Transcript of Bacterial Pathogenesis: Stages, Determinants and Virulence | This is How Bacteria Cause Damage

assalamualaikum friends welcome back to the channel today we are going to talk about bacterial pathogenesis in detail we are going to cover all the nitty-gritty details about this topic but before starting the lecture I'd like to tell you guys that these videos are meant for educational purposes things and treatments may change with time if I get wrong or miss anything your input is always welcomed in the comments section grab a pen and a notepad and let's get started bacterial pathogenesis is a process by which bacteria cause disease in a host host can be a human animal bird but here we are concerned with humans it involves a series of interactions between bacteria and the host bacteria after getting entry into the host will stop to form colonies this process is called colonization then it will start Innovation and after that it will elicit a host immune response lecture outline now we are done with the introduction of bacterial pathogenesis but I'll also introduce you a bit more with bacterial pathogensis then we will move on to stages determinants and treatment and after that we will look at more trending topics nowadays that is bacteria and cancer is bacteria responsible for causing the cancer we'll also discuss one bacterium having different strains is responsible for causing different diseases so there are many bacteria who've got different strains and these strains are responsible for different diseases we'll have a look at that human body has got the suitable environment for bacteria like moisture warmth food shelter and protection when bacteria will live in a place it will be protected from all the nasty stuff from outside the world that is why we say like shelter in shelter the bacteria is protected with time bacteria evolved and now bacteria can invade environment can survive in a particular Niche for a long period of times it can now better metabolize food and one important thing it can also with detection by immune system for example a thief escapes the police so in this case bacteria is a thief and immune system is the police the bacteria is going to escape if this is why I've written a way to detection by immune system virulence measure of a microbe's ability to cause a disease for example a highly virulent microbe requires fewer organisms to cause disease than a less virulent one bacteria have virulence factors such as toxins for example endotoxins and exotoxins if you want to know about them I've got detailed videos about them Linked In the description and certain enzymes what or the relent bacteria these are those bacteria that grow and Thrive at the expense of the host when we are talking about the virulence it's important to know symptoms one is infectious dose and the other one is the lethal dose infectious dose is denoted with ID it is the number of organisms needed to cause infection in the host for example I've written id50 it is the number of organisms needed to cause infection in half the hosts we look at the lethal dose it is denoted with LD it is a number of organisms needed to kill the host for example ld50 is the number of organisms needed to kill half the hosts prior to knowing how to treat the bacterial infection we should first assess the degree of the disease for assessing we've got three important points number one we look at the importance of the affected tissue or organ for example if the affected tissue is CNS it will be really deadly because CNS has got cells these are called neurons they have degenerative capacity and they do not have the regenerative capacity so they will not regenerate this is a really bad infection then it will take time to be treated or even it will not be treated if we compare that CNS infection with a finger cut finger cut will take small amount of time to be treated plus the cells in the finger have the regenerative capacity number two is we'll look at the strain of bacteria either this is the one strain that is produced by one bacterium or there are many strains produced by one bacterium or there are different bacteria producing different strains and the inoculum size inoculum size means the number of organisms required to cause a specific disease for example diarrhea is caused by shigella and salmonella but the difference is that only 100 shigella are required to cause diarrhea as compared to salmonella which are required in hundred thousand and then we'll also look at the status of the host either the host is immunocompetent having the strong immunity to deal with the infection or immunocompromised having the weak immunity trying to deal with the infection but it's not that good that infection will not occur stages of bacterial pathogenesis before everything else you should know that first stage is always going to be the entry of the pathogen into the house the question might arise that word is a pathogen that pathogen is any microbe that is capable of causing the disease in host after the entry of bacteria bacteria will start to Wade the primary host defenses what are the host defenses there are some physical barriers like skin mucous membranes and there are certain proteins and phagocytic cells and there is a gastric juice if the organism is getting entry through or oral cavity so there's a gastric juice in our stomach so this is also part of the primary health defense so bacteria will evade all of them after that bacteria will adhere to the surfaces in the host body and when I will adhere there it will start to reproduce it will start to form colonies and after that the disease symptoms will appear after the appearance of the symptoms host responses to third fourth and fifth stages and the last stage is either the disease will progress or it will be resolved after knowing what are the stages of bacterial pathogenesis let's talk about their determinants first one is transmission the mode of transmission of microbes include both human to human and non-human to human processes non-human sources include animals soil water and food human diseases for which animals of the reservoir are called zoonosas human to human transmission can occur either by direct contact or indirectly via a vector such as insects notably texts or mosquitoes animal to human transmission can also occur either by direct contact with animal or indirectly via a vector the main portals of entry into the body are respiratory tract gastrointestinal tract skin and genital tract the second one is adherence to cell surfaces bacteria will use one of its special structures that is called pylie pilai are the main mechanism by which bacteria adhere to human cells they are fibers that extend from the surface of bacteria that mediate attachment to specific receptors on cells bacteria will also use glycocalyx which is a polysaccharide slime layer secreted by some strains of bacteria that mediates strong adherence to certain structures such as heart walls prosthetic implants and catheters the third determinant is Invasion inflammation and intracellular survival invasion of tissue is enhanced by enzymes secreted by bacteria for example hyaluronic days produced by streptococcus pyrogens degrade hyaluronic acid in subcutaneous tissue allowing the organism to spread rapidly the capsule surrounding bacteria is anti-fagocytic I.E it retards the phagocyte from ingesting the organism inflammation it is an important host defense induced by the presence of bacteria in the body there are two types of inflammations number one is pyrogenic and number two is granulomatous pyogenic is related to the post-producing bacteria the pygienic Pig and the granulomatous inflammation is related to granuloma producing bacteria such as mycobacterium tuberculosis intracellular survival bacteria can evade or host defenses by a process called intracellular survival I.E bacteria that can live within cells are protected from Attack by macrophages and neutrophils the fourth determinant is Toxin production toxins like exotoxins which are polypeptides secreted by certain bacteria that alter specific cell functions resulting in symptoms of disease and they are produced by both from positive and gram-negative bacteria whereas endotoxins are found only in gram negative bacteria and endotoxins are lipopolysaccharides and they are not secreted by a bacteria if you want to know them in detail I've got their links in the description the last determinant is immunopathogenesis in certain diseases such as rheumatic fever and acute glomerulonephritis it is North the organism itself that causes the symptoms of the disease but the immune response to the presence of organism for example in dramatic fever antibodies are formed against the M protein of asparagens which cross-react with joint heart and brain tissue inflammation occurs resulting in arthritis carditis and choria that are the characteristic findings in the disease how to treat bacterial pathogenesis it is treated with antibiotics and these antibiotics work in two ways number one by targeting specific bacterial populations and number two by interfering with bacterial growth and replication antibiotic resistant strains are quite necessary because some antibiotics are not going to work against those strains we're going to use those antibiotics that are effective against these resistant strains bacteria and cancer traditionally bacterial infections have not been considered major causes of cancer recently it has shown that bacteria can be linked to cancer through two mechanism number one by induction of chronic inflammation and number two biode production of carcinogenic bacterial metabolites for example the conversion of helicobacter pylori infection into gastric carcinoma same bacteria different strains and different diseases how do bacteria that belong to the same genus and species called search widely Divergent diseases answer is that individual bacteria produce different Wilderness factors that give those bacteria the capability to cause different diseases the different virulence factors are encoded on plasmids on transposons on the Genome of temporary lysogenic phages and are pathogenicity islands these transferable genetic elements may or may not be present in any single bacterium which accounts for the ability to cause different diseases now we are familiar with the process of same bacteria having different strains responsible for causing different diseases we should know what is a strain it is a genetic variant or subtype of the microorganism and that's it for today's video I hope you got the itsy bitsy details about the bacterial battery and you've got any suggestions feel free to leave them Below in the comments sections and also if you want to connect with me on my socials I've got my Instagram I've got my Twitter and I do upload blogs I'll catch you next time till then assalamu alaikum