Microbiology 2 - Bacterial Diseases Flashcards
What are the two sources of bacteria?
Intrinsic - non-sterile sites inside the body, and extrinsic - outside the body.
List the main intrinsic sources of bacteria
- Nasal cavity and sinuses
- Mouth
- Stomach
- Skin
- Lower genital tract
- SI/LI
Define the term normal microbiota
The bacteria that are normally present inside the body.
What are the two types of routes of entry of pathogens?
Expected - normal microbiota enter by an expected route (eg. From mother to baby)
Unexpected - normal microbiota entering at an unusual site/pathogens entering
What is the pathway of bacteria acquired via the upper respiratory tract?
Infection in the upper respiratory tract (eg. Tonsillitis) to the adjacent tissues (brain, middle ear) to the bloodstream (or to the lower respiratory tract)
Describe the pathway taken by bacteria that enter through the urogenital tract
UTI, genital tract infection, pregnancy related infection, and may spread to bloodstream
What is an example of an extrinsic source of entry to the urogenital tract?
Bacteria entering through a catheter in hospital.
What are the possible ways of a pathogen entering the skin?
- Wounds/surgery
- Skin diseases
- Injecting drugs
- Insect bites
- Cannulae
What is the name for the route of entry through the gastrointestinal tract?
Faeco-oral route
What are the possible consequences of infection acquired by the GI tract?
- Diarrhoeal illnesses
- Bacteremic infections
- Toxin mediated disease
What are pathogens and what are their two types?
Pathogens are bacteria that cause disease - true pathogens always cause disease, opportunistic pathogens need specific conditions.
What are commensals?
Bacteria that don’t cause disease
Define infectivity
The general features favouring infection - infectious dose is the amount of a pathogen needed to cause a disease
What factors contribute to pathogenicity?
- Transmission to a host
- Ability to colonise
- Motility
- Ability to replication speed
- Ability to avoid the immune system
Define virulence.
Features that enhance disease causation
What are the factors that affect virulence?
- Production of toxins
- Complete immune evasion
- Enzymes that degrade host molecules, or interrupt normal host processes
List the main gram negative bacteria
- Neisseria
- Haemophilus influenzas
- Eschericha coli
- Salmonella
- Shingella
- Vibrio cholerae
List the main gram positive bacteria
- Staphylococcus aureus
- Streptococcus
- Colostridum
- Listeria
Give an example of some pathogens that infect by droplet transmission and what disease they cause
- Tonsilltis is caused by streptococcus pyogrnes
- Meningococcal septicaemia is caused by neisseria meningitidis
Give some examples of bacteria that transmit to upper respiratory tract and what disease they cause.
- Strep pneumoniae causes pneumonia
- Also travels to the brain alongside strep milleri and haemophilus influenzae
Give an example of a pathogen transmitted by faeco-oral transmission
Cholera - transmitted to Hati following hurricanes due to American soldiers.
Give an example of transmission to the urogenital tract
- Group B steep infects neonates, from the GI tract of the mother
- Causes meningitis, septicaemia and death.
Give some examples of pathogens that enter through the skin
S. aureus produces toxins that destroy neutrophils, leading in pus formation
Define the infectious dose
The average number of organisms required to initiate infection.
Define pathogenicity
Ability to cause disease
List the main intrinsic routes of infection
- Broken skin
- Migration from naso-pharynx to lungs
- Gut to urinary tract
List the main extrinsic routes of infection
- Water and food
- Coughs (droplet)
- Sexual transmission
- Nosocomial transmission (in hospitals)
