Lecture 5 - Infection Control Flashcards
What was the prevalence of HAI in scottish hospitals in 2016?
4.5%
What are the most common types of HAI?
urinary tract infections (24.5%)
respiratory infections (22.4%)
surgical site infections (16.5%)
What does each infection mean?
additional NHS costs, greater patient discomfort, and reduced patient safety
Cost of HAI?
> £1.6 billion/year in UK
How much could HAIs be reduced?
estimated ~30%
Escherichia coli bacteraemia?
E coli is most common pathogen causing bacteraemia
usually develops as a consequence of other infections
90 per 100,000 acute bed days
C. difficile infection?
usually causes diarrhoea and significant morbidity and mortality
develops as complication of other infections e.g. UTI
incidence of 2.8%
Surgical site infection?
when microorganisms get into the sterile area
causes significant morbidity and mortality
18.6% of all HAI
Urinary tract infection?
most common cause of HAIs
many associated with catheterisation
most common isolates are E. coli and K pneumoniae
Staph aureus infection?
When S. aureus breaches body defences it can cause a range of illnesses from minor skin infections to bacteraemia
32 per 100,000 acute bed days
What is the incidence of MRSA?
2.2 per 100,000 acute bed days
Norovirus?
highly infectious and spreads easily
no lasting immunity
causes significant morbidity and mortality
outbreaks result in ward closure and affects hospital work patterns
present in autumn/winter and causes vomiting and diarrhoea
HAI in ICU?
highest prevalence compared to other parts of hospital
critically ill patients have multiple co-morbidities and invasive procedures
2.5% incidence
Most common pathogens associated with HAI?
enterobacteriaceae (E. coli) 33%
staph aureus (20.2%)
clostridium difficile (5.3%)
What is a reservior?
a location where possible pathogens may live and multiply
Examples of a reservoir?
in or on a person or animal (host) (e.g. opportunistic pathogens)
in soil (e.g. C difficile)
in water (pseudomonas spp, legionella)
How can pathogens exit the reservoir?
ear (wax)
broken of infected skin (pus or blood)
skin (flakes)
anus (faeces)
eyes (tears)
nose (secretions)
mammary glands (milk, secretions in females)
vagina (secretions, blood)
urethra (urine)
seminal vesicles (semen and lubricating secretions)
How much skin does the body shed per day?
15g of skin per day, these can host up to 8-10 bacteria per skin square
What do nasal secretions indicate?
infected sinuses or respiratory infections
Direct contact transmission?
body surface to body surface between an infected individual and susceptible person
Example of direct contact transmitted infections?
influenza, chlamydia
Droplet contact transmission?
generated during coughing or sneezing
meningococcus spp, influenza, coronaviruses
Airborne transmission?
generation of aerosols (<5um) which are airborne and can spread considerable distances e.g. TB, varicella virus
Surface transmission?
infectious agent deposited onto an object or surface and survives long enough to transfer to another person who touches the surface
examples of surface transmission?
enterococcus spp, staph spp
Vehicle transmission?
usually a single contaminated source spreads infection
Example of vehicle transmission?
legionella outbreak in edinburgh 2012
4 deaths
pathogens grow in stagnant water, the vapour from this can then be inhaled
Vector borne transmission?
transmission by an insect or animal e.g. mosquitos, ticks etc
Droplet transmission?
transmitted when an infected person sneezes, talks or coughs
Pathogens transmitted via droplet transmission?
COVID-19
adenovirus
influenza B
measles
strep pyogenes
Infection control of droplet transmission?
Isolation of infected individual
use of PPE
How far can droplets travel?
larger droplets can travel around 1m
smaller droplets can remain entrained in air for much further distances
Toilet hygiene?
females > males
60% vs 40%
faecal matter may be retained on hands so handwashing is important
What is airborne transmission?
residue from evaporated droplets or dust particles containing microorganisms remain suspended in the air
pathogens capable of surviving for long periods outside the body and are resistant to drying
transmission by inhalation
Examples of pathogens transmitted by air?
mycobacterium tuberculosis, measles and varicella virus
Portal of entry into the body?
broken skin
insect bites
anus
conjunctiva of eyes
nose
mouth
penis/vagina
Examples of gram positive bacteria that can survive for months?
gram pos S aureus (MRSA) S pyogenes enterococcus species C difficile
Examples of gram negative bacteria that can survive for months?
acinetobacter species
E. coli
P. aeruginosa
serratia marcescens
Gram negative bacteria that can persist for days?
H influenzae
bordetella pertussis
proteus vulgaris
vibrio cholera
Respiratory viruses that can persist for hours?
coronoviruses
coxsackie virus
influenza virus
SARS virus
Blood borne viruses that can persist for more than a week?
HIV
hepatitis B
CMV
herpes simples (1&2)
Fungal pathogens that can survive for many months?
candida albicans
What is regular surface sanitisation critical for?
maintaining an environment which has as a low a population of pathogenic microorganisms present
this reduces potential transmission rates
What are disinfectants used for?
to wipe high touch areas
shown to be more effective than cleansing agents
What is needed to disinfection to be effective?
a high rate of compliance (>80%) to daily disinfect wipe down of the high touch points
Why do small numbers of pathogens give a good chance of preventing infection?
there needs to be a large number of pathogens overwhelming the immune system to cause infection
What can regular sanitisation reduce?
HAIs
MRSA
C difficile
vancomycin resistant enterococci
Alcohol used as disinfectants?
ethanol
propanol
isopropyl alcohol
What are alcohols active against?
vegetative forms of bacteria, fungi and coated viruses
Contact time of alcohol?
limited due to rapid evaporation from surfaces limits antimicrobial activity
Concentration of alcohol disinfectants?
70-90%v/v
Why are alcohols not effective at higher concentrations?
needs water to participate in hydrogen bonding between the alcohol and the pathogen
Chlorine based disinfectants?
most widely used disinfectants in hospitals and insutry
What happens in chlorine solutions?
the hypochlorite (ClO-) ion is in equilibrium with hypochlorous acid, the chemical species responsible for antimicrobial activity
Hypochlorous acid acitivity?
bactericidal, fungicidal, virucidal against both coated and uncoated viruses
What is the antimicrobial activity of hypochlorous acid dependent on?
pH
pH > 9 the antimicrobial is lowest since the hypochloride ion predominates
pH < 7 hypochlorous acid predominates
Concentrations of chlorine based disinfectants?
10,000ppm
10mcg/ml
Use of chlorine based disinfectants in highly soiled areas?
concentration needs to be increased dramatically for cleaning vomit/urine/faece
Iodinated disinfectants?
iodine has bactericidal, fungicidal, sporicidal and virucidal activity
What does the activity of iodinated disnifectants lie with?
primarily resides with I2
What is iodine used for?
used clinically as an iodophor product
iodine carrier or releasing agent
Types of iodine disinfectants used?
povidone iodine (povidone is a complexing agent) (used in UK)
poloxamer iodine (poloxamer is a surfactant solubiliser)
What are iodine disinfectants mainly used for?
skin disinfectants (pre-surgery) as they are less irritating than iodine tinctures
yellow colour shows areas that have been disinfected easily
Peroxygens?
hydrogen peroxide (20-35%v/v) (H2O2)
peracetic acid (0.3%w/v) (CH3COOOH)
What peroxygen is inactivated by organic matter?
hydrogen peroxide
What are peroxygens used for?
bother are bactericidal, fungicidal, virucidal
peracetic acid is sporicidal
What is the antimicrobial activity of peroxygens due to?
through generation of hydroxyl free radicals
What are the 3 quaternary ammonium compounds (QAC) used as disinfectants?
benzalkonium chloride
cetrimide
cetylpyridinium chloride
What do QACs do?
adsorb and penetrate the cytoplasmic membrane
this causes loss of membrane integrity and escape of intracellular contents
also causes loss of membrane bound enzyme function
What are QAC always carrying?
a positive charge
they have a long lipophilic chain associated with the head group
Concentrations of QAC?
1-20%
What is a downside of QAC?
readily inactivated by organic matter so are not good for heavily soiled areas
What factors place a person at risk of infection?
age (extremes)
immune status
genetics
current co-morbidities
nutritional status
(above all related)
behaviours
What can the innate immune system be influenced by?
environment and nutritional state
Potential interventions at individual level?
vaccination
clinical intervention to prevent diabetes (glucose control), COPD (smoking), malnutrition
How to reduce the chance of disease transmission?
minimise disease exposure (isolation)
behavioural change (condoms)
enhance PPE (mask, gloves)
What is hand-mediated transmission?
a major contributing factor in the acquisition and spread of infection in hospitals and community
When to wash hands with soap?
when the hands are visibly soiled or potentially contaminated by biological fluids
when interacting with patients with vomiting or diarrhoea
When to use alcohol based hand rubs?
before/after direct contact even if wearing gloves
What are alcohol based hand rubs not effective against?
C difficile
What % of vaccination is needed for heard immunity?
> 95%
