Cross InfectionInfection Control

11/17/08

Cross Infection

Introduction of a pathogen from oneperson to another in a clinical environment Patient to staff

Patient to patient

Human to human

Animal sources

Inanimate sources

Cross Infection

Source Person with the infection Index case

Vehicle or mode Physical carrier of pathogen Bodily fluids, fomites

Route Portal of entry Inhalation, ingestion, inoculation

Source

Patients with overt symptoms Easy to spot

Patients in the prodromal stage Contagious but hard to define

Healthy carriers Asymptomatic Convalescent

When and where

Secretion/deposition Distribution of fluids/tissue during

procedures in operatory Generation of contaminated droplets by high-

speed instruments

Contamination of equipment/fomites Probes, scalpels, needles, gauze, etc.

How

Inhalation CMV, measles, mumps, rubella, influenza, cold

viruses, Strep. pyogenes, Mycobacterium

Inoculation HIV, HBV, HCV, Neisseria

Ingestion Oral/faecal bacteria, HAV

Infection control

Aims at controlling exposure to vehiclesand restricting routes of transmission

Standard precautions All bodily fluids (except sweat), non-

intact skin and mucous membranes aretreated as infectious

Routes of transmission of vehicles arecontained (asepsis)

Getting things clean

Sterilization A process that kills or removes all

organisms Disinfection

A process that kills or removes allpathogens EXCEPT BACTERIAL SPORES

Antisepsis Application of chemicals to live tissue to

kill or inhibit pathogens

Sterilization Moist heat

Autoclave Dry heat

Oven Chemicals

Ethylene oxide, bleach, etc. Radiation

UV, gamma rays

Sterilization Limiting factor is often penetration

Limit the size/load Get the crap off first

Presterilization cleaning Scrubbing, ultrasonics

Packaging Material must be packaged such that it does

not become contaminated before reachingpatient Bags, trays, etc.

Your friend the autoclave High pressure steam allows you to heat material to

over 100C Typical operating conditions are 121C for 15

minutes FOLLOW THE MANUAL

Excellent penetration Kills viruses, bacteria and their spores Prions?

Dry heat sterilization

Hot air oven 160 C for 2 hours Great for metal hardware Bad for many plastics

Most plastics are disposable

Chemical sterilization

Ethylene oxide Works at lower temperatures Good for plastics, fabrics,

electronics 50% of commercial materials are EO

sterilized

Flammable, toxic

Radiation sterilization UV light

Low penetration Surgical suites

Gamma radiation (X-ray) Excellent penetration

Very specialized equipment

Is it working? Monitoring is crucial for successful infection

control Biological indicators (BIs)

Spores of indicator bacteria (ex. Bacillussubtilis) Test strip is treated and set for analysis of

viability (efficacy of procedure) Chemical indicators (CIs)

Test strips for autoclaves/oven Colour change indicates effective treatment

Disinfection

Bleach Sodium hypochlorite

Hydrogen peroxide Ozone

Antiseptic

Ethanol 70% is better than 90%

Chlorhexadine