• Clinical science

Infection prevention and control

Abstract

Antisepsis refers to measures of reducing pathogens to prevent infection. The most commonly used measures are disinfectants containing biocidal substances. Alcohols, phenols, and iodine are used for disinfecting the skin and/or mucous membranes. Surfaces are preferably disinfected with aldehyde, halogens, oxidants, and ammonium compounds. Hand disinfection is particularly important in a healthcare setting. A distinction can be made between hygienic hand and surgical hand disinfection.

Infection prevention

Infection prevention and control measures reduce the risk of pathogen transmission to patients, health care professionals, and other clients. Some of the measures include performing hand disinfection, use of gloves, gowns, mask, and eye protection as needed, and potentially isolation.

Hand disinfection

Basics

  • Hand disinfection vs. hand washing
    • Hand disinfection decreases transient skin flora more effectively and dehydrates the skin to a lesser extent compared to handwashing.
    • Washing with soap should be kept to a minimum.
    • Use of skin care products is recommended to prevent skin irritation (e.g., during breaks, after work).
  • Hygiene regulations
    • Fingernails should be cut short. Artificial nails should not be worn.
    • No jewelry on the hands and forearms
    • Special rub-in technique for hygienic hand disinfection
      • Apply a sufficient amount of disinfectant onto dry skin.
      • Attention should also be paid to the fingertips, thumbs, and the spaces between the fingers.
    • Wall-mounted dispensers are preferred to pocket-sized sanitizers.

Hygienic hand disinfection

  • Aim: decrease the number of pathogens in transient skin flora
  • Indication
    • Before and after contact with each patient
    • Before work, before and after breaks, as well as before (self-protection) and after going to the bathroom.
    • Before handling medication, syringes, and infusions
    • After removing contaminated gloves
  • Substances: alcohol and phenol mixtures
  • Procedure
    1. Disinfection → minimum contact time: 30–60 s
    2. If desired, the hands may be subsequently washed.

Surgical hand disinfection

  • Aim: Decrease the number of pathogens in transient and resident skin flora.
  • Indication: before every surgical procedure
  • Substances: alcohol and phenol mixtures
  • Procedure
    1. Scrubbing of hands and forearms
      • Disinfectants may have a decreased efficacy after contact with soap → thoroughly rinse off the remaining soap.
    2. Disinfection of hands and forearms → minimum contact time: 1.5–5 min (depending on disinfectant used)

Isolation precautions

In healthcare facilities, implementing isolation precautions prevents contact-, airborne-, or droplet-mediated pathogen transmission.

  • Contact precautions
    • Used for the care of patients with drug-resistant pathogens (e.g., MRSA, VRE), enteric infections (e.g., Clostridium difficile, Escherichia coli O157:H7), scabies, impetigo, and draining abscesses
    • Includes performing hand hygiene and wearing gloves and gowns when getting into the patient's room (even when direct contact with the patient or infected material is not expected).
    • Patients should be kept in isolation or in cohort
    • Medical equipment should be dedicated to a single patient. If not possible, disinfect before reuse.
  • Droplet precautions
    • Used for the care of patients with suspected or confirmed infection with pathogens that spread with droplets, such as Neisseria meningitidis, Bordetella pertussis, influenza, parainfluenza, adenovirus, Haemophilus influenzae type b, Mycoplasma pneumoniae, and rubella
    • Patients should be kept in isolation or in cohort.
    • Includes wearing masks within a distance of 3– 6 feet from the patient and masking patients during transport
    • Implement hand hygiene after contact with respiratory secretions.
  • Airborne precautions
    • Used for the care of patients with suspected or confirmed tuberculosis (TB), measles, varicella, smallpox, and severe acute respiratory syndrome (SARS) infections
    • Patients should be kept in a private room with negative air pressure; the door of the isolated room must remain closed.
    • Individuals must wear a respirator when entering the room.
    • Minimize transport of patients and mask them if it is mandatory.
    • Implement hand hygiene after contact with respiratory secretions.

Prevention of cathether-associated urinary tract infection

Measures

  • Avoiding unnecessary catheterization
  • Using sterile technique during catheter placement
  • Cleaning the catheter surrounding area with soap and water suffices for maintenance.
  • Prompt removal when the catheter is no longer needed
  • Using clean intermittent catheterization in patients with neurogenic bladder: In this technique, the catheter is immediately removed after bladder drainage and gets either discarded (single-use catheter) or cleaned (reusable catheter).

Use of antibiotic-coated catheters or prophylactic antibiotics should be avoided as it might lead to the development of drug-resistant pathogens.

Prevention of intravascular catheter-related infections (e.g., central venous line infection)

Measures

  • Implementing hand hygiene and strict aseptic technique during insertion
  • Using a cap, mask, long-sleeved sterile gown, sterile gloves, and a sterile full body drape
  • Preparing skin with chlorhexidine and alcohol before inserting the catheter
  • Systemic anticoagulation and antibiosis may be considered in oncology patients who require long-term central venous access.
  • Changing dressings regularly

Disinfectants and antiseptics

Common disinfectants and antiseptics

Disinfectants destroy or inhibit the growth of microorganisms on nonliving objects while antiseptics do so in or on living tissues without causing tissue damage.

Agent Mechanism of action Active against Sporicidal
Alcohols (e.g., isopropyl alcohol and ethyl alcohol)
  • Bacteria
  • Enveloped viruses
  • Fungi
  • No
Bisbiguanides (e.g., chlorhexidine)
  • At low concentrations: leakage of intracellular components due to cell membrane disruption
  • At high concentrations: cause precipitation of intracellular proteins and nucleic acids
Phenol (e.g., orthophenylphenol and ortho-benzyl-para-chlorophenol)
  • At low concentrations: inactivates essential enzymes and induces leakage of metabolites
  • At high concentrations: disrupts cell wall and precipitates cell proteins
Halogen-releasing agents Iodine and iodophors (e.g., povidone-iodine and poloxamer-iodine)
  • Bacteria
  • Viruses
  • Fungi
  • Yes (with prolonged contact time)
Chlorine-releasing agents (e.g., sodium hypochlorite and chlorine dioxide)
  • Yes (e.g., effective against highly resistant spores of Clostridium species)
Hydrogen peroxide
  • An oxidant that produces hydroxyl free radicals (OH), which damage essential cell components, including lipids, proteins, and DNA
  • Yes (only at higher concentrations and longer contact times)
Aldehydes (e.g., glutaraldehyde)
  • Microbicidal effect is mediated by alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups of RNA, DNA, and proteins.
  • Yes
Quaternary ammonium compounds (e.g., benzalkonium chloride)
  • Bacteria (not mycobacteria)
  • Enveloped viruses
  • Fungi
  • No

Skin and/or mucous membrane disinfection

  • Commonly used agents: alcohols (e.g., ethanol) , biguanides, phenols
  • Mechanism of action: protein denaturation
  • Advantage: rapid onset of action and well tolerated
  • Disadvantages:
    • Ineffective against bacterial spores and nonenveloped viruses
    • Decrease in antiseptic/disinfecting efficacy after contact with proteins (e.g., blood)
  • Alternative: iodine preparations

Surface disinfection

  • Commonly used agents: aldehyde, halogens, ammonium compounds, oxidants (e.g., hydrogen peroxide)
  • Mechanism of action: denaturation of various structures (proteins, nucleic acids, cell nuclei)
  • Advantage: high efficacy also against spores and non-enveloped viruses, minimal decrease in antiseptic/disinfecting efficacy after contact with proteins (e.g., blood)
  • Disadvantage: poorly tolerated
  • Alternative: quarternary ammonium compounds
    • Disadvantage: ineffective against gram-negative bacteria, mycobacteria, and mycoplasma; decreased efficacy after contact with proteins

Sterilization and pasteurization

Sterilization

  • Refers to a technique that completely destroys or removes all microbial life, including spores on a surface of an object or in a fluid.
  • Medical devices that come in contact with sterile body parts or fluids must be sterilized.
  • Heat-stable equipment is primarily sterilized by steam sterilization (autoclave).
  • Heat- and moisture-sensitive equipment (plastics, electrical devices, and corrosion-susceptible metal alloys) require a low-temperature sterilization technology such as ethylene oxide, hydrogen peroxide gas plasma, and peracetic acid.

Sterilization techniques for heat stable equipment

  • Steam sterilization (autoclave):
    • Exposing equipment to direct steam at a certain temperature and pressure for a specified period of time
    • Mechanism of action: irreversible coagulation and denaturation of enzymes and structural proteins
    • Active against; bacteria, fungi, viruses, and spores
    • Treated at > 121°C; : Typically uses 134°C for three minutes or 121°C for 15 min
    • Prions are not destroyed by standard autoclaving. They must be sterilized at 121°C–132°C for 60 min (not a standardized method).
  • Dry air sterilization:
    • Exposing equipment to dry heat, which gets absorbed by the external layer and transferred inward to the interior layer by a process called conduction
    • Denatures and oxidizes proteins and other cell components
    • Commonly uses 170°C (340°F) for 60 min, 160°C (320°F) for 120 min, and 150°C (300°F) for 150 min

Sterilization techniques for heat- and moisture-sensitive equipment

  • Ethylene oxide gas sterilization
    • Ethylene oxide: flammable and explosive gas
    • The sterilization process includes preconditioning and humidification, gas introduction, exposure, evacuation, and air washes.
    • Mechanism of action: alkylation of protein, DNA, and RNA
    • Microbicidal against all microorganisms, but spores are somewhat resistant
    • Disadvantages: lengthy cycle time, costly, and hazardous
  • Hydrogen peroxide gas plasma sterilization
    • Hydrogen peroxide diffusion and gas plasma generation → forms free radicals
    • Free radicals damage enzymes, nucleic acid, and disrupt cellular metabolism
    • Active against; bacteria (including mycobacteria), yeasts, fungi, viruses, and bacterial spores

Pasteurization

  • Aim: pathogen destruction through brief heating, especially of milk and other protein-containing products
  • Procedure: treated with mild heat (< 100°C)
  • Efficacy spectrum: destruction of a broad spectrum of bacteria but not heat-resistant spores