Topic 16: Introduction to Body System Infections Flashcards
Define pathogenicity
The ability of a microbe to cause disease
Define virulence
How harmful a pathogen is to a host
What is the parenteral route?
Access through broken skin
What are the portals of entry?
Mucous membranes (oral, respiratory, sexual routes)
What is an example of adherence and penetration?
N. gonorrhea = attaches to urethra and vagina
Define adhesins/ligands (adherence and penetration)
They bind to specific receptors on host cells (eg. suckers, hooks, pili, fimbriae)
Define invasive pathogens (adherence and penetration)
Invasive pathogens penetrate and enter host cells often using secreted extracellular enzymes
Give an example of invasive pathogens
- Invasins
- Apical complex
- Hemolysins
- Beta hemolytic stretococci (secrete hemolysins that cause the complete lysis of RBC’s)
Dissolving the extracellular matrix (adherence and penetration)
Several other enzymes are secreted which help pathogens enter, dislodge or destroy cells (eg: collagenase)
What is an example of adherence and penetration (coli)
E.coli
- has ‘virulence factors’ (adhesins and toxins) that make a pedestal in the intestine
Define median lethal dose (LD50)
The amount of toxin or # of pathogens required to cause disease in 50% of individuals
Define median infectious dose (ID50)
The # of pathogens required to cause disease in 50% of individuals
What is the LD and ID with more virulent?
Low ID, low LD
What is the LD and ID with less virulent?
High ID, low LD
Evasion of host defenses simplified
Some bacteria produce capsules that inhibit phagocytosis by host immune cells (eg: Streptococcus pneumoniae Gram +)
Define antigenic variation (evasion of host defences)
Some pathogens change the structures on their surfaces;. The immune system does not recognize the pathogen during re-infection (eg: influenza virus)
What are 4 ways that damage to host cells can happen?
- Stealing host nutrients
- Damaging immune response
- Endotoxins (Cytological Effect)
- Exotoxins (Cytological Effect)
What is cytopathic effects?
Structural damage within the cell (most often due to multiplication of a virus)
How are cells damaged? (exotoxins)
- Secreted proteins (mostly Gr+)
- May be waste products
- Some are very potent
How are cells damaged? (endotoxins)
- Part of outer membrane (Gr-)
- Released when the cell dies
- May lead to septic shock
What is the exotoxin Botulism
?
Prevents the release of an excitatory neurotransmitter
- 10mg can kill 25 people
ex: Clostridium botulinum
(ex: botox)
What is clostridium botulinum?
An anaerobic, spore-producing inhabitant of soil
What does the tetanus toxin do (exotoxin)?
Prevents release of an inhibitory neurotransmittter (ex: clostridium tetani)
What happens to the muscles because of tetanus?
Both muscles fully contract. The arm flexes because biceps brachil is larger and stronger
What is cytolysins (exotoxins)?
Cholera toxin - An A-B enterotoxin which indirectly actives chloride pumps in the cell
What does A part of cytolysins do?
- Activates “G proteins”
(modify behaviour of chloride channels) - loss of chloride causes loss of fluids –> diarrhea
What does B part of cytolysins do?
- attaches to host cell surface
- lets A part in
Give 4 examples of A-B toxins
- Enterotoxin
- Petussis toxin
- Diphtheria toxin
- Ricin
What are portals of exit?
Generally the same as portals of entry (with the exception of feces and urine)
- Respiratory system
- GI tract
- Urogenitcal system
- Skin
- Blood
What are the 9 predisposing factors to infectious disease?
- Gender
- Inherited traits
- Climate and weather
- Fatigue
- Diet
- Age
- Lifestyle
- Immunodeficiencies
- Chemotherapy
What is the incubation period?
No signs/symptoms
What is the prodromal period?
Vague, general symptoms
What is the illness stage?
Most severe signs/symptoms
What are the 5 stages of an illness?
- Incubation period
- Prodromal period
- Illness
- Decline
- Convalescence
Define disease
An abnormal state in which the body (or mind) is not functioning normally
Define pathology
The diagnostic study of disease
- Fields include anatomy (gross pathology), histology, cytology, immunology, and molecular biology
Define a symptom
A change in body function that is described by the patient
Describe a sign
Measured by an observer
Describe syndrome
A specific set of signs and symptoms that generally accompany a particular disease
Define a non-communicable disease? (Give 2 examples)
From a source other than another host (eg. soil bacterium) or where an organism of the normal flora is opportunistic
Ex: Botulism, tetanus
Describe a communicable disease and give 3 examples
It is spread from one host to another by direct or indirect contact
Ex: Chicken pox, herpes, influenza
What is direct contact?
eg: touching, kissing, sexual contact
What is indirect contact?
eg: respiratory droplets, feces
What is an acute duration/severity of a disease?
Rapid, short
What is a chronic duration/severity of a disease?
Slow, continual, recurrent
What is latent?
Inactive for a long time
What is sub-clinical diseases?
Asymptomatic - infection is unnoticed (eg: typhoid mary)
