Term
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Definition
| Microorganism that causes disease |
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Term
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Definition
| Microbe that doesn’t cause disease (in normal circumstances) |
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Definition
| Entry, growth, & multiplication of a microorganism in the body that leads to symptoms & impairs health (disease) |
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Definition
Entry, growth, & multiplication of a microorganism in the body that causes no apparent clinical symptoms
establishment of bact colony w/in a host |
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Definition
| Ability of microorganism to cause disease |
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Definition
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Definition
| Characteristics of a microorganism that enhance ability to cause disease |
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Definition
| Infectious disease of animals that can cause disease when transmitted to humans (but not always causing symptomatic infection) |
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Term
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Definition
Habitat where pathogen lives, grows, & multiplies
-humans, animals, envir |
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Definition
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Term
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Definition
Rate ppl acquire infection in pop
Ex. 500 cases per month |
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Definition
| Death rate from infection in pop |
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Term
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Definition
| Microbes residing in host |
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Definition
| All microbes & combined genomes |
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Definition
| Microbes w health-promoting fxns |
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Definition
| Permanent residents that can cause disease via opportunistic infections |
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Definition
pathogen expressed during certain favorable conditions like antibiotic-induced dysbiosis
C diff, UPEC, UTIs |
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Term
| All transmission modes + pathogen examples |
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Definition
Direct contact:
-person-to-person (touching- Grp A strep & EC o157, sexual- C trachomatis & N gonorrhoeae, droplets- M TB & B pertussis, in utero- Grp B Strep & L monocytogenes)
Indirect contact:
-vehicle-borne (contaminated obj/substance like food- EC O157, blood- S aureus, doorknobs- Grp A strep)
-airborne (suspended in air for long periods- Legionella pneumophila)
-vector-borne (mechanical = direct transfer- flies w EC O157, biological = parasite inside reservoir/vector- mosquito w malaria) |
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Term
| Chain of infection: EC O157 |
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Definition
Shiga toxin, intimin, acid resistance genes
Animals-> fecal contaminated food-> mouth |
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Term
| Chain of infection: Bacillus anthracis |
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Definition
Sporulation, poly-γ-d-glutamic acid capsule, edema factor, lethal factor
Soil, hides, animal blood-> inhalation, intestinal, cutaneous, injection |
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Term
| Chain of infection: Clostridium difficile |
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Definition
Sporulation, flagella, surface layer proteins, polysaccharide capsule, D-alanylation of teichoic acids, hydrolytic enzymes, toxins A & B
Feces-> spores on fomites-> mouth ingestion |
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Term
| Chain of infection: Grp A Strep |
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Definition
M proteins, A capsule, pyrogenic toxin
human nasopharynx-> saliva, nasal secretions-> mouth or skin break |
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Term
| Chain of infection: Mycobacterium tuberculosis |
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Definition
Ag 85 complex, cord factor, KatG, SodA, glycolipid envelope, granulocma formation, tissue damage
Human respir tract-> droplet spread-> mouth |
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Term
| Chain of infection: V cholerae |
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Definition
Polar flagellum, toxin coregulated pills, cadA, biofilms, cholera toxin
Feces-> Contaminated water-> mouth |
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Term
| Factors that impact host susceptibility |
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Definition
Immune status
Exposure lvl (ex. Crowds)
Children/elderly
Behaviors (needle sharing, sexual activity, ex)
Pre-existing infections
Genes
Pathogen characteristics
Malnutrition
Medications (antibiotics, chemotherapy, etc) |
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Term
| Specific & nonspecific host defenses |
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Definition
Specific: acquired, protective Abs
Non-specific: innate, skin, nasal hairs, coughing reflex, cilia, enzymes in saliva & tears, low pH, phagocytes, genes |
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Term
| Ways that chain of infection can be broken to prevent disease |
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Definition
| Each link is required for infection, break anywhere to control disease |
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Term
| describe & draw Koch’s postulates + experiments |
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Definition
1. Suspected pathogen is present in every case of disease
2. Pathogen can be isolated & grown in pure cultures
3. Pathogen causes same disease when put in healthy host
4. Pathogen can be reisolated from now diseased host
-Then, conclude that pathogen causes the disease
-Shown in B anthracis from cows to mice
-Shown in TB from apes, humans, & cattle to guinea pigs
-VC failed bc not all healthy hosts introduced to pathogen developed disease |
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Term
| Problems w Koch’s postulates + examples |
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Definition
1. Assumes disease symptoms are completely due to microbe (autoimmune conditions, pathogen interactions)
2. Assumes bacterium can be cultured (Mycobacterium leprae)
3. assumes bact characteristcs dont change during infection or after culture (Shiga toxin-producing EC)
4. Assumes pathogens are equal in ability to cause disease (Grp A strep variation by host susceptibility & virulence)
5. Requires experimental infection to new host (need adequate animal models)
-Modified to include virulence genes-> can be modified to inactivate |
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Term
| Compare/contrast infectious disease trends (outbreak, sporadic, endemic, pandemic, etc) |
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Definition
Sporadic: isolated cases that cant be linked to others
Endemic: background lvl of disease in pop
Outbreak/epidemic: sudden increase in frequency in specific pop > endemic lvls
Pandemic: epidemics over wide geographic area affecting high proportion of pop |
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Term
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Definition
| Get E from food, absorb vitamins, regulate immune sys to recognize some microbes as self, metabolize drugs, protect against disease-causing microbes |
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Term
| Factors that influence microbial composition |
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Definition
O2, pH, water, surface T, nutrients, UV exposure
Age, gender, diet, drugs, immune status, genes, race, behaviors, infections, hormones, exercise, weight, climate, skin care |
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Term
| Why some microbes more common at certain sites |
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Definition
O2, pH, water, surface T, nutrients, UV exposure
Diff sites = diff conditions = favorable to diff microbes |
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Term
| Why microbes diff across ppl |
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Definition
| Age, gender, genes, behaviors affect microbiome |
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Term
| Diff methods to characterize microbiome |
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Definition
16S rRNA seq: variable regions dictate phyla & # of reads dictates abundance
Culturing: difficult bc 20-60% microbes non-cultivable
Metagenomics: random shotgun seq of DNA, includes all viruses/phage/fungi/bact, can make predictions abt fxn
Transcriptomics: random shotgun RNA seq: transcriptional active genes, predictions abt fxn
Mass spec: proteomics & metabolomics, which proteins of metabolites present, metabolomics is best rep of given sys bc gives picture of full spectrum of chem rxns occurring |
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Term
| How microbes can prevent pathogens from causing infection |
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Definition
Produce inhibitory molecules
Nutrient deprivation
Prevent colonization
Limit inflammatory responses |
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Term
| How microbiome develops & changes over t |
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Definition
Microbiome changes after birth
Becomes more stable by early childhood
Can change w treatments, malnutrition, obesity
Older indiv have more unhealthy microbiome |
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Term
| Characteristics of healthy vs diseased microbiomes |
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Definition
Healthy: balanced level of firmicutes & bacteroidetes, high diversity
Unhealthy: more proteobacteria, less diversity |
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Term
| How specific factors (ex. Antibiotics) impact microbiome & pathogenesis of bacteria (ex. C. difficile) |
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Definition
Abs decrease microbiome diversity & select for resistant bact pops that can persist-> enrichment in virulence gene abundance & enhance inflammatory responses
Inflammation & deletion of some symbionts allow some pathogens to invade & proliferate |
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Term
| Pili vs fimbriae vs afimbrial adhesins |
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Definition
Pili & fimbriae: rod shaped filament our proteins on cell surface
-pili = longer & thicker, “hair”, tip attaches to host cell receptors, made of pilin protein
-fimbriae = shorter & thinner, “thread”
Afimbrial adhesins: embedded in cell surface, not long or filamentous, proteins, mediate tight binding, often used after initial attachment by pili |
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Term
| Nonspecific vs specific adherence, diff types |
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Definition
Nonspecific: reversible attachment, “docking”, attractive Fs
-HPho, electrostatic, acid-base, van der waals
Specific: irreversible, “anchoring”, bonds betwn complementary molecules
-adhesin + receptor |
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Term
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Definition
| Structure/molecule on pathogen surfaces that mediates binding to host cells |
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Term
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Definition
Molecule on host cell surface that binds to adhesin
-glycoproteins or carb residues
-extracellular matrix molecules |
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Term
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Definition
Pap pili & type I fimbriae
Intestinal & urogenital tracts-> feces, urine, genital secretions-> sexual contact, fecal-oral, fomites-> mouth, urogenital tract |
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Term
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Definition
Type IV pili, effector proteins, intimin
Intestinal tracts-> feces-> mouth |
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Term
| Chain of infection: N go off |
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Definition
Type IV pili, Opa proteins, endothelial I would
Urogenital tracts-> sex & fecal-oral-> mouth/urogenital tract |
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Term
| Adherence mechs for UPEC, EPEC, N gonorrhoeae, & EC O157 |
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Definition
UPEC: pap pili assembled via chaperone usher sys in kidneys, type I fibriae in bladder
EPEC: type IV pili (bundle-forming)-> type III secretion sys inserts Tir into host cells-> initimin attachment
NG: Type IV pili loose-> Opa intimate
O157: Intimin protein |
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Term
| Why is adhesin specificity important & what does it predict |
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Definition
Determines site of colonization (tissue tropism) & host range (host specificity)
Variability in adhesin genes dictate specificity |
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Term
| How pili are assembled via chaperone usher sys, role of diff proteins |
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Definition
Ex. Pap pili, type I fimbriae
Proteins thru IM via Sec sys-> chaperone brings to FimD “usher”-> adhesive FimH tip & PapG thru 1st-> FimA forms majority of shaft |
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Term
| How phase variation works in type I fimbriae |
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Definition
Regulatory switch element: fim switch is invertable DNA element w/ promoter for fimA
Recombinases fimB & E bind to inverted repeat to turn fimA transcription on/off |
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Term
| Adherence strategy/steps in UPEC vs EPEC vs N gonorrhoeae |
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Definition
UPEC: diff adhesins for diff areas during movement, colon-> urethra-> type I fimbriae in bladder-> pap pili in kidneys
EPEC: type IV pili attaches to host cells & other EPEC cells-> type III secretion sys inserts Tir (tranlocated intimin receptor) into host cell-> intimin attaches to tir to trigger cell rearrangements |
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Term
| Role of type IV pili in N gonorrhoeae, how assembled, retraction, twitching motility, competence |
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Definition
Attach to host epithelial cells & each other to form microcolonies
Pilin proteins translocations across IM as pre-pilins-> PilD protease cleaves N-term leader seq-> mature PilE peptide released-> extension via PilQ secretion pore-> extension & retraction by ATP conversion, proteins degraded during retraction
Extension/retraction results in twitching motility along a surface
Upon retraction, pseudopilus in PilQ pore w/ pore connected to Com proteins that allow DNA uptake
Roles: adherence, twitching motility, natural competence |
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Term
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Definition
| Enzymes (proteases & transpeptidases) that recognize pilin proteins |
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Term
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Definition
Microbial surface components recognizing adhesive matrix molecules
G+ pathogens (ex. S agalactiae)
Surface-associated molecules covalently attached to PG by sortases (but not pili)
Important for intimate attachment, invasion, & biofilms |
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Term
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Definition
| Microbes growing on surfaces encased in self-secreted EPS matrix |
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Term
| Extracellular polysaccharide substance (EPS) |
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Definition
Self-secreted matrix of biofilms
Composition affects conditions of biofilm & varies by pathogen |
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Term
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Definition
| Biofilms of diff microbes |
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Term
| Chain of infection: Strep agalactiae |
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Definition
Pili, MSCRAMMs, capsule, hemolysin toxin
Gastrointestinal & urogenital tracts-> sex, fecal-oral, placenta |
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Term
| 3 routes of invasion by S agalactiae |
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Definition
Invade membrane of host cells by
1. Pl3K & Akt
2. FAK + Paxillin
3. Rho/Rac |
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Term
| Adherence mechs for S agalactiae |
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Definition
Pili loose attachment
MSCRAMMs for intimate attachment |
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Term
| 3 virulence factors for S agalactiae |
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Definition
Pili loose attachment
MSCRAMMs intimate attachment
Rho/Rac for cellular invasion
Hemolysis toxin
Protective capsule |
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Term
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Definition
G+: lipoteichoic acid (LTA) anchors cell wall to IM & can be used for adherence, cross-linked PG covalently linked to teichoic acid, polysaccharide capsule, “cell wall” of thick PG
G-: LPS can be used for adherence, thin PG separating IM & OM |
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Term
| Adherence in G+ vs G- bact, pathogens that use chaperone-usher vs type IV pili assembly sys vs sorta set assembly sys |
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Definition
G+: pili anchored to PG, LTA can be used for adherence, pili assembly requires sortases
G-: pili anchored to OM, LPS can be used for adherence, chaperone-usher assembly, & type IV assembly thru PP, type I & IV pili |
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Term
| How sortases aid in assembly & presentation of adhesins on G+ bact |
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Definition
recognize & cleave LPXTG motif & link together pilin monomers-> pilin can be anchored to PG at peptide cross-bridges
SrtA: “house-keeping”, anchors proteins to cell wall
SrtC: “pious-specific”, recognizes & links pilins |
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Term
| Microbial communities vs biofilms, 5 steps of biofilm formation, why there is heterogeneity in biofilms |
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Definition
| loose attachmen (pioneers) (reversible)-> intimate attachment (settlers), micro colony formation (irreversible)-> signaling & aggregation (society), proliferation (EPS production, QS, channel formation)-> community, maturation-> dispersal of planktonic bact |
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Term
| Specific components of EPS in biofilms |
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Definition
Polysaccharides: major component, gel-like, alginate promotes water retention, cellulose & poly-N-acetyl glucosamine (PNAG) provide structure
proteins: enzymes digest compounds for nutrients or dispersal
DNA: extracellular eDNA provides structure during early formation & horiz gene transfer
water, lipids
Extracellular polymeric substance |
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Term
| Why biofilms important for some pathogens, examples |
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Definition
Poor Ab recognition
Avoids killing by antibiotics, phagocytes, & antibacterial peptides
Contains nutrients, metabolites, & water
Cell-to-cell communitarian
DNA exchange
Switch from planktonic to biofilm is an important virulence trait
Can spread to other locations
Dental plaque of cavities
S aureus in wounds
Catheter & implant infections
UPEC UTIs
Enteroaggregative EC in mucus layer (EC O104:H4 is shiga toxin-producing & biofilm-forming) |
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Term
| Factors that impact composition of microbes in biofilms |
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Definition
| Oxygen & nutrient gradient |
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