Infection Control and Isolation Comprehensive Study Guide to Isolation Precautions
The Chain of Infection
The chain of infection is defined as a sequence of necessary pieces that must be in place for an infection to occur. This process is cyclical and involves several specific components that must align to facilitate the spread of disease. The primary components include the infectious agent, the reservoir, the portal of exit, the mode of transmission, the portal of entry, and the susceptible host. If any link in this chain is broken, the infection is prevented from spreading to a new host.
Infectious Agents and Reservoirs
An infectious agent is any substance or organism that is capable of producing an infection. These agents include bacteria, fungi, viruses, parasites, or prions. The presence of these agents is the first requirement for the chain of infection to begin. Once an infectious agent exists, it requires a reservoir to survive. A reservoir is defined as the habitat of the infectious agent; it is the specific environment where the agent lives, grows, and reproduces or replicates itself. Without a suitable reservoir, the infectious agent cannot maintain its population or readiness to infect a host.
Portals of Exit and Entry
For an infection to move from a reservoir to a new host, it must have a means of escape and a means of entry. A portal of exit is the designated means by which the infectious agent leaves its reservoir to seek a new host. Conversely, a portal of entry provides a location for the infectious agent to enter a new host so it can replicate or for a toxin to act. Portals of entry can include any body orifice, such as the ears, nose, or mouth, and can also occur through the skin. These portals are critical checkpoints in the transmission process.
The Susceptible Host
The final link in the chain is the susceptible host, which is required for the infectious agent to take hold and eventually become a new reservoir for infection. It is important to note that exposure does not always result in illness; not everyone who is exposed to an infectious agent becomes sick. The susceptibility of a host depends on various factors, including their immune status and overall health. A host is only considered part of the chain when the agent successfully establishes itself within their system.
Contact Precautions and Transmission Types
Contact precautions are implemented when microorganisms move from an infected person to another person. Clients under these precautions require a private room to prevent the spread of pathogens. The required Personal Protective Equipment (PPE) for contact precautions includes gloves and a gown. Additionally, healthcare providers may use non-PPE items such as disposable equipment, including disposable stethoscopes, to further protect other patients from cross-contamination. Specific diseases that require contact precautions include Staphylococcus aureus, Extended-spectrum beta-lactamases (ESBLs), and Methicillin-resistant Staphylococcus aureus (MRSA). Clostridium difficile, while a contact-based infection, specifically requires enteric precautions.
There are two primary types of contact transmission. Direct contact transmission occurs when microorganisms are moved directly from the infected person to another person without any contaminated object or person acting as an intermediary. Examples of direct contact transmission include the spread of herpes simplex virus (HSV), scabies, or blood coming into contact with an open abrasion. Indirect contact transmission occurs when microorganisms move from the infected person to another person through a contaminated object or person in between. Staphylococcus aureus is particularly notorious for spreading through indirect contact transmission.
Droplet and Airborne Precautions
Droplet precautions are necessary when respiratory tract droplets from a client travel through the air and land on the mucosa of a host. Clients in this category require a private room and are mandated to wear a mask whenever they leave their room to prevent the spread of infectious particles. The PPE required for healthcare workers includes gloves and a mask, potentially supplemented with a face shield. Diseases requiring droplet precautions include Norovirus, Rhinovirus, Coronavirus, Influenza, and Pertussis.
Airborne precautions are utilized when small particulates move into the airspace of another person. These particulates can remain suspended in the air for longer periods. Clients require a private room equipped with negative-pressure airflow to ensure air is not circulated into general hospital hallways. The required PPE for airborne precautions is an N-95 mask. Diseases that necessitate airborne precautions include Varicella (chickenpox), Rubeola (measles), Tuberculosis (TB), and Covid-19.
Specific and Nonspecific Immunity
The body protects itself through two main types of immunity. Nonspecific immunity refers to the action of neutrophils and macrophages, which function as phagocytes. These phagocytes identify, eat, and destroy microorganisms to protect the body from harm. Both neutrophils and macrophages are released during the inflammatory response. Specific immunity, on the other hand, involves the work of antibodies, also known as immunoglobulins, and lymphocytes. Antibodies bind to infectious agents and signal white blood cells and the complement system to destroy the invaders.
The Inflammatory Response and Stages of Infection
The inflammatory response follows a specific four-step process. In Step 1, pattern receptors on the surface of cells recognize harmful stimuli. In Step 2, inflammatory pathways are activated within the body. In Step 3, inflammatory markers are released into the system. Finally, in Step 4, inflammatory cells are recruited to the site of the stimuli to address the threat.
Infections progress through five distinct stages. The first stage is the Incubation period, where the infection enters the host and begins to multiply. The second stage is the Prodromal period, where the client begins to experience the first signs of symptoms. The third stage is the Acute illness phase, where the manifestations of the specific infectious disease process become obvious and may reach their peak severity. The fourth stage is the Decline period, where manifestations begin to wane as the degree of infectious disease decreases. The fifth and final stage is Convalescence, during which the client returns to their normal state of health or establishes a "new normal."
Local versus Systemic Infections and Sharps Safety
Infections are categorized by their reach within the body. Local infections are confined to a single area and are typically treated with topical or oral antibiotics. Systemic infections, however, often start as local infections but then spread into the bloodstream to infect the entire body. To prevent the spread of bloodborne pathogens, the safe disposal of needles is paramount. Nurses must engage the safety device immediately after using a needle. Furthermore, sharps containers must be replaced once they are approximately full to prevent overfilling and accidental needle sticks.
Hand Hygiene Standards and Compliance
Hand hygiene is a broad term encompassing any type of hand cleansing and is considered the most important step in preventing the spread of infection. It includes washing with soap and water for a duration of seconds, using alcohol-based hand sanitizers, utilizing antiseptic handwashes or rubs, and performing surgical hand antisepsis. While alcohol-based sanitizers are an acceptable method of hand hygiene, soap and water are necessary in certain contexts. Healthcare workers should hold their hands below their elbows while rinsing off soap during the washing process.
Despite its importance, compliance with hand hygiene among staff members is often recorded at less than . This lack of compliance contributes to the statistic that out of clients will obtain a Healthcare-Associated Infection (HAI) while at a facility. It is essential that clients are also taught about the importance of hand hygiene to participate in their own infection prevention.
Medical Asepsis and Equipment Cleaning
Medical asepsis, often referred to as clean technique, is defined as the elimination of and absence of disease-causing microorganisms. Maintaining medical asepsis involves specific equipment handling protocols. For instance, a blood-soiled blood pressure cuff should be placed in a waterproof container for transport; notably, disinfectant should not be applied directly to the cuff. All equipment must have visible material removed before undergoing disinfection. High-level disinfectant is specifically required for cleaning endoscopic equipment. When cleaning any equipment soiled with organic material, healthcare workers must utilize proper protective eyewear to prevent splashes.
Standard Precautions and Healthcare-Associated Infections (HAIs)
Standard precautions are the defined infection prevention practices applied to every client regardless of their diagnosed infectious status. These precautions are the baseline for all clinical interactions. Failure to follow these or more specific precautions can lead to Healthcare-Associated Infections (HAIs). There are four major types of HAIs. Central Line-associated Bloodstream Infections (CLABSIs) occur via PICC lines (peripherally inserted central catheters) or Midlines. Catheter-associated Urinary Tract Infections (CAUTIs) are linked to indwelling urinary catheters. Surgical Site Infections (SSIs) occur at any area of the body where surgery was performed. Ventilator-assisted Pneumonias (VAPs) are associated with mechanical machines that move air in and out of the lungs.
Personal Protective Equipment Responsibilities
It is the primary responsibility of the nurse to determine the correct type of Personal Protective Equipment (PPE) required for the specific care needs of their clients. This responsibility extends beyond selection to the technical mastery of donning (putting on) and doffing (taking off) PPE appropriately. Proper technique in these procedures is vital to ensure the safety of the healthcare provider and to prevent the transmission of pathogens between patients.