Understanding the Infection Process and Agents (LPN)

The Infection Process

• A pathogen is an organism that causes disease in a host (an infected person).
• Colonization occurs when pathogenic microbes are present without causing symptoms or an immune response.
• Infection occurs when a microbe multiplies within a host.
• Subclinical infection involves an immune response (increased antibody level) without symptoms.
• To prevent infection, the chain of infection must be broken.
• If infection occurs, focus treatment on breaking the chain to prevent its spread.

Infectious Agents

• Microorganisms causing infection: bacteria, viruses, fungi, protozoa, helminths, and prions.
• Normal flora are harmless organisms naturally on a body part.
• Intestinal flora (bacteria) aids in vitamin K production which is needed for blood clotting.
• Pathogens are organisms that cause disease when normal flora get into other areas of the body, such as the blood.
• Pathogen: pathos (suffering) + genes (producer of).

Bacteria

• Bacteria are single-celled organisms that can live and reproduce outside a host.
• Cell walls are susceptible to antibiotics.
• Bacteria can mutate to survive.
• Bacteria are named by shape: spherical (coccus), rod (bacillus), and spiral (spirillum).
• Gram-positive bacteria stain purple, while Gram-negative bacteria lose purple stain and stain pink with a second dye.
• Acid-fast bacteria keep purple stain when acid is applied.

Viruses

• Viruses are smaller than bacteria.
• To live and reproduce, they depend on host cells.
• Viruses can immediately trigger disease or remain dormant for years, like varicella-zoster virus.
• Antiviral drugs can decrease viral load and symptoms.
• Antibiotics are not effective against viruses.

Fungi

• Fungi include yeasts and molds and can produce resistant spores.
• Normal flora includes many fungi in the mouth, skin, vagina, and intestinal tract.
• Most fungi are not pathogenic, and serious infections are rare.
• Antifungal medications are available if required.

Protozoa

• Protozoa are single-celled parasitic organisms with flexible membranes that live in the soil.
• Humans can be infected by protozoa through fecal-oral contamination, ingestion of contaminated food or water, host-to-host contact, or insect bites.

Helminths

• Helminths are wormlike parasitic animals such as roundworms, flatworms, tapeworms, pinworms, hookworms, and flukes.
• Disease transmission occurs through skin penetration of larvae or ingestion of helminth eggs.
• Trichinosis, caused by Trichinella spiralis, is transmitted by eating raw or undercooked meat with Trichinella larvae.

Prions

• Prions are transmissible pathogenic agents that cause abnormal folding of prion proteins, mainly in the brain.
• They cause damage with no inflammatory response, progress rapidly, and are fatal.
• Creutzfeldt-Jakob disease in humans is an example of a prion disease.

Reservoir and Portal of Exit

• A reservoir is where infectious agents live, multiply, and reproduce, animate (people, insects, animals, plants) or inanimate (water, soil, medical devices).
• The portal of exit is the path by which the infectious agent leaves its reservoir.

Mode of Transmission

• A direct or indirect transfer to a susceptible host is needed once the causative agent exits the reservoir.
• Direct transmission occurs through direct contact (touching, kissing, sexual intercourse) or droplet spread (sneezing, coughing, talking).
• Indirect transmission includes vehicle-borne (biological products, soiled items, food, instruments) and vectorborne (fleas, mice, mosquitoes, rats, ticks).
• Airborne transmission involves infectious agents carried by dust or droplet nuclei, suspended in the air for longer distances and can be inhaled.
• Mycobacterium tuberculosis (TB), rubeola virus (measles), varicella-zoster virus (chickenpox), and SARS-CoV-2 (COVID-19) are examples of airborne transmission.

Portal of Entry

• To produce disease, organisms enter a susceptible host through blood, genitourinary tract, GI tract, mucous membranes, skin, or respiratory tract.
• Disease is determined by the host's condition, the organism's virulence, and other factors.

Susceptible Host

• Body defense mechanisms prevent infection.
• Factors increasing susceptibility are burns, chronic disease, immunocompromised status, invasive procedures, malnourishment, stress, and age.

Gerontological Issues

• Fever may not be a common sign of an infection for an older adult.
• Watch for atypical signs of infection like behavioral changes, or symptoms masked by chronic conditions.

Human Body's Defense Mechanisms

• Intact skin and mucous membranes are the body's first line of defense against infection.
• Skin dryness and cracking can be prevented with lotion to keep it intact.
• Oral mucous membranes have many layers to protect against organisms.
• The skin is acidic.
• The normal flora impairs growth of pathogens on the skin and in the GI tract.
• Cilia are hairlike structures that trap and remove mucus, pus, dust, and foreign particles.
• Gastric acid (pH 1 to 5) destroys most organisms in the stomach.

Antibodies and Leukocytes

• Antibodies, or immunoglobulins, are proteins produced by plasma cells to identify and destroy foreign antigens.
• Leukocytes (WBCs) protect against infection and tissue damage.
  • Neutrophils ingest and destroy bacteria and fungi.
  • Lymphocytes recognize antigens and produce antibodies.
  • Monocytes become macrophages, ingesting and destroying tissue debris.
  • Eosinophils destroy parasites and respond to allergic reactions.
  • Basophils are involved in inflammatory and allergic reactions.
• Phagocytosis means ingesting foreign antigens.
• Lysozymes are bactericidal enzymes in WBCs and body fluids that dissolve bacterial walls.
• Interferon helps destroy infected cells, inhibit the virus within these cells, and may inhibit tumor cell growth.

Inflammatory Response and Immune system

• The inflammatory response occurs with any injury to the body.
• Local vasodilation increases blood flow to the injured area, causing redness and heat.
• Increased blood vessel permeability lets plasma move out of capillaries, causing swelling and pain.
• The final step is the destruction of pathogenic organisms by leukocytes through phagocytosis, forming pus.
• The immune system is the body's final defense and a breakdown can result in infection.
• Phagocytosis: phagein (to eat) + cytos (cell) + osis (condition).

Risk Factors for Infection

• Risk factors for infection: Aging, chronic disease, dysphagia, the environment (hospitals, long-term care facilities), immobility, immunocompromised, incontinence, instrumentation, invasive procedures, malnutrition, medications.
• Older adults are at greater risk for respiratory infections, health-care-associated infections, sepsis, skin infection, and UTIs.

Infectious Disease: Localized Infection and Sepsis

• Localized infection involves increased microbes and the inflammatory response.
• Symptoms include pain, redness, swelling, and warmth at the site, and fever >= 100.4°F (38°C).
• Sepsis is “life-threatening organ dysfunction caused by dysregulated host response to infection”.

Laboratory Assessment

• A Gram stain uses gentian violet to identify bacteria: Gram-positive stain purple, Gram-negative stain pink.
• A culture and sensitivity (C&S) detects illness-causing organisms and determines the most effective antibiotic for treatment.
• A serum antibody test measures reaction to antigen; it doesn't always mean that an active infection is present.
• A complete blood cell count with differential (CBC with diff) measures levels of leukocytes.
• Erythrocyte sedimentation rate (ESR) screens for inflammation by measuring how quickly red blood cells settle in a tube.
• Other tests include x-rays, CT scans and MRI, and skin tests like the PPD test for TB.

Pandemic and Immunity

• An epidemic involves a rapid rise in cases.
• A pandemic is an infection affecting large numbers of people and spreads across continents/the world. New infectious diseases can result in a global pandemic because no one is immune and there is no cure.
• Immunity is the body's ability to protect itself.
• Natural immunity occurs in species and prevents illnesses found in other species.
• Innate immunity is genetic/hereditary.
• Acquired immunity comes actively or passively through exposure, vaccination, or immunoglobulins.
• Herd immunity is when a significant community portion becomes immune to a disease through infection or vaccination, offering disease protection to others who are not vaccinated.

Types of Infectious Diseases

• COVID-19 was identified in 2019, creating a pandemic from a new virus with no prior exposure or immunity: CO = corona, VI = virus, D = disease, 19 = 2019.
• Ebola virus was discovered near the Ebola River in 1976; survivors develop lasting antibodies for about 10 years.

COVID-19 Transmission

• Direct contact via respiratory droplets (coughing, sneezing, talking).
• Airborne is possible in poorly ventilated, enclosed spaces.
• Indirect contact involves contaminated surfaces and mucous membranes.

COVID-19 Symptoms

• Symptoms may appear 2-4 days after exposure: fever, cough, diarrhea, fatigue, headache, loss of taste or smell, muscle aches, nausea, vomiting, shortness of breath.

Ebola Virus Disease Transmission

• Transmission includes direct contact with infected blood/body fluids and infected fruit bats or primates.

Zika Virus Disease

• Zika virus is a member of the Flaviviridae family.
• Transmission occurs through an Aedes mosquito bite or maternal-fetal, and symptoms include conjunctivitis, fever, headache, muscle/joint pain, rash.
• There is no cure.

Infection Control in the Community

• Organizations collaborate to control communicable diseases.
• Global monitoring and surveillance support early virus identification with pandemic potential.
• The WHO and CDC teach standards to prevent, monitor, and control disease outbreaks.
• Local health departments teach prevention and help control outbreaks.
• Immunization programs help to reduce diseases.

Infection Control in Health-Care Agencies

• A community-acquired infection is one a patient already has upon admission.
• A healthcare-associated infection (HAI) results from care provided in a healthcare agency.
• Patients often debilitated, malnourished, or immunocompromised are at risk.
• Burn, critical care, dialysis, neonatal, and oncology units have increased HAIs.
• Healthy People 2030: (1) reduce C. diff infections (2) reduce MRSA bloodstream HAIs.
• E. coli is the most common pathogen causing health-care-associated UTIs.
• Staph. aureus (staph) is the most common pathogen causing surgical wound infections.
• Pseudomas. Aeruginosa is the most common pathogen in health-care-associated pneumonia.

Hand Hygiene and Asepsis

• Proper hand hygiene controls and prevents infection.
• Clean hands before & after every patient contact to prevent organism transmission.
• Follow CDC guidelines by hand washing before and after glove use.
• Proper hand washing: wet hands (warm water), soap and lather (20 sec), interlace fingers, rub nails, rinse pointing down, dry (clean paper towels/air dry), turn off faucet.
• The Clean Hands Count campaign improves HCP adherence and patient empowerment to ask HCPs to use hand hygiene.
• Asepsis is freedom from organisms accomplished by using aseptic techniques to protect patients.
• Medical asepsis, referred to as clean technique, reduces the number or prevents pathogen transmissions by using frequent hand hygiene, PPE, special ventilation, disinfectants, and precautions.

Surgical Asepsis

• Surgical asepsis, referred to as sterile technique, is an area or item that is free of all microorganisms and spores.

Infection Prevention and Control Guidelines

• CDC guidelines for infection control and isolation precautions are used in policies at healthcare facilities.
• Follow CDC and agency guidelines for patient and your protection.
• Two tiers of precautions: standard precautions and transmission-based precautions.

Standard Precautions

• Follow standard precautions for all patient care which assumes precautions require you to assume that all patients are infectious regardless of their diagnosis.
• PPE is required for all patients with draining wounds or secretions.

Transmission-Based Precautions

• Use private room for infectious patients.

Airborne Precautions

• Examples: Mycobacterium tuberculosis (TB), rubeola virus (measles), varicella-zoster virus (chickenpox), and SARS-CoV-2 (COVID-19) for aerosol generating procedures.
• Provide private room with regulated airflow.
• Keep the door closed.
• Wear a fit-tested (N95) disposable respirator or PAPR.
• Have the patient with TB also wear a surgical mask during times that care is performed.

Droplet Precautions

• Droplet examples: Adenovirus, coronavirus (COVID-19), diphtheria (pharyngeal), Haemophilus influenzae, influenza, mumps, mycoplasma pneumonia, Neisseria meningitidis, pertussis, pneumonic plague, rubella, and group A streptococcus.
• Respiratory Protection

Contact Precautions

• Contact examples: Cellulitis, Clostridioides difficile, coronavirus (COVID-19), skin infections, conjunctivitis, viral hemorrhagic infections, and herpes zoster.
• Use a private room or place patient with same infection and no other infection.
• Use gloves, gown, and foot covers.

Preventing Respiratory and Genitourinary Tract Infections

• Healthcare-associated pneumonia has the highest infection mortality rate.
• Strategies to prevent infections such as ventilator-associated pneumonia (VAP) are “bundled."
• CAUTI is the most common HAI,
• Appropriate reasons for urinary catheter use may include urinary obstruction, a neurogenic bladder condition, shock, and palliative care.
• Indwelling urinary catheters should be removed as soon as possible.
• Use strict aseptic technique and anchor catheter securely.

Prevention of Surgical Wound Infections

• The initial dressing for surgical wounds is applied in the operating room using sterile aseptic technique when monitoring wound for signs of infection.

Antibiotic-Resistant Infections

• Antibiotic-resistant infections are a worldwide health concern and can result in death.
• Remember bacteria is what antibiotics kill.
• The CDC's Antibiotic Resistance Solutions Initiative aims to detect, respond to, contain, and prevent resistant infections.

Methicillin-Resistant and Vancomycin-Resistant Infections

• MRSA resulted from long-term use of unnecessary antibiotics.
• MRSA include painful warm red bumps, fever, drainage.
• Treatment includes draining skin boils or administering antibiotics such as vancomycin hydrochloride.
• Contact precautions should be used.
• VRE is a pathogenic strain transmitted via direct or indirect contact.
• Preventive VRE measures focus on proper hand hygiene, education of HCPs, aggressive infection control, and restricting vancomycin use.

Medications Used to Treat Infections

• Penicillins are antibacterial agents that inhibit cell wall synthesis for gram-positive organisms.
• Carbapenems are antibacterial agents that inhibit cell wall synthesis for moderate to severe infection.
• Cephalosporins are antibacterial agents that inhibit cell wall synthesis. Caution should be used if there is a penicillin allergy or renal or hepatic dysfunction.
• Aminoglycosides are gram-negative antibacterial agents that inhibit protein synthesis. Report signs of allergy, tinnitus, vertigo, or hearing loss.
• Fluoroquinolones are antibacterial agents that inhibit bacterial DNA replication .
• Nitroimidazoles inhibit nucleic acid synthesis in anaerobic bacteria and protozoa. Instruct patient to avoid alcohol at least 48 hours after treatment.
• Glycopeptides inhibit the synthesis of cell walls in gram-positive cocci.
• Tetracylcines: protein synthesis inhibitor for most organisms. Caution: do not take during pregnancy.
• Macrolides: protein synthesis inhibitor for most organisms.
• Lincomycins inhibit protein synthesis within bacterial cells for serious infections.
• Sulfonamides inhibit growth and multiplication for most organisms mainly in UTIs, pneumocystis jiroveci pneumonia, and otitis media.
• Oxazolidinones are synthetic protein synthesis inhibitors for complicated infections caused by gram-negative microorganisms.
• Amphotericin B interferes with the fungal cell wall structure for life-threatening infections.
• Triazoles Inhibit cell membrane ergosterol synthesis for yeast or fungus infections.

Treatment of Antibiotics

• Antibiotics treat only bacterial infections, not viruses, fungi, helminths, or prions.
• Antiviral medications treat viral infections, not cure them.
• Antifungal drugs treat fungal infections but may require extended use.
• Bactericidal agents kill bacteria and Bacteriostatic agents inhibits bacterial growth.
• Antibiotic levels fluctuate depending on organ function, age, sex, & health.
• Serum peak and or trough levels are monitored to ensure nontoxic therapeutic levels.

Antibiotic-Associated Diarrhea (AAD)

• Antibiotics can upset the balance of the natural microbiota in the intestine, causing AAD.
• C. difficile: can cause fever, diarrhea, abdominal pain and is transmitted by the fecal-oral route from surfaces; Lidless toilets can increase C. difficile by spraying contaminated surfaces. Vaccines are still in trials to prevent CDI.

Fecal Microbiota Transplantation

• If CDI reoccurs, fecal microbiota transplantation can cure it by transplanting donated feces to restore the intestine bacteria; for patients with gravely recurrent CDI it transplants donated feces to make them infection-free.

Risk for Infection Intervention and Implementation

• Report signs of infection such as redness, warmth, and fever promptly--especially for neutropenic patient who may only have a low-grade fever alone.
• Monitor lab cultures and WBC counts.
• Use standard & transmission-based precautions.

Respiratory Tract Intervention and Implementation

• If not contraindicated, encourage fluids to thin secretions.
• Encourage coughing and deep breathing.
• Provide pain relief.
• Use sterile water when providing oral care to prevent pnuemonia.
• Maintain bed at 30 degree elevation.

AOD Signs and Symptoms

• Report anorexia, anorexia, cramping, diarrhea, fluid loss, nausea, and vomiting.
• Encourage fluid intake to replace fluid lost.
• Teach water/soap only hand-hygeine.

Interventions for Genitourinary Infection

• Do not request a urinary catheter unless there is a justifiable reason.
• For catheters: use sterile technique.