Lecture 4 Oxygen and Drugs Flashcards
What does obligate aerobe mean?
Oxygen is essential
What is the molecular formula for normal atmospheric oxygen?
O2
Why are highly reactive forms of oxygen toxic?
They are oxidising (is able to steal electrons from other compounds)
What would happen if I gave oxygen to an obligate anaerobe?
It would die lmao
What does an oxidising agent do?
Steals electrons from other compounds.
Causes the electron depleted compound to steal electrons from another compound.
So on and so forth
Creating a chain of vigorous oxidation
ToD: Oxidation dmg is reversible
False.
Oxidation dmg is irreversible to cells.
What compounds are oxidised causing irreversible dmg?
Proteins
Lipids
How many forms of oxygen are there?
Four
What does Singlet Oxygen look?
O2
What happens to the electrons found within Singlet Oxygen?
Aerobic metabolism causes the electrons to be boosted to a higher energy state
What cells use Singlet Oxygen?
Phagocytic cells use singlet oxygen to oxidise pathogen
How reactive is Singlet Oxygen?
Very reactive oxidising agent
What is the molecular formula for Superoxide Radical?
O2-
How are Superoxide Radicals formed?
O2- forms during the incomplete reduction of O2 during electron transport in aerobes
&
the metabolism by anaerobes in the presence of oxygen
ToD: Only Anaerobes create Superoxide Radicals
False.
Both aerobes and anaerobes can create superoxide radicals
What do aerobic organisms create to detoxify themselves of superoxide radicals?
Superoxide dismutase
What do anaerobic organisms create to detoxify themselves of superoxide radicals?
Nothing
What is created when you combine two superoxide radicals and two protons?
Hydrogen peroxide (H2O2) + Oxygen
What is the molecular formula for Peroxide Anion?
O2 2-
What do aerobes have to detoxify themselves of peroxide anion?
Catalase or Peroxidase
How are peroxide anions created?
They are produced as a biproduct of reactions catalysed by superoxide dismutase
What can you use peroxide anions to make?
Hydrogen peroxide
What can hydrogen peroxide be used for?
It’s an antimicrobial agent
If there are more metal ions in the body, which form of oxygen is created more?
Superoxide radical
Out of the 4 forms of oxygen, which is the most reactive?
Hydroxyl radical
What is the molecular form of hydroxyl radical?
OH
How are hydroxyl radicals formed?
From ionising radiation and from the incomplete reduction of hydrogen peroxide
What enzymes get rid of the hydroxyl radicals?
Catalase and peroxidase
ToD: Aerobes produce catalase and peroxidase to get rid of hydroxyl radicals?
True. The build up of hydroxyl radicals can damage proteins, lipids and DNA.
What vitamins are considered antioxidants?
Vitamin C
Vitamin E
What makes vitamins antioxidants?
Able to provide electrons that can reduce the toxic forms of oxygen
What are facultative anaerobes?
Can live in various oxygen concentrations
What are the two processes that help facultative anaerobes survive?
Fermentation
Anaerobic respiration (least efficient due to lack of oxygen)
What bacteria is an example of a facultative anaerobe?
E.coli
What bacteria is an example of aerotolerant anaerobes?
Lactobacilli
What kind of metabolism does aerotolerant anaerobes use?
Anaerobic metabolism
At what percentage of atmospheric oxygen are microaerophiles damaged by?
21%
What bacteria is an example of an microaerophile?
Helicobacter pylori- ulcer causing pathogen in the stomach
What percent of IDU hospital admissions are due to infections?
40%
What are the three different types of injection?
Intravenous
Intra-muscular
Subcutaneous
What can cause local abscess formation?
Minor bacterial infections
What can cause severe illness if it contaminates injected material or paraphernalia?
Clostridial spores
Of IDU hospital admission, what percentage results in death?
20%
Where can you find Clostridia?
Widely distributed in soil and gut
ToD: Clostridia is gram positive?
True
What are the characteristics of Clostridia?
Gram Positive
Anaerobic
Spore-forming rods
Resistant to environmental conditions
Can exist as exo-spores
May release powerful exotoxins
What is required for clostridia spores to germinate?
When introduced to an oxygen-reduced environment
What can injecting substances into the muscle tissue do?
Increases the risk of infection via clostridium spores
What can be observed on the soft tissue if someone is infected by clostridium spores?
Abscess
Cellulitis
Fasciitis
Myositis
What are severe localised symptoms if someone is infected by clostridium spores?
Extensive swelling
Pain
Oedema
Erythema with blackening/blistering at centre
Extensive necrosis
Necrotising fasciitis
Hypothetically if you took drugs and the veins on your arms were too dmged to take more drugs what would you do?
Other areas of the body are free real state
e.g Groin area, behind the knees, neck
Where can you find C.novyi Type A?
Widely distributed in soil
What can be seen on the blood agar if C.novyi Type A is being grown?
After 24H: Small, flat, rough or rhizoidal, translucent haemolytic colonies with a spreading edge
After 48-72H: Colonies often coalesce to give fine spreading growth
Why shouldn’t colonies of C.novyi Type A be exposed to air?
Toxic because the colonies haven’t begun sporulation
4 Characteristics of C.novyi Type A
Unreactive in commercial anaerobe identification kits (API Anaerobe)
Gram-variable
Rod shaped
Some sub-terminal spores
Where can you find C.perfringens?
Post-mortem contaminant
Basically dead bodies and necrophiles
What are the characteristics of C.perfringens?
Gram-variable
Rod shaped
No spores
What should you see if C.perfringens is growing on blood agar?
24H: Large discrete colonies. Flat and rough-edged or smooth and domed.
Non-haemolytic or with a narrow zone of complete haemolysis inside a larger zone of partial haemolysis
What are the characteristics of C.septicum?
Grows rapidly
Haemolytic
Gram variable
Rods
Numerous sub-terminal spores
Where can you most commonly find C.septicum?
Can be found from blood cultures of patients with malignancies of the colon
What diseases can C.botulinum cause?
Food-borne illnesses
Cases of wound botulism
What are the characteristics of C.botulinum?
Haemolysis is variable
Gram variable bacilli
Profuse sub-terminal and free spores
What is observable on the blood agar if C.botulinum is being grown?
Proteolytic types A, B and F will initially produce discrete rhizoidal colonies that spread and coalesce
What is observable on the blood agar if C.tetani is being grown?
May produce fine swarming growth
What can be seen on the Gram stain of C.tetani?
When left overnight, you will be able see over-decolourised long bacilli without spores
What three antibiotics can be given to treat C.histolyticum
Penicillin
Metronidazole
Clindamycin
What is the treatment for patients presenting with compartment syndrome?
Urgent decompression
Excision of surrounding oedematous tissues
What are the three early surgical interventions for C.histolyticum?
Exploration
Drainage
Extensive debridement
