Chain of infection

Objectives: Chain of Infection1. List the factors involved in the Chain of Infection2. State the key role of the nurse in relation to the chain of

infection3. 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 site6. Briefly explain what is meant by the term ‘portal of exit’7. Define ‘mode of transmission’, differentiating between

contact, common vehicle, airborne and vector borne8. 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-organisms3. 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 viruses11. Briefly explain the growth requirements

for viruses and method of reproduction12. Outline the main differences between

fungi and bacteria13. 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

ReservoirDefinition: 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 vehicleVia a common source such as contaminated food or water

Mode of Transmission

AirborneThrough 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 TransmissionFrom 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: SkinWhen 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 TractThe 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

PrimaryIncrease the resistance of the

patientInterrupt the chain of infection Restrict the spread of infection

SecondaryDetecting disease at earliest possible time to:

Begin treatmentStop progression Protect others

TertiaryLimit the progression of disabilityTreat symptoms and rehabilitate (varies with each specific disease)