Chapter 25: Asepsis and Infection Control

Components of the Infection Cycle

The infection cycle describes the process by which infectious agents are transmitted and cause disease. Understanding each component is essential for effective infection control.

• Infectious agent: Microorganisms such as bacteria, viruses, fungi, and parasites that can cause disease.

• Reservoir: The natural habitat where the organism lives and multiplies (e.g., humans, animals, soil).

• Portal of exit: The route by which the organism leaves the reservoir (e.g., respiratory tract, blood).

• Means of transmission: How the organism is transferred (direct contact, indirect contact, airborne).

• Portal of entry: The route by which the organism enters a new host (e.g., breaks in skin, mucous membranes).

• Susceptible host: An individual who lacks effective resistance to the infectious agent.

Infectious Agents

Microorganisms vary in their ability to cause disease and their prevalence in healthcare settings.

• Bacteria: Most significant and prevalent infection-causing agents in hospitals.

• Viruses: Smallest microorganisms; cause diseases like the common cold; not responsive to antibiotics.

• Fungi: Plant-like organisms (molds, yeasts) found in air, soil, and water.

• Parasites: Organisms that live on or in a host and depend on it for nourishment.

Classification of Bacteria

Bacteria are classified by shape, Gram stain reaction, and oxygen requirements.

• Shape:

  • Spherical (cocci)

  • Rod-shaped (bacilli)

  • Corkscrew-shaped (spirochetes)

• Gram Staining:

  • Gram-positive: Retain crystal violet stain

  • Gram-negative: Do not retain crystal violet stain

• Oxygen Requirement:

  • Aerobic: Require oxygen

  • Anaerobic: Can live without oxygen

Factors Affecting Disease Production

The likelihood of disease depends on several factors:

• Number of organisms

• Virulence (ability to cause disease)

• Competence of host's immune system

• Length and intimacy of contact

Identification of Infectious Agents

• Endemic: Disease occurs predictably in a specific region or population.

• Pandemic: Global outbreak of a new or previously unidentified virus.

Possible Reservoirs for Microorganisms

• Other people

• Animals

• Soil

• Food, water, milk

• Inanimate objects

Portals of Exit

• Respiratory tract

• Gastrointestinal tract

• Genitourinary tract

• Breaks in skin

• Blood and tissue

Means of Transmission

• Direct contact

• Indirect contact

• Vector (e.g., insects)

• Fomite (contaminated objects)

• Droplet

• Airborne

Stages of Infection

Infections progress through distinct stages:

• Incubation period: Organisms grow and multiply; no symptoms.

• Prodromal stage: Most infectious; vague, nonspecific symptoms.

• Full stage of illness: Specific signs and symptoms appear.

• Convalescent period: Recovery phase.

Inflammatory Response

The inflammatory response is the body's reaction to infection or injury, aiming to neutralize and eliminate the offending agent.

• Vascular phase: Vasodilation increases blood flow (redness, heat); histamine increases vessel permeability (swelling, pain, loss of function).

• Cellular stage: Leukocytes (especially neutrophils) consume debris; damaged cells are repaired.

Immune Response

The immune response protects the body from harmful agents.

• Humoral immunity: Production of antibodies in response to antigens.

• Cell-mediated immunity: Increase in lymphocytes that destroy or react with harmful cells.

Factors Affecting Risk for Infection

• Intact skin and mucous membranes

• Normal pH levels

• Body's white blood cells

• Age, sex, hereditary factors

• Immunization (natural or acquired)

• Fatigue, climate, nutritional and general health status

• Stress

• Use of invasive or indwelling medical devices

Laboratory Data Indicating Infection

• Elevated white blood cell count (normal: 5,000–10,000/mm3)

• Increase in specific types of white blood cells

• Elevated erythrocyte sedimentation rate

• Presence of pathogen in urine, blood, sputum, or draining cultures

Outcome Identification and Planning/Infection Control

• Effective hand hygiene and personal hygiene

• Identification of infection signs

• Adequate nutritional intake

• Proper disposal of soiled articles

• Appropriate cleansing and disinfecting techniques

• Awareness of proper immunizations

• Stress-reduction techniques

Asepsis

Asepsis includes all activities to prevent infection or break the chain of infection.

• Medical asepsis: Clean technique to reduce pathogens (e.g., hand hygiene, gloves).

• Surgical asepsis: Sterile technique to keep area free from microorganisms (e.g., inserting catheters).

Five Moments for Hand Hygiene (WHO)

• Before touching a patient

• Before a clean or aseptic procedure

• After a body fluid exposure risk

• After touching a patient

• After touching patient surroundings

Bacterial Flora

• Transient flora: Loosely attached to skin; easily removed.

• Resident flora: Found in skin creases; requires friction to remove.

Health Care-Associated Infections (HAIs)

HAIs are infections acquired in healthcare settings. Seven targeted types include:

• Catheter-associated urinary tract infection (CAUTI)

• Surgical site infection (SSI)

• Central-line–associated bloodstream infection (CLABSI)

• Hospital-onset methicillin-resistant Staphylococcus aureus (MRSA) infections

• Clostridioides difficile (C. diff) infections (CDIs)

Multidrug-Resistant Organisms

• Methicillin-Resistant Staphylococcus aureus (MRSA)

• Vancomycin Intermediate-Resistant Staphylococcus aureus (VISA), Vancomycin-Resistant Staphylococcus aureus (VRSA), Vancomycin-Resistant Enterococci (VRE)

• Carbapenem-Resistant Enterobacteriaceae (CRE)

• Acinetobacter baumannii (CRAB)

• Clostridioides difficile (CDI)

Sterilization and Disinfection Methods

The choice of sterilization and disinfection depends on:

• Nature and number of organisms present

• Type and intended use of equipment

• Available means for sterilization/disinfection

• Time required

Personal Protective Equipment (PPE)

• Gloves

• Gowns

• Masks

• Protective eyewear

Standard Precautions

Standard precautions are used for all patients, regardless of infection status, and apply to blood, body fluids, secretions, excretions (except sweat), nonintact skin, and mucous membranes.

• Includes respiratory hygiene/cough etiquette, safe injection practices, and mask use for high-risk procedures.

Transmission-Based Precautions

Used in addition to standard precautions for patients with suspected infections transmitted by airborne, droplet, or contact routes.

• PPE must be donned when entering the room and removed when leaving.

• Three types: airborne, droplet, contact (may be used alone or in combination).

Patient Teaching for Medical Asepsis at Home

• Wash hands before preparing/eating food

• Cook foods at high enough temperatures

• Wash hands, cutting boards, utensils before/after handling raw meat

• Keep food refrigerated

• Wash raw fruits and vegetables

• Use pasteurized milk and juices

• Wash hands after bathroom use

• Use individual care items

Evaluating Patient Goals

• Correct use of medical asepsis techniques

• Identification of health habits promoting health

• Recognition of infection signs and symptoms

• Identification of unsafe situations in the home

Key Questions and Answers

Additional info:

• Alcohol-based handrubs should contain 60–95% alcohol for effectiveness.

• White blood cell count formula:

• Gram stain procedure is a fundamental microbiological technique for bacterial classification.