3. Javier Ratchett: Hospital Acquired Infection Flashcards
What is a HAI?
-Infections patients get white receiving treatment for medical/surgical conditions
-Many HAIs are preventable
What usually causes HAIs?
Invasive devices such as catheters/ventilators used in medical procedures
Where do HAIs typically occur?
- Acute care hospitals
- Ambulatory surgical centres
- Dialysis facilities
- Outpatient care
- Long-term care facilities
What is a central line-associated bloodstream infection (CLABSI)?
- serious HAI that occurs when pathogens enter the blood stream through the central line
- results in 1000s of deaths
What is Methicillin-resistant Staphylococcus aureus (MRSA)?
-Type of bacteria resistant to many antibiotics
-Causes life-threatening bloodstream infections, pneumonia and surgical site infections
What are 2 sources of HAI?
- CLABSI
- MRSA
What are the 5 common types of HAIs?
- Catheter-associated urinary tract infections
- Surgical site infections
- Bloodstream infections
- Ventilator-associated pneumonia
- Clostridium difficile
Why are HAIs important ?
-source of complications across the continuum of care
-can be transmitted between different health care facilities
What are the 4 risk factors of HAIs?
- Medical procedures and antibiotic use
- Organisational factors
- Patient characteristics
- Behaviour of healthcare providers and interactions with healthcare system
How can we reduce the occurrence of HAIs?
- Proper education and training of healthcare workers to increase compliance
- Infection control
- Hand hygiene
- Attention to safety culture
- Antibiotic stewardship
What are a few examples of ‘best practices’?
- Careful insertion, maintenance, prompt removal of catheters
- Careful use of antibiotics
- Decolonisation of patients - evidence based method to reduce transmission of MRSA in hospitals
Why do HAIs tend to occur in outpatient settings?
Limited capacity for oversight and infection control compared to hospital-based settings
What is the chain of infection?
Sequence of events that show how infectious diseases spread
Outline the Chain of Infection.
- Agent leaves its reservoir/ host
- Through portal of exit
- Mode of transmission
- Enters through portal of entry
- Into susceptible host
What is the reservoir of an infectious agent?
Habitat in which the agent normally lives, grows and multiplies
-inc: humans, animals and environment
What are asymptomatic/passive healthy carriers?
Those who never experience symptoms despite being infected
Who are incubatory carriers?
Those who can transmit the agent during the incubation period before clinical illness begins
Who are convalescent carriers?
Those who have recovered from their illness but remain capable of transmitting to others
Who are chronic carriers?
Those who continue to harbour a pathogen for months/years after initial infection
-e.g/Hep B
What is zoonosis?
Infection disease that is transmissible from vertebrate animals to humans
What are examples of environmental reservoirs?
-plants/soil/water
-usually fungal agents
What is the portal of exit?
-path by which a pathogen leaves its host
-usually corresponds to site where pathogen is localised
-some blood borne agents can exit by crossing the placenta from mother to foetus (syphilis)
-exit through cuts/needles in skin (Hep B)
-blood sucking arthropods (malaria)
What are the two classifications of modes of transmission?
- Direct: direct contact; droplet spread
- Indirect: airborne; vehicle borne; vector borne
What is direct transmission?
Infectious agent is transferred from a reservoir to a susceptible host by direct contact or droplet spread
What is direct contact?
-skin-to-skin contact
-kissing/sex
-contact with infected soil
What is droplet spread?
-spray with large, short-range aerosols
-sneezing/coughing/talking
-e.g/meningitis
What is indirect transmission?
Transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects or vectors
What is airborne transmission?
-infectious agents carried by DUST or DROPLET NUCEI suspended in air
-DUST = settled on surfaces - resuspended by air currents
-DROPLET NUCEI = suspended in air for long periods of time
E.g/measles
What is vehicleborne?
-food
-water
-biological products (blood)
-fomites (handkerchiefs/bedding/scalpels
What are vectors?
-mosquitoes/fleas/ticks carries infectious agent through MECHANICAL means
-BIOLOGICAL transmission = agent undergoes maturation in intermediate host before transmission to humans (e.g/malaria)
What is the portal of entry?
Manner in which a pathogen enters a susceptible host
Must provide access to tissues for pathogen to multiply in
What portal of entry do pathogens that case gastroenteritis follow?
Fecal-oral route
Describe the fecal-oral portal of entry route.
Exit host in feces —> carried on unwashed hands —> contaminate vehicle (food) —> enter new host through mouth
Give examples of 4 portals of entry.
- Fecal-Oral
- Skin (hookworm)
- Mucous membranes (syphilis)
- Blood (Hep B)
What factors contribute to the susceptibility of a host?
- Genetic/constitutional factors
- Specific immunity
- Nonspecific factors
How can genetic factors affect susceptibility of a host?
May increase/decrease susceptibility
How can specific immunity affect susceptibility of a host?
-protective antibodies that are directed against a specific agent
- develops in response to an infection/transplacental transfer from mother to foetus/injection of antitoxin or immune globulin
How can non-specific factors affect susceptibility of a host?
Decrease: skin, mucous membranes, gastric acidity, cilia in respiratory tract, cough reflex
Increase: malnutrition, alcoholism, disease
Where are interventions directed at?
- Controlling/eliminating agent at source of transmission
- Protecting portals of entry
- Increasing host’s defences
How can we intervene at the source of transmission?
- Treating sick patient with antibiotics to eliminate infection
- Treating asymptomatic patient - reduce transmission
- Soil decontaminated to prevent escape of agent
How can we intervene at the mode of transmission?
Direct: isolation of infected person/ advising to avoid contact
Vehicleborne: elimination/ decontamination
Fecal-oral: rearranging environment to reduce contamination/ behaviour change - hand washing
Airborne: modifying ventilation, air pressure/ filtering air
Vectorborne: controlling population - insecticides
How can we intervene at the portal of entry?
- Bed nets - sleeping people from mosquitoes
- Mask and gloves - protect from blood/secretions/droplets
- Insect repellent - prevent bites
How can we intervene to increase host’s defences?
- Vaccinations - a.b stimulation
- Prophylactic use of drugs
How can we intervene to prevent a pathogen from encountering a susceptible host?
Herd immunity - high proportion vaccinated then less likely for the vulnerable to become infected
What is the name given to defence strategies against antibiotics?
Resistance mechanisms
What is the the resistance mechanism ‘restrict access of the antibiotic’?
Pathogens restrict access by charging the entryways/limiting number of entryways
What is the resistance mechanism: ‘eliminating antibiotic’?
Getting rid of antibiotics by using pumps in their cell wall before they enter the cell
What is the resistance mechanism: ‘change/destroy antibiotic’?
Using enzymes to break down the drug
What is the resistance mechanism: ‘changing the target’
Pathogens change the antibiotic’s target so it can no longer bind and do its job
What is the resistance mechanism: ‘bypass the effects of the antibiotic’?
Pathogens develop new cells processes that avoid antibiotic’s target
How does antibiotic resistance move directly from pathogen to pathogen?
Mobile genetic elements
What are the different mobile genetic elements?
- Plasmids
- Transposons
- Phages
What are plasmids?
Circles of DNA that can move between cells
What are transposons?
Small pieces of DNA —> go into cell —> change overall DNA
Can move to chromosomes and plasmids and back
What are phages?
Viruses that attack germs and can carry DNA from pathogen to pathogen
What is transduction?
Resistance genes transferred from one pathogen to another via PHAGES
What is conjugation?
Resistance genes can be transferred between pathogens when they DIRECTLY CONNECT
What is transformation?
Resistance genes RELEASED FROM NEARBY PATHOGENS that can be picked up directly by other pathogens
What should be considered in an antimicrobial stewardship programme?
- Monitoring/evaluating PRESCRIBING - how it relates to RESISTANCE PATTERNS
- Providing regular FEEDBACK to prescribers: using correct codes/ patient safety incidents
- Providing EDUCATION and TRAINING
- INTEGRATING AUDIT
