Practice For Final Flashcards
What’s a virulence factor?
A physical or biochemical trait of a microbe that enables it to cause disease
What virulence factor does Staphylococcus aureus have?
Staphylococcus aureus uses the enzyme coagulate to form fibrin clots to make a protective wrap from immune cells. This is why S. aureus forms pus infections
Is nuclease and lipase a virulence factor? If so, what does it do and match it with the pathogen that utilizes these enzymes
Staphylococcus uses lipase and nuclease as a virulence factor so that they spread infection faster. Nuclease breaks down nucleic acid while lipase breaks down lipids.
What is Hyaluronidase?
Streptococcus pyrogenes uses hyaluronidase to dissolve HA in connective tissue to increase pathogen invasion
Streptokinase is used by——-. It is used to dissolve fibrin clots to spread infection further. This same pathogen uses Hyaluronidase to dissolve HA in connective tissue
Streptococcus pyrogenes
What disease does streptococcus cause
Pus forming infections
Clostridium perfringins causes…
Gas gangrene and food poisoning
Streptococcus causes what disease
Pus forming infections, scarlet fever, strep throat
What enzymes does clostridium perfringens use
Collage base to break down collagen and protease to break down protein
True or false: Virulence factors can be in the form of of exotoxins and endotoxins
True
Define exotoxin and endotoxin differences
Exotoxin: Proteins that are secreted by gram positive or gram negative bacteria and generally heat labile (as heated beyond a certain temperature, hydrogen bonding breaks and they lose their 3D shape and can’t serve as toxins). Specifically, these proteins are secreted when they are alive. These are very specific in their activities and are very deadly. They bind to specific cell receptors and tissues
Endotoxin: lipopolysaccharides (and protein) released from gram negative cells as they die and lyse. These mainly cause fever, diarrhea, and vomiting which resolve in a few days (they are self limiting). They are associated with gastrointestinal illness because they are ingested
Within an endotoxin, the LPS is not released until the cell dies. What is the Lipid A in LPS? What is the core O-specific polysacchuride?
Lipid A: It has the component that inserts fatty acids into the first half of the outer membrane
Core polysaccharide:
O-specific polysaccharide: usually unique to a gram negative bacteria
Pathogenic bacteria produce exotoxins and cytotoxins. Describe an AB toxin, a cytotoxin, superantigen, and exotoxins
AB toxin: two protein subunits where the B subunit binds to a host cell receptor and the A subunit enter the cell to exert cytotoxic effect
Cytotoxin: a toxin that damages a host cell membrane to cause it to lyse
Superantigen: is a toxin that causes a massive rapid immune response, possibly leading to shock
Exotoxins: encoded by plasmids and/or lysogenic bacteriophages, where endotoxins are chromosomally encoded
What is botulinum toxin?
It is produced by clostridium botulinum where it blocks release of acetylcholine and prevents muscles from contracting. When this occurs on a broad scale with major muscle system, the effect can be disastrous
True or false: Botulinum toxin causes flaccid paralysis
True
What toxin does clostridium tetani produce?
Tetanus toxin prevents release of glycine and prevents muscles from relaxing. Some microbes like clostridium tetani can inhibit a favorable region but the toxin may travel to other parts of the body. This microbe prefers to reside in deep tissue such as muscle because it requires an anaerobic environment where there can be a puncture wound. For example, something affecting your leg may affect your jaw
Enterotoxins are a class of…
Exotoxins. They act on small intestine. They cause massive secretion of fluid into intestinal lumen and lead to diarreah. Cholera toxin produced by vibrio cholera is an example
Virulence factors in salmonella
These species produce a mixture of toxins that act as a virulence factor. They produce enterotoxin, endotoxin, and cytotoxin.
The siderophore is a molecule that chelates iron thus depriving your cells of it
Microbial virulence is assessed using a test for the dose of a microbial cells that kills 50% of population of mice. This is knows as LD50. Describe virulence factors like capsule and how different amount of virulence factors influence its ability to spread disease
Streptococcus pneumoniae has one virulence factor: capsule
Salmonellae enterica has several
It takes 1000 times less S. pyrogenes cells to reach the LD50 in mice than it does S. Enterica. More virulence factors don’t mean a microbe is more deadly. What virulence factors are affecting the body are more important to consider
Tetanus toxin or tetanospasmin binds to inhibitory neurons to prevent release of…
Glycine. Glycine itself stops release of acetylcholine. Glycine is used to help release muscles and acetylcholine is used to contract muscles. When glycine is inhibited, acetylcholine goes out of control and starts binding to help muscles constantly contract
Flaccid paralysis is to botulinum toxin and spastic paralysis is to
Tetanus toxin
Cholera is what type of toxin and why
An enterotoxin (exotoxin that affects the intestine) because it binds to the instestinal epithelium to cause an enzyme adenylate Cyclase to activate. This causes an elevation of an intermediate called Camp. This causes blockage of sodium ion movement into the lumen. There is a movement of chloride into the lumen and a massive movement of water which leaves the body in the form of diarrhea
What does a cytotoxin do?
Prevents protein synthesis in host cell
Difference between strepto pneumoniae and salmonella
Strepto pnuemoniae is typically a respiratory pathogen and inhibit breathing. Salmonella causes gastrointestinal symptoms. This is like an exotoxin and endotoxin difference since one is more dangerous and the other is just self limiting.
The body’s defense mechanism is divided into three levels or lines:
- Physical and biochemical barriers against microbes to keep them from entering and colonizing sterile body tissue
- Phagocytosis against microbes in general to destroy them when they have entered this sterile body tissue
- The activity of the immune system to target specific microbes that may have evaded the first two lines of defense
What is a first line of defense
Nonspecific host defenses. They target microbes and especially bacteria. They don’t act against a single microbe. Some examples of the first line of defense are:
- Skin: a barrier against microbes that is dry and acidic
- Mucus and cilia lining the tracheae-the cilia push up bacterial cells upward until they are caught in oral secretions and swallowed
- Acidity I’m the stomach: most pathogens won’t survive a trip through the stomach with its pH of 2
- Resident microorganism in the intestine: usually outcompete pathogens for nutrients
- Lysosome: the kidney and eye are bathed with this peptidoglycan dissolving enzyme
2nd and 3rd lines of defense against microbes are
- Innate(non specific): immunity relates to the general ability of certain cells of the body to phagocytize microbes. This second line of defense usually occurs within a few hours of the sterile tissue being exposed to the microbes.
- Adaptive (specific) immunity relates to a system being triggered by innate immunity. This 3rd line of defense involves a set of cells such as T and B cells (T and B lymphocytes) that target specific pathogens
True or false: phagocytosis cells are the second line of defense
True
Adaptive immunity (dependent on innate immunity signaling and uses T and B lymphocytes) involve?
Immune memory like antibodies (from plasma cell) and cytotoxic T cells help clearing infection
Post exposure immunity by B and T memory cells is common
B cells and T cells are what line of defense
Third line of defense
