M1: Host Parasite Relationship Flashcards
Types of Symbiosis
Mutualism, Commensalism & Parasitism
Means living together. Describes the relationship of the host and MO
Symbiosis
Both the host and symbion benefits from each other. No harm is done. Ex: lactobacilli in the intestines
Mutualism
One way relationship. One benefits while the other do not. Symbion benefits from the host. Host is neither harm or benefits from the symbio . Example is staph on the skin.
Commensalism
The symbiont harms from the host while it benefits from it. Symbiont benefits & Host is harmed.
Parasitism
Organisms that colonize the body’s surfaces without normally causing disease
Normal flora/microbiota
Types of Normal Flora
Resident & Transient
Part of the normal flora of the body all throughout life. Mostly commensals.
Resident
Remain in the body for short period. Found in the same regions. Cannot persist in the body because either compete from other MO, gets eliminated by defense system & certain body changes.
Transient
No normal flora
Alveoli
Naturally cool environment
Nose
Has alot of anaerobic MO
Lower colon
Development in womb free MO (axenic). Normal flora begin to develop during birthing process. Much of one’s resident microbiota established during first months of life.
Acquisition of Normal Flora
Organisms that always cause a disease. Example is Neisseria gonorrhea
Strict pathogens
Normal microbiota that cause disease under certain conditions. Example is candida albicans.
Opportunistic pathogens
Conditions the provide opportunities to pathogen: intro of flora into unusual ______ of the body
Site
Conditions the provide opportunities to pathogen: ________ suppression
Immune
Conditions the provide opportunities to pathogen: changes in normal ________ or changes in the relative abundance.
Microbiota
Mere presence of microbes in or on the body
Colonization
When organism evades body’s external defenses, multiplies and becomes established in the body. Cause harm.
Disease
MO are already there but is slowly replicating
Infection
Sites through which pathogens enter the body.
Portals of entry
Four major pathways
Skin mucous, membrane, placenta and parenteral routes
Outer layer of dead ______ cells acts as barrier to pathogens. Some pathogens can enter through openings or cuts. Others enter by burrowing into or digesting outer layers of skin.
Skin
Skin thickness in the back
3mm
Skin thickness in the eyes
.5
Most common site of entry from inhalation
Respiratory tract
Line the body activities that are open to the environment
Mucous membrane
Forms effective barrier. Pathogens may cross here and infect fetus.
Placenta
Most common placental pathogen
Toxoplasma
Not a true portal of entry, can be circumvented. Deposit itself to underneath the skin.
Parenteral route
process by which MO attach themselves to cells. Required to established colonies within the host.
Adhesion
Inability to make attachment proteins or adhesins renders MO
Avirulent
Biofilm
Thin slippery covering of the bacteria
Invasion of host by a pathogen
Infection
Invading pathogen Alters the normal functions of the body. Morbidity.
Disease
Germ theory of disease. Caused by infections of pathogenic MO. Developed a set of postulates one must satisfy to prove a particular pathogen causes a particular disease.
Robert Koch/Koch’s Postulate
Koch Postulate
Isolate, Grow culture, Inoculate a healthy culture & Reisolate
Ability of MO to cause disease
Pathogenicity
Degree of pathogenicity. Infective dose and exposure, penetration of anatomic barriers, attachment, replication, cell tissue damage and cell disruption the immune defense of host.
Virulence
Virulence factors that contribute to an organism virulence
Adhesion factors, enzyme, Toxins & Antiphagocytic factors.
Increase the potential to cause the disease
Infective dose and exposure
Acquired entry through oral or skin penetration
Protozoan & Helminths
Attachment through adhesion factors
Adhesins, glycoproteins, fibronectin & n acetylglucosamine conjugates
Invading the mucosal layer of colon
Entamoeba histolytica
Duffy blood group antigens attachment for
Plasmodium Vivax
Intracellular or extracellular. Tissue tropism & temperature.
Replication
Environment where MO can actually survive
Tissue tropism
Secreted by the pathogen. Dissolve structural chemicals in the body. Help pathogen maintain infection, invade and avoid body defenses.
Extracellular enzymes
Chemicals that harm tissue or trigger host immune responses that cause damage
Toxin
Toxin in the blood
Toxemia
Causes fever
Endotoxin
Prevent phagocytosis by the host’s phagocytic cells
Antiphagocytic factors
Composed of chemical not recognized as foreign
Bacterial capsules
Subjective characteristics of disease felt only by the patient
Symptoms
Objective manifestations of the disease observed or measured by others
Signs
Symptoms and signs that characterize a disease or abnormal condition
Syndrome
No symptom but may still have signs of infection
Asymptomatic/Subclinical
Five stages following infection
Incubation period, prodromal period, illness, decline & convalescence
No signs or symptoms
Incubation period
Vague general symptoms
Prodromal
Movement of pathogens out of hosts. The same way they enter os the same area they leave.
Portal of Exit
Most pathogens cannot survive long without host. Maintained as a source of infection.
Resevoir
Disease caused by animal to humans. Direct contact with animal, eating animals.
Zoonoses
Asymptomatic but infective to others. Develop illness when immune system is down.
Human carrier
Soil, water and food can be reservoir of infection. Presence of MO due to contamination.
Nonliving Reservoir
From a reservoir or a portal of exit
Transmission
