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MICROBIOLOGY PART 1 303 > Anaerobic Bacteria > Flashcards

Anaerobic Bacteria Flashcards

(46 cards)

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1
Q

What do anaerobic organisms not require?

A

Anaerobic organisms do not require oxygen

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2
Q

What are the main categories of anaerobic microorganisms?

A

Obligate anaerobes = harmed by presence of oxygen
Facultative anaerobes = can grow without oxygen but use oxygen if it’s present
Microaerophiles = grow in atmosphere of low oxygen <5%

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3
Q

Features of anaerobiosis?

A

Anaerobic respiration/fermentation

  • Produce energy without oxygen
  • May use fermentation or anaerobic respiration
  • In presence of oxygen = faculative anaerobes can use aerobic respiration
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4
Q

What occurs in anaerobic fermentation?

A

Organic electron acceptor in the absence of oxygen

Glucose - pyruvate (organic e receptors, 2ATP plus acids > incomplete breakdown products) - TCA cycle

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5
Q

What are the fermentation products?

A

Lactic acid
Acetic acid
= streptococcus, lactobacillus

H2, CO2, acetic acid, ethanol, lactic acid, propionic acid
= Enteric bac (E.coli)

H2, CO2, Ethanol, butanol, acetone
= Clostridium
= Live in mouth

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6
Q

How much glucose is produced by aerobic respiration?

A

38/mol glucose

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7
Q

What is respiration?

A

Converting energy from e.g. glucose into a usable form

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8
Q

What is aerobic respiration?

A

ATP is released as electrons are transported along chain to final acceptor O2 (forms water)

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9
Q

What is anaerobic respiration?

A

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+)

Allows growth in low O2 environs
Drawbacks for obligate anaerobes; no ability to resist presence O2 or other radicals that are by-products of aerobic life
Inefficient process
Anaerobes often slower growing

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10
Q

How are anaerobes diagnosed/studied?

A

Jars/cabinets to exclude O2 subculture
Gram stain, spore stain, anaerobes = sensitivity to metronidazole
Sugar fermentation
Toxin production - Clostridia
Gas-liquid chromatography - fatty acid end products
16s RNA sequencing

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11
Q

Give examples of major anaerobic bac in humans?

A 
Clostridia
Bacteriodes
Fusobacterium 
Porphyromonas and black pigmented
Gardnerella
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12
Q

Features of clostridium species?

A 
Large, straight, gram pos bacilli
Produce endospores and exo-toxins
Cl.perfringens - food poisoning 
Cl.botulinum = botulism (food)
Cl.tetani - tetanus
Cl.difficile - pseudomembranous colitis
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13
Q

Cl. perfringens features?

A

Capsulated, non-motile, gram pos rod
Polysaccharide capsule, repeating units of 6 sugars
Fast growing, spread, BETA hemolytic colonies on BA

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14
Q

Exo-toxins are differentiated based on? What are the types of exo-toxins?

A

Differentiated based on production of major lethal toxins

5 toxigenic types; A-E

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15
Q

Features of the major exo-toxin?

When are enterotoxins formed? Features?

A

Alpha-toxins;

  • Phospholipase C
  • Luses RBCs, platelets, leukocytes, endothelial cells
  • Inflam and major swelling
  • Oedema, bleeding
  • Haemolysis
  • Kidney damage - renal failure
  • Myocardial dysfunction

Other VFs; proteases and hyaluronidase - destroy tissue
Enterotoxin - pore forming, heat labile - produced upon sporulation of ingested bac in stomach acid secretion

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16
Q

How to test for toxins?

A

Nagler test - half plate infiltrated with antitoxin, rxn = fuzzy area, no rxn = colonies grown
clowdiness on side without alpha antitoxin

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17
Q

Name the diseases caused by Cl.perfringens? Treatment?

A

Gas gangrene

  • Spore contamination of wounds - source - soil, animal and human excreta
  • Oedema, gas formation, necrosis, toxaemia, cellulitis
  • Treatment - surgery (amputation), antibiotics
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18
Q

Features of food poisoning?

A

Incubation 10-12hrs
Abdominal cramps, diarrhoea
Resolves in 24hrs

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19
Q

How is diarrhoea from food poisoning caused?

Study These Flashcards
A

C. perfringens/ spores in soil and animal gut
C. perfingens grows in food- meats
spores survive cooking, germinate in food.
Food ingested
Bacteria sporulate and produce Enterotoxin in stomach
Intestinal epithelim damage, inhibition of glucose transport
= DIarrhoea

20
Q

Tatanus features? What causes it?

Study These Flashcards
A

Acute spastic paralysis caused by potent bacterial neuro-exotoxin
Trismus, rictus grin
Caused by uncontrolled contraction of muscles - mostly in CNS

21
Q

Cl.tetani features?

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A

Incubation 10-14 days
Enters body through wounds, splinters, cuts
Spores ubiquitous in environment
Spores in soil, contaminates wounds
Grows in wounds, toxin released into bloodstream
Motile - thin spreading film on agar (drumstick)

22
Q

Name the tetanus toxins and their features? (How does Cl.tenani cause disease)

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A

Classic A-B neurotoxin;
= Tetanospasmin, TeNT
- A domain contains active site
- B domain > carbohydrate receptor binding - sialic acid containing poly-sialic-gangliosides

Zinc endopeptidase (A domain)
- Breaks down synaptobrevins
- Prevents release of inhibitory transmitter (muscle relaxant)
Absorbed from infectious focus 
- Travels along alpha fibres to CNS
-2.5ng/kg kills a human
23
Q

What treats tetanus?

Study These Flashcards
A

Anti-toxin/immunoglobulin plus penicillin and metronidazole

Prevention - immunisation; toxoid

24
Q

What causes botulism?

Study These Flashcards
A

Ingestion of preformed toxin from contaminated food containing Cl.Botulinum bacteria
- Mostly in foods that have been heated, then cooled and stored for long periods

25
Symptoms/signs of botulism?
Flaccid paralysis Drooping eyelids, progressive motor loss, flaccid paralysis Neurological symptoms - dizziness, resp and cardiac failure
26
Cl.botulinum features?
Motile Gram-positive bacillus; - Sub-terminal spores - Widely distributed saprophyte e.g. soil - Optimum growth 35°C, some can grow 1-5°C Causes botulism - Severe form of food poisoning - Incubation 1-2 days Toxin released as Progenitor complex to protect during passage through stomach>> intestine> bloodstream
27
Botulinum toxin features?
Potent neurotoxin - BoNT - 7 types - A-G (A, B, E most common) - A domain contains active site - B domain > carbohydrate receptor binding - sialic acid containing DI-sialic-gangliosides - Zinc endopeptidase; Affects peripheral cholinergic synapses, blocks release of acetylcholine, irreversible binding
28
How to treat botulinum toxin?
Remove toxin | Polyvalent anti-toxin
29
What can botox do? How?
Can weaken muscles temporarily when injected in small amounts Uses botulinum toxin
30
What can botox treat?
Used to treat spasms and dystonias e.g. - Strabismus (cross eye) - Bruxism = bone loss - Toricolis (neck spasms) - Muscle spasms in cerebral palsy
31
Antibiotic associated diarrhoea C.difficile features?
Associated with broad spectrum antibiotic use - clindamycin and ampicillin Outcompetes rest of pop after antibiotic course complete Risk in elderly Spore forming - resistant to heat and disinfectants, shed in faeces Severe diarrhoea 2 exotoxins A and B Pseudomembranous colitis; bowel disease - can lead to rupture
32
What is Pseudomembranous colitis?
Antibiotic-associated diarrhoea
33
Cl. Difficile- treatment?
Therapy is vancomycin or metronidazole + remove offending selective antibiotic e.g. clindamycin Prevention measures: cleaning, hand-washing, quarantine Limit use of broad-spectrum antibiotics in ‘at-risk’ patients Treatment; Removal of broad spectrum antibiotic - metronidazole or vancomycin
34
Name the other gram pos and gram neg anaerobes
Gram-negative anaerobes - Bacteroides =Abdominal wound infections, Peritonitis - Prevotella = Oral and genital infections - Porphyromonas = Oral infections - Fusobacterium = F.nucleatum - oral and vaginal infections, F.necrophorum - Necrobacillosis - systemic sepsis and multisystem abscesses Gram-positive anaerobes - Peptostreptococcus (Parvimonas) - Eubacterium - Bifidobacterium - Gardnerella
35
List the black pigmented anaerobes
Prevotella Porphyromonas Fusobacterium
36
Features of prevotella? What can it cause?
Gram neg, non-motile, rod shaped Colonise in oral cavity by binding or attaching to other bacteria in addition to epi cells = larger infection in previously infected areas Abscesses, bacteraemia, wound infections, bite infections, periodontitis
37
Porphyromonas features?
Non motile, Gram negative, rod-shaped PD - P.gingivalis = commonly found in biofil with other spp. Forms black colonies on blood agar
38
What does P.gingivalis do?
Releases cysteine proteases - gigipains = bind and degrade erythrocytes, destroy receptors, degrade complement components and subvert cell signalling
39
Fusobacterium features? Treatment?
LONG Rod shaped spindle-shaped bacillli, Gram negative Associated with periodontal disease (F.nucleatum), skin ulcers, respiratory infections, BV, ANUG- often in mixed infection Highly effective at biofilm formation Treatment – antibiotics (Clindamycin, Chloramphenicol) main spp. F.nucleatum - oral and vaginal infections, PTB F.necrophorum - Necrobacillosis - systemic sepsis and multisystem abscesses- Lemierres syndrome- rare head and neck origin
40
What is F. nucleatum linked to?
Colon cancer - FadA adhesin stimulates oncogenic response in colon
41
What is GPAC?
‘GPAC’- Peptostreptococcus- normal flora of all mucocutaneous surfaces (inc. oral) Often isolated from infections such as chronic deep organ abscesses, obstetric and gynecological sepsis + intraoral infections. Not well studied: difficulties with laboratory identification, isolated from mixed infections.
42
Features of Eubacterium and Bifidobacterium?
Gram Positive rods, rarely isolated from abdominal infections POST oral/ genital trauma.
43
Features of Gardnerella and Mobilincus?
Bacterial Vaginosis in females, associated with dysbiotic communities and PreTerm Birth
44
Cl.difficile toxins?
Produces TcdA and TcdB - GluActivate host neurons >>> diarrhoea Induce cytokines>>> attract PMNs >>> disrupts cell junctions>>> Tcd-B damages underlying mucosa and tissues Septicaemia and bowel damage cosyltransferases - Toxin present in pt's stool (primary diagnostic marker) Cell receptor for TcdA is disaccahride Gallß1-4GlcNac Inactivates Rho (family of GTPases) - Actin condensation, rounding of the cells, membrane blebbing, cell apoptosis - Leads to neutrophil infiltration, disruption of tight junctions, fluid accumulation
45
Cl.difficile toxin mechanisms?
TcdA and TcdB: - Activate host neurons >>> diarrhoea - Induce cytokines>>> attract PMNs >>> disrupts cell junctions>>> Tcd-B damages underlying mucosa and tissues Septicaemia and bowel damage
46
Bacteriodes Fragilis features?
Most common anaerobe recovered from non-oral clinical infecs - Abdominal, pelvic, brain, liver - Involved in bacterial vaginosis Gram neg bacillus Toxigenic strains - some cause diarrhoea - Toxin cleaves E-cadherin Resistant to numerous antibiotics - clindamycin, some strains of metronidazole

MICROBIOLOGY PART 1 303 (12 decks)

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