Infectious process: Nursing pathophysiology

The infectious process refers to the steps that occur when a pathogen which is a disease causing microorganism enters the body multiplies spreads and causes tissue damage.

Ok. So the body has lines of defense to protect itself against pathogens.

The first line of defense includes physical and chemical barriers that prevent entry of pathogens into the body, like intact skin and mucous membranes and molecules like lysozyme found in body fluids like tears and mucous that can break down the cell walls of certain pathogens.

Another key aspect of defense is the microbiome or the collection of microorganisms that normally live in and on the body.

These microorganisms don't normally cause disease and they help protect against invading pathogens by mechanisms like physically occupying space and even producing substances that inhibit the colonization of pathogens.

If a pathogen gets past these barriers, it encounters the second line of defense, the inflammatory response where immune cells like macrophages and neutrophils, octoides or ingest bacteria and cellular debris.

Other systems like the complement system also get activated which assist in the killing of pathogens. Both the 1st and 2nd lines of defense are innate, meaning they're natural inborn defense mechanisms and they're nonspecific because they respond the same way to all pathogens.

Now, if these mechanisms are not able to stop the invasion of the pathogen, the third line of defense adaptive immunity kicks in it involves cellular immunity, primarily with T lymphocytes and B lymphocytes and the formation of antibodies which is also called humoral immunity.

Adaptive immunity mechanisms attack the current infection and it even has a memory. So the next time the body is exposed to this same pathogen, it can start attacking it faster.

All right. So, infections are caused by pathogens like bacteria, viruses and fungi.

Each of these organisms have their own characteristics that contribute to their pathogenicity or their capacity to cause disease and virulence, which is the degree of pathogenicity of a specific microorganism.

Bacteria have certain characteristics that help them cause infection in an individual who becomes the host to the pathogen.

These include Pyle, which are small hair like appendages that help them adhere to host cells, toxic secretions including exotoxins, endotoxins, and enzymes that damage host cells capsules or an outer covering that prevents their destruction by the immune system and biofilm a matrix they excrete to further protect themselves from destruction.

Viruses are obligate intracellular parasites, meaning they need a host cell in order to replicate. They do this by using their genetic material to take control of the reproductive machinery of the host cells to create new viruses in the process.

They cause host cell destruction or lysis and cause disease. Viruses can resist the immune system by evading recognition and hiding within host cells.

Fungi can cause superficial infections of the skin and mucous membranes, but they also can cause systemic infections. Some fungi secrete enzymes that damage host tissue.

Other fungi can also use mechanisms to avoid being recognized by the immune system or produce substances that inactivate host immune defenses.

Risk factors for infections include several host characteristics like genetic predisposition. Extremes of age presence of chronic disease, malnutrition and severe stress.

Additionally, being under or unimmunized or immunosuppressed and having a break in physical barriers such as the skin also contribute to infection risk.

Now, the infectious process involves several steps. First contact and transmission begins when an individual encounters a pathogen.

The pathogen can be exogenous when it comes from external sources like contaminated food or another individual or endogenous, which can happen if there is an imbalance in the normal microbiome that causes an overgrowth of certain microorganisms.

Transmission can be direct when there is physical contact between an infected individual and an uninfected individual or indirect, which can occur through fomites or contaminated inanimate objects such as doorknobs, inhalation of respiratory droplets, ingestion of contaminated food or water and even through the bite of an infected insect, like a mosquito transmission can also be characterized as horizontal where pathogens are transmitted to an individual by another individual or animal or vertical.

From a birthing parent to a child through the placenta during delivery or from breast milk. Next colonization occurs when the pathogen starts to multiply on or within the host.

While invasion or penetration occurs when the pathogen crosses a protective barrier or directly invade cells. After invasion, the pathogen can disseminate or spread by extending into surrounding tissue or traveling through blood or lymphatic vessels.

Finally, tissue damage occurs directly during cellular lysis or from release of toxins or indirectly from inflammation or tissue necrosis.

Now, clinical manifestations of infections generally progress through several stages. First, the incubation period is the time after the initial contact transmission and colonization of the pathogen.

During this time, there aren't enough pathogens to cause symptoms. So most individuals don't know they're infected.

Next. The prodromal stage is when the pathogen has replicated enough to begin affecting the body and symptoms start to appear.

These symptoms are typically mild and nonspecific like fatigue, discomfort or headache. This is followed by the acute illness stage where the pathogen is rapidly multiplying and invading tissues.

Symptoms at this stage are typically more pronounced and are related to the triggering of the immune response along with specific symptoms related to the type of infection.

Lastly, the convalescent stage occurs after the pathogen has been successfully removed and symptoms begin to dissipate. On the other hand, sometimes the pathogen can enter a latency stage to be reactivated later while other times the infection causes so much damage that it's fatal.

All right, as a quick recap, the infectious process occurs when an individual encounters a pathogen. Usually, bacteria, viruses or fungi.

After transmission, it colonizes, invades, disseminates and causes tissue damage. Clinical manifestations of infection progress through incubation, prodromal, acute illness and convalescence stages.