Javier Ratchett - Hospital Acquired Infection Flashcards
Describe the chain of infection
1) Agent leaves reservoir/ host through portal of exit
2) This is conveyed via some mode of transmission
3) Enters through appropriate portal of entry to infect susceptible host
What is a resevoir?
Habitat that the infectious agent normally lives and multiplies in eg. humans, animals environment
What is the portal of the exit?
The path by which pathogen leaves the host and usually the site where the pathogen is localised
What are the different modes of transmission?
DIRECT
- Direct contact
- Droplet spread
INDIRECT
- Airborne
- Vehicleborne
- Vectorborne
What is the portal of entry?
The manner in which pathogens enter susceptible hosts
What is the impact of HAIs on healthcare systems
- Increases bed pressure
- 2 billion pound cost for the NHS
- 60 000 days lost healthcare workers contracting HAIs
- Increase in mortality and morbidity
- More complaints and dissatisfaction
What is meant by zoonosis
Infectious disease that is transmissible under natural conditions from vertebrae animals to humans
What are the 4 main risk factors of HAIs?
- Medical procedures and antibiotic uses
- Organisational factors
- Patient characteristics
- Behaviour of healthcare staff
If someone has an infection, what are their WBC count, CRP level and respiratory rate?
WBC count - High
CRP level - High
Respiratory rate - High
What is D-alanyl-D-alanine carboxypeptidase transpeptidase also known as and what is its function?
- Penicillin Binding Protein
- Assists with peptidoglycan matrix assembling by creating crosslinks between chains
What are the mechanisms in which bacterial resistance occurs?
- Decreased uptake of drug
- Mutated channel so drug cannot enter
- Enzyme digests/breaks down drug
- Inactivating enzymes
- Horizontal gene transfer
- Alternative enzyme to bypass the reaction that the drug inhibits
How do antibiotics inhibit D-alanyl-D-alanine carboxypeptidase?Ho
Antibiotics binds to the enzyme and inhibits the action of it preventing it from forming the cross links in the peptidoglycan layer, killing the bacteria.
How do bacteria evade beta-lactam containing antibiotics
They can express a beta-lactamase enzyme which breaks beta-lactam of antibiotic, rendering the antibiotic useless
Why would a patient not respond to amoxicillin but respond to co-amoxiclav
Bacteria inhibits amoxicillin via beta lactamases but co amoxiclav contains clavulanic acid which inhibits those beta lactamases therefore the amoxicillin has can inhibit the bacteria
Why would a patient taking co-amoxiclav develop a C.difficile infection
The antibiotic reduces gut flora therefore decreases competition for c.diff and so creates an environment that c.difficile can survive in.
What is sepsis?
Body’s extreme response to an infection which can rapidly lead to tissue damage, organ failure and death
What is the sequence of septic shock?
Hypotension(low BP)
tachycardia (high heart rate)
tachypnoea(high respiratory rate)
What can sepsis lead to?
- Tissue damage
- Organ failure
- Death
What is hospital acquired infection?
An infection that patients get while receiving treatment for medical or surgical conditions
When are HAIs usually acquired?
- During procedures such as surgery
- From devices used in medical procedures such as catheters and ventilators
Can be HAIs be caused by microorganisms already present in the patient’s body? How?
YES - Medical procedures can weakend the body’s defences causing them to be more susceptible to infection.
Where is the most common place for a patient to contract an HAI?
Outpatient settings
What is CLABSI?
Central line associated bloodstream infections
What is MRSA?
Methicillin resistant staphylococcus aureus
What are the 5 common types of HAI?
- Catheter associated HAI
- Surgical site infections
- Bloodstream infections
- Pneumonia
- Clostridium difficile
What are the 4 risk factors of HAI?
- Medical procedures and antibiotic use
- Organisational factors
- Patient characteristics
- Behaviour of healthcare providers and their interactions with the health care system
What is indirect transmission?
Transfer of an infectius agent from reservoir to host by:
- Suspended air particles
- Inanimate objects (vehicles)
- Animate intermediates (vectors)
What is specific immunity?
Protective antibodies are directed against a specific agent. These are acquired by:
- Response to infection, vaccine, toxoid
- Transplacental transfer
- Infection of antitoxin or immune globulin
What processes in the chain of infection do the interventions target?
- Controlling or eliminating the agent at the source of transmission
- Intervening with the mode of transmission
- Protecting portals of entry
- Increasing host’s defences
What are the 5 moments of hand hygiene?
1) Before touching a patient
2) Before a clean/aspetic procedure
3) After body fluid exposure risk
4) After touching a patient
5) After touching patient surroundings
What is the difference between gram positive and negative cell walls
Gram positive - Peptidoglycan (same as murein)
Gram negative - thin layer of peptidoglycan and an outer membrane with lipopolysacharride
What is the difference between gram positive and negative stains?
Gram positive - Purple
Gram negative - Red/pink
What is shock?
An imbalance in supply and demand
What are the test results that indicate infection
- High C reactive protein level
- High WBC count
- Dip in normal oxygen saturation levels (lower than 95% is abnormal)
- High respiratory rate (12-20 normal for adults)
What are the signs of infection from catheter specimen urine?
- Positive for epithelial cells
- High number of organisms and WBCs
What are the 4 mechanisms antibiotic resistance occurs via
1) Altered target site
2) Inactivation of the antibiotic
3) Altered metabolism profile
4) Decreased drug accumulation
What are sources of antibiotic resistance genes?
Plasmids - contain resistant genes and can be swapped between bacteria
Transposons - allows transfer of resistant genes from plasmid to chromosome
Naked DNA - DNA from dead bacteria containing resistant genes is taken up by bacteria to incorporate into their DNA
Bacteriophages - viruses that attack bacteria and carry DNA from bacteria to bacteria
How are antibiotic resistance genes spread?
Transduction - via bacteriophages
Conjugations - resistance genes can be transferred between bacteria and they connect via a pilus
Transformation - naked dna
What are the 3 categories of antibiotic resistant bacteria?
Urgent
Serious
Concerning
