Module 3 Flashcards
Host Microbe Interactions and Disease Development
Symbiosis
Where all organisms have some kind of relationship with each other
What are the 3 types of Symbiotic Relationships
Mutualism
Commensalism
Parasitism
Mutualism
2 independent organisms live together with mutual benefits
Comensalism
Where 1 benefits without causing any harm to the other organism
Can become a parasitism if it causes an infection
Parasitism
Where 1 benefits at the expense of another
The damage could be mild or could also result in the death of the organism
Microbiota
Normal flora (microorganisms that inhabit the human body without causing disease)
Resident flora
permanently resides on the skin and the mucosal surface
Transient flora
Colonises the skin and mucosal surfaces
Potential Pathogens
Contaminants
transient flora that is carried for short periods on the hands and other skin surfaces. Is usually removed by physical means
What are the sterile sites of the human body
Blood stream and internal organs
Candida albicans
Thrush
Caused from long term use of antibiotics)
reduction of lactobacilli which can lead to overgrowth of yeast (vaginal infection)
4 sites that normal microbiota reside on
Skin
Respiratory Tract
Gastrointestinal Tract
Urinary Tract
Skin (normal microbiota)
Bacteria is found in or on the dead layers of skin
Contaminants
Resident microbiota (warm, moist areas)
Survives off surface secretions (oils and fatty acids)
Staphylococcus epidermidis (dry areas of skin) Staphylococcus aureus (moist area)
Respiratory Tract (normal microbiota)
mainly upper respiratory tract
Colonised with normal flora that have pathogenic potential
Gastrointestinal Tract (normal microbiota)
From mouth to anus
Most microorganism can not grow past the stomach due to its acidity
Upper intestine is slightly alkaline compared to the stomach is relatively free of bacteria
Lower intestine harbours a large population of bacteria (30% of faeces)
Urinary Tract (normal microbiota)
lower urethra consists of normal flora
kidney, bladder, upper urethra is usually sterile
They control the flush of liquids and bacteria
Endogenous Infection
source of pathogen is human host itself
caused from normal flora
Congenital Infections
(source of pathogen is from mother to foetus)
Exogenous Infections
Caused by organism from the external environment
HCAIs
Iatrogenic infections
HCAIs
exogenous infection that occurs during a stay in a hospital or health-care facility
Iatrogenic Infection
Infections from a medical procedure, treatment or contact with medical equipment
What are the 4 aspects when establishing a disease
Pathogenicity/Virulence
Opportunistic Infections
Host Resistance/susceptibility
Predisposing Factors
Pathway ofPathogenicity
Ability of an organism to cause a disease
Gain entry into host
Attach to host tissues and multiply
Evade host immune defence
Damage tissue and produce disease symptoms
Infectious Dose
The number of organisms that is required to enter to establish an infection in the host
Opportunistic Infections
Infections that are from organisms that usually don’t cause a disease.
What is the difference between Signs and Symptoms
Signs are measurable changes
Symptoms are not visible but felt
Development of Disease (stages)
Incubation Period
Between time of exposure and appearance of symptoms
Prodromal Period
Signs and Symptoms
Acute (invasive) Period
Pathogen invades and damages host tissue
this period determines outcome of disease
Decline Phase
decline in microorganisms due to treatment or immune system
Convalescence period
Where body repairs itself
Localised Infections
Confined to 1 area
Disseminated infection
infection that is spread throughout the body
Infection spreads from primary site via bloodstream or lymphatic system
Systemic Disease
Infection of the bloodstream and/or multiple organs
Mixed infections
Caused by more than 1 pathogen
Primary Infection
Infection that is the cause of the initial illness
Secondary Infection
Following a primary infection, whilst they are in a weakened state
Superinfections
Secondary infection that is caused from the destruction of normal flora (usually from extensive antimicrobial therapy)
Subclinical Infections
elicits the immune response without producing any signs or symptoms
