INFECTION DR. HANA OMER

Symbiotic RelationshipsSymbiosis means “to live together”

Describes the relationship between microorganisms and their host

Three types MutualismCommenalismParasitism

The Three Types of Symbiotic Relationships

Normal MicrobiotaAlso termed normal flora .

Refers to the organisms that colonize the body’s surfaces without normally causing disease .

Two typesResident microbiotaTransient microbiota

Resident MicrobiotaAre a part of the normal microbiota

throughout life .Most are commensal .Like : streptococcus bacterium can live for

months in the throat without causing harm and then suddenly cause an acute attack of tonsillitis .

Resident Microbiota

Resident Microbiota

Transient MicrobiotaRemain in the body for only hours to months

before disappearing .Cannot persist in the body…because…

Competition from other microorganismsElimination by the body’s defenses cellsChemical or physical changes in the body

Example Clostridium difficile in The intestine .

Contamination vs. InfectionContamination – it is the presence of

microbes in or on the body .

Infection – results when the organism has invaded the body’s external defenses, multiplied, and become established in the body .

Portals of EntrySites through which pathogens enter the

body

Four major types :-SkinMucous membranesPlacentaParenteral route

Infection vs. DiseaseInfection is the invasion of the host by a

pathogen .

Disease results only if the invading pathogen alters the normal functions of the body .

The most common cause of infection 1. Bacteria .2. Fungi (yeasts and molds) .3. Viruses .4. Protozoa .5. Helminths ( worms ) .