Normal Flora Flashcards
Normal flora can cause disease in 2 ways
being displaced from its normal site and colonizing another
overgrowing at its natural site
Transient flora
microorganisms that inhabit an anatomical site for a short period of time
Selective anatomical distribution of NF includes:
attachment of organisms to specific receptor, nutritional needs, competition of other flora, lack of inhibitory substances, permissive environment
Host specific factors contribute to NF composition
age, gender, nutrition, diet
In healthy individuals, what areas are FREE of NF?
blood, CSF, synovial fluid, urine, lower respiratory tract, uterus, internal tissue (heart, brain, liver, peritoneal cavity)
Benefits of NF - stimulation of innate immune response
Vagina (NF: lactobacilli and propionibacteria) produced H2O2 which is converted to HOCl- this along with lactic acid and propionic acid inhibit other bacteria from growing
Benefits of NF - stimulation of adaptive immune response
Gut (NF: E. coli) antibodies formed against E. coli capsular polysaccharide are cross-reactive to H. flu
NF can prevent colonization by pathogenic organisms by
occupying and competing for receptor sites, competing for nutrients, producing inhibitory or toxic substances
NF synthesize essential nutrients of the host, such as
Vitamin K and Vitamin B complex
Broad spectrum antibiotics for long periods of time can
result in overgrowth of yeast, result in nutritional deficits
How can hospitalizations be detrimental in regards to NF?
NF may shift from gram (+) to Gram (-) in the upper airway, skin increases colonization of enterococci and gram (-) bacteria, NF in intestines may permeate intestinal barriers, lower GI NF retrograde movement into upper GI, catheters and intubation can lead to infections
How can antibiotics usage be detrimental in regards to NF?
C. diff in GI tract overgrows leading to antibiotic-associated pseudomembranous colitis, vaginal candidiasis, or UTI if displaced
How can immunocompromise be detrimental in regards to NF?
Allows overgrowth of NF or new colonization with different flora
Probiotics
help restore NF homeostasis, esp in GI tract of people with recurrent C diff. infections
Probiotics consists mainly of
Lactobacillus and Bifidobacterium
Sterilization
absolute removal of all microorganisms and spores, but does not remove LPS since it is heat-stable
Pyrogen free
free of all biologically relevant levels of LPS and other pyrogens of microbial origin
Cidal
killing of microorganism (irreversible) i.e. bactericide
Static/stasis
halts growth of microorganism but may resume when agent is removed
Disinfection
reduction in the number of microorganisms (kill many but not all microorganisms)
High level disinfectant
effective against most pathogens but not large numbers of spores - may be sporecidal over time
Intermediate level of disinfectant
effective against mycobacteria and other vegetative bacteria, most fungus and viruses - not effective against spores
low level disinfectant
effective against ,pst vegetative bacteria and enveloped viruses and some fungi, not against mycobacteria or spores
Sanitization
clean and free of dirt to reduce the occurrence and growth of bacteria, viruses, and fungi
Pasteurization
elevated temp followed by rapid cooling to kill important pathogens, NOT sterilization
Antiseptic
chemicals used to kill microorganisms on the surface of skin
Asepsis
without infection, techniques to maintain sterile environment
Decontamination
destruction and removal of contaminants/microbes present
Difficult to eliminate all bacterial products, esp
LPS
Factors affecting sterilization
application time, type of pathogen , agent used, number of organisms, physiologic state of microbe, spores are highly resistant
Concentration of agent
concentration increases, time needed to disinfect decreases (not for EtOH which is best at 70%)
Temperature of agent
higher temp, decreased time to kill
Barrier Technique to preventing infection spread
HAND WASHING, PPE
Silver Nitrate
Topical Antiseptic (binds -SH, breaking disulfide bonds in membrane molecules)
Iodine
topical antiseptic (damages DNA, proteins, etc)
Hydrogen Peroxide
antiseptic (ROS damage to CM)
Anionic detergents
Antiseptic - clean wounds by disrupting microorganism membrane
Alcohol 70-90%
antiseptic - denatures proteins
Quaternary ammonium chloride
Antiseptic - preoperative of skin, body cavities
Bleach
Disinfectant - strong oxidizer
Phenol
disinfectant - fecal material
Boiling
disinfectant - denatures macromolecules
Pasteurization (74C 3-5s, 4C)
disinfectant - wine, milk, vaccines by denaturing macromolecules
Air filtration
disinfectant for aseptic environment
Examples of preservation to inhibit bacterial growth
Refrigeration (unless psychrophile), Freezing, Filtration, Pasteurization, Mercury salts
Examples of sterilization
Incinerating/Burning, Dry Heat (not LPS), Autoclaving (not LPS), Ionizing radiation, UV radiation, Microwave irradiation
Sterilization with chemicals
Ethylene, Formaldehyde or Gluteraldehyde, beta-propiolactone, peroxygen
