Chapter 27 Flashcards
What is normal microbial flora
Microorganisms usually found associated with human body tissues, most are just parasites and on’t harm the host.
What are pathogens
Microbial parasites that harm the host
What is pathogenicity
The ability of a parasite to inflict damage
What is virulence
The quantitative measure of pathogenicity, a relative term
What is an opportunistic pathogen
Causes disease only in the absence of normal host resistance
What is an infection
Microorganism is established and growing in a host, whether or not the host is harmed
What is a disease
Damage or injury to the host
Where do infections usually begin
Infections usually begin in mucous membranes in contact with the environment, animals provide many favorable environments for the growth of microorganisms
Where can microorgansims generally grow and can’t grow on the body
The skin is generally dry, acid environment that does not support their growth. Moist areas (sweat glands) are readily colonized by G+ bacteria and other normal flora
What factors influence skin microflora
Environmental factors, weather, humidity, and host facts: age and hygiene
Describe the microflora of the oral cavity
It is a complex heterogenous microbial habitat, high concentrations of nutrients that promote growth. Saliva contains antimicrobial enzymes and microbes can grow on teeth and tougne as biofilms
Describe the biofilm formation of bacteria on teeth
Bacteria colonize the teeth by attaching to acidic glycoproteins deposited by saliva and extensive growth of microorganisms result in bacterial biofilm. As plaque develops, anaerobic bacterial species begin to grow by fermentation and produce lactic acids that decalcify the tooth enemal
Describe the human GI tract
Stomach, small intestine and large intestine. Responsible for digestion of food, absorption of nutrients, and production of nutrients by indigenous microflora. Contains a lot of microbial cells
Describe the urogential tract
The bladder is typically sterile in both males and females but altered conditions can allow potential pathogens in the urethra to multiply
Describe a pathogens strategy for virulence (cause disease)
First there is an exposure to the pathogen and it will adhere to the surface. Then it will invade into the the epithelium and colonize and grow producing virulence factors. Can result in either toxicity or invaseiness, both of which cause tissue damage and disease
How do you measure virulence
LD50, the amount of an agent that kills 50% of the animals in a test group
What is toxicity
Organism causes disease by producing toxin
What is a toxin
Toxins can travel to sites within host distant from site of pathogen invasion
What is invasiveness
The ability of a pathogen to grow in host tissue, can cause damage without producing a toxin
Describe pathogen invasion
Starts at the site of adherence, may spread throughout the host via the circulatory or lymphatic systems
What is specific adherence
Bacteria and viruses often adhere specifically to epithelial cells through macromolecular interactions
What facilitates bacterial adherence
Can be facilitated by extracellular macromolecules (slime layer, capsule). And fimbriae and pilli. Helps them stick to surface better
What is the goal of pathogen invasion
The avaliability of nutrients is important for pathogen growth and their goal is to get food and grow, host damage is just a side effect. They can grow locally at site of invasion or spread throughout the body
What type of enzymes do pathogens produce
Enzymes that enhance virulence by breaking down or altering host tissue to provide access to nutrients. And enzymes that protect the pathogen by interfering with normal host defense mechanisms.
