General
Bacteria: 0.1-10µm
Viruses: 0.03-0.3µm
Protozoa Fungi: 4-40µm
Bacteria
Viruses
Structure
Structure
Gram Staining
Process
- Stain with crystal violet
- Wash alcohol
- Stain Saffrin
Peptidoglycan maintains crystal violet better so positive (blue), negative (red)
Implications
Negative more resistant:
LPS outer membrane blocks diffusion of low molecular weight compounds. (eg. antibiotics/lysozymes)
Differences
Negative: Endotoxin
Positive: No Endotoxin
Negative: LPS (Spans between Cell wall layer & Outer membrane)
Positive: No LPS
Negative: More lipid
Positive: Less lipid
Cell Membrane
Negative: Thinner less crosslinking
Positive: Thicker more crosslinking
Positive (2layers):
- Cell wall (60-100% Peptidoglycan)
- Cytoplasmic membrane
Negative (3layers):
- Outer membrane
- Cell wall (5-10% Peptidoglycan)
- Cytoplasmic membrane
Negative: Periplasmic Space, Porin channel
Positive: No space, No Porin channel
Mycobacteria:
- Weakly gram positive
- Stains: Acid fast aka. Ziehl Neelsen
- Hot carbol fuchsin, Acid-alcohol wash
- Mycobacteria retain thick waxy cell walls
Mycoplasma
- No cell wall
- Are not stainned
Prokaryotic
Smaller Ribosome
DNA/RNA/Plasmid
No mitochondria
Endospores only by 2 genus (Gram positive)
- Resistant to heat
- Resistant to cold
- Dormant
- Resistant to drying and chemicals
- Multi-layered protective coat
Capsular:
- Usually more pathogenic
- Harder to detect by WBC
Prions
Examples
Fatal Familial insomnia (FFI)
Kuru (Shivering)
Creutzfeldt-Jakob (CJD)
Gerstmann-Straussler-Scheinker (GSS)
Properties
Long incubation
No immune response
Non-inflammatory process
Macro: Normal
Micro: Spongiform changes
What are they
Inanimate, mishapen proteins that multiply in the brain
Implications
Hard to detect
Very resistent to heat, disinfectants (Iatrogenic transmission)
Oral Flora
- Pneumonia
- Bacterial Endocarditis
- Atheromatous
- Diabetes
Variation
Age
1y/o (Mucosal)
Hours from birth (Mucosal):
Teeth errupt (Mucosal, Tooth, Crevice)
Adolescence
Increases
Old age
Locality
Edentulous (Same as pre-erruption)
Acrylic (Candida)
Staphylococcus Aureus
Lactobacilli
Yeast
- Anaerobes
Porphyromonas
Prevotellas
- S. mutans
- S. sanguis
- Actinomyces
Sub-Gingival
- Fusobacteria
Sub-Gingival
- Streptococci
Supra-gingival
- Staphylococci
- Neisseriae
- Lactobacilli
- Veillonella spp
Sub-Gingival
Supra-Gingival
Sub-Gingival
Anaerobes
- Actinomyces
- Gram negative
Streptococci
L2: Spread
L3: Lab Diagnosis
Classification
Active:
- Pathogen
- Symptoms
- eg. Influenza, Common cold
Carrier
- May go on to develop
- Source of infection
- Chronic Carriage: Unable to eradicate infection
- eg. HIV, Hep B & C, herpes
Prodromal
- Early signs
- Not full blown
- eg. (Measles, Mumps, Chickenpox)
Routes
Faceal-oral
- Fingers
- Flies
- Fomites
- Food
- Fluids
Airborne
- Droplets
- Droplet nuclei
- Spores
- Skin scales
Contact
- Horizontal: Between generation
- Vertical: Mother to child
Percutaneous & Mucous membrane
- Needles
- Vectors eg. Mosquitos
- Splash of blood into eye / mucous membrane
- Encourage bleeding
- Wash/rinse
- Post-exposure prophylaxis
Investigations
Serology (serum)
Culture
Microscopy
Antigen detection
Molecular Biology
Ziehl Neelsen / Acid Fast
Bacteria Florescence
Gram Stain
Disadvantages
- Limited information
Advantages
- Same-day tests
- Faster than culture
Advantages
- More info than microscopy
- Definitive identification (Individual)
Disadvantages
- Slow (1day-weeks)
Solid / Liquid
- Cannot see individual cells
Selective: Supress normal flora
Differential: Indicate presence
Enrichment: Liquid to amplify
Advantages
- Measures Ab in late phase
- When PCR and culture negative
Advantages
- Faster than culture
- Requires little sample
Disadvantages
- More expensive
Disadvantages
- Long wait time
Only on surface
Immunofluorescene
- Streptococcus Salivarius
Ecological plaque hypothesis
(Marsh, 1991, 1994)
Periodontal disease results from
upset in microbial balance
Health/Disease
Blue: Facultative Anaerobes
White: Obligate Anaerobes
Disease
Periodontitis
Obligate Anerobes
Gram -ve
- Porphyromonas gingivalis
- Tannerella forsythia
- Treponema denticola
Health
Experimental Gingivitis in Man
(Loe et al 1965)
Initial: Gram +ve cocci & rods (>80%)
Gingivitis: Gram +ve cocci & rods (45-60%)
Fusobacteria, Gram -ve
Biofilm
Attachment
Transport
Pellicle formation
Co-aggregation
Detachment
Early Colonizers: +ve Facultative Anaerobes
Late Colonizers: -ve Obligate Anaerobes
Obligate Aerobes: Requires O2
Obligate Anaerobes: Cannot have O2
Facultative Anaerobes: With or without O2
Capnophilic: Like CO2
Obligate Anaerobes
- Tannerella forsythia
- Porphyromonas gingivalis
- Proteolytic
- Raise pH
- Promote bacterial growth
Health
Facultative Anerobes
Gram +ve
Gingivitis
Obligate Anaerobes
Gram -ve
Aggressive/LJP
- High numbers of A.actinomycetemcomitans
Pili/Fimbria:
- Attachment: To host and cause disease
- Conjugative: Transfer genetic material
Toxins
Endotoxin (LPS membrane)
- Stable can withstand high temp
- Released at cell death, after phagocytosis
Triggers host immunity - Usually gram negative
- Fever
- Cannot be converted to toxoid
- Non-specific, fever, aches
- Acts via multiple mechanisms
- Blood clotting (anyhow)
- Anyhow fibrinolysis
- Cytokines
Porphyromonas Gingivalis
- Gram -ve
- Strict anerobe
Exotoxin
Collagenase
Proteases
- Destroy immunoglobulins
- Antibody reduction
- Immune suppression
Gingipains
Hemolysins
- Break down RBC
- Requires Heme
Tannerella forsythia
- Gram -ve
- Strict anerobe
A.actinomycetemcomitans
- Gram -ve
- Capnophilic
Endotoxin
Exotoxin
Cytolethal distending toxin
- G2/M arrest
- G1 Cell substance multiply
- S Chromosome multiply
Leukotoxin
- Kill WBC
- Found in aggressive Perio
Slide 19
Perio II
No cytoplasm
Envelope (Optional)
- Having an envelope makes it easier to kill
Genome
Capsid Protein
- Helix
- Icosahedral
RNA
DNA
Sense
Antisense
Double stranded
Linear
Circular
Single stranded
Double stranded
Determinants of Pathogenicity
Treatment of Sepsis - Endotoxin
- Deal with underlying infection
- Support failing body systems
- Block harmful inflammation
Exotoxin
- Denaturable
- Excreted
- Usually gram positive
- No fever
- Can be converted to toxoid
eg. cytolethal, collagenase - Specific sites / effects
- Acts directly
Pathogenicity
- Viral replication kills target cell
- Affect structure & function
- Expression of viral antigens immune cytolysis
Persistent (Non-lytic)
eg: Adeno, Hep B/C, measles, rubella, HSV, HIV
Latent-recurrent
- Incorporation of DNA
- mRNA inhibit lytic cycle
- allow integration
- Activated upon stress immune suppression
eg: Chickenpox (Varicella)
Abortive
- Failed infection
- No multiplication
Transforming
- Immortalizing
- Stimulate uncontrolled cell growth
Recurrent
- Latency then viral production
Latent
- No virus synthesis
Chronic
- Nonlytic
- Productive