MICROPARA (14): Pathogenesis of Infectious Diseases

Pathogen

a microbe

capable of causing

disease

Pathology

the study of the

structural

and functional

manifestations of disease

disease

The prefix path- comes

from the Greek word

"pathos,

" meaning

Pathologist

a physician

who has specialized in

pathology

Pathogenicity

the ability to cause

disease

Pathogenesis

the steps or mechanisms

involved in the

development of a

disease

infectious disease

is a disease

caused by a microbe, and the microbes

that cause infectious diseases are

collectively referred to as pathogens.

Infection

to mean colonization by a pathogen; the pathogen may or may not go on to cause disease.

Why Infection Does Not Always Occur

Anatomic site

Receptor site

Antibacterial Factors

Competition with Indigenous Microflora

Bacteriocins

individual's nutritional and overall health status

Immunity

Phagocytic white

blood cells

Bacteriocins

Indigenous

microflora at the

site may produce

antibacterial

factors (proteins

called

Phagocytes

present in the blood

and other tissues

may engulf and

destroy the

pathogen

Four Periods or Phases in the Course of an Infectious Disease

1. The incubation

period

2. The prodromal

period

3. The period of

illness

-The convalescent/Disability/Death period

Localized Infection

Once an infectious

process is initiated,

the disease may

remain localized to

one site or it may

spread. Pimples,

boils, and abscesses

Systemic Infection

When the infection has spread

throughout the body, it is referred

to as either a systemic infection or

a generalized infection.

Miliary tuberculosis

Mycobacterium tuberculosis, may

spread to many internal organs, a

condition known as

acute disease

has a rapid onset,

usually followed

by a relatively

rapid recovery;

measles, mumps,

and influenza are

examples.

Subacute disease

Some diseases, such as

bacterial endocarditis,

come on more suddenly

than a chronic disease, but less suddenly than an acute disease; they are referred to as

bacterial endocarditis

chronic disease

has an insidious

(slow) onset and

lasts a long time;

examples are

tuberculosis, leprosy

(Hansen disease),

and syphilis.

symptom of a disease

is defined as some evidence of a disease that is experienced or perceived by the

patient; something that is subjective.

Symptomatic

(or clinical

disease) is a disease in which the patient

is experiencing symptoms.

Asymptomatic disease

(or subclinical

disease) is a disease that the patient is unaware of because he or she is not

experiencing any symptoms.

Sign of a disease

is defined as some

type of objective evidence of a disease

that the physician perceives; for example

abnormal heart or breath sounds, blood

pressure, pulse rate, and laboratory

results etc.

Latent Infection

from the Greek

word "latens,

" meaning to lie

hidden. Herpes virus infections, such as cold sores (fever blisters),

genital herpes infections, and shingles

primary infection

first disease is referred to as a

secondary infection

the second disease is

referred to as a

Steps in the Pathogenesis of Infectious

Disease

1. Entry of the pathogen into the body.

2. Attachment of the pathogen to

some tissue(s) within the body.

3.Multiplication of the pathogen.

4.Invasion or spread of the pathogen.

5.Evasion of host defenses.

6.Damage to host tissue(s).

Virulent (pathogenic) strains

are capable of causing disease

avirulent (nonpathogenic)

strains

particular species that is not capable of causing disease

10

only takes about __

Shigella cells to cause shigellosis,

100

and 1,000

It takes between ___Salmonella cells to cause salmonellosis.