Madeleine McPherson. RN. MACN
Infection Prevention and Control Consultant
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The normal human body is host to trillions of
microbes. All are acting as a part of our normal
defence mechanism against possible invaders.
Number varies between 4000 and 400,000 in
each square centimetre of our skin and mucous
membrane which, if stretched out covers 8
tennis courts!!!!!!.
Staphylococcus aureus (golden staph) is one of
those found on the skin and in moist areas of
50% of healthy individuals.
The number of bacteria on the bowel equals the
number of people who have ever inhabited this
planet.
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We do not live in a sterile world, thank goodness.
Microbes are the most numerous living thing on
earth. They are all around us.
Nearly all of them function to break down the
bodies of plants and animals after they have
died, to release vital nutrients that are used
again.
Only a few are able to attack their larger
neighbours while they are still alive, to cause
disease.
To cause an infection the microbes must come in
sufficient numbers and be able to reach a
susceptible site.
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In the early days of microbiology, a simple
Bacteriologists found that Streptococci , exposed
to the air, after being shed from the body of a
person with an infection, suffer from progressive
damage before they die.
In this pre-morbid state, they can still be detected
in the laboratory, but they have lost their virulence.
Meers, McPherson, Sedgwick,.
Infection Control in Healthcare
(2000)
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1976
An epidemic of respiratory disease occurred
during an American Legion convention in
Philadelphia which resulted in 220
hospitalisations and 34 deaths.
L. pneumophila was present in the airconditioning system of the hotel where they
were all staying.
Subsequent epidemics have occurred in
hotels hospitals, cruise liners, shopping
centres etc.
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A slow growing gram negative rod-shaped
organism.
L pnemophila multiples inside amoebae
that inhabit the same ecological niche.
The ecological niche must provide the
right temperature, plenty of organic matter
and a vehicle of infection.
Severe legionellosis is seen in individuals
predisposed to smoking, chronic lung
disease alcoholism, old age and
immunosuppressant.
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Legionella is an example of wholly
environmental infection when the causative
microbe may not be derived from a living
thing.
There are many members of the genus but
over two thirds of human infections are
caused by L.pneumophia serotype 1.
Another common species is Legionella
Longbeachie which is found in potting mix.
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Survives and multiples in water including
rivers, lakes, streams.
Airborne dispersal may occur when aerosols
are created.
Temperature dependant. Prefers between 600
and 200.
Insensitive to pH.
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Does not pass from person to person.
Acquired from contaminated droplets.
Found in poorly maintained air conditioners,
shower heads, mixer taps.
Control. Showers and taps that are not
frequently used should be flushed through
weekly for 5 minutes.
Thermostat mixing valves should be cleaned
and serviced quarterly.
Source
Route of transmission
Port of Entry
Incubation period
Infection
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The immune system in the host becomes
important.
To cause an infection, a microbe must have
come from somewhere ‘source of infection’.
Finds a port of exit to escape from the
source and needs a ‘vector’ or vehicle of
infection to conduct an ID along a pathway
to reach a ‘portal of entry.
Legionnela a very good example. Aerosol
transmission and a susceptible host
(Legionnaires)
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A place in which ‘infecting’ microbes can be
found.
All microbes require transport.
Example Semmelweis.
No doubt contaminated the walls, floors,
bedding, furniture and air were heavily
contaminated with streptococci, yet hand
washing on its own reduced infection rates
from 10%-1%.
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Renamed – Healthcare Associated
Infections.
Facts:
75% of all HAI are self infections.
24% cross infection.
<1% equipment.
The focus on equipment control could be
said to be out of proportion to their overall
significance.
Note: Since we were born, our hands have been
used to sample the environment. Where they
end up is very important in the health care
setting:
 HAND WASHING IS THE SINGLE MOST
IMPORTANT MEASURE IN THE PREVENTION OF
INFECTION.
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ROUTINE:
15 seconds
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ANTISEPTIC:
1 minute
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SURGICAL:
2 minutes
THOROUGH DRYING IS AS IMPORTANT AS
THOROUGH AS WASHING.
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Transient flora.
Microorganisms isolated
from the skin that are not usually present.
(derived from contact with previous patient of
the environment)
Resident flora.
Microorganisms that
permanently reside on the skin.
After an aseptic hand wash, the hands could
be recontaminated via the tap.
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Hand basins must be readily available and
their use encouraged
The modern trend to alcohol rubs is not
always a substitute for soap and water.
The water flow must not be over the outlet.
(millions of microbes in the drain doing no
harm until they are given help, e.g. Splashing)
The hand basins also designed not to permit
splashes.
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In areas where asepsis is required (ORs,
Procedure rooms etc) elbow taps are
required. (foot taps have problems).
In areas where antisepsis is required, wrist
taps are acceptable.
Sensor taps excellent if they can be
guaranteed.
Hand taps in all other areas
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Hungarian appointed to the Obstetric Division
of the Vienna General Hospital.
Comprised two clinics. Medical students in
one and trainee midwives in the other.
Maternal death rate significantly higher in the
first clinic. 10% as to 3%.
Semmelweis, worried, investigated.
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Semmelweis.
No doubt contaminated the walls, floors, bedding,
furniture and air were heavily contaminated with
streptococci, yet handwashing on its own reduced
infection rates from 10%-1%.
Streptococci still causes serious newsworthy
sepsis.
Innovative medically acquired and opportunistic
pathogen.
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Infection Control must be based on science.
Rituals are an expensive, ridiculous waste of
time.
Know your policies, they are based on
science.
Monitor and recognise changing patterns.
Question the questionable.