Lecture 8-9 Gram negative bacteria Flashcards Preview

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Flashcards in Lecture 8-9 Gram negative bacteria Deck (26):

Gram negative rods are a major part of our normal flora especially where in our body?



What are the 5 F's for transferring infection

Food, Fluids, Fingers, Flies and Feces


Explain the most important characteristic of Enteric Gram negative rods that deals with virulence factors

These bacteria are able to 'share' virulence factors by gene transfer via plasmids, conjugation, transformation, or by bacteriophage transduction.


The "sharing" of virulence factors in Enteric Gram negative rods leads to what?

Spread of antibiotic resistance among pathogens and produces variant strains of typically normal flora.


Define Zoonotic

a disease or microbe that normally exists in other animals, but can be transmitted and infect humans.


Name 5 diseases that enteric gram - bacteria can cause

1. GI infections (diarrhea, colitis, etc.)
2. Food "poisoning"
3. Urinary Track Infections (Major Cause 75%)
4. Sepsis & Bacteremia
5. Ulcers & Gastritis


4 major characteristics of Enteric Gram- Rods

1. Non-fastidious (but sensitive to drying)
2. Metabolically diverse
3. Facultative Anaerobes
4. Normally found in GI tract of humans and other animals


Name the 4 enteric g- bacteria that are a part of our normal flora

Escherichia coli


Describe the three designations give to these bacteria for serological typing

Flagella = H-antigens
Capsules = K-antigens
Endotoxins = O-antigens


What is Antigen Variation

Often multiple genes are available for each antigen, and an individual bacterium can change back and forth between these genes to change the epitopes on the cell surface. This is very helpful to evade the adaptive immune response!!!!


What is macrophage taxis?

Where bacteria can grow and survive inside the macrophage. It is then transported throughout the body.


What is the use of Adhesions in enteric g- bacteria

These bacteria must adhere firmly to surface mucosal sites because of the innate flushing that occurs in the gut. These adhesins (often fimbrae-associated) determin where the bacteria binds.
It is also sometimes a cause of pathology


What is bacterial-directed endocytosis and how is it used in enteric g- bacteria?

Some species of bacteria can actually initiate actin assembly and commence their own internalization into the cells they attach to. Some strains enter the cytoplasm of cells (Shigella and E. coli) while others enter the macrophages (Salmonella and Yersinia)


How do Salmonella and Yersinia use bacterial-directed endocytosis differently than E. coli and Shigella?

Salmonella and Yersinia invade mucosal epithelium and enter MACROPHAGES.
E. coli (EIEC strain) and Shigella enter muscoal epithelium and divide in the CYTOPLASM of those cells.


EPEC strains of E. coli use adhesions in what specific way which causes what dysfunction?

They attach to gut epithelial cells and cause the microvillus structure to become altered, causing malabsorption. They flatten and destroy the microvilli.


T or F, Endotoxins are the LPS layer found in ALL gram negative bacteria



What is the method by which endotoxins or LPS works?

LPS causes massive activation of macrophages (and other cells) resulting in production of huge amounts of pro-inflammatory cytokine mediators such as IL-1 and TNF-alpha.
TNF-alpha stimulates endothelial cells to produce NO that causes pre-capillary sphincters to relax and capillary beds to open.


What happens when Gram negative bacteria enter the body in SMALL numbers

They are aggressively attacked by our entire innate inflammatory system with waiting for an adaptive immune response. LPS activates macrophages, Platelets, hageman factor and alternate complement pathway


If Gram negative is present in the blood stream in LARGE numbers what happens?

Initiates a massive inflammatory response that causes Sepsis (too much inflammation in body), which can be quickly fatal.
- Hypovolemic Shock
- Disseminated intravascular coagulation


What characteristic produces unique pathogenic strains of otherwise normal enteric g- bacteria?

Variety of exotoxins produced by genes that are often acquired and transferred via conjugation plasmids or by bacteriophage transduction.


What is the main protein exotoxin secreted by enteric g- bacteria

Mostly A-B exotoxin


3 major classes of A-B exotoxins that are produced by enteric gram - pathogens

-Two A-B enterotoxins that cause ribosylation of regulatory proteins in gut epithelial cells
- An A-B toxin that cleaves ribosomal RNA, thus blocking protein synthesis mainly within endothelial cells of kidney and CNS


What is the most common method of transfer for enteric gram negative bacteria

Fecal-Oral route (the 5 F's with emphasis on feces)


What is one of the major ways to test whether drinking water has been contaminated with fecal materials?

Assay for the presence of enteric gram negative rods, especially E. coli, in water


What is the disease causing potential

(Virulence X Dose)/ Host Resistance


T or F, Diseases caused by enteric gram negative rods tend to decrease during the summer

False, They increase