M3: Anaerobic bacteria Flashcards
What is an obligate anaerobe
- organism unable to grow in oxygen presence
- require low redox potential
What is a facultative anaerobe
- organism which grows under aerobic or anaerobic conditions
What is an obligate aerobe
- organisms unable to grow in absence of oxygen
What is a microaerophile
- organism which requires small amounts of oxygen less than the atmospheric level
What is a capnophile
- organisms that require 5-10% CO2 for growth
How can anaerobic jars be used to grow anaerobes
Vacuum/Replacement method
- remove air with a vacuum pump
- replace atmosphere with gas mix
- include palladium catalyst
How can gas-generating sachets be used to grow anaerobes
‘Anaerogen’ sachets; will absorb oxygen and produce carbon dioxide, no catalyst is needed and no water is added
How can an anaerobic cabinet be used to cultivate anaerobes
- provides complete working chambers for anaerobes
- materials pass in and out via air lock
How can roll-tube techniques/ hung ate method be used to cultivate anaerobes
- pre-reduced anaerobically sterilised media
- work under constant stream of oxygen-free gas
How can Robertsons cooked meat medium be used to cultivate anaerobes
Meat particles in liquid produce anaerobic environment
List the types of clinically important gram positive anaerobes
1 Cocci; peptostreptococcus
- Spore-forming rods; clostridium
- Non-spore forming rods; propionibacterium, eubacterium, actinomycetes, bifidobacterium
List the types of clinically important gram negative anaerobes
- Cocci; veillonella
- Rods + filaments; bactericides, fusobacterium, campylobacter
- Spirochaetes; spirochaeta, treponema
What are dentoalveolar/periapical abscesses
Abscesses that develop around apices of teeth with necrotic and infected root canals - oral streptococci and many oral anaerobes are involved
If the abscess if left untreated then the pus can drain to skin surface and this can be treated with metronidazole
What is osteomyelitis
A rare disease causing inflammation of the jaw bone cavity due to anaerobic gram negative rods and streptococcus species
What is chronic marginal gingivitis
Inflammation confined to soft tissues of the gingiva as a result of dental plaque accumulation with no particular species of bacteria involved
What is acute ulcerative gingivitis
Grey gingival pseudomembrane which is easily removed to reveal a bleeding area and destruction of the interdental papillae; this could be due to spirochetes and is treated with metronidazole
What is periodontitis
Gingival inflammation extending to the deeper tooth supporting structures with destruction of periodontal ligament and alveolar bone caused by p. gingival, p. intermedia and AGA
Describe the anaerobic locations within the mouth
- Below the gum margins
2. On the tongue in-between papilla
What is pericoronitis
Inflammation of the soft tissues that surround the crown of partially erupted teeth especially around mandibular third molars; oral anaerobes involved include p. intermedia and fusobacterium nucleatum = gram negative
What is peri-implantis
Inflammation around implant systems that replace missing teeth which involves P.gingivalis and P.intermedia
What is actinomycosis
The formation of a chronic granuloma with swelling, in chronic cases multiple discharging sinuses are observed and this is due to actinomyces israelii and presents as ‘sulphur granules’
What is sialadenitis
Infection of the salivary glands by streptococcus species, staphylococcus aureus and gram negative anaerobes
Describe infections with non-spore forming anaerobes
- occurs at various body sites
- commonly polymicrobial
- often found in abscesses and wound infections
- may be associated with foul-smelling pus or discharge
- good anaerobic isolation techniques needed for diagnosis
- treatment may include drainage and antibiotics
What are the general features of clostridium
- Gram positive large anaerobic rods
- Produce endospores enabling organism to survive in adverse conditions
- Found in human and animal intestine, soil, water, decaying animal and plant matter
- Pathogenic species produce potent exotoxins
Which clostridium species cause the following
- Botulism
- Gangrene, food poisoning
- Tetanus
- Pseudomembranous colitis
- Gas gangrene
- C. botulinum
- C. perfringens
- C. tetani
- C. dificile
- C. histolyticm, novyi, septicum, sordelli
What is tetanus caused by
Clostridium petani following from contamination of deep wound injury with spores in soil
C. tetani will produce tetanospasmin (neurotoxin) and tetanolysin (haemolysin)
What does tetanus result in and how can it be treated
Causes trismus (lockjaw), dysphagia, muscle spasms, death by respiratory or cardiac failure
- can be prevented by immunisation with tetanus toxoid
- passive immunisation with antitoxin
What is botulism caused by
Clostridium botulinum following ingestion of pre-formed toxin in food which produces extremely potent neurotoxins that blocks the release of acetylcholine from peripheral motor nerve endings
What can botulism result in and how can it be prevented
Vomiting, thirst, muscle paralysis, death by respiratory or cardiac failure
It is prevented through rigorous controls of processed food
How is gas gangrene caused
By polymicrobial infection of wounds caused by histotoxic clostridia that produce a range of lethal and necrotising toxins and there is a three stage infection process
- Contamination
- Clostridial cellulitis
- Myonecrosis
What can gas gangrene result in and what can it be prevented by
Results in gas formation in tissues (crepitus) causing fever, shock, delirium, coma and death and treatment may require amputation
This can be prevented by proper wound management
