1.1 Microbial Toxins and Mycotoxins Flashcards
What is the difference between endo and exotoxins?
exotoxins:
- baterial proteins, typically released during bacterial growth
endotoxins:
- components of the outer membrane of gram negative bacteria (the lipid A part of the LPS complex)
- they are released when the bacteria dies
- recognized by PRR on host cells, leading to the release of cytokines
- results in fever (via hypothalamus), hypotension, inapporpriate coagulation and complement activation, loss of effective circulation, etc.
List the types of exotoxins mentioned in lecture.
(1) cytolytic toxins: streptococcus equi (produces streptolysin S)
- toxins that can lyse host cells
- benefitial in many ways (e.g., iron aquisition)
(2) enzymes: phospholipase C of clostridium spp. (alpha toxin)
- many functions (often tissue digestion)
(3) enterotoxins: cholera toxin, ET E. coli
- ADP-ribosylation toxins: activation of cAMP activity on specific transport proteins
(4) neurotoxins: botulinum / tetanus toxin
- spastic or flaccid paralysis
(5) superantigens: staphylococcus aureus
- over-activates immune system, causing toxic shock syndrome
- binds invariable regions on antigen presenting cells
- normal infection = 0.01% of T cells are activated; superantigen = 10-20% of T cell activation
(6) type III secretion systems (T3SS): salmonella
- needle-like structure in some bacteria
- sensory probe and secretion of effector proteins directly into eukaryotic cell (proteins facilitate bacteria entry into cell)
What are the three main mycotic toxin mechanisms?
- toadstool poisoning: direct sontact/ingestion of toxic mushroom
- mycotoxicosis: ingestion of molded feeds
- ergotism: ingestion of plant pathogenic fungi
Recall the ergot life cycle
ingestion of plant pathogenic fungi: ergotism
- ergots are not the only plant mycotoxin, but they are the most common in veterinary path
- ergots: Claviceps purpurea
What is the most important of the three mycotic toxin mechanisms?
mycotoxicosis: the ingestion of molded feed
- by far the most common, and there are no antidotes, neutralizing agents, or antibodies available
How does mycotoxicosis occur?
mycotoxicosis occurs from improper storage of feed
- these molds aren’t specific to an animal or plant, but rather simply grow on decaying matter
- there are a number of different toxins that are a result of this process, but aflatoxins are one of the most common
- it was named aflatoxin because it was found in [A]spergillus [FLA]vus
- aspergillus flavus: found in imported ground nut meal produced from moldy nuts, and cause “turkey X disease”
- alflatoxins are often fluoresced green/blue for identification
- acute alflatoxin poisoning now rare
The screening of feeds makes acute poisoning very rare now. There are thresholds of toxins, which, when crossed require the distruction of the feed. Chronic disease probably still exists (e.g., kidney and liver disease), but it is near impossible to distinguish mycotoxicosis as the cause.
