Infection control

• Infection


  The process where an infectious agent (microorganism) invades and multiplies in the body tissues of the host resulting in the person developing clinical signs and symptoms of infection
• Infection control


  The policy and procedures implemented to control and minimize the dissemination of infections in hospitals and other healthcare settings with the main purpose of reducing infection rates

  
• Colonization


  When microorganisms, including those that are pathogenic, are present at a body site, but cause no harm if they remain on the skin, if transfer to another site, e.g. a wound, or another person, it can cause an infection
• Common resident micro-organisms

  • Staphylococcus aureus (skin, nasal passages)
  • Escherichia coli (intestine)
  • Candida albicans (vagina)
• Contamination


  The presence of an infectious agent on a body surface, on or in clothes, beddings, toys, surgical instruments or dressings, or other articles or substances including water and food
• Source


  The thing, person, object or substance from which an infectious agent passes immediately to a host
• Reservoir


  The habitat in which the infectious agent normally lives, grows, and multiplies, including humans, animals, and the environment
• Human reservoirs

  • Sexually transmitted diseases
  • Measles
  • Mumps
  • Streptococcal infection
  • Respiratory pathogens (e.g. Influenza, Tuberculosis)
• Animal reservoirs

  • HIV/AIDS
  • Ebola infection
  • SARS
• Environmental reservoirs

  • Fungal agents (e.g. histoplasmosis)
  • Legionella pneumophila
• Infectious agents / pathogens / germs

  Microorganisms that are so small they can only be seen by using a microscope, including bacteria, viruses, fungi, protozoa parasites, and rickettsiae
• Significant and common causative organisms

  • Bacteria (Staphylococcus aureus, Escherichia coli, Vibrio cholerae)
  • Viruses (Norovirus, Hepatitis, HIV, Influenza, SARS, Coronavirus)
  • Fungi (Yeasts, moulds, Candida albicans)
  • Protozoa parasites (Entamoeba histolytica, Malaria)
  • Rickettsiae
• Modes of transmission

  • Direct transmission (direct contact, droplet spread)
  • Indirect transmission (airborne, vehicle-borne, vector-borne)
• Direct contact


  An infectious agent is transferred from a reservoir to a susceptible host by direct skin-to-skin contact, kissing, sexual intercourse, or touching infected materials
• Droplet spread / Droplet infection


  Relatively large (>5μm), short-range aerosols containing pathogens that are transmitted when an infected person coughs, sneezes or talks
• Airborne transmission


  Infectious agents are carried by dust or droplet nuclei (dried residue of less than 5 microns) suspended in air
• Vehicle-borne transmission


  Pathogens are transmitted through vehicles such as water, food, blood, and inanimate objects
• Vector-borne transmission


  Infections transmitted by the bite of infected arthropod species like mosquitoes, ticks, and fleas
• Herd immunity


  The level of resistance of a community or group of people to a particular disease, providing an immunological barrier to spread of disease
• If herd immunity is sufficiently high, the occurrence of epidemics is unlikely, but it has not prevented outbreaks of some diseases like measles and rubella even with high immunization levels
• Herd immunity does not protect against Tetanus
• Preventing air-borne diseases

  • Healthcare staff should wear N95 mask according to infection control guideline
  • Patient must be isolated in negative pressure room with door closed
  • Patient needs to wear surgical mask while being transported
• Herd immunity


  • The level of resistance of a community or group of people to a particular disease
  • Provides an immunological barrier to spread of disease in the human herd
  • If herd immunity sufficiently high, the occurrence of epidemic is unlikely
  • If high level of immunity is achieved and maintained, it may even lead to elimination of a disease e.g. Polio
  • In practice, herd immunity has not prevented outbreaks of measles and rubella in populations with immunization levels as high as 85% to 90%
  • Herd immunity does not protect against Tetanus
• Chain of infection

  The 6 main sources necessary for infection to develop: 1) Infectious agent, 2) Reservoir, 3) Portal of exit, 4) Mode of transmission, 5) Portal of entry, 6) Susceptible host

  
• Portal of entry


  The point at which the organisms enter a new host, often the same as the exit route from the prior reservoir (e.g. mucous membrane, GI tract, GU tract, respiratory tract, broken skin)
• Portal of exit


  The path by which a pathogen leaves its host through secretions, excretions, or droplets (e.g. influenza viruses and Mycobacterium tuberculosis exit the respiratory tract, some bloodborne agents can exit by crossing the placenta, others exit through cuts/needles in the skin or blood-sucking arthropods)
• Factors affecting the chain of infection

  • Organism factors (dose, virulence)
  • Transmission route (contact, aerosol, insect vector, etc.)
  • Host factors (immunity, integrity of non-specific immune defenses)

  
• Breaking the chain of infection

  1. Eliminate, inactivate or prevent survival of infectious agent in reservoir

  2. Manage portal of exit through good infection prevention and control practices

  3. Prevent transmission through good infection prevention and control practices

  4. Protect portal of entry

  5. Reduce susceptibility of patients receiving health care

  
• Standard precautions


  • Guidelines to prevent transmission of bloodborne pathogens from exposure to blood and other potentially infectious materials
• Hand hygiene


  Handwashing, antiseptic handwash, antiseptic hand rub or surgical hand antisepsis
• 5 steps for proper hand washing

  Wet hands with water, 2) Apply soap and rub for at least 20 seconds, 3) Rinse with water, 4) Dry with paper towel, 5) Use paper towel to turn off faucet
• Hand rubbing with 70-80% alcohol-based hand rubs (ABHR)


  Apply a palmful and cover all hand surfaces, rub for at least 20 seconds until hands are dry
• 5 moments for Hand Hygiene

  • Before touching a patient, 2) Before clean/aseptic procedures, 3) After body fluid exposure/risk, 4) After touching a patient, 5) After touching patient surroundings

  
• Other aspects related to hand hygiene

  • Keep nails short and avoid artificial nails, avoid wearing rings, use gloves for contacts with mucous membranes/secretions/non-intact skin, change gloves when contaminated, perform hand hygiene after removing gloves
• Mask, Goggles/Eye Visor, and/or Face Shield


  • Wear during procedures that may spray or splash blood/body fluids/secretions/excretions to ward off pathogens and prevent infection
• Gown


  • Wear to prevent soiling of clothing during activities likely to generate splashes or sprays of blood/body fluids/secretions/excretions
• Needles and Other Sharps


  • Do not break, bow, or directly manipulate used needles, recapping is not recommended but if necessary use one-handed scoop technique, discard all used sharps in puncture-resistant containers
• Barriers to Hand Hygiene Practices in clinical environment

  • Facilities: Inconveniently located sinks, shortage of sinks, lack of soap/paper towel
  • Others: Skin irritation and dryness, healthcare workers are too busy, understaffing/overcrowding
• Frequent handwashing related skin problems

  • Dermatitis occurs in ~25% of staff, feeling dryness/burning, skin feeling "rough", erythema, scaling or fissures
• Prevention of frequent handwashing related skin problems

  Careful selection of hand hygiene agents, use of hand lotions and emollient hand cream