37 Infection control Flashcards
HAI
Which organisms are most commonly implicated?
UTI - e. coli K penumoniae Staph saprophyticus Enterococcus
SSTI -
Staphylococci - MRSA
Enterococci
E. coli
Pneumonia -
Staph aureus
Pseudomonas
GI -
C. difficile
What are sources of HAI?
Route of spread same as community - airborne, droplet, direct, fomite
Staff
Visitors
Fomites
IV lines
Catheter
Surgical prosthesis
Wound infections
Why might certain patients be at higher risk for HAI?
Lacking immunity - unvaccinated
Underlying diseases - e.g diabetes, HIV
Medications - antibiotic disrupt flora, steroids lower host defences
Trauma - disturbance to natural host barrier
What increases risk of post-operative infection?
Length of pre-operative stay
Presence of intercurrent infection
Length of operation
Nature of operation
Presence foreign bodies e.g shunts/ protheses
State of tissue - vascular supply/ drainage of tissues
What are general principles for reducing HAI?
Reduce risk from environment - sterile equipment etc
Interruption of infection chain - ventilation systems, isolate patient, hand washing
Ensure host ability to resist infection - care of catheters/ IV lines, immunisation, prophylactic antibiotics
What is role of infection control team?
Surveillance of hospital infection
Establish monitoring of polices e.g disinfectant policy, catheter care policy
Investigation of outbreaks
Environmental cleaning/ disinfection/ disposal of waste
What information is used for surveillance?
Lab reports - key organisms e.g MRSA
Ward rounds - regular review of certain patients e.g C. DIff
Investigation of outbreak requires combination of microbiological and epidemiological information.
What do we need to know?
Who is infected/ how many
When were they admitted
Where were they admitted - all on same ward?
When did they develop infection
What is common exposure/ treatment?
Identify pathogen - depends on patient symptoms
What are steps in outbreak investigation?
Identify outbreak -
- two or more cases linked in time/ place
- single case of rare disease e.g VHF
- greater infection rate compared to usual background rate
Identify organism - should have common strain. Perform typing
Declare outbreak
- agree case definition
- hypothesis generation
Contain outbreak and prevent further spread
Identify cause/ source of outbreak
Review investigation at conclusion - identify if could be prevented
Identifying organism is important for epidemiological purposes.
What are methods of identifying?
Antibiotic susceptibility pattern - e.g VRE
DNA whole genome sequencing
DNA plasmid sequencing
Restriction fragment length polymorphism analysis - RFLP. Ribosome sequences highly conserved in species, can be used to identify bacteria by ribosome analyisis e.g 16S RNA
Decontamination
Physical cleaning must first be performed to remove dirt, and reduce bacterial load. Dirt can also protect microbes from sterilisation/ disinfection.
What is sterilisation?
What is disinfection?
Sterilisation - kill/ remove all viable organisms
Disinfection - removes most pathogens. Chemicals kill pathogens, but may not kill viruses/ spores. Boiling may not kill every bacteria, but will reduce bacterial load significantly - pasteurisation
Pasteurisation heats fluids to levels to kill most viable microbes, without affecting taste e.g 65 deg for 30 mins
What are techniques for sterilisation?
Heat - autoclave (with steam)
Radiation - gamma/ ultraviolet
Filtration
Chemicals - liquid/ gas
Freezing/ ultrasound/ electricity are techniques employed, with variable evidence of efficacy
Prions are extremely resistant to all sterilisation techniques. Requires high heat/ pressure, which living tissue would not survive
Most devices are not inert, and induce local immune response.
How does this increase risk of infection?
Local immune response can deplete complement/ neutrophils, and cause minor tissue damage.
Increasing risk of infection
Devices do not have blood supply, so bacteria can multiply on device, and difficult for immune system to clear them. Means device may need removed
Patient has long term TPN through CVC.
Which has minimal role in prevention of CVC-associated infection?
Antibiotic-impregnated CVC Antimicrobial CVC locks CVC fixation CVC hub disinfection policy CVC sub-cutaneous tunnelled line
Antibiotic impregnated CVC - do not retain antimicrobial activity beyond a few weeks.
So can be useful in ITU, but no use in long term CVC line in this case
How does Staphylococcus aureus gain resistance to methicillin?
Acquisition of mec A gene
mec A encodes for penicillin-binding protein PBP2a, which has low affinity for penicillins
