Chain of infection

Objectives: Chain of Infection 1. List the factors involved in the Chain of Infection 2. State the key role of the nurse in relation to the chain of infection 3. Define the term ‘pathogen’ 4. Briefly explain what is meant by the term ‘reservoir’ 5. Outline the distribution of body flora, giving an example from each site 6. Briefly explain what is meant by the term ‘portal of exit’ 7. Define ‘mode of transmission’, differentiating between contact, common vehicle, airborne and vector borne 8. Briefly explain what is meant by the term ‘portal of entry’ 9. Outline the means by which the skin, mucous membranes, the GI tract and the GU tract protect the body from infection 10. Explain what is meant by susceptible host

Objectives: Introduction to Microbiology 1.Briefly explain the importance of understanding microbiology in terms of the nurse’s role 2.List 4 types of micro-organisms 3.Label a diagram of a typical bacterium (indicating nucleic acid, cytoplasm, cell membrane, cell wall, capsule, ribosome, storage material, flagellum, pili 4.Briefly explain the function/s of the above structures 5.State the significance of the Gram negative and Gram positive terms 6.State three features which may be used to classify bacteria 7.List four distinct requirements for bacterial growth

Objectives: Introduction to Microbiology 8. Name the main method by which bacteria reproduce 9. Briefly explain the difference between viruses and other microbes 10. Give three example of common viruses 11. Briefly explain the growth requirements for viruses and method of reproduction 12. Outline the main differences between fungi and bacteria 13. State which type of organism is responsible for: hospital acquired infections, community illnesses, mycoses

Chain of Infection The infective process involved in the development of disease hinges upon a complex interaction between: Pathogen Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host Together these factors are termed: The Chain of Infection

Pathogen Definition: Disease producing micro-organism Question: Are all microbes harmful? Question: Are some microbes beneficial? Question: Are these beneficial organisms ever harmful? What is the name for microbes that colonise the human body in health?

Breaking the Chain Given the right circumstances, potentially all micro-organisms may cause disease Nurses need to reduce this risk by: * Recognising the components and * Breaking the chain in as many places as possible

Reservoir Definition: a location or environment where a micro-organism can survive and multiply Reservoirs may be: * Animate e.g. human, animal, bird, plant OR * Inanimate e.g. food, water, air, soil, excreta, dust and fomites such as bedding or toys

Distribution of Normal Body Flora

Portal of Exit Definition: Place from which the micro-organism escapes the reservoir e.g. -Sputum -Blood -Vaginal secretions -Semen

Mode of Transmission Definition: Route via which the micro- organism is transmitted to the host Can be classified as: a) Contact b) Common vehicle c) Airborne / Droplet spread d) Vector borne e) From mother to baby

Mode of Transmission Contact Direct e.g. skin to skin Indirect e.g. shared needles

Mode of Transmission Common vehicle Via a common source such as contaminated food or water

Mode of Transmission Airborne Through contact with infected secretions produced when a person talks or sneezes. Particles may be contained in: * large droplets * droplet nuclei / dust

Mode of Transmission Vector borne Via insects or animals e.g. malaria spread by mosquitoes

Mode of Transmission From Mother to Baby Pre-natal Peri-natal Post-natal

Portal of Entry Definition: Route via which micro-organisms enter the host This may occur via: Skin Mucous membranes Gastro-Intestinal tract Genito-Urinary tract

Portal of Entry: Skin When intact – the skin is a very important barrier The skin: … Acts as a mechanical barrier … Has a slightly Acid pH … Has skin flora All the above provide a hostile barrier for pathogenic organisms When breached – microbes may enter

Portal of Entry: Mucous membranes Some protection via: … muco-ciliary clearance... lysozyme … secretion of a special antibody However, ulceration, or loss of cilia can lead to microbes gaining entry via this route

Portal of Entry: GI Tract The GI Tract is protected by: … Acid pH of the stomach … Pancreatic enzymes … Bile … Normal flora of the tract … Peristaltic action of the gut

Portal of Entry: GU Tract The GU Tract is protected by: … Frequent flushing of urine … Secretion of Ig A … Antibacterial action of sperm … Acid pH of vagina … Normal flora of the tracts

Susceptible host Definition: An individual who succumbs to the effects of invading microbes due to breaches in exterior defences (e.g. skin or mucous membranes) and / or an inability to mount an immediate / sustained specific immune response

Preventing the spread of infection: Role of the Nurse Disruption and blockage of chain of infection Protection of susceptible patients

Prevention of Infections Primary Increase the resistance of the patient Interrupt the chain of infection Restrict the spread of infection Secondary Detecting disease at earliest possible time to: Begin treatment Stop progression Protect others Tertiary Limit the progression of disability Treat symptoms and rehabilitate (varies with each specific disease)