1037DOH - Oral Microbiology

microbiology for trimester 2

what is a microbiome?

• the collection of genomes from the total culturable and unculturable microorganisms

• includes biomolecules within a defined habitat

what is a microbiota?

• total collection of resident microbes within the microbiome

what are two features of microorganisms you can use classify and categorise them? briefly describe what these are

• phenotype

  • observable characteristics/traits of an organism

• genotype

  • organism’s complete set of heritable genes/genes that can be passed down from parents to offspring

what are the three domains of life?

1. bacteria (prokaryotes)

2. archaea (prokaryotes)

3. eucarya (eukaryotes)

describe the possible shapes and typical size of bacteria (MORPHOLOGY OF BACTERIA)

shapes

• cocci (spherical)

• bacilli (rod shapes)

• spirochaetes (helical)

• pleomorphic (appear as both cocci and bacillary forms)

size

• 0.2 - 5 µm

describe the flagella structure on bacteria

• motile - whip like filaments

• made of flagellin (a type of protein)

• monotrichous - single + one ended

• lopotrichous - many + one ended

• peritrichous - all over outer surface

what are fimbriae and pili on bacteria?

• pilin is a protein

• both are fine, hair-like short structure

• they mediate adhesion of bacteria to receptors on host (human) cell surface

what is the glycoalyx? (bacteria)

• polysaccharide coating covering bacteria’s outer surface

• allow adhesion to structures - eg teeth, oral mucosa, heart valves and catheters

• contribute to formation of biofilms

• eg streptococcus mutans - contributes to dental caries

what is the capsule layer around bacteria?

• amorphous gelatinous layer surrounding bacteria

• polysaccharide formed - may also contain protein

• polysaccharides vary between bacteria and within a species (serological type)

what is the cell wall in bacteria?

• multi-layered structure

• allow rigidity

• porous and permeable to substances with a low molecular weight

• inner layer is peptidoglycan (protein + sugar)

• inner layer varies in thickness and chemical composition (depending on gram-staining property of the bacteria)

describe gram positive, gram negative stains and LPS

gram positive

• dark blue/purple stain

• indicates thicker peptioglycan layer (inner cell wall)

gram negative

• pink stain

• indicates thinner peptidoglycan layer

• indicates complex outer membrane (including lipopolysaccharide (LPS), lipoprotein, and phospholipids, and porins (transportation of molecules)

LPS

• toxic (endotoxin)

• released when cell lysed

describe the cytoplasmic membrane of bacteria

• phospholipid bilayer

  • similar to eukaryotic cells, but bacterial ones dont normally contain sterols

• allows…

  • active transport + selected diffusion of molecules in and out of the cell

  • cell wall precursors synthesis

  • secretion of enzymes and toxins

  • electron transport

  • oxidative phosphorylation (in aerobic species)

• has supporting receptors and other proteins of the

  • chemotactic and

  • sensory transduction systems

describe aerobes, facultative aerobes and anaerobes

aerobes

• organism able to live and reproduce only in the presence of free oxygen

facultative aerobes

• grow either with or without free oxygen

anaerobes

• grow in absence of free oxygen

• those that grow only in absence of oxygen are called obligate/strict anaerobes

describe the cytoplasm structure of bacteria

• thick solution (amorphous matrix)

• fills each cell

• enclosed by cytoplasmic membrane

• mainly composed of water, ions, metabolites and proteins

• structures:

  • nuclear material

  • ribosomes

• in eukaryotes, cytoplasm includes all of the material inside the cell and outside the nucleus

describe the nuclear material (nucleoid) of bacterial DNA

• single, supercoiled and circular chromosome

• 2000 genes

• 1mm long

• undergoes semi-conservative replication bidirectionally from a fixed point

describe the nuclear material (nucleoid) of eukaryotic DNA

• contained within the nucleus

describe function of ribosomes

• in bacterial (prokaryote) ribosomes are in the cytoplasm

• in eukaryotes, ribosomes are attached to the rough endoplasmic reticulum

• facilitate protein synthesis

what is E. coli’s full name?

escherichia coli

what is S. mutan’s full name?

streptococcus mutans

name the 3 anaerobic bacterial species identified in carious coronal dentine (GRAM POSITIVE)

1. peptostreptococcus (COCCI)

   • P. anaerobius

   • P. parvulus

   • P. micros

2. eubacterium (RODS)

   • E. alactolticum

   • E. aerofaciens

   • E. saburreum

3. propionibacterium

   • P. acnes

   • P. avidum

   • P. lymphophilum

name the 3 facultative bacterial species identified in carious coronal dentine (GRAM POSITIVE)

1. streptococcus (COCCI)

   • S. mutans

   • S sobrinus

   • S. intermedius

2. actinomyces (RODS)

   • A. israelii

   • A. odontolyticus

3. lactobacillus (RODS)

   • L. casei

   • L. plantarum

   • L. minutus

name 4 gram negative anaerobic bacterial species identified in carious coronal dentine

1. fusobacterium nucleatum (RODS)

2. porphyromonas (RODS)

3. prevotella (RODS)

4. veillonella (COCCI)

describe fungi

• eukaryotic, single-celled microorganisms

• genus Candida yeasts are pathogenic

describe viruses

• not living

• can infect all types of life forms

• exist in form of independent particles or virions

• DNA or RNA is their genetic material

• shapes range from simple helical/icosahedral forms to complex structure

• about 1/100th the size of bacteria

when infected with a virus, a ____ cell is forced to rapidly produce thousands of identical copies of the original ______

1. host

2. virus

what is pulpitis?

• inflamed pulp

• pain in A-delta and C-type nerves

what is pulp necrosis?

• affects dental pulp

• after-effect of pulpitis/trauma

• total necrosis is symptomless

• partial necrosis may display pulpitis

what is periapical granuloma?

• affects periapical tissues

• usually resulting from long-standing infection or necrotic pulp

• 3 stages

  1. primary acute apical periodontitis

     • new, acute inflammation at the root

  2. chronic apical periodontitis

     • long-term, low-grade inflammation (can lead to granuloma)

  3. secondary acute apical periodontitis

     • chronic lesion that flares up

     • becomes acutely painful again

what is a periapical abscess?

• localised collection of pus at the root tip due to bacterial infection

• two types

  1. primary acute apical abscess

     • occurs at the first sign of infection

     • usually painful

     • swelling may occur

  2. secondary acute apical abscess

     • flare-up of chronic infection

     • becomes acutely infected

     • forms pus

what type of infection is oral candidiasis/candidosis?

• opportunistic infection

• i.e occurs in ‘compromised’ patients

where do primary and secondary oral candidiasis/candidosis occur?

• primary

  • only in oral/perioral tissues

• secondary

  • oral/perioral tissues

  • other mucous/cutaneous surfaces

what is candida associated denture stomatitis?

• fancy for sore mouth from dentures

• very common

• treatment is denture hygiene or improving its quality

• medical factors (eg diabetes) contribute to this

• antifungals can also help

what is median rhomboid glossitis?

• papillary atrophy

• can be ellipitcal or rhomboid

• in the midline of the tongue and anterior to the circumvallate papillae (the round tastebuds at the back of the tongue)

• oral hygiene and antifungals can help this

what is angular stomatitis/cheilitis?

• lesions on the angles of the mouth

• candida species and staph. aureus contribute to this

• denture stomatitis, topical antifungals and underlying medical conditions treatment can help this

what is otitis media (chronic suppurative otitis media)?

• infection or middle ear

• appears as earache

• can have discharge and pain

what is sinusitis (chronic sinusitis)?

• occurs in frontal and maxillary sinuses

• can occur during common cold

• can appear with headache, pain, nasal obstruction, and can mimic toothache

what are some complications of a streptococcal sore throat?

• rheumatic fever

• chronic heart valve disease

• acute glomerulonephritis

explain the rheumatic fever complication of a strep throat

• symptoms are fever, pain and swelling in the joints

• pancarditis: inflammation of all parts of the heart

explain the chronic heart valve disease complication of a strep throat

• damage to heart valves over time, esp mitral and aortic valves

• increases risk of bacterial endocarditis (infection of heart valves)

• requires prophylactic antibiotics before dental procedures to prevent infection

explain the acute glomerulonephritis complication of a strep throat

• kidney glomeruli are inflamed

• can cause blood in urine

• swelling

• and high bp

describe bacterial/infective endocarditis

• predominately bacteria-caused

  • streptococci (60%)

  • staphylococci (25%)

  • other bacteria (15%)

• can happen thru periodontal treatment

• identify at-risk patients

• use preventive dental care

what bacteria cause bronchitis?

• H. influenzae

• S. pneumoniae

what is a major effect of cystic fibrosis?

• compromised natural defence mechanisms

what causes pertussis (whooping cough)>

• bordetella pertussis

• happens in children

• prevent via vaccinations

what bacteria causes tuberculosis?

• mycobacterium tuberculosis

what is human immunodeficiency virus?

• RNA virus

• leads to acquired immune deficiency syndrome (AIDS)

common oral signs of AIDS (orofacial manifestations)

• fungal infections

  • oral candidiasis (thrush) - white patches in mouth

• viral infections

  • herpes simplex virus

    • herpetic stomatitis (cold sores)

  • human herpesvirus 8

    • kaposi’s sarcoma (purple/red lesions)

  • epstein-barr virus

    • hairy leukoplakia (white hairy patches on the side of the tongue)

• severe, necrotising gingivitis and periodontitis

3 distinct particles of Hepatitis B

• Dane particle

  • 42 nm

  • complete infective virus

• spherical forms

  • 22 nm

  • non-infective

• tubular forms

  • 22 × 100 nm

  • non-infective

describe chronic persistent hepatitis

• does not develop liver damage

• produces viral liver antigen (HBsAg)

describe chronic active hepatitis

• extremely infectious

• Dane particles present in blood

describe HCV (hep C)

• affects 3% of the population

• parental route is blood products

• persistent chronic infection

_______ result in cell aggregation, leading to improved clearance of _______ from the oral cavity during swallowing, chewing and speaking

• agglutinins

• bacteria

what do lysozymes do?

• breaks down bacterial cell walls

• part of the defence mechanisms of the oral cavity

name some antimicrobial peptides (defence mechanisms of the oral cavity)

• Histatin 5

• Human beta defensin-1 (and defensin-2)

• Magainin II and Magainin II amide

how do tonsils contribute to the defence mechanism of the oral cavity?

• house B and T lymphocytes and macrophages

• lymphoid tissue

how does epithelium defend the oral cavity?

• inhibits bacterial adhesion

• facilitates shedding of cells

• has a keratin layer

what does connective tissue possess that makes it part of the oral cavity’s defence mechanism?

• highly vascular so has lots of inflammatory response cells

why is gingival crevicular fluid a good oral cavity defence mechanism?

• continuous flow of fluid

• has albumin, transferrin and lysozymes

• has components of the immune system (lymphocytes, plasma cells and macrophages)

what does dentinal tubule fluid do?

• protect pulpo-dentine complex from bacterial antigens or toxic by-products

• allow pulp healing

• deposits serum in dentinal tubules to inhibit bacterial invasion of dentin by S. gordonii and E. faecalis

describe the colonisation of microbial biofilms

• first bacteria adhere to host tissue

• they utilise available nutrients

• compete and co-operate with other species in the immediate environment

• contend with host defence mechanisms

• cells divide and grow

• host becomes colonised in multiple sites

describe the biofilm benefit to cells

• reduction of the antimicrobial concentration in the bulk fluid surrounding the biofilm

• failure of the antimicrobial agent to penetrate the biofilm

• adoption of a resistant physiological state/phenotype by at least a fraction of the cells in the biofilm

clin sig

• reduced effectiveness of chemical management of pathogenic plaque/biofilm

• reduced effectiveness of chemical management of pathogenic endodontic biofilm

list the 5 factors that affect the development and characteristics of biofilms

• flora

• ecology

• nutrients

• anatomy

• time

nutrition factor of characteristics/development of biofilms

• mouth contains decaying tissue, fluids from the root canal and serum-like substances

• key nutrients are carbohydrates, amino acids/peptides (for protein prod.) and vitamin K and hemin (necessary for some bact.)

• first phase sugar-eating bacteria eat carbs

• second phase: proteins broken down, aids in fermentation + digestion of remaining carbs

• final phase: more protein breakdown, involving bacteria like P. intermedia, F. nucleatum and eubacterium

_______ anaerobes dominate initially and develops with ________ anaerobes

• facultative

• obligate

presence of _____-_______ _________ (eg prevotella) associated with advanced disease

gram-negative anaerobes

what are macrophages?

• phagocyte

• detect, engulf and destroy pathogens and apoptotic cells

what are dendritic cells?

• antigen-presenting cells

• process antigen material

• present it on the cell surface to T-cells

what do B and T lymphocytes do respectively?

B

• make antibodies

T

• help kill tumor cells and control immune responses

what does the complement system do?

• enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells

what do cytokines do?

• they are small secreted proteins released by cells

• have a specific effect on the interactions + communications between cells

types of cytokine (list them)

• lymphocytes

• monocytes

• chemokine

• interleukin

what is PAMP (pathogen associated molecular pattern)?

• small molecular motifs conserved within a class of microbes

• vast array of different types of

  molecules can serve as PAMPs

what are pattern recognition receptors?

• toll-like receptors (TLRs) and others