anaerobic organisms Flashcards
categories of anaerobic organsims
obligate anaerobes
faculatative anerobes
microaerophiles
obligate anerobes
harmed by the presence of oxygen
facultative anerobes
can grow without oxygen but uses oxygen if present
microaerophiles
grow in atmosphere of low oxygen less than 5%
what is the terminal e- acceptor in anaerobic respiration
lactic acid (organic) inorganic (sulphate nitrate)
fermentation products and products from incomplete fermentation
lactic acts (feeds NAD back into muscles when there is oxygen starvation
products from incomplete fermentation
1) Vingear
2) propionic acid
3) some yeast produce alcohol
aerobic respiration vs anaerobic respiraton
1) Aerobic respiration - ATP is released as electrons are transported along chain to final acceptor O2 (forms water)
2) Anaerobic respiration uses electron transport chain but the final electron acceptor is not O2
• Nitrate (NO3- reduced to nitrite NO2-, or N2)
• Ferric iron (Fe3+ reduced to Fe2+)
what do organisms have to stop oxygen radicals and what do they do
superoxide dismutase
catalase
perioxdase
convert radicals to water
what can be used for study of anaerobes
Obligate anaerobes can process the metronidazole, allows diagnosis of anaerobic organisms
lab diagnosis of anaerobes
Sugar fermentation (species specific?) Toxin production (clostridia) Gas liquid chromatography measures fatty acid end products (VFAs)
major anaerobic bacteria in humans
1) clostridia
2) Bacteroides
3) fusobacterium
4) porphryromonas and black pigmenters
5) Gardnerella and GPACs
clostridium species
- large, straight, gram + bacilli
- produce endospores
- produce exo toxins
important clostridium species in prominent diseases
1) Cl. perfringens
- gas gangrene
- food poisoning
2) Cl. Botulinum
- botulism (food)
- uses in botox
3) Cl. tetani
- tetaus (Environmental)
4) Cl. difficile
- pseudomembranous colitis
cl perfringens
- Capsulate
- non motile
- gram + rod
- polysaccharide capsule
- spreading, fast growing, double BETA hemolytic colonies on BA (also has some alpha hemolysis)
- i.e. several types of hemolysis
exo toxins of cl perfringens
5 toxigenic types A-E
major toxin is alpha toxin
what can exo toxins lead to
- phospholipase C/lecithinase
- lyses RBCs, platelets, leukocytes and endothelial cells
- inflammation and major swelling
- oedema, bleeding (antiplatelet activity)
- haemolysise
- kidney damage- renal failure
- myocardial dysfunction
enterotoxin
- pore forming
- heat labile
- produced upon sporulation of ingested bacteria in stomach acid reaction (important in diarrhoeas)
- activated in the stomach
toxin detection what is used and positive test
nagler reaction/plate
Alpha toxin – used to confirm perfringens
- Antitoxin on one side of plate, not on the other side
- presence of the toxin leads to precipitate when toxin is present
- neutralised with antitoxin, no ppt
- sporogenes does not produce toxin therefore no difference
treatment of gas gangrene and what causes it
cl perfringens
surgery(amputation) antibiotic
what causes food poisoning
clos perfrigens enterotoxins
what causes tetanus / what is tetanus
cl tentant
Acute spastic paralysis caused by a potent bacterial neuro-exotoxin (muscles contract uncontrollably)
cl tentani and how does it spread/track
Motile
Gram + rods
- thin spreading film on agar
- drum stick spores
toxin released into body, tracks along nerves to CNS
tetanus toxin and how it works etc
Classic A-B neurotoxin - Tetanospasmin, TeNT 2 domains – A domain contains active site – B domain> Carbohydrate receptor binding- Sialic acid containing poly-sialic-gangliosides (found on the outside of nerve cells) Zinc endopeptidase (A-domain) - Prevents release of inhibitory transmitter (Gamma-aminobutyric acid- muscle relaxant) Absorbed from infectious focus – Travels along a-fibres to CNS
treatment and prevention of tetnus
Treatment -antitoxin/immunoglobulin +penicillin +metronidazole Prevention - immunisation - tetanus toxoid
botulism and symptoms
Caused by ingestion of preformed toxin from contaminating Cl.Botulinum Symptoms - drooping eyelids - progressive motor loss - flaccid paralysis Neurological sypmtoms - diziness - respiratory and cardiac failure
cl botulinum type of bacteria
Endospore that is subterminal
- motile gram + bacillus
- subterminal spores
Toxin released as progenitor complex to protect during passage through stomach, intestine then bloodstream
botulinum toxin and how it works
7 types A-G
A B and E most common
- A domain contains active site
- B domain – carbohydrate receptor binding – sialic acid containing DL – sialic- gangliosides
Zinc endopeptidase
- affects peripheral cholinergic synapses
- blocks release of acetylcholine (blocks stimulatory molecule)
- irreversible binding, relaxation
- stronger binding than tentaus toxin
treatment of botulism
- remove toxin
- polyvalent antitoxin
antibiotic/hospital associated diarrhoea
Cl. difficle
- spores of the organisms germinate and can overwhelm gut flora can cause psudomemntanous colitis (lesiosn in the gut)
- need to give a narrow rather than broad antibiotic
Antibiotic associated diarrhoea
- associated with broad spectrum antibiotic use, clindamycin and ampicillin
- outcompetes rest of population after antiobtic course complete
psudomembranous colitis
Antibiotic associated diarrhoea
Adherent membrane of inflammatory cells and necrotic debris
cl difficile toxins and how do they work
Produces TcdA and TcdB
- glucosyltransferases
- toxin present in patients stool (primary diagnostic marker)
Cell receptor for TcdA disaccharide GalB I – 4GlcNac (bind via glycoproteins)
Inactivates Rho (family of GTPases)
- actin condensation, rounding of cells, membrane blebbing and apoptosis of cell
- leads to neutrophil infiltration, disruption of tight junctions, fluid accumulation
treatment and prevention of c difficile
Therapy is vancomycin or metronidazole
- + remove offending broad spectrum, selective antibiotic eg clindamycin
- cleaning
- hand washing (to remove transmission of spores)
- quarantine
Limit use of broad spectrum antibiotics in at risk patients
bacteroides fragilis
Gram – bacillus - capsulate (CPA, LPS) Toxigenic strains - some cuase diarrhoea - toxin cleaves E- cadherin
what is bactericides fragilus resistant to
- clindamycin
- metronidazole (some strains)
prevotella
black pigmented anaerobe
gram -
non motile
rod shaped
porphyrumonoas
black pigmented anaerobe
- non motile
- gram –
- rod shaped
- PDD – gingivalus commoly found in biofilm with other spp (eg T forsythia)
- forms black colonies on blood agar
fusobacterium and treatment
- long rod shaped spindle shaped bacilli, gram –
- associated with PDD, skin ulcers, respiratory infections
- highly effective at biofilm formation
black pigmented anerobe
treatment
- antibiotics clindamycin
black pigmented anerobe examples
prevotella porphymonas fusobacterium GPAC- peptostreptococcus eubacteria and bifidobacterium
b fragilis
causes 25% of non clostridia anaerobic infections
