Microbial Pathogenesis

Disease

Any condition in which the normal structure or functions of the body are impaired

Diseases types

-infection by pathogen

-genetics (deficiencies)

-environmental causes

-inappropriate immune response

Infection

successful colonization of a host by a pathogen (type of disease)

Disease signs

objective and measurable.

- HR

- Temp

- breathing rate

- BP

Disease symptoms

subjective and felt or experienced by the patient

- nausea

- loss of appetite

- pain

Pathogenicity

the potential ability to cause disease. (qualitative)

Virulence

disease producing power of an organism compared within a group. (quantitative)

Infectious Dose (ID)

number of pathogen cells required to cause infection in 50% of exposed patients

-# changes for different pathogens

-# changes for portal of entry

Lethal Dose (LD)

number of pathogenic cells required to kill 50% of exposed patients

____ quantifies _____

virulence; pathogenicity

World Health Organization (WHO) and International Classification of Diseases (ICD) track what?

-morbidity (the number of cases of a disease)

-mortality (the number of deaths due to a disease).

Communicable Disease

contagious diseases-easily spread from person to person

Non-communicable Disease

infectious disease that are not spread by people

Iatrogenic Disease

contracted from medical procedures

Nosocomial Disease

diseases are acquired in hospital settings

stages of an acute infectious disease

the number of pathogen particles correlate with the severity of signs and symptoms

Zoonotic Disease

diseases that can be transmitted from animals to humans

Acute disease

short time (e.g., hours, days, or a few weeks) and involve a rapid onset of disease conditions

Chronic Disease

longer time spans (e.g., months, years, or a lifetime.)

Latent Disease

pathogen goes dormant for extended periods of time with no active replication. (Herpes, chickenpox)

Koch's Postulates

cultivating RBC and pathogens and injecting them with the pathogen to establish causative relationship between pathogen and disease.

Primary Pathogens

cause disease in a host regardless of the host's resident microbiota or immune system.

Opportunistic Pathogens

only cause disease in situations that compromise the host's defenses

-body's protective barrier

-immune system

-normal microbiota.

Pathogenesis Stages

exposure,

adhesion,

invasion,

infection

Exposure Stage

-Mucosal surfaces are the most important portals of entry for microbes

-pathogens are suited to a particular portal of entry bases on adaptations, enzymes, and toxins

Adehsion Stage

capability of pathogenic microbes to attach to the cells of the body using adhesion factors.

- fimbriae

- pilli

- capsules

-spikes

Invasion Stage

spread of a pathogen throughout body by producing exoenzymes

Invasion: Exoenzymes types

different classes have different functions

- Glyeohydrolases: degrade hyaluronic acid

- Nucleases: degrade DNA

- Phospholipase: degrade phospholipid bilayer

-Protease: degrade collagen

Infection Stage

-successful multiplication of the pathogen

-primary infection/ first infection caused by on e pathogen can lead to secondary infection by another pathogen

Infection stage types

- local : confined to a small area of the body,

- focal: a localized pathogen can spread to a secondary location.

- systemic: an infection becomes disseminated throughout the body.

Portals of Exit for transmission of disease

Respiratory track

- coughing and sneezing

Gastrointestinal track

- feces and saliva

Genitourinary track

-urine

Skin

Blood

-needles and syringes

how virulence factors contribute to signs and symptoms of infectious disease

production of toxins is a virulence factor that contribute to signs and symptoms of the disease

Toxins

poisonous substances produced by microorganisms

Toxigenicity

ability of a microbe to produce a toxin

Toxemia

presence of toxin in host blood

Intoxications

presence of toxin without microbial growth

Endotoxins

-proteins

-most gram-positive

-highly toxic

-inhibit metabolic factors

Exotoxins

-lipid A portion of lipopolysaccharide

-gram-negative

-low toxicity

-inhibit coagulation