host cell receptors.
Adhesins (ligands)
are considered to be virulence
factors because they enable bacteria to attach to
surfaces, such as tissues within the human body.
Pili (bacterial fimbriae)
Pathogens that must live within host cells in order to
survive and multiply are referred to as
obligate intracellular pathogens
live within white blood cells, causing diseases known as
ehrlichiosis and anaplasmosis.
Intraleukocytic pathogens
examples of intraerythrocytic pathogens
Plasmodium spp. (which cause malaria) and
Babesia spp. (which cause babesiosis)
are capable of both an
intracellular and extracellular existence
Facultative intracellular pathogens
Exoenzymes released by bacteria include:
Necrotizing enzymes
Coagulase
Kinases
Hyaluronidase
Collagenase
Hemolysins
Lecithinase
poisonous substances released by various
pathogens.
Toxins
2 types of Toxins
Endotoxins
Exotoxins
• Part of the cell wall structure of Gram-negative
• Can cause serious, adverse physiologic effects such asfever and shock
Endotoxins
Poisonous proteins secreted by a variety of
pathogens
Exotoxins
Some pathogens evade the immune system by changing their surface antigens
Antigenic Variation
Some organisms conceal their foreign nature by coating
Camouflage and Molecular Mimicry
Some pathogens produce IgA protease, an enzyme that destroy some of the host’s antibodies
Destruction of Antibodies
