microbiology 227 Flashcards
gram staining
Done with crystal violet stain
Gram positive retain the violet dye
A counterstain is added (commonly safranin or fuchsine) and this will wash off the crystal violet from those bacteria which haven’t retained the stain i.e Gram negative
gram +ve
tend have a single membrane (monoderm) surrounded by a thick peptidoglycan
gram -ve
posses a thin layer of peptidoglycan between 2 membranes (diderms)
bacterial morphology options
5 stages in bacterial biofilm growth
- Reversible attachment of planktonic cells
- First colonisers become irreversibly attached
- Growth and cell division
- Production of EPS (exopolysaccharides) and formation of water/nutrient channels
- Attachment of secondary colonisers and dispersion of microbes into new sites
caries progression
S.Mutans is exposed to sucrose in the oral cavity and metabolises it producing two things
- Lactic Acid - that demineralises the tooth tissue
- Glucans - these allow adhesion of S.Mutans to other organism
- Soluble (water) glucans
- Insoluble glucans
The pH of the environment decreases to more acidic, but the bacteria, gain ATPase pumps to put out H+ ions to gain acid tolerance
streptococci and acid production
In normal ph they use the Phosphotransferase system to uptake sugars
In low ph environments they can utilise a lower affinity transport system to take up sugars to survive
- which if they didn’t have it would mean they would starve
They do this by taking advantage of the ph gradient
ICF – high ph , ECF – low ph
use this to uptake sugar
key organisms in caries
- sterptococcus mutans
- streptococcus spp
- lactobacillus acidophilus
key organisms in periodontal disease
- pophymonas gingivalis
- treponema denticola
- prevotella intermedia
- agrregnacter actinomycetemcomitans
- fusobacterium nucleatum
key organisms in endo infections
porphyromonas endodontalis
prevotella intermedia
enterococcus faecalis
fusobacterium nucleatum
key organisms in candiasis
candida albicans
candida glabrata
candida tropicalis
staphylococcus aureaus (in angular chelitis)
Newtown’s type 1 inflammation
localised
Newton’s type II inflammation
diffuse
Newton’s type III inflammation
granular
4 bacterial resistance mechanisms
- blocking entry
- inacivating enzymes
- alteraion of target molecule - enzymes in the organism alter the receptor the antibiotic/fungal would previously bind to
- efflux of antiobiotic - efflux pumps
fluoride 2 actions
remineralises enamel
inhibits ATPase’s ability to produce hydrogen ions
supragingival plaque predominately
aerobic bacteria
subgingival plaque predominately
anaerobic bacteria
p gingivalis properties
has pilli that allow it to co-aggregate with other bacteria
produce gingipains can degarde chemokines
inc MMPs - cause dysbiosis (unbalanced mucrobial community)
Periostat
doxycycline - inhibits MMPs
reduces immune inflammatory response
denture stomatitis is only
pseudomembranous
not tissue invasion
c albicans or glabrata more resistant to azoles
c glabrate
if see hyphae in scraping more likely albicans
azoles are
fungostatic
need mechanical action to kill of bacteria
denture stomatitis caused by
plaque biofilm
non specific
what can occur if abscess left untreated
endotoxic shock or super-antigen infection
incision and drain to take sample for anaerobes
potentially life threat of submandibular abscess
respiratoy compromise
habitat
site where organism grows
microbial community
MO growing in particular habitat
ecosystem
MO community in a specific habitat and their surroundings
- Physical, Chemical and Biological properties dictate composition of community
- Those which survive and dominate and those which die
niche
function of an organism within its community – organisms compete for a niche, in mixed communities it is only stable if there is a niche for all the different types of organisms
resident microflora
organisms regularly isolated (found) in a site
pathogens
MO with potential to cause disease
oppurtunistic pathogens
organisms with the potential to cause disease
dental plaque
Bacteria and degraded mammalian cells , surrounded by matrix containing both protein and polysaccharide
saliva role in MO in mouth
Lubricates mouth
Buffering effect
Mucins and Glycoproteins (saliva components) do the following
- Adsorb to tooth surface – create pellicle for mic-orgs to attach
- Nutrient source for bacteria (Carbohydrate, Protein)
- Aggregate mic-orgs and clear them from the mouth
- Inhibit growth of some bacteria
gingival crevicular fluid role in MO in mouth
Serum-like fluid
Nutrient source
Flow can remove non-adherent organisms
IgG, IgA, IgM, complement system
factors affecting microbial growht in the mouth
7
temperature
anaerobiosis
pH
nutrients
adherence
antimicrobials
host defences
pH and microbial growth
pH 6.5 in mouth ideal for microbial growth
pH 5.0 after sugar intake – lactate produced by bacteria, saliva can’t penetrate plaque at the enamel surface
pH gradient exists, in caries acid producers like Strep and Lactobacilii assume a larger niche = ph falls even lower
factors in microbial adherence
EPS promotes adherence to surfaces
- Adhesins (lectins, fimbrils, lipoteichoic acid)
- Receptors (sialic acid on epithelial cells, collagen, fibronectin) – host derived factors
colonisation
6 steps
- Obtain Nutrients from Saliva and diet
- Tolerate variables – ph, oxygen tension, ionic strength
- Overcome host defences
- Grow at rate either greater than or equal to other species
- Resist other bacteria that may prey on them or that produce toxins
- Adhere to surfaces
gram +ve bacteria morphology
Cell wall
- Thick multi layered
- Cross linked Peptidoglycan
- Teichoic and lipoteichoic acid
- Retains crystal violet stain
gram -ve bacteria morphology
Cell wall
- Doesn’t retain the gram stain
Outer membrane
- Unique to gram –ve
- Contains transmembrane proteins e.g porins
- Allow diffusion of hydrophilic molecules through membrane
Periplasmic space
- Between outer membrane and cytoplasmic membrane
- Contains sugar transport systems
- Hydrolytic enzymes (breakdown macromolecules for metabolism)
2 types of passive transport
simple diffusion
facilitated diffusion
simple diffusion
molecule moves directly through opening/pore in membrane without interacting with another molecule
- Through a lipid bilayer
- Through a membrane pore
- Through a channel in a protein cluster
facilitated diffusion
Molecules transported across membrane by binding to one or more carrier protein in the membrane
- Single transport protein
- Delivery by several protein components
- Through a gated channel in a transmembrane protein
Transport molecules involved in Facilitated diffusion
- Uniport – Single solute carrier from one side
- Symport – Co-transport of two different substances in the same direction
- Antiport – co-transport of two different substances in the opposite direction
active transport
Energy required to move substances uphill against a concentration gradient
- provided by ATP and a specific ATPase
3 types of active transport
H+/lactose symporter
phophotransferase sysyem
histidine periplasmic system
H+/lactose symporter
active transport
Ionic gradients/membrane potential provides energy
Co-transport of sugar/amino acid along ionic conc. Gradient
H+ translocation creates electrochemical gradient that drives uptake of lactose
phosphotransferase system
active transport
Glucose phosphorylated into glucose-6-P > GLYCOLYSIS > PEP
Glucose + PEP -> Glucose-6-P + pyruvate
catalysed by an enzyme II complex
histidine periplasmic system
active transport
Occurs between outer membrane (where histidine enters) and the cytoplasmic membrane
HisJ binding proteins wait in the periplasmic space
Histidine forms a complex with HisJ
Histidine-HisJ complex binds to membrane components
Intracellular ATP hydrolysed by the complex which allows Histidine to cross over into the inside of the bacteria
EPS contains
mutans
dextrans/levans
mutans in EPS
gel like - inc bulk of plaque
insoluble so create highly anaerobic conditions between plaque fluids and saliva
assist in bacterial attachment
dextrans/levans in EPS
carbohydrate reserve
levan is rapidly metabolised and is degraded v quickly by oral bacteria
carbohydrate production and acid production in aerobic conditions
outer surface of plaque
Pyruvate is completely oxidised to CO2 and H20 via Kreb’s cycle and respiratory chain
NADH formed in krebs cycle is oxidised by respiratory chain
carbohydrate production and acid production in anaerobic conditions
inner surface of plaque
Pyruvate -> lactate
orther organic acids are formed - low pH in dense plaque
Kaposi’s Sarcoma
Affects mucous membranes, skin and lymph nodes
Purple lesions
Associated with HHV-8 (Human Herpes Virus 8)
HIV and AIDS
Acute primary infection
o Glandular fever like
o 10% symptomatic
Latent period
o Patient asymptomatic
o Can be latent 8-10 years
Symptomatic stage
o ARC (AIDS related complex)
o Hyperactive B-cell response
o Follicular/mixed hyperplasia of lymph nodes
Oral Lesions associated w/ HIV
- Erythamatous Pseudomembranous Candidiasis
- Hairy Leukoplakia
- Kaposi’s sarcoma
- Non-Hodgkin’s Lymphoma
- Periodontal disease
- Linear gingival erythema
- Necrotising Ulcerative gingivitis
- Necrotising Ulcerative periodontitis
- Paediatric HIV – Parotid Enlargement
bacteriostatic
inhibit proliferation of bacteria
bacteriocidal
substance kills bacteria
detergent
group of synthetic organic water soluble agents that contain the following
▪ wetting agents
▪ emulsifying agents
▪ soil holding properties
disinfectant
process for the removal/destruction of microbes (not usually bacterial spores)
staphylococcus aureus
desc
virulence factor
disease
DESCRIPTION
- gram positive, occurs in clumps
VIRULENCE FACTOR
- Panton-Valentine Leukocidin toxin > leads to tissue necrosis
DISEASE
- Pyogenic infections – pus (boils, abcesses, wound infections)
- Toxin mediated- Toxic shock syndrome
streptococcus pyogens
desc
virulence factor
disease
DESCRIPTION
- gram positive
VIRULENCE FACTOR
- Super antigens, toxic shock syndrome
DISEASE
- Acute Rheumatic fever, Glomerulonephritis, Meningtitis, pharyngitis, toxic shock
streptococcus anginosus
desc
virulence factor
disease
DESCRIPTION - gram positive
VIRULENCE FACTOR - Intermedilysin
DISEASE- Bacteremia, Splenic Abcess
clostridium perfingencs
desc
virulence factor
disease
➢ DESCRIPTION - Anaerobes
➢ VIRULENCE FACTOR - Alpha toxin (Lecinthinase)
➢ DISEASE - Myonecrosis, Haemolysis
herpes simplex
desc
virulence factor
disease
DESCRIPTION - DNA envelope virus
VIRULENCE FACTOR - Causes cell lysis
DISEASE - Herpes labialis
candida albicans
desc
virulence factor
disease
DESCRIPTION - Gram +ve fungi
VIRULENCE FACTOR- Phospholipase
DISEASE- Erythamatous Candidiasis, Pseudomembranous Candidiasis
impetigo
epidermis infection
requires fibronectin to infect breaks in skin
caused by staph
angular chelitis
epidermis infection
candida albicans or staph
erysipelas
infection of dermis
rasied rosy rash
disappears on pressure
group A staph
folliculitis
infection of hair follicles
staph
treated with antibacterial soad and antibiotics (cephalosporin, dicloxacillin)
cellulitis
infection on subcutanous
non suppartive bacterial infection
group A staph
infection of connective tissue and interstitum and not cells themselves (misnomer)
necrotising fascitis
infection of fascia
can result in septicaemia
gram +ve and -ve bacteria
myonecrosis
clostridium perfringens
casues deep trauma with groww contamination
infection of muscle
gangrene
wet type is bacterial
clostridium perfringens and bacillus fusiformis
infecition of muscle
