Unfortunately, some of these adaptations can wreak havoc on our bodies in many cases bacteria might gain or develop enhanced virulence factors, which allow them to more. Effectively cause disease virulent bacteria by definition grow and Thrive at the expense of their hosts. For instance
- Some bacteria might release toxins that can travel through the blood causing life-threatening disease
- Others might be able to directly degrade our tissues or trigger aggressive Cascades within our immune system. In fact in many cases the symptoms that we experience are actually caused.
Some bacteria like shigella which causes food poisoning require a relatively tiny inoculum size like around 200 to cause serious gastrointestinal distress. While others like salmonella might require several orders of magnitude more inoculum, like a million or more to cause a serious infection. However, the particular host factors into this equation as well. If you are immunocompromised for instance, it might take much less salmonella to make you sick. the common routes that bacteria use to enter the body.
Our bodies have natural defense mechanisms such as Skin, earwax, stomach acid, tears and mucus membranes.
Our skin prevents microorganisms from invading, our tears contain enzymes that attack bacteria, our Airways filter out harmful particles in our mucous membranes are coated with secretions that fight off microorganisms. Despite our bodies best efforts. Some of these microbes are able to bypass these defenses for instance:
- Bacteria such as salmonella vibrio, bacillus cereus and shigella can enter the body through ingestion. This could be from a picnic lunch left out in the sun for too long or as the result of poor hand washing.
- Other bacteria such as streptococcus mycobacterium for Legionella enter through inhalation, perhaps after a sick person’s sneeze or infected aerosol particles floating through the air clostridium TEC-9 the causative agent of tetanus enters through trauma or a wound other portals of Entry include a mosquito bite needle stick injuries or sexual transmission.
Another bacterial adaptation that promotes colonization is the formation of biofilms which are collectives of one or more types of microorganisms. Within a biofilm bacteria forms sticky webs of polysaccharides that bind bacterial cells together into a community providing protection from antibiotics or host defenses. Bacteria, like pseudomonas aeruginosa can sense when enough bacteria are present and Trigger biofilm formation through a process called Quorum sensing.
Biofilms are particularly common on catheters in Dental plaque or on implanted surgical devices such as pacemakers. Now that we’ve covered the ways that bacteria colonize and invade bodies. Let’s talk about specific ways. They cause damage for some bacteria natural byproducts of their growth can cause tissue Destruction for instance in your gut. Anaerobic bacteria those that don’t Higher oxygen for growth can produce toxins enzymes gas and acid all of which destroy the surrounding tissue some examples are staphylococcus I or streptococci once the process has begun the bacteria have momentum with these enzymes facilitating the spread of disease next bacteria can produce harmful substances called toxins meant to either attack other bacteria in their vicinity or Damage the host they’ve settled in typically toxins cause degradation or lysis of cells or triggered destructive immune responses.
For some diseases symptoms can be fully attributed to toxin production with damage occurring right where the infection is in other cases such as with tetanus or certain staphylococci Associated infections the toxin May travel through the bloodstream and cause symptoms somewhere else in the body the components that make up the bacterial cell wall in particular can set off a powerful Chain Reaction Within .The immune system for instance during an infection of gram-positive bacteria the peptidoglycan and the products it breaks down into can stimulate a fever or inflammation with devastating effects on the body or lipopolysaccharide produced by gram-negative bacteria is categorized as endotoxin in low doses endotoxin can activate the immune system or protective responses such as a fever. Or in higher doses endotoxin can trigger extremely high fever shock or skin lesions which can be deadly exotoxin proteins on the other hand can be produced by either gram-positive or gram-negative bacteria proteins that fall into this category include those that cause cytolysis which causes the cell to burst from osmotic pressure or receptor binding proteins that either cause cell death or change their
Altogether exotoxins are often encoded on a plasmid or a phage another category of toxins is super antigens, which activate the immune system to a life-threatening degree causing toxic shock syndrome. Finally bacteria have developed multiple mechanisms to escape our host defenses, especially in the case of long-term infections. They might alter their surface proteins to evade detection. It’s like neisseria gonorrhea physically hide within cells in the body or inactivate our standard antibacterial defenses. One of the most powerful virulence factors that some bacteria have our slime layers called capsules. These capsules can mimic the surface of a host cell shielding the bacteria from typical immune responses.
Other bacteria Create makeshift Shields within the site of infection like staphylococcus aureus which forms a barrier using coagulase. Ultimately bacteria have a wide array of tricks up their sleeves some might Express one virulence mechanism While others might Express several in tandem altogether these mechanisms are ultimately what trigger disease symptoms.
What are the characteristics of a pathogenic bacteria?
- They have optimal growth temperate that corresponds to the body temperature of host. So, most pathogenic bacteria of human have optimum growth temperature of about 35–37C.
- They may have capsule. Capsule prevents the bacterial cell from being phagocytosed and it also helps to adhere to host cells.
- They may produce either of many toxins produced by most pathogenic bacteria. Toxins can be enterotoxin, toxic-shock-syndrome toxin, exfoliatin, etc.
- They may possess enzymes like coagulase (capable to clot blood) and DNA-ase (capable to denature DNA).
- They possess antigenic structures in them which can elicit immune response in host.
- They may have flagella that helps in motility of bacteria inside the host body.
- They may have the cellular mechanism that renders them ability to protect themselves from antibiotics (resistance to antibiotics). Efflux pumps, modification in gene (protein) so that antibiotics can no longer bind to it, etc.
Role of bacterial biofilms
A biofilm is formed when microorganisms attached to and grow on a variety of biotic and abiotic surfaces. The initial attachment is usually reversible and often involves attachment by flagella fimbriae or other cell surface structures. This is followed by growth of the microorganism and production of an EXO polymer which makes the attachment irreversible. Growth within the biofilm is not uniform channels develop which permit incorporation of fresh nutrients and oxygen metabolic activities of microorganisms in a biofilm can create changes in the micro environment. For example, an oxygen gradient can develop that permits anaerobic metabolism near the interior and aerobic metabolism on the exterior nutrient and pH gradients are also produced in the natural environment.
And biofilms often consists of different types of organisms that function together in the cycling of the elements. For example, breakdown of cellulose on the surface of a decaying plant may result in release of glucose and other carbohydrates which supports the growth of non cellulose degraders carbohydrates are converted to organic acids and methane by anaerobic bacteria. And the methane can then be degraded by aerobic microorganisms.
The steps must happen for bacteria to cause disease in a host? In order to survive and multiply in a host, a successful pathogen must be able to:
- Colonize the host
- Find a nutritionally compatible niche in the host body
- Avoid, subvert, or circumvent the host innate and adaptive immune responses
- Replicate, using host resources
- Exit and spread to a new host. Under severe selective pressure to induce only the correct host cell responses to accomplish this complex set of tasks, pathogens have evolved mechanisms that maximally exploit the biology of their host organisms.
Microorganisms play a vital role in human survival. In fact Life as we know it would be impossible without them. But how does that work? How does our dependence on bacteria begin?
Let’s start from conception as a human fetus develops its protected within the sterile womb of its mother as soon as it’s born an infant is immediately exposed to microbes from Its mother and the surrounding environment protective microbes begin to grow first on the infant’s skin, then their oral pharynx which is the back of the throat. The gastrointestinal tract is colonized next followed by other mucosal surfaces. These populations of bacteria are called microbial flora and they perform a wide variety of crucial tasks:
- They help protect us from infection by virulent microorganisms.
- They stimulate the immune response.
- They helped us metabolize our food
- they provide essential growth factors.
As we age the balance of microbe Books that are on us and in us are influenced by factors such as what we eat our overall health hormonal changes in personal hygiene. Drastic changes in any of those factors can disrupt the intricately balanced ecosystem of microbes which can in turn make us sick. For example taking antibiotics can wipe out all of the good and bad bacteria in the gut completely disrupting the equilibrium of microbial populations within.