Oral microbiology Flashcards
What are the main features of the mouth as a habitat that are relevant for bacteria?
- Teeth
- Mucosal surfaces
- Saliva
- Gingival crevice fluid
True/false: plaque is found on the teeth of both healthy and diseased animals.
True
What makes teeth a good place for bacteria to colonise?
- Non-shedding surface
- Number of surfaces/crevices/ridges
- Bacteria can accumulate in a biofilm
What features of the oral mucosa are relevant for bacteria if they try and colonise?
- Stratified, non-keratinised epithelium with layers that can be worn off and replaced
- Non-sterile: has a population of commensal bacteria that can stop others colonising
- Houses immune cells in the tissue; if damaged can initiate inflammation
What features of saliva are relevant for bacteria trying to colonise the mouth?
- Washes mouth to help physically remove material
- Has a buffering capacity
- Contains antimicrobial factors important to control microorganisms
- Provides a source of nutrition for microbes, can help aggregation of bacteria
What features of the gingival crevice fluid are relevant for bacteria trying to colonise the oral cavity?
- GCF: serum-like fluid
- Increased production of GCF e.g. during infection can lead to localised rise in pH, changing the type of bacteria that can grow
- Contains a variety of enzymes e.g. collagenase, elastase, trypsin
- GCF has antimicrobial properties: IgG and sometimes leucocytes
Give some non-specific antimicrobial factors in the oral cavity
- Saliva flow
- Mucins and agglutinin
- Sloughing of surface epithelial cells
All the above physically remove microorganisms
Give some innate (general) antimicrobial defenses in the oral cavity and describe their modes of action
- Lysozymes cause bacterial cell lysis
- Lactoferrins sequester iron, block some viral receptors and have anti-bacterial and anti-yeast activity
- Sialoperoxidase inhibits glycolysis
- Antimicrobial peptides disrupt the microbial membranes of bacteria or yeast
- Neutrophils patrol tissue and engulf pathogens
Give some adaptive (specific) immune defenses in the oral cavity
- Serum antibodies (sIgA) prevent/disrupt adhesion, reducing the capacity of bacteria to colonise
- Complement binds to and promotes phagocytosis of pathogens. Also activates neutrophils.
List the clinical signs of periodontal disease
- Problems picking up food
- Bleeding/red gums/blood in water bowl or on toys
- Loose teeth
- Halitosis
- Unusual noises when eating
- Chewing on one side of the mouth
- (If advanced) sneezing/nasal discharge
Explain the causes and mechanisms of gingivitis development in companion animals
- Plaque develops, changing the micro-environment
- This allow anaerobes to establish
- Mineral deposition can occur
- Sub-gingival deposits and growth will trigger inflammation
- Bacteria also secrete enzymes, weakening the tissue and causing more damage
Plaque
a biofilm that builds up on teeth
Calculus
a.k.a. tartar
calcified dental plaque
Briefly describe, using this diagram, how plaque develops
- Glycoproteins enable pioneer (aerobic) species to establish.
- Bacteria in a biofilm contribute to each others’ metabolism, allowing complex plaque to develop
- As bacterial growth/plaque builds up, the environment becomes one of reduced oxygen –> eventually anaerobic bacteria can establish
- Plaque formation is not uniform: some sites are more at risk - gingival sulchus vs. smooth surfaces
- Mineralised phosphates are deposited around the bacteria (sub- or supra-gingivally) forming calculus
- Periodontal pathogens cause tissue to secrete cytokines, which leads to activation of odontoclasts which resorb bone and enamel
How is calculus formed?
- Mineralised phosphates are deposited around the bacteria. This can occur sub- or supra-gingivally
- The contact between pathogens and tissue can cause the tissue to secrete cytokines which activate odontoclasts, leading to bone resorption
- Once formed, calculus takes a lot of force to remove
- Dental products may contain compounds to reduce mineralisation
Describe how dental caries (decay) arises
- Occurs due to increased acids causing local mineralisation
- The change to the environment (e.g. reduced pH) can lead to altered cell activity
- Example: Feline Odontoclastic Resorptive Lesions
Give the causative agent, route of infection, pathology and treatment for lumpy jaw (actinomycosis)
Cause: Actinomyces bovis
Pathology: Mucosal commensal that invades tissues through breaks in the lining of the mouth (rough forage, sharp teeth)
- Tumour like swellings slowly develop.
- These are immovable and hard swellings on the upper/lower jawbones around central molar level.
- They consist of honeycombed thin bone filled with pus. Advanced cases can show pus discharge/gritty yellow granules in this.
Treatment is tetracyclines/iodine therapy or PTS
Describe the causative agent and pathology of Wooden tongue (a.k.a. timber tongue)
Cause: Actinobacillus lignierseii
- Commensal of mucous membranes, invades tissue through breaks in the lining of the mouth
Pathology: sudden onset with tongye becoming hard, swollen and painful.
- There is then chronic pyogranulomatous inflammation of soft tissue
- Infection is limited in most cases to soft tissue of tongue and lymph nodes of head
Ulcer
loss of epidermis, dermis and sometimes deeper tissue
Describe the clinical signs of FMD
Clinical signs
Cows
- Fever
- Loss of appetite
- Marked milk drop
- Profuse salivation
- Foot and oral lesions; Vesicles on tongue and gums; smacking of lips causes rupture
- Ruptured vesicles form large denuded ulcerative lesions
- Secondary bacterial infection can lead to mucoprurulent nasal discharge
- Pregnant cows may abort (due to high fever; virus doesn’t cross placenta)
Pigs
- First sign often lameness; severe and painful foot lesions
- Large vesicles that quickly rupture on snout
Other animals
- Mild clinical signs characterised by foot lesions and lameness
Describe the clinical signs, diagnosis and control of swine vesicular disease virus
Clinical signs
- Lesions on the coronary bands; less commonly snout, lips, tongue
- Main sign is lameness
Diagnosis
- ELISA/virus isolation needed to distinguish from other vesicular diseases
Control
- Susceptible and in-contract animals are culled
Describe the causes and clinical signs of cat flu caused by FCV
Cats present with upper respiratory tract disease.
2 main causes: Feline calcivirus (FCV) and Feline herpes virus (FHV)
Clinical signs
- Conjunctivitis
- Rhinitis
- Tracheitis
- Pneumonia
- Vesiculation/ulceration of oral epithelium
- Fever
- Lethargy
- Anorexia
- Stiff gait
Describe the causes and clinical signs of cat flu caused by FHV
Cats present with upper respiratory tract disease.
2 main causes: Feline calcivirus (FCV) and Feline herpes virus (FHV)
Clinical signs
- Sneezing
- Nasal discharge
- Dehydration
- Anorexia
- Pyrexia
- Ocular signs including chemosis, keratoconjunctivitis, corneal ulceration
