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The normal microbiota or microflora
An ever-present dynamic population of microorganismsthat inhabits most of our epithelial/mucosal surfaces TERM 2
Symbiosis
DEFINITION 2 living together or close association of two dissimilar organisms TERM 3
Mutualism
DEFINITION 3 beneficial to both (microbe & host) TERM 4
Commensalism
DEFINITION 4 beneficial to one (microbe) , neither harmful or beneficial to other (host TERM 5
Parasitism
DEFINITION 5 beneficial to one (microbe), harmful to the other (host) = pathogenic
Mutualism Benefits to the Host
synthesize and excrete vitaminsenteric bacteria secrete Vitamin K and Vitamin B12 / germ-free animals Vit K deficient lactic acid bacteria produce certain B-vitaminsprevent colonization by pathogenspossibly most important beneficial aspectcompete for attachment sites &/or for essential nutrientsgerm-free animals infected by 10 Salmonella; ID for normal animals is ~ 106 TERM 7
Mutualism Benefits to the Host -Continued
DEFINITION 7 antagonize/ control other normal flora & pathogenic bacteriaproduction of substances which inhibit or kill other indigenous bacteriarelatively nonspecific fatty acids and peroxides to highly specific bacteriocins stimulate the production of cross- reactive antibodiesantigenic primingbehave as antigens & induce an immunological responsecross react with certain related pathogens"natural" antibodies - lacking in germ-free animals TERM 8
What % of the cells you carry around
everyday are you & what % are microbes?
DEFINITION 8 ~91% microbes, ~9% humanmore bacterial cells (~10^14) associated with your body than there are human ones (~10^13) TERM 9
ECOLOGY
DEFINITION 9 relationship between living organisms & their environment TERM 10
Physical (Host) Factors
DEFINITION 10 nature of host tissue surfaceoxygen availability pHtemperatureavailable nutrients
some microorganisms exclusively associated
with disease
Vibrio choleraeYersinia pestis TERM 17
some microorganisms very rarely cause
disease (NON-PATHOGENS
DEFINITION 17 Micrococcus speciesLactobacillus species TERM 18
many microorganisms between these two
extremes
DEFINITION 18 Escherichia coliStaphylococcus aureusStreptococcus pneumoniaPseudomonas aeruginosa TERM 19
How do exogenous pathogens get to
you?
DEFINITION 19 pass from one person to another TERM 20
Modes of Transmission
DEFINITION 20 congenitaldirect contactaerosol/respiratoryingestiontraumaIV transfusion / percutaneoussexual
Portals of Entry -for exogenous
pathogens
skin Staphylococcus aureus respiratory tract Mycobacterium tuberculosisgastrointestinal tract Salmonella typhigenitourinary tract Treponema pallidum TERM 22
OPPORTUNISTIC PATHOGENS
DEFINITION 22 microorganisms that are capable of producing disease given the opportunitymany opportunistic pathogens are members of the normal microbiota TERM 23
OPPORTUNITIES FOR OPPORTUNISTIC
PATHOGENS
DEFINITION 23 impaired host defense immunocompromised / chemotherapy / antibiotic treatmentaccidental access to blood or tissues TERM 24
Antibiotic-induced opportunistic infection -
Pseudomembranous colitis
DEFINITION 24
- diarrhea, yellowish-white plaques on colonic mucosa, may be life threatening - caused by treatment with clindamycin & other broad spectrum antibiotics - frequently used to treat B. fragilis infections
- other normal colonic bacteria are also sensitive to clindamycinClostridium difficle - normal microbiota in ~ 3% of population - naturally resistant to clindamycin - overgrowth of C. difficle causes pseudomembraneous colitis TERM 25
Accidental access of normal microbiota to
blood or tissues of host
DEFINITION 25 Streptococcus sanguinis Gram-positive facultative coccus - normal inhabitant of dental plaque - entry into bloodstream & colonize heart valves - most common cause of bacterial endocarditis
