• Clinical science

Infection prevention and control


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, masks, and eye protection as needed, and potentially isolation.

Hand disinfection


  • 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.

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

  • 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)

  • 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 antibiotics may be considered in oncology patients who require long-term central venous access.
  • Changing dressings regularly


Pre-surgical infection prevention measures

  • Aim: reduce the risk of an intraoperative surgical site infection through contamination with bacteria from the skin
  • Who: all sterile staff members of a surgical team in the operating room (OR)


  • Appropriate surgical attire [5]
    • The fingernails should be short. No artificial nails and/or nail polish should be worn.
    • All jewelry should be taken off.
    • The surgical staff member should wear:
      • Surgical scrubs
      • Surgical footwear (e.g., closed rubber clogs or shoe covers)
      • Surgical cap
      • Surgical mask
      • Protective eyewear
  • Material: Gowns and gloves have to be prepared before scrubbing.
    1. Gowns: Place the gown package on a clean surface. Pull on the outer edges of the wrapping to expose the gown without touching the sterile content that is inside.
    2. Gloves: Open the plastic packaging and let the inner sterile glove packet drop onto the gown.

Pre-scrub wash

  • Indication: only required before the first case of the day or when the hands are visibly soiled
  • Instructions
    1. Adjust the water temperature to a comfortable, lukewarm level.
    2. Open the scrub sponge package and set it on the side. The sponge is not used during the pre-scrub wash.
    3. Wet the hands and arms and apply antimicrobial soap.
    4. Start by washing the hands, followed by the arms, and lastly the elbows.
    5. Use the nail pick from the scrub sponge package to clean the subungual spaces under running water.
    6. Thoroughly rinse off the soap from the hands and arms.

Surgical hand disinfection

Scrubbing in (surgical scrub)

  • Indication: before each operation, before gowning and gloving
  • Methods: Every institution has its own protocol for scrubbing in. The two most common are the brush stroke method and the timed method.
    • Brush-stroke method: A specific number of brush strokes is applied to each surface of the fingers, hands, and forearms. (See instructions below.)
    • Timed method: The scrub is performed for a specific amount of time (typically 3–5 minutes).
  • Substances
    • The most common scrub solutions contain one of the following agents:
    • Mechanism of antimicrobial action
      • Elimination of transient bacterial flora, reduction of resident bacterial flora
      • Inhibition of bacterial growth under the glove
  • General rules
    • Always hold the hands at a higher level than the elbows.
    • Start with the fingertips and work towards the elbows.
    • Every area is only scrubbed once. Do not return to a previously scrubbed area.
    • To ensure thorough cleaning, the fingers, hands, and arms should be seen as having four sides , each of which has to be brushed individually.
    • Completely finish one side (left/right) before moving to the other hand and arm.
    • The abrasive side of the scrub sponge (nail brush) is only used to clean the fingernails. [6]
    • Neither the hands nor forearms should come in contact with any non-sterile object or surface (e.g., the scrubs, the tap). Otherwise, the entire scrubbing procedure needs to be repeated.
    • After scrubbing, the hands should stay at a level between the waist and the neck at all times.
  • Instructions for the brush-stroke method [7]
    1. Remove the scrub sponge from the wrapper and moisten it under running water until you work up a sufficient lather.
    2. Put the fingertips of one hand together and brush the fingernails with the abrasive side of the scrub sponge for 30 strokes.
    3. Use the nonabrasive side of the scrub sponge to apply 10 strokes to all four sides of each finger, starting with the thumb. Do not forget the interdigital folds!
    4. Apply 30 strokes to the palm and 30 strokes to the back of the hand.
    5. Move on to the forearm. Mentally divide the arm into three equal increments, the most proximal of which ends two inches above the elbow. Scrub all four sides of each increment with 10 strokes, moving from distal to proximal.
    6. Switch sides and repeat steps 2–6.
    7. Discard the scrub sponge into the bin.
    8. Rinse off the foam.
      • Start at the fingertips and move forward under the water in a single fluid motion.
      • Do not move back and forth under the water.
      • Completely rinse off one side before moving to the other.
    9. Wait and let the water drip from the elbows. Do not shake the arms.
    10. Dry off the hands with the sterile towel from the already opened gown package. (See “Preparation” above.)
      • Take the towel without touching anything else.
      • Dry off one side completely (hand before arm), then continue with the opposite side.
      • Dab with the towel, rather than rub.

Alcohol-based disinfection (hand rub)

  • Indication: This method is an alternative to scrubbing with a sponge.
  • Substances: disinfectants containing alcohol and phenol mixtures
  • Instructions
    1. Wash hands and forearms with non-antimicrobial soap. Thoroughly rinse off all foam.
    2. Completely dry off the hands and forearms with disposable paper towels.
    3. Use the elbow to dispense the disinfectant into the opposite hand.
    4. Set a timer and use the hands to thoroughly rub disinfectant on the hands and forearms for ≥ 3 minutes.
    5. During the set time, reapply disinfectant if necessary. All areas should have constant contact with the disinfectant.

Do not touch non-sterile objects and/or surfaces during the disinfection process. Otherwise, the entire routine needs to be repeated.

The hands should always be held at a higher level than the elbows.


  • Indication: A sterile gown has to be donned for all surgical procedures. Often, surgeons are being gowned by an assistant that is already wearing sterile attire. However, every sterile member of the surgical team should be able to perform self-gowning.
  • Instructions: The gown needs to be prepared before scrubbing (see “Preparation” above).
    1. Pick up the folded gown, only touching the inner side.
    2. Identify the sleeve openings and slide the hands into it on both sides.
    3. Take a step back to ensure that the gown can not touch any non-sterile objects while unfolding.
    4. Let the gown unfold while simultaneously sliding the arms into the sleeves. At no point should the hands exit the sleeve cuffs. Keep the hands above waist level.
    5. An assistant will fasten the gown and secure it with a velcro tab at the neck and upper back.
    6. Proceed with gloving (see closed gloving method below).
    7. Pull only the left (shorter) tie out of the gown pass card.
    8. Pass the card to an assistant without letting the remaining tie slip from the card.
    9. Make a 360° turn so that the tie that is held by the assistant wraps around your waist.
    10. Pull the tie out of the card and secure both ties with a bow at your waist.

The gown is not considered sterile on the back, below the waist, or above the neck because these areas are more likely to come in contact with unsterile objects.


Closed glove method

  • Indication: preferred method when preparing for a surgical procedure
  • Instructions: Before starting closed gloving, a sterile gown must be donned.
    1. Open the sterile wrapper containing the gloves while the hands remain in the gown sleeves.
    2. Pick up the right glove by grabbing the folded cuff edge with the left sleeve-covered hand.
    3. Make sure the palm of the right hand faces the ceiling in the gown sleeve.
    4. Place the right glove on the right hand with the fingers of the glove pointing towards the shoulder. The palm of the glove should face the palm of the hand.
    5. Grab the palm-facing side of the folded cuff of the glove with the right sleeve-covered hand and hold onto it.
    6. Pull the ceiling-facing side of the folded cuff with the left sleeve-covered hand.
    7. Pull the glove up with the left hand and over the right hand.
    8. Pull the gown and glove up the arm to position your fingers inside the glove.
    9. Remove excessive gown sleeve from underneath the glove by pulling only on the gown. Make sure that the gown cuff stays fully covered by the glove cuff.
    10. Using the gloved hand, repeat the procedure for the other glove.

The gown cuff has to be fully covered by the glove cuff.

Open glove method

  • Indication: predominantly used for smaller procedures that only require the hands to be sterile, e.g.:
  • Instructions
    1. Ask an assistant to help you in retrieving the sterile wrapper containing the gloves from the plastic packaging.
    2. Place the sterile wrapper on a clean surface.
    3. Unfold the wrapper by grabbing the outer edges without touching the inner surface. The gloves should now be exposed.
    4. Take the folded edge of the right glove with the left hand and hold onto it. Insert the right hand into the glove and pull the cuff over the hand.
    5. Slide the fingers of the gloved hand underneath the rolled cuff of the left glove.
    6. Lift the glove so that the opening is facing upwards.
    7. Widen the opening with the fingers of the gloved hand that are underneath the cuff.
    8. Insert the fingers of the left hand and pull the cuff over the hand.

Needlestick infection prevention measures

Needlestick or sharps injuries [8]

  • Definition: injuries caused by accidental penetration of the skin by any sharp object (e.g., scalpel, wires, pins, needles, glass shards), which pose a risk of infection with bloodborne diseases such as hepatitis B, hepatitis C, or HIV
  • Epidemiology: ∼ 384,000 needlestick injuries (NSI) and other sharps-related injuries per year in the US


Prevention of needlestick or sharps injuries

  • Use of personal protective equipment (e.g., gloves, eye and face protection, gowns)
  • Disposal of used needles in appropriate sharps disposal containers; no recapping
  • Use of medical devices with inbuilt safety features (e.g., blunt-tip suture needles, safety syringes)
  • Hepatitis B vaccination for health care workers

The approximate risk of disease transmission from a needle stick injury if the source is known can be easily remembered using the rule of threes: up to 30% risk for hepatitis B, up to 3% risk for hepatitis C, and up to 0.3% risk for HIV.

In the United States, the Clinicians’ Post Exposure Prophylaxis (PEP) Line can be contacted at 1-888-448-4911 (http://www.nccc.ucsf.edu/) for information on the management of needlestick and sharps injuries.

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)
  • 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)
  • Yes
Quaternary ammonium compounds (e.g., benzalkonium chloride)
  • No

Skin and/or mucous membrane disinfection

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


  • 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


  • 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