1.2 Bacteria and Diseases

• Mechanical: Invasiveness

• Chemical: Toxin Production

• Immunology

How Organisms Produce Disease

Mechanical: Invasiveness

Directly damaging tissues or body surfaces.

Invasion of the epithelial surface and penetration into deeper tissues.

Colonization

Ability of the invading organism to enter the susceptible host and establish itself in the portal of entry

Staphylococcus Aureus

secretes coagulase enzyme

Mycobacterium Tuberculosis

phagosome-lysosome fusion

Neisseria Gonorrhoeae

multiplies within the host cell and is extruded to infect other host cells.

Causes direct destruction of the host cells

Clostridium Perfringens

produces collagenase

Gas Gangrene

Clostridium perfringens - produces collagenase development of disease called ___________

Toxins

poisonous substances that contribute to disease production

• Endotoxin

• Exotoxin

Types of Chemical: Toxin Production

Endotoxin

Integral components of the outer membrane of Gram-negative bacteria.

Lipopolysaccharide

Endotoxin
- The specific component responsible for the activity is ___________

• Lipid A

• Polysaccharide

lipopolysaccharide (LPS); divided into two components:

Lipid A

Endotoxin: Toxic Activity

Polysaccharide

Endotoxin: Antigenic

Lysis

Endotoxin
- Exert effect: when bacteria dies, cell walls undergo ______

True

ALL endotoxins produce similar signs and symptoms.

Exotoxin

• Intracellular products as part of their growth and metabolism.

• Mainly proteins and enzymes

• Soluble in body fluids, easily diffused in the blood.

• Cytotoxin

• Neurotoxin

• Enterotoxin

Exotoxin: 3 Principle Types

Cytotoxin

KILL host cell or affect their function

Neurotoxin

interfere w/ normal nerve impulse transmission

Enterotoxin

cells lining the G.I. tract

Immunologic

Consequence to the immune response of the host to the microorganism or its product.

Antibodies

are produced against the virus

• Based on how they behave within a host and within a given population

• Based on the source of the microorganisms

• Based on the occurrence of the disease

• Based on the severity or duration of a disease

• Based on the extent of host involvement

Classification of Infectious Disease

Symptom

A change in body function that is felt by a patient as a result of disease.

Sign

A change in a body that can be measured or observed as a result of disease.

Syndrome

A specific group of signs and symptoms that accompany a disease

• Communicable

• Non-communicable

Based on how they behave within a host and within a given population

Communicable

a disease that is spread from one host to another, either directly or indirectly.

Non-communicable

• not spread from one person to another.

• usually caused by organisms

• normally inhabit the body and produce disease ONLY occasionally

• organisms that produce disease only when introduced into the body. (Clostridium tetani)

• Exogenous

• Nosocomial Infections

• Endogenous

Based on the source of the microorganism

Exogenous

if the source of the infectious agent is from outside the body (e.g., cholera)

Nosocomial Infection

Also called Hospital acquired infections, an exogenous infection, obtained from the hospital environment.

Endogenous

if the source of the causative agent is from inside the body (e.g., Escherichia coli)

• Sporadic Disease

• Endemic Disease

• Epidemic Disease

• Pandemic Disease

Based on the occurrence of the disease

Sporadic Disease

A disease that occurs occasionally (e.g., rabies, tetanus)

Endemic Disease

A disease that is constantly present in a population at low levels (e.g., Malaria in Palawan)

Epidemic Disease

If a great number of people in a given locality develop an infectious disease in a relatively short time. (e.g., Influenza)

Pandemic Disease

Has a worldwide occurrence or involves at least 3 regions in the world. (e.g., SARS)

• Acute Disease

• Chronic Disease

• Latent Disease

Based on the severity or duration of a disease

Acute Disease

develops rapidly but lasts only for a short period of time

Chronic Disease

develops more slowly and occurs for long periods of time.

Latent Disease

the causative organisms remains inactive for a time but can become active again and produce symptoms of the disease.

• Localized Infection

• Systemic Infection

• Focal Infection

• Primary Infection

• Secondary Infection

• Subclinical/Inapparent Infection

Based on the extent of host involvement

Localized Infection

Invading organisms are limited to a relatively small area of the body.

Systemic Infection

or Generalized infection, where causative organism or their products are spread throughout the body through blood or lymph.

Focal Infection

Causative agents of a localized infection may enter a blood or lymphatic vessel, spread to specific parts of the body and become confined to specific areas.

Primary Infection

an acute infection that causes initial illness.

Secondary Infection

caused by opportunistic pathogens after the primary infection has weakened the body’s defenses.

Subclinical/Inapparent Infection

one that does not cause noticeable illness.

• Incubation Period

• Prodromal Period

• Period of Illness

• Period of Decline

• Period of Convalescence

Stages of Infectious Disease

Incubation Period

Time between the initial appearance symptoms.

Prodromal Period

Characterized by appearance of first mild signs and symptoms.

Period of Illness

Disease at its height: all disease signs and symptoms apparent.

Period of Decline

Signs and symptoms subside

Period of Convalescence

Body returns to prediseased state, health is restored