Micro

• Portal of entry – broken skin, mucous membrane, respiratory, urinary tract
• Susceptible host – neonates, children, weak immune system, unimmunized
• Mode of transmission – the manner in which the infectious organism is acquired by the host.
• Chain of infection

  How an individual acquires the infectious agents, including the infectious agent, the source of infection or its reservoir, how the organism is transmitted, and the organism's portal of entry into the susceptible host
• Components of the chain of infection

  • Causative agent
  • Reservoir
  • Portal of exit
  • Mode of transmission
  • Portal of entry
  • Susceptible host
• Standard precautions

  The specific measures used to prevent the spread of infection
• Contamination

  Denotes contact of a sterile or aseptic item with microorganisms
• Decontamination

  The process where physical or chemical means are used to remove, inactivate, or destroy pathogens
• Disinfection

  The process of using physical or chemical means to destroy pathogens, excluding the spores
• Sterilization

  The process by which all pathogens are destroyed, including the spores
• Antiseptic

  A chemical solution that inhibits the growth of some microorganisms. Most antiseptics can be used directly on the skin (e.g., alcohol and iodine)
• Healthcare associated infection

  Any infection that is acquired during the time a patient is admitted in a healthcare facility
• Iatrogenic infection

  Infection that is acquired in the course of undergoing diagnostic tests or therapeutic procedures
• Occupational exposure

  The acquisition or exposure to an infectious agent of a healthcare worker during the course of his/her work
• Personal protective equipment (PPE)

  Specialized equipment and attire used by healthcare workers to protect them from infections. These include gloves, masks, gowns, and goggles
• Sepsis

  A clinical condition where infectious agents are spread throughout the body of an individual from a localized site of infection and manifest with symptoms of organ damage
• Asepsis

  The absence of disease producing organisms, divided into medical asepsis and surgical asepsis
• Medical asepsis (Clean technique)

  Aimed at reducing the number of disease producing organisms to prevent its spread from healthcare workers to the patients and vice versa
• Surgical asepsis (Sterile technique)

  Aimed at total elimination of disease producing organisms particularly in areas in the body where surgical procedures will be performed
• Handwashing

  The most basic and universally accepted measure used to prevent the spread of infection
• Importance of handwashing

  • Reduce the flora on the healthcare workers skin
  • To protect in the event that there is a break in the skin
  • Reduce risk of contact of infectious diseases
  • Reduce the chances of disease transmission
• Personal protective equipment (PPE)

  Specialized equipment and attire used in healthcare facilities to protect not only the healthcare workers but also the patients and visitors against infections. These include masks, gowns, and goggles
• Transmission based precautions

  • Contact precautions- ex. gowns and gloves
  • Droplet precautions- ex. surgical masks
  • Airborne precautions- ex. N85 mask, facemasks, higher level of respirators
• Contact precautions

  Prevent the spread of infection transmitted through touching of patients or items in the room where infectious agent is present hahaha
• Droplet precautions

  Prevent transmission of infections spread in tiny droplets caused by coughing and sneezing
• Airborne precautions

  Prevent transmission of infections spread through the air from one person to another
• Physical sterilization methods

  • Heat
  • Radiation
  • Filtration
• Dry heat sterilization methods

  • Red flame- wire loops, spatula, forceps
  • Open flame- mouth of test tubes, scalpels, glass slides, cover slips
  • Incineration- burning the organism into ashes/contaminated dressings, beddings
  • Hot air oven- 160c for 1 hour
  • Infrared rays- 180c for 7.5 min//metallic equipment and glassware
• Radiation sterilization methods

   UV Light/Non-ionizing Radiation- 200-280 nm

   Ionizing Radiation

   Electron Beams – used to sterilize syringe, gloves, dressing packs, food

   Electromagnetic rays (Gamma rays) –sterilize vitamins, antibiotics, hormones, glassware
• Filtration

  Used for liquid solutions that will be destroyed by heat or freezing such as serum, antibiotic solutions, or urea solution. This method can be used to remove bacteria from culture media
• Agents that damage the cell membrane

  • Surface active agents
  • Phenolic compounds
  • Alcohols
• Surface active agents- compounds have long chain hydrocarbons that are fat-soluble and ions that are water-soluble.


  • Cationic agents- Fat soluble (cetrimide and benzalkonium chloride)
  • Anionic agents- Water soluble (soaps and bile salts)
• Phenolic compounds- these act by disrupting cell membranes as well causing precipitation of inactivation of enzymes


  • Phenol- carbolic acid//no longer used as disinfectant//toxic to human cells
  • Cresols- derivative from phenol//safer than phenol///Lysol//disinfectant
  • Chlorhexidine- skin disinfectant //isopropanol alcohol//C3H8O//Molecular formula
  • Chloroxylenols- topical purposes//application to body surface//gram+ bacteria
  • Hexachlorophene- Chlorinated diphenyl//gram +
  • Triclosan- Organic phenyl ether//gram + and gram -
• Alcohols- disorganize the lipid structure of the cell membrane, dehydrate cells and cause denaturation and coagulation of cellular proteins.


  • Ethyl alcohol- Skin antiseptic//bactericidal//CH3CH2OH//ETHANOL
  • Isopropyl alcohol- Has greater bactericidal compared to ethyl alcohol//C3H8O
  • Benzyl alcohol- used mainly as preservatives//C7H8O
  • Methyl alcohol- Fungicidal and sporicidal/CH3OH
• Agents that modify the functional groups of proteins and nucleic acids


  • Heavy metals
  • Halogens
  • Alkylating agents
• Heavy metals- cause damage to the enzyme activity of bacteria.


  • Mercurials- are biocidal and are used as antiseptics. Ex. Mercurochrome and merthiolate
  • Silver compounds- are bactericidal. Ex. Silver nitrate and silver sulfadiazine
• Halogens- bactericidal oxidizing agents that can cause oxidation of essential sulfhydryl groups causing inactivation of the enzymes.


  • Iodine- considered as the best antiseptic. (sporicidal, bactericidal, fungicidal, viricidal, amoebicidal//combined with polymers to produce iodophores//povidone-
  • Chlorine- mainly used in the treatment of water. hypochlorites used for sanitizing dairy and food processing equipment//higher concentrations//disinfect swimming pools
  • Hydrogen peroxide- weak antiseptic. Used only for cleaning wounds
• Alkylating agents

  • Aldehydes- damage nucleic acids by alkylation of amino, carboxyl, or hydroxyl groups.

  1. Formaldehyde – used for surface disinfection. Formalin//sterilize beddings and furniture///used to kill mycobacterium tuberculosis in sputum and fungi in

  2. Glutaraldehyde – sporicidal and used as a cold sterilant in sterilizing medical equipment.

  Therapy machine

  • Ethylene oxide- also sporicidal and is used in the gaseous sterilization of heat sensitive materials or equipment. heart-lung machine, respiratory and dental equipment.
• Antimicrobial classification

  • Based on spectrum of activity
  • Based on antimicrobial activity
  • Based on absorbability
  • Based on mechanism of action
• Antimicrobial classification based on spectrum of activity

  • Broad spectrum antibiotics- are those wide coverage of activity against a wide spectrum of microorganisms. * Empiric treatment of non-documented infections
  • Narrow spectrum antibiotics- are those with a limited coverage of activity.*Targeted treatment of documented infections