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Bacterial exoenzymes and toxins as virulence factors

After exposure and adhesion, the next step in pathogenesis is invasion , which can involve enzymes and toxins. Many pathogens achieve invasion by entering the bloodstream, an effective means of dissemination because blood vessels pass close to every cell in the body. The downside of this mechanism of dispersal is that the blood also includes numerous elements of the immune system. Various terms ending in –emia are used to describe the presence of pathogens in the bloodstream. The presence of bacteria in blood is called bacteremia . Bacteremia involving pyogens (pus-forming bacteria) is called pyemia . When viruses are found in the blood, it is called viremia . The term toxemia describes the condition when toxins are found in the blood. If bacteria are both present and multiplying in the blood, this condition is called septicemia .

Patients with septicemia are described as septic , which can lead to shock , a life-threatening decrease in blood pressure (systolic pressure<90 mm Hg) that prevents cells and organs from receiving enough oxygen and nutrients. Some bacteria can cause shock through the release of toxins (virulence factors that can cause tissue damage) and lead to low blood pressure. Gram-negative bacteria are engulfed by immune system phagocytes, which then release tumor necrosis factor , a molecule involved in inflammation and fever. Tumor necrosis factor binds to blood capillaries to increase their permeability, allowing fluids to pass out of blood vessels and into tissues, causing swelling, or edema ( [link] ). With high concentrations of tumor necrosis factor, the inflammatory reaction is severe and enough fluid is lost from the circulatory system that blood pressure decreases to dangerously low levels. This can have dire consequences because the heart, lungs, and kidneys rely on normal blood pressure for proper function; thus, multi-organ failure, shock, and death can occur.

A picture of a person with a swollen right hand.
This patient has edema in the tissue of the right hand. Such swelling can occur when bacteria cause the release of pro-inflammatory molecules from immune cells and these molecules cause an increased permeability of blood vessels, allowing fluid to escape the bloodstream and enter tissue.

Exoenzymes

Some pathogens produce extracellular enzymes, or exoenzyme s , that enable them to invade host cells and deeper tissues. Exoenzymes have a wide variety of targets. Some general classes of exoenzymes and associated pathogens are listed in [link] . Each of these exoenzymes functions in the context of a particular tissue structure to facilitate invasion or support its own growth and defend against the immune system. For example, hyaluronidase S, an enzyme produced by pathogens like Staphylococcus aureus , Streptococcus pyogenes , and Clostridium perfringens , degrades the glycoside hylauronan (hyaluronic acid), which acts as an intercellular cement between adjacent cells in connective tissue ( [link] ). This allows the pathogen to pass through the tissue layers at the portal of entry and disseminate elsewhere in the body ( [link] ).

Questions & Answers

I am about to enter school and am going for MCB
Olugbenga Reply
What is DNA damage and repair
Sree Reply
removal of nucleotide bases from DNA is damage n addition or insertion of bases in DNA is repair.
Rashmi
replication is a term related to generation of new DNA from a parental DNA.
Rashmi
role of microorganism as pathogens
Parteek Reply
to live inside the host body, reproduction n destroy the immune system of host body.
Rashmi
what is replication
rajesh
please give me ans
rajesh
replication is a term related to generation of new DNA from parental DNA.
Rashmi
difference between endotoxin and exotoxin
Binkheir Reply
toxins released inside the cell or a body is endotoxin n toxins released outside the cell or a body is exotoxin.
Rashmi
please I want the names of bacteria and the diseases they cause.
Ibrahim Reply
there are many we classify it according to their shapes gram negative or gram positive
Tharra
so u may refer the book u guess or by when u want I can do a list for you and send u here
Tharra
😊
Tharra
please do a list for me
Ibrahim
I have the lost but it's too much to type ..
Tharra
MSc entrance prepare books and questions LA etha base pani irukum..
Guhan Reply
kushal always prescott is the imp book to follow.search some objective mcqs books based on your syllabus
deepthi Reply
I want to clear entrance of ms university so I have no more idea so my preparation is based on my bachlor studies.
Kushal
what are the opportunistic infection in aids stage
Kalkak
certain cancer or pneumonia 🤔
Kushal
penicillium crysogenum
Kushal Reply
salam am also studying microbiology in university of Ilorin
Abubakar Reply
Salam am studying physiotherapy in bayaro university kano
Tasiu
Walaikum salam
Hakeeb
Hw u
Tasiu
HRU frinds
Arhaan
any good reference for oncology?!!!!
Pankaj Reply
K.D tripathi
Vinod
what is the microbiology
Fadumo Reply
it is the study of microorganisms
Sneha
microorganis means
Ghuge
the organism can not be seen by eyes they can be seen with the help of microscope
rajesh
microbiology is the study of microorganism and microorganism are such as bacteria ,parasite, viruses and fungi and etc.. those are cant be seen with asked eyes and can be seen with help of microscope . I hope this helps you
Tharra
what is virology
Bismarck Reply
the study of viruses
Adan
what is myrology
Bismarck
myrology or mycology?
Adan
mycology
Bismarck
the study of fungi.
Adan
Mycology study fungi
Hakeeb
study of viruses
Rashmi
what are the major topics that you cover under micro biology
Bismarck Reply
virology,mycology,bacteriology
Adan
identification n application of microorganisms
Rashmi
How do u apply micro biology in medicine
Bismarck Reply
in preventing, diagnosis and treatment of infectious diseases.
Adan
and also in carrying out test And Analysis
Hadiyat
what is micro biology
Bismarck Reply
study of microorganisms
Adan
thanks
Bismarck
OK thanks alot
Bismarck

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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