microbiology need to know Flashcards
how is a biofilm formed?
- adhesion to surface via weak VDW forces- if not removed then anchor onto surface more permanently using cell adhesion structures such as pili
- colonisation-biofilms grown via cell divison and recruitment
- accumulation
- complex community
- dispersal- biofilms spread and colonise new surfaces
what factors affect colonisation growth?
- surface roughness
- whether the surface is hydrophobic or hydrophillic
what is a biofilm?
a matrix-enclosed bacterial or fungal population adherant to each other and/or surfaces or interfaces
what is the difference between candidosis and candidiasis?
candidosis affects the mouth
candidiasis has systemic general effects
give examples of candida species
- albicans
- glabrata
- tropicalis
- parapsilosis
- krusei
which 2 organisms are resistant to flucanozole?
- candida glabrata
- candida krusei
define “faculatively anaerobic”
usually respires aerobically but can respire anaerobically if no air present
define “obligately anaerobic”
can only breathe anaerobically
harmed in the presence of oxygen
define “canophilic anaerobic”
thrive in high cone of CO2
define micro aerophilic
requires oxygen but at a lower cone than is available in the atmosphere
give 5 methods of identifying micro-organisms
- gram staining
- ziehl-neelsen staining
- PCR
- blood agar, selective agar (mannitol salt)
- H&E staining
what microorganism causes caries (most commonly)?
streptococcus mutans
what gram stain is streptococcus mutans?
gram positive cocci
give 4 examples of cariogenic bacteria
- streptococcus mutans
- lactobacillus acidophilis
- acitnomyces viscosus
- nocardia spp
give virulence factors of cariogenic bacteria
- synthesis of glucans
- extrsuion of hydrogen ions through ATPase
- polysaccharides store glycogen and protect the matrix
what bacteria are responsible for periodontal disease?
- prevotella intermedia
- porphyromonas gingivalis
which microorganisms are found in the red section of Socransky’s model?
porphyromonas ginigivlalis
tannerella forsythia
treponema denticola
what are the virulence factors of candida albicans?
phospholipase contributes to host cell penetration
haemolysin facilitates hyphal invasion
proteinase aids in adhesion to epithelial cells
how is denture stomatitis diagnosed in the lab?
smear test / microscopy
swab /culture on sabouraud’s agar / germ tube formation
angular cheilitis and acute pseudomembranous candidosis also the same
what term is used to describe a collective group of microorganisms within the oral cavity and what are they referred to when they attach to a surface
microbiome
attached to surface - biofilm
what are key microbial stages of caries plaque formation
adhesion
collonisation
maturation
acid prodcution
what are virulence factors used by strep. mutans for enamel dissolution
glucans (glucosyltransferase - attach)
ATPAse (control pH)
what is the bacterium associated with secondary endodontic infections
enterococcus faecalis
what are virulence factors of enterococcus faecalis
gelatinase
superoxide
cytolysins
adhesins
collagenase
why is it difficult to determine causality from a specific bacteria in endodontic infection
sterile sampling procedures
active/functional bacteria
what culture independent technique could be used to assess changes in the oral microbial populations following antibiotic exposure
next generation sequencing
what is the limitation of next generation sequencing
limited to describing what is present rather than what communities are causing the problem
what are systemic diseases associated with periodontal biofilms
periodontitis
Rheumatoid arthritits
why do biofilms not allow antibiotics to penetrate them?
- biofilms can produce a penetration LPS which prevents antimicrobials and antibiotics from penetrating
- require mechanical disruption- medication alone will not remove them
what is the process that leads to inflammation?
- vasodilation- increased blood flow (redness and warmth)
- increased permeability- causes swelling
- concentration of red cells- decreased velocity, stasis of blood flow
- leukocyte adhesion and migragion- accumulation of inflammatory cells
give 2 bacterial dection methods
- PCR test
- culture on suitable agar medium
what is required into order to complete a PCR test?
- double strnaded DNA template
- primers specific to the particular gene
- dNTPs
- enzyme Tag SNA polymerase- catalyses the synthesis of new DNA strands
what gene do PCR primers target?
165 rRNA gene
what is the main microorganism associated with endodontic infections?
E. faecalis
What are the classifications for candida
Pseudomemranous - thrush
Erythematous - denture/HIV
Hyperplastic - Leukoplakia
Angular Chelitis
Chronic Mucocutaneous
What microbes because candida infections
Albicans
Glabrata
Krusei
Tropicalis
Parasilosis
What candida species are resistant to fluconozole
Glabrata
Krusei
why is it difficult to determine which bacteria is the cause of an endodontic infection?
sterile sample procedures are required
difficult to determine between active/functional bacteria
What are virulence factors of Candida Albicans
Phospolipase - host cell penetration
Hemolysin - Facilitates Hyphal invasion
Proteinase - Adhesion to epithelial cells
What are risk Factors for candida
Denture wearer
HIV
Immunocompromised patients
Prolonged Steroid/Antibiotic
Diabetic
name virulence factors of E. faecalis
- gelatinase
- superoxide
- cytoglycins
- adhesins
- collagenase
What are the treatments for patients with candida
Immunocompromised - systemic (fluconozole) and topical (nystatin or chlorhexidine)
Dry mouth - Topical only
Good OH - Systemic or topical
Bad OH - OHI and CHLORHEXIDINE
what do gram + bacteria stain purple?
thick petigloglycin layer in cell wall
what microbes area associated with gingivitis
A. A.
Provotella Intermedia
Fusobacterium
what microbes area associated with perio
P. Gingivalis
T. forsynthia
T. Denticola
Provatella intermedia
What are systemic implications of periodontal microbes
Diabetes
RA
what does it mean if clearing appears around a metronidaole disc on an agar plate?
a gram negativ anaerobe is forming
What are virulence factors of perio microbes
Adhesion - Fimbriae
Elaboration of Proteases - Phospholypase
Endotoxins
Capsular Polysaccharides
Metabolic By-Products
describe next generation sequencing
culture independent
assesses changes in a population
only determines what is present
What are methods for sampling
Oral Rinse
Oral Swab
Biopsy
Plaque sample
what microorganisms are responsible for caries?
- streptococcus mutans
- lactobacillus
- prevotella spp
- actinomyctes
What is the methodology of antibiotics
inhibit cell wall synthesis
cause injury to the plasma membrane of bacteria
Inhibit transcription so cant reproduce
Inhibit protein synthesis - cant reproduce
give virulence factors for cariogenic microbes
- extracellular polysaccharides - adhesion
- glucans- adhesion
- ATPase- control pH
- acidogenicity- produces acid
- acid tolerant- survives at low pH
How do bacteria become resistant to treatment
adapt cell wall to block entry of antibiotics
Produce inactivating enzymes that destroy active component of drug treatment
Alter target molecule to stop drug binding to bacteria and evade detection
Efflux pump - bacteria produce efflux pump which removes drug out of the cell and lowers drug concentration inside cell
what is a contra indication of fluconazole
warfarin and statin
hoe do you break the chain of infection
Infectious agent - diagnosis/treatment
Reservoir - disinfection
Portal of exit - hand-washing and control aerosol/splatter
Means of transmission - isolation, disinfection and hand-washing
Portal of entry - first aid and hand hygiene
Susceptible host - immunisation and treat underlying disease
what are the stages of caries plaque formation?
adhesion
collonisation
maturation
acid production
