Lecture 5 - Normal Flora Flashcards
What is a microbiome?
total community of microorgs in an enviro or body loc
What is normal flora?
microorgs present in or on a healthy animal
constant change in #’s and species within body
relationship btw normal flora and host is symbiosis
What is symbiosis?
An association of two or more diff species/organisms
refers to 1) bacteria/virus/yeast and 2) anima/plant in microbiology
relationship can be pos or neutral
How do you describe a symbiosis on or in the host?
ectosymbionts - on host
endosymbionts - in host
What is mutualism?
Both orgs benefit from relationship
A -> B -> A
What is commensalism?
Only one org benefits from relationship. The other is neither helped nor harmed
commensal is the org that is helped
A -> +B (Commensal)
What is competition symbiosis?
occurs when 2+ orgs share space
compete for available resources
2 outcomes
1: one will out compete the other(A,A,A,B,A)
2: both will exist at lower lvls(A,A,B,B)
What is the 4 roles of normal flora?
- aid w/ food product digestion (ruminant to digest insoluble fiber)
- Provides essential nutrients (GI flora synth vita’s, AA’s)
- Stims immune response (maintains low-lvl of ongoing immune activity for fast response to infection)
- Protect against infect by more virulent microbes
How does the normal flora help protect against infection by more virulent microbes?
- trhu comp. for space, nutrients
-bact alter pH to inhib growth of other microbes
-bact prod their own anti-microbial factors (bacteriocins) that prevent colonization - maintains low lvls of immune stim
- bind to + block pathogenic bact from binding to receptors on cell surface
What are two ways to control normal flora?
- competition - each popu. exists in low #’s than if only one popul. was present
- Immune system - balance btw normal flora + immune system (immune system to maintain normal flora lvls)
In regards to normal flora, when does disease occur? (3)
- too much normal flora
- too little normal flora
- normal flora moves to new loc not normally found in
What happens if there is an overgrowth of normal flora?
- common cause is decreased func of immune systems bc can’t maintain normal flora lvls
- when normal flora causes disease, now called opportunistic pathogen
when infection caused by normal flora is called a oppertunistic infection
What happens with a loss of normal flora?
- can be dec in all overall numbers of bact or dec. # of species
- = lack of compete., lack of bacteriocins, pathogenic bact have space to attach
-allows for pathogenic species to colonize or allows inc. in #’s of one species normally present in low numbers
-anims grown in labs w/o normal flora very high risk of infect/Dz
What normal flora is found in the nose?
staphylococcus aureus + Staphylococcus epidermidis
inside nostrils
What normal flora is found in the oro-nasopharynx
combo of aerobic + anaerobic bact
Common : Staphylococcus, streptococcus, haemophilus
mostly non-pathogenic bact unless they gain access to tissues that are normally sterile (sinues, middle ear, brain)
What normal flora is found in the trachea
“transiently colonized” by bact from oronaspharynx
microbes continually removed by mucociliary elevator
What is the mucociliary elevator
-mucus traps microbs + particles
- cilia loc on mucosal epithelial cells sweep mucus up into oral cavity to be spit our or swallowed
- main mechanism to keep microbes out of lower airways
-damage (virus infect, smoke inhale) will inc. infection risk
What is the normal flower of the lower resp tract?
NONE! Generally sterile
May transiently colonize w/ bact from upper respt tract butbact cannot establish
- microbes removed by mucociliary elevator
- phagocytosis by alveolar macrophages
- lysozyme in mucus
What are the risk factors for microbial colonization of the lower respt tract?
- acute/chronic aspiration - inhale infection material into lung via stomach/esophagus + inc risk of megaesophagus, chronic vomit
- Damage to mucus-generat cells + vilia of upper R tract - traumatic/chem injury, primary viral infect causes damage to cells, inflam (asthma)
What is the normal flora of the skin?
- Few bc hostile enviro (dry, oils, sloughing of skin cells)
- NoF tends to be transient
-Common Flora (most to least com)
Staphlococcus intermedius
Staphylococcus aureus
Fungi (malasezzia) in moist areas like groin, armpits
less often: Corynebacterium, streptococcus
What happens with normal flora and abnormal skin?
- if skin is warm/moist = inc bact + yeast - can cause pathology
-breach of intact skin allows bact to adhere to underlying subcutis and proliferate
-if bact popul. is disrupted, yeast popul may go into “overgrowth” and cause disease
What is the lay term for bacterial pyoderma?
A hot spot, red inflammed flesh
What is the normal flora of hair, fur and wool?
- contam by anything in enviro
- always considered a contaminant
-diff flora w/ external hair versus hair follicle (bact, mites) - can support its own biofilm under certain enviro conditions
What is the normal flora of the eye/ear
EYE: Sm #’s of bact present on conductive. Includes staphylococcus + streptococ. #’s held in check by lysozyme in tears
Ext Ear: sim bact + yeast on skin, common is staphylococ, also streptococ, Pseudomonas, enterbacteriacae
What is the normal flora of the mouth?
2 popul’s - aerobic (associated w/ teeth) facultative anaerobes, anaerobes (periodontium)
- bact plaque = mats of microbes (biofile) solidly attached to teeth.
inc. colonization if enamal wear/scratches, malocclusion, diet high in fermentable carbs
if plaque extensive, will extend subgingivally where change from aerobic to anaerobic populs’
what is the normal flora of the stomach - monogastric?
limited # of normal flora
most common lactobacillus, enterococc, helicobacter felis
Describe rumen flora
-distinct + complex
-allows anim to digest + extract nutr.s from cellulose
-microbes also digested by anim for macronutrints
-ability to derive nutr.s from cellulose and NoF enable ruminants to survive under very harsh nutr.s/ enviro conditions
10^12 microbes/ml rumen fluid
What are rumen normal flora composed of? What is typically found there?
composed of bact, protozoa, funci, archaea, virus
gram neg bact predominat
common E. coli, Lactobacilli, Streptococ bovis, Bacteroids
-Fibrolytic microbes brake down cellulose
-mostly strict (some facul.) anaerobes
- anaerobic bact ferment sugars to alcohols + acids that absorb thru rumen wall
lactobacilli prod building blods for milk sugar prod
What are archaea?
archaea are evolutionarily “old” prokaryotic organisms
make-up ~3% of microbial mass
convert H gas and Co2 to methane
methane belched out during rumination
What are viruses?
bacteriophage are viruses that infect + kill bact
causes cells to lyse
contents are then used as nutr.s by anim
Explain colonization of viruses in ruminants?
colonization of rumen is slow
microbes transmitted btw animals via nursing or transfer of cud
primary factor determining bact profile is diet
diet change must be slow (proper microbes reg to digest new diet takes 2-3 wks to estab)
What is the normal flora for sm intestine?
bact, fungi, protozoa
vry few microbes in duodenum
microbes #’s inc. moving distally towards cecum
mixed anaerobes (strict anaerobes > facul. anaerobes) (enterococ, E. coli, Enterobacteriaceae, clostridum
som pathogenic bact present in VERY sm #’s in healthy anims (salmonella, campylobacter)
What is the func of the sm intestinal flora?
- vita synth (Vita K prod + Vita B9, B12)
- contribute to digestion, (fiber)
- enhance segmental contractions
- inhib colonization by patho bact (via compet. prod of bacterocins)
- stim immune tissues in sm int
- take part in drug metab pathways
what is the normal flora of the lg intestine?
- lgst microbial popul. in body
- 10^11 bact/gram feces
-mostly anaerob bact (strict + facul) - dom species is e.coli in feel, k0 catl
also fecal streptococ, enterococ, klebsiella, bacteroides, clostridium, lactobacillus
-strains of e.coli that are pathogenic to humans found in 30% of dog feces sampled in 1 study
When does colonization start with normal flora in lg intestine?
colonization starts at birth w/ ingestion of birth canal secretion + feces
also acquired thru nursing
profile of flora changes w/diet
will also change w/ GI inflam
rapidly affected by oral antib’s
lack of balance btw normal flora and immune system can contribute to irritable bowel disorder
What are coliforms?
-rodshaped, gram neg, motile
-nonsporeforming bact
-can ferment lactose
-normallyfound in feces
-also found in water, soil, vegetation
- fecal coliforms include: Escherichia, enterobacter, klebsiella
What is SIBO? Sm int bact overgrowth
- when normal flora of sm int starts to resemble the colon
-occurs when there is dec. peristalsis and/or damage to the cecum -> allows normal lg int flora to migrat to sm int
Colon bact: creat gas -> gas distension, interfere with digestion/absorption, compete for nutrients
results in inflam, diarrhea, colic
