In the 1800s Aseptic techniques invented toprevent contamination of surgical wounds
Many organizations classified infectioncontrol systems and substances into:• Physical methods.• Chemical methods. Referred broadly as Germicides
Germicidal systems fall into three categories:1. Decontamination.2. Disinfection.3. Sterilization.
1. Decontamination:• Reduction of pathogenic microorganisms to be safe to handle without protective attire.• The Lowest level of control.• Includes physical cleaning with soap and detergents and removing of most organic and inorganic materials.• It is the critical step toward disinfection and steilisation.
2. Disinfection:• Disinfectants are liquid chemical agents that kill targeted pathogens but not spores . It can also be solid or gaseous.• It is the next level of control.
3. Sterilization• The complete elimination of viable organisms including spores.• The highest level of control
Factors influencing disinfection• Number of microorganisms.• Species and type of microorganism.• Temperature.
Physical ChemicalAntimicrobial Antimicrobial Agents agents Destruction of Microorganisms
Physical Antimicrobial Agents • Physical environmental agents can destroy large concentrations of microorganisms in lab cultures or a clinical specimen.
AutoclaveMoist heat- Steam sterilization 121OC for 15 min
Dry heat160OC for 2 hours OR 170OC for an hour
Chemical Antimicrobial Agents• In considering their application to patient care, two general classes: 1. Those destroying pathogenic microorganisms in the environment (disinfectants) or on skin (antiseptics). 2. Those administered to patients for treatment of infectious diseases (antimicrobial agents, often called antibiotics).
Desinfectants Disinfectant Bctericidal Sporicidal Fungicidal Viricidal Ethyl and Good Poor Good good isopropyl alcohols Chlorine Good Good Good Good DisinfectantsFormaldehyde Good Good Good Good andGlutaraldehyde Hydrogen Good Good Good Good peroxide Iodophors Good Poor Good Good
Evaluating a disinfectant• Direct spray method.• Testing the quality of disinfectant from different brands.
Testing Disinfectant from Different Brands 0.5 mL 5 mL Bacterial 5 mL Clorox 5 mL DAC 5 mL Gento 5 mL DettolSuspension in Nutrient Broth (Control)
Testing Disinfectant from Different Brands Water BathBacterial Suspension in Nutrient Bacteria in DAC Bacteria in Gento Bacteria in Dettol Broth (Control) Bacteria in Clorox
Testing Disinfectant from Different Brands 2 Loopfulls 48 hrs Water Bath Incubation in the 37O C After 5min After 10 min in After 20 min inBacterial Suspension in in Water Bath Water Bath Water BathNutrient Broth (Control)
What is food spoilage?!• Noticeable damage; compromise quality which renders food undesirable to eat or inedible.• Spoiled food detected by: – Sight: appearance and color – Taste – Odor – Texture: squishy, no longer firm.
Types of Spoilage1. Physical spoilage2. Spoilage due to insects or rodents3. Chemical and enzyme spoilage4. Microbial spoilage
What do microorganisms do to fruits and vegetables?! Positive effect Negative effect• Influencing the taste • Rotten food• Increasing the shelf-life • Ex.:• Ex.: – Turning milk to sour and curdled. – Lactic acid bacteria to make cheese and yogurt from milk. – Putrid smell of meat. – Yeast in making beer and bread
Eating rotten food can cause Food contamination Food poisining• Occurs when a person • Occurs when the food is consumes a large number of containing the poisonous living micro-organisms in a waste products secreted by meal. the bacteria.• Disturb the digestive • Heating the food does not system. help in this case: the• can be prevented by bacteria will be killed, but sufficient heating, it will kill the poisonous waste will the micro-organisms. remain unharmed.
Preservation methods• Heating• Cold• Fermentation: sugar• Reduce the moisture: drying and smoking• Chemical preservation: Sodium benzoate, nitrites• Oxygen exclusion: canning in glass or metal, air tight wraps.• Ultra high pressure.• Irradiation: change texture and taste, public fear• Packaging: protection of food from contamination after processing
Objectives• Some infection control terms.• Factors influencing disinfectants.• Physical destruction of microorganisms.• Chemical destruction of microorganisms.• Methods of evaluating disinfectants.