Portal of Entry
Pathogens need a portal of entry to gain access to a person’s body. They can enter through the respiratory, gastrointestinal, urinary, and reproductive systems and through breaks in the skin or mucous membranes. Open wounds, incisions, puncture sites from injections, or body orifices into which catheters (tubes) or similar devices are inserted are common portals of entry. To prevent organisms from entering a host, take these measures:
• Keep the client’s skin clean and dry. Apply moisturizers to dry skin or lips, to prevent cracking.
• Be very careful if clipping a client’s nails. Urge clients not to bite their fingernails or cuticles and not to pull on hangnails.
• Avoid positioning clients against tubes or objects that could cause skin breaks.
• Frequently reposition clients who have impaired mobility.
• Provide clean, dry, wrinkle-free linen.
• Make sure urine collection bags are lower than the client.
• Disinfect tubes and ports before collecting specimens from drainage tubes or intravenous lines.
• Keep wounds that are draining and breaks in skin covered.
• Use sterile technique when performing invasive procedures.
As a healthcare worker, you are at risk for infection. Wear gloves to protect yourself when handling any blood or body substances or other potential pathogenic reservoirs (i.e., contaminated equipment). Wear protective eyewear, masks, gowns, and shoe covers if any danger exists of splashing or spraying body substances.Procedures, such as careful handwashing and proper wound and catheter care, also help to break the chain of infection.
Susceptible Host
Normally, healthy people have a variety of defenses against infection, both non-specific (e.g., skin as a barrier, fever, phagocytosis) and specific (e.g., immunity). Ill or inactive people or hospitalized clients, however, are more susceptible to infections. Their immune systems may be compromised. Chronic fatigue and poor nutrition weaken the body’s ability to respond fully. Injury, wounds, shock, and trauma further weaken the body. Side effects of some medications also contribute to a person’s susceptibility. Emotional factors, such as anxiety, may play a role in altering the body’s defenses. Infants, young children, and older adults are especially vulnerable.
Help to reduce each client’s susceptibility to infection by treating the client’s underlying condition. Provide adequate rest and skin care. Give nutritional support. Help to reduce anxiety. Encourage adequate fluid intake. Help with coughing and deep breathing when the client is immobilized. Encourage proper immunization of children and older adults who are at high risk of acquiring communicable diseases. Practice infection control measures. Preventing infection is the daily job of every healthcare worker.
Nursing Alert Observe Standard Precautions in all nursing care. Assume that all clients have an infection and act accordingly
NCLEX Alert The NCLEX can provide clinical situations that mention specific pathogens. The correct answer may reflect your understanding of Standard Precautions or Transmission-Based Precautions. Care of clients can require knowledge of the mechanisms of contamination or the processes of how infections spread.
Actions of Pathogens in the Body
Pathogenic microorganisms have two possible damaging effects within the body: local destruction of tissue or production of poisonous substances that migrate. Although some microorganisms destroy the tissues in which they live, many organisms cause damage to host tissues far from the infection site. This is because of the action of poisonous toxins produced by the pathogenic microorganisms.
Toxins cause harmful effects by traveling through the circulatory system to damage other body cells. The wide variety of their cellular effects includes interrupting cellular metabolism, stopping protein synthesis, and destroying cell membranes. Toxins can cause many different symptoms.
Microorganisms produce two types of toxins. Endotoxins are part of the cell walls of gram-negative bacteria. When a microorganism dies, the cell wall decays and releases the toxins. Exotoxins are toxins manufactured by the microorganism and excreted into the surrounding tissue. They are released into host blood vessels, where they are carried to other body parts.
RESPONSE TO INFECTION
Whether or not a pathogen produces an active infection depends on both the organism and the host. A healthy individual often can muster physical defense mechanisms to ward off disease. Persistent and effective pathogens, however, can overwhelm even the healthiest person.
Normal Course of Infection
When an infection occurs, it usually follows a progressive course. The first stage is the incubation period, the time from when the pathogen enters the body to the appearance of the first symptoms of illness. For example, after the varicella organism (which causes chickenpox) enters the body, it takes 2-3 weeks before any lesions appear. The second phase is the prodromal stage, the period from the onset of initial symptoms (e.g., fatigue or low-grade fever) to more severe symptoms. Many illnesses are the most contagious during the prodromal stage. The third phase is the full stage of illness. During this period, the symptoms are acute and specific to the type of infection, such as a high fever, lesions covering the body, cough, headache, or congestion. The final stage is the convalescence stage. During this period, the acute symptoms of the infection subside and the person recovers.
Factors That Influence the Development of Infection
Normally, the body has a variety of defense mechanisms that contribute to its resistance to pathogenic infection. Although the individual is unaware of it, his or her body is almost constantly defending itself against foreign invaders. Review that topic for a better understanding of how the human body naturally defends itself against pathogenic microorganisms.
Several factors other than the strength of the body’s natural defenses help determine whether or not disease-causing microorganisms will ultimately cause an infection.
Specific Portal of Entry
In general, microorganisms cause disease only if they gain access to the body through a specific portal of entry. For example, Streptococcus pneumoniae causes pneumococcal pneumonia only when it enters the respiratory system; use of any other portal of entry does not result in infection. Likewise, the typhoid bacillus must enter the digestive tract. Meningococcus uses the nose as its chief portal of entry.
Number of Microorganisms
Usually, large numbers of microorganisms are needed to cause infection. If the number of pathogens entering the body is small, the body’s natural defenses can easily overcome them. The greater the number of pathogens, the greater the opportunity they have to cause disease.
Virulence
A pathogen’s strength to cause disease is called its virulence. Some bacteria form protective capsules that increase their virulence by making them less likely to be destroyed by the host’s white blood cells. Other bacteria produce enzymes that destroy blood cells, stop normal blood clotting, or consume muscle fibers. Each of these enzymes increases the virulence of the particular species that produces them.
As previously described, some pathogens are able to mutate so they are not susceptible to certain antibiotics. These organisms are more virulent just because commonly used antibiotics will not destroy them.
Host Resistance
Naturally occurring microorganisms in the body do not cause disease in healthy people. In fact, some of them play a necessary role in disease resistance and in maintenance of health and body functioning. The ability of some species of microorganisms to live together is called symbiosis. An association in which one species of microorganism prevents the growth or actually destroys members of another species is called antibiosis. (The term antibiotic is derived from the term antibiosis.) Some naturally occurring body flora have this type of antibiotic relationship with pathogens and contribute to an individual’s overall health.
If a person is immunocompromised as a result of illness or another factor, he or she will not be able to fight off disease. Examples include people with AIDS or agammaglobulinemia (congenital absence of normal gamma globulin), people undergoing some forms of chemotherapy for cancer, or people recovering from a bone marrow transplant. In these cases, even normally occurring microorganisms can cause disease (opportunistic infections).
KEY POINTS
• Some microorganisms are beneficial in nature. Others, called pathogens, cause disease in human beings.
• All microorganisms, except viruses, engage in the same general life functions as do other plant and animal cells. These functions may occur in a modified form.
• The reproductive processes and spread of infection caused by pathogens depends on the proper set of conditions.
• Culture and sensitivity reports and staining identify pathogens and suggest appropriate treatment for them.
• Microorganisms are classified by their physical and biologic characteristics into basic groups, each with distinguishing means of reproducing and, if they are pathogens, of infecting people.
• With the number of drug-resistant and multi-drug-resistant microorganisms increasing, prudent use of antibiotics is essential.
• Viruses cause disease by taking over the host cell’s metabolism and genetic material and by reproducing in extremely large numbers.
• Most common microbial diseases are communicable and are spread within the population by direct or indirect contact; by contaminated air, water, or food; or through vectors.
• Healthcare professionals who practice antiseptic techniques and Standard Precautions can help to break the chain of infection.
• Infections follow a progressive course. Many factors contribute to the microorganism’s ability to result in disease.
