Bacterial Toxins & Metabolism Flashcards
Explain the differences between endotoxins and exotoxins regarding their production, chemical nature, immunogenicity, and toxicology
Endotoxins:
-LPS of cell wall (main) (only gram negative); peptidoglycan and lipo/techoic acids (gram positive) (fever and drop in blood pressure)
-heat-stable, vigorous immune response, responsible for septic shock, fever, and disseminated intravascular coagulation (DIC)
-not a good toxoid
Exotoxins:
-very specific damaging effects, most potent toxins known & major cause of damage to host
-secreted by bacterium or leak into surrounding tissue following cell lysis
-toxins act locally or systemically
-made of protein – heat labile and good toxoids
-fatal damage can occur before adequate immune response is mounted
-antitoxin can be given as treatment
-3 functional categories: cytotoxins, enterotoxins, neurotoxins
-classes: AB toxins, membrane damaging toxins, and superantigens
Define cytotoxins
- damage to a variety of cells
- damage caused by interference w/ cell function or cell lysis
Define enterotoxins
- damage to digestive tract
- major symptoms are vomiting and diarrhea
Define neurotoxins
- damage to nervous system
- major symptom is paralysis
Describe AB toxins
- A unit = active/toxic subunit
- B unit= binding subunit
- can use B subunit for vaccines
Describe membrane damaging toxins
- disrupts plasma membrane/causes cell lysis
- some toxins produce pores in membrane to allow fluids in causing cell destruction
- phospholipases are part of this group
- remove polar head groups of phospholipids (destabilizes membrane)
Describe superantigens
- override specificity of T-cell response/overactivates
- massive release of cytokines by large number of helper T cells
- binds MHC Class II and T cell receptor
Differentiate between aerobic respiration, anaerobic respiration and fermentation
Aerobic respiration: oxidizing agent is O2
Anaerobic respiration: oxidizer is non-O2 inorganic molecule such as nitrate or sulfate
Fermentation: oxidizer is organic (derived from food)
Efficiency: aerobic > anaerobic; repiration > fermentation
Define toxoid
chemical/heat treated exotoxin that has lost toxicity but retains antigenicity
- used as a vaccine
- cannot use for endotoxins
Define antitoxoid
antibodies produced in an animal immunized with toxoid or toxin
-neutralize toxin for treatment and emergency immunization
Illustrate aerobic respiration in the context of glucose oxidation
pyruvate is completely oxidized by O2
- 38 ATP, CO2, H2O
Illustrate anaerobic respiration in the context of glucose oxidation
pyruvate is completely oxidized by nitrate or sulfate
-34 ATP + NH3 + H2S
Illustrate fermentation in the context of glucose oxidation
organic oxidizer is pyruvate or derivative
after recieving electrons, pyruvate is converted to small organic acids or alcohols + 2 ATP
Differentiate between aerobic, facultative and anaerobic bacteria
Aerobic: requires O2
Facultative: prefers O2, but anaerobic or fermentation possible
Anaerobic: inhibited or killed by O2
Which anaerobe is most adaptive?
Facultative
What are aerotolerant anaerobes?
doesn’t use O2 but tolerates it
Explain why oxygen is toxic to cells and how aerobes detoxify reactive oxygen species
- O2 is a strong oxidizer and will kill anaerobes
- O2 ETC leaks electrons –> forming reactive oxygen species that destroy lipids and DNA easily
