Microorganisms and the chain of infection Flashcards
What is a healthcare associated infection? ( HCAI)
A problem which develops as a direct result of healthcare interventions.
How are HCAI’s transmitted?
Any from:
- transmitted via blood, body fluids, secretions
- Inhalation of droplets or airborne infections
-inoculation incidents
- contact with non-intact skin or membranes
- any equipment that has been contaminated
What are the risks of developing a HCAI
- increased length of stay
- mortality and morbidity
- drain on financial resources
Where are the most common sites of HCAIs?
-Respiratory infections
- surgical site infections ]
- UTI’s
General factors affecting the risk of a HCAI
- Age : weaker immune system in elderly and young children
- Mental state: unable to reach self actualisation
- Nutrition: poor diet = susceptible host
What are the local factors of HCAIs
- Oedema ( build up of fluid in the body; makes tissues swollen)
- Skin lesions
- Foreign Body
- Ischaemia ( lack of blood flow)
What are invasive procedures?
Surgery, Catheterisation, cannulation, intubation.
What are the main classification of microorganisms?
-> fungi
-> viruses
-> bacteria
-> protoza
Infection vs Colonisation
Colonisation presence of bacteria on a body surface without causing disease in the person i.e response to the presence of a microbe is absent / slight.
Infection: when pathogens / disease causing micro-organisms gain access to host tissue and elicit an immune response.
What is commensal?
microbes that live in close association with their host & in the correct environment do not harm it and can positively benefit it e.g skin flora
Pathogen
a microorganism that is able to cause disease
Pathogenicity
ability to cause disease in a host organism
Pathogenesis
process of how a microorganism produces disease
Virulence
The degree of pathogenicity e.g. genetic,structural or biochemical features
What is microbial flora?
Microbial flora refers to the microorganisms that live on or inside the body, such as bacteria and fungi
What is resident flora
less likely to be associated with infections, but may cause infections in sterile body cavities, the eyes, or on non-intact skin.
Transient flora
colonises the superficial layers of the skin, is more amenable to removal by routine hand hygiene.
How does a microbe establish an infection in a host?
Gain access to a host cell
Adhere to, enter and move to a favourable site
Penetrate or evade host defences in order to multiply
Dissemination of new pathogens within or outside of the host ( exocytosis)
What is the chain of infection
Infectious agent: bacteria etc
Reservoirs: people, food etc
Portal of exit: blood, excretions
Modes of transmission: physical
Portals of entry: broken skin
Susceptible host: age
What makes microorganisms good pathogens
- Flagella for movement
- Multiple bacteria grouped together
- Spores – enhance ability to survive in unfavourable conditions
- Fimbria – enhance adhesion to surfaces
Components of a virus
Nucleic acid- dna or rna
Capsid- protective protein coat composed of capsomers
Envelope: lipidprotein membrane
Glycoprotein spikes: attachment and recognition
Viral replication
1)virion attaches to host cell
2) Virion penetrated cell and its dna is uncoated
3)early transcription and translation
4) Late transcription, DNA is replicated
5) Late translation: capsid proteins and synthesized
6) Virions mature
7) Virions are released
