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35 Cards in this Set

  • Front
  • Back
What is normal flora?
-microorganisms that are usually found in healthy body tissue
What is commensalism?
-microbe benefits
-host neither benefits nor is harmed
*Staphylococcus epidermidis
What is mutualism?
-both microbe and host benefit
*E. coli: vit K synthesis in intestine
What is parasitism?
-microbe benefits
-host is adversely affected
*Vibrio cholerae
What is infection (colonization)?
-growth within the host
*does NOT always equal disease!
What is disease (morbidity)?
-injury to the host
How many microorganisms are found in the human body?
-about 10^14 microorganisms!
Where are most microorganisms found in the human body?
-mostly in regions exposed to environment such as skin and mucous membranes
What are some reasons that normal flora is important?
-physiologically important commensal organisms
-keep harmful microbes out
-remove or out-compete microbes that become harmful
Describe the mucous membrane of the mouth, respiratory, gastrointestinal and urogenital tracts.
-single layer
-tightly packed epithelial cells that exist in direct contact with external environment
-covered by protective mucus layer
-major sites of infection!
How do microbial interactions occur?
-binding of ligand (on microbial surface) to receptors on cells (usually sugars or glycoproteins)
What are biofilms?
-a microbial colony attached to a surface and encased in an adhesive polysaccharide material
-can contain all types of microorganisms
-accounts for 2/3 of bacterial infections in humans
How are biofilms good for microbes contained within it?
-sheilds against immune system
-limits access to antibiotics
What are some common Nosocomial biofilm bacterial species?
-S. epidermidis and aureus
-P. aeruginosa
-E. coli
-Actinomyces israelii
-C. albicans
Why is the mouth a good microbiological niche?
-moist environment with plenty of nutrients and physiological pH
-microbes need to be able to adhere to surfaces due to salivary flow
-each mL of saliva contains >10^6 microbes; mostly bacteria but also fungi
Generally, how does colonization of the tooth occur?
-sterile at birth, then aerobes, then teeth come in, then anaerobes can occur
What is a pellicle?
-thin organic film of salivary glycoproteins on tooth surface
In detail, what are the colonizers on the tooth?
-Streptococci (excpecially S. sanguis and S. mutans)
-in 12-24 hrs later, Fusobacteria
-late colonizers interact with Fusobacteria but not the early colonizers: Actinomyces
What is dental plaque known as?
-a biofilm!
What is the etiological agent in dental caries?
What are its virulence factors?
-Streptococcus mutans
-Dextran and pili allow biofilm formation on the tooth
What is the susceptibility of dental caries?
-consuming high sucrose diets
-S. mutans breaks down sucrose to glucose and fructose (which is food for microbes)
How can you prevent dental caries?
-proper brushing and flossing of teeth and use of fluoridated toothpaste and water
What adverse affect can taking antibiotics cause?
-kills normal flora and allows resistant species to flourish
-opportunistic pathogens can also flourish!
What are probiotics?
-harmless commensal organisms that displace harmful microbes
-Such as: Lactobacilli and Bifidobacteria. *5 x 10^10 bacteria / capsule
What are some biochemical or metabolic conributions of intestinal microorganisms?
-vitamin synthesis
-gas production
-odor production
-organic acid production
-glycosidase reactions
-steroid metabolism (bile acids)
Describe the normal flora of the skin
-transient and resident populations
-primarily Gram + bacteria and fungi
-most organisms are associated with the sweat glands
What things can affect the type and number of organisms found in teh skin?
-weather (humidity)
-personal hygiene
What are some microorganisms found in the upper respiratory tract?
-Staphylococcus*, Streptococcus*, Moraxella, Haemophilus, Lactobacillus, Veridonella, Fusobacterium, Candida (fungus)*
Describe the normal floar found in the lower respiratory system.
-usually devoid of resident flora
-cleared by antibodies and ciliary action
Describe the normal flora of the urogenital tract.
-upper regions are normally sterile
-urethra are colonized with faculatative aerobic Gram - bacteria (E. coli, Proteus mirabilis)
-normal flora of the vagina changes with age/development
What are the resident microbiota found in female urogental area?
-Lactobacillus*, Streptococcus, Staphylococcus, Bacterioides, Clostridium, Candida, Trichomonas (protozoan)
What are the resident microbiota found in male urogential region?
-Staphylococcus, Streptococcus, Mycobacterium, Bacteriodes, Fusobacterium, Peptostreptococcus
What prevents colonization into the urethra?
-the flow of urine
Which part of the GI tract is sterile?
What is found in the small intestine?
-Enterococci and Lactobacilli
What is found in the Lg. intestine?
-Bacteroides*, Enterobacteria, E. faecalis, Bifidobacterium, Eubacterium, Peptococcus, Peptostreptococcus, Ruminococcus, Clostridia, Lactobacili, Streptococcus, Staphyloccocus