Bacterial Pathogenesis & Zoonoses Flashcards
What is Germ or Contagion Theory?
Infection spread by random contacts BETWEEN infected and susceptible people (or animals)
Koch’s Pustulates definition
- Proving that a specific organism is causative to a species disease
- In simple terms:
You find the suspect (the germ), make sure it’s guilty (by making someone sick), and then prove it was there all along (by finding it again). That’s Koch’s postulates!
Koch’ Postulates steps (4)
- Isolated organism from disease, but not from a healthy animal.
- Growth of pure culture of organism.
- Introduce organism to susceptible animals.
- Re-isolated organism from susceptible animals.
Normal flora
T/F: Body of a healthy fetus is sterile in the uterus (AKA no flora)
True!
After they are born they become exposed to their natural flora through their mother and environment.
Symbiosis
Living together in harmony
Mutual
Relationship benefits both organism and host
Commensal
Relationship benefits one, but has no affect on the other
Pathogen is ____ to the host
The relationship hurts/harmful to the host
Microbial Antagonism
Belief that normal flora protect host from growth of pathogens (ex. vagina)
Symbiosis
Benefit of relationship to both host and organism (ex. rumen)
Normal flora: Skin (3)
- Bacteria
Staphylococcus epidermidis (on the skin)
Propionibacterium acnes (on hair follicles)
Corynebacterium species (skin surface) - Fungi
Malassezia species (on skin)
Candida species (yeast-like on skin) - Viruses
There are various viruses. EX:
Bacteriophages (reg bacterial populations)
Normal flora: Intestines (2)
DOUBLE CHECK
- Bacteroides - high numbers.
- Enterobacteriaceae (E coli) - low number
Normal flora occur where? (6)
- Mouth & nose
- Conjunctiva (eye area)
- Urethra
- Vagina
- Prepuce
- Rumen/cecum
Biofilm
Community of microorganisms adhered on surface.
“City of bacteria with different cultural backgrounds”
EX: plaque on teeth
Sterile body regions (organism free) (3)
- Lower respiratory tract (trachea, lungs)
- Upper urinary tract (bladder kidneys)
- Upper reproductive tract (uterus, prostate)
How can normal flora cause disease?
Hint: Cult. these areas don’t produce helpful info!
- Gains access to a body region it doesn’t normally reside (ex: UTI in elderly female dog).
- Overpopulate a specific region (overgrowth).
Environmental transmission
Food, drink, water-borne infection
Direct or indirect contact transmission
Spread from patients, carriers, or environment to animals or persons who are contacts.
EX: Feces to oral, sexual transmitted, skin/mucous memb contact (wound infection).
Percutaneous infection transmission
Insect borne transmission via bite of an infected insect directly with saliva or indirect from insect feces contaminating wound.
EX: Lepto
Air-borne transmission
Infectious organisms can be inhaled as
- Droplets (tuberculosis)
- Aerosols
- Dust
- Spores (anthrax)
Nosocomial infections
Infection acquired in hospital are usually bacterial.
- Environmental resistance
- Antibiotic resistance
Direct transmission (2)
- Vertical: through placenta or egg, mother to offspring
- Horizontal: one adult to another (secretion, sneeze/cough, sexually)
Indirect transmission
Hint: Less common with viruses
- Mechanical: passive vectors.
- Flies, birds, rodents, vet staff. - Biological: vectors that are also reservoir hosts.
- AKA they are infected. EX mosquito.
Examples of how bacteria can be transmitted from one species to another species
- Host of origin may have active disease.
- Host of origin may be asymptomatic.
- Disease may cycle in host of origin and form a reservoir for the other species.
List the Bacterial Virulence Factors (5)
- Adhesion
- Capsules
- Toxin production
- Enzyme production
- Mobility
Define bacterial virulence factors
Properties of micro-organism that cause disease in host or increase ability to colonize host
Bacterial virulence factors:
Adhesion (5)
- Cell surface components or appendages.
- Facilitate adhesion or adherence to other cell surfaces.
- Essential step in pathogenesis or infection.
- Required for colonizing new host.
- Potential target for prophylaxis or treatment.
Define “Pathogenicity”
Ability to cause disease
Bacterial virulence factors:
Adhesion & Capsules (2)
- Pili
Hair like extensions on bacteria that enable organism to attach to tissue. Can be tissue specific. - Glycocalyx
Polysaccharide coat that protects against phagocytosis and increases ability to take in nutrients.
Bacterial virulence factors:
Toxins (2)
- Exotoxins
- Endotoxins
Exotoxins
Destroyed by heat. Proteins excreted by bacteria.
- EX: Botulism and Endotoxins
Endotoxins
- Toxic components of cell wall of G- bacteria lipopolysaccharides.
- These get released when the cell dies. So, the patient may get worse then get better.
G- bacteria signs (4)
- Fever
- Shock
- Severe diarrhea
- Change immune status
Enzymes
REVISIT
- Are usually proteins
- Destroy cellular structures
- Destroy extracellular matrix
Tips to avoid zoonotic diseases (6)
- Wash hands frequently.
- Up to date on vaccines
- Wear long pants and proper PPE.
- Use gloves.
- Disinfect scratches & bite wounds, then cover.
- Learn safe & humane animal-handling techniques.
