Sterilization is the highest
level of disinfection.
Because tattoo and piercing needles penetrate into the body they are required to be sterile. To maintain sterility
everything that touches that needle is a potential source of
Sterility is a probability, not an absolute.
Though "Sterilization" is meant to convey an
absolute (the destruction or inactivation of all
microorganisms - either something is sterile or it is not)
A. It cannot be known whether all
have been killed.
1. We may not
be aware of the existence of some.
2. We may not
actually be culturing for all microorganisms.
B. We cannot prove the existence of a
Therefore the approach is to employ a "process"
Sterilization is the process by which living organisms are
removed or killed to the extent that they are no longer detectable
in standard culture media in which they had previously
proliferated. (Block, 4th Edition, Dis. Ster. Pres.)
Both the process and the methods used to test are equally important.
In actuality it is a probability and not an absolute.
Sterility measurement is expressed as a probability.
Sterility is considered achieved when it reaches what
is called a "log of minus 6 of reduction" rather than as an
absolute and is called the "Sterility Assurance Level" (SAL) which
can be quantitatively (in numbers) expressed. This means: One million microbes is the basis for the calculations, which is
why prior cleaning is necessary. Too many microbes on the items,
more than one million, would require a greater processing time or
Each negative log represents a 90% reduction of microbes.
Imagine a glass full of water. Assume for a moment the water
represents the microbes and it equals one million microbes (estimated to be on your
product). This is a "Log of 6" ( a log of 6 equals 1 million
If we empty 90% of the water it leaves 10% of the
water. Our original one million microbes - our water, minus 90% is
100,000 microbes left. Because we are reducing we go down the number
of reductions by 90% logs, as it were,
and now have a "log of 5" or, now only 10,000 microbes. 90%
of the 100,000 have been
killed or inactivated).
Repeating our process again, we empty 90% of what is left over in the
glass. This is a "log of 4" (10,000-10% microbes left over
from the first step, minus 90% leaves 1,000
106 1,000,000 microbes
105 1,000,000 minus 90% = 100,000
104 100,000 minus 90% = 10,000
103 10,000 minus 90% = 1,000
102 1,000 minus 90% = 100
101 100 minus 90% = 10
100 10 minus 90% = 1
10-1 1 minus 90% of 1? - can't have 10% of one microbe
but we can think of it as 1 microbe among
10 items. = -1
If we do this a total of 6 times we have a
"log of 0", which would be one microbe left. If we
now continue and want to empty 90%
of what's left (our 1 microbe) of course we can't empty 90% of just
But we can think of it as a probability: In other words
If we had one item we would have one microbe on that item.
If we had 10 items we can say we might have one microbe among ten items
(a 90% reuction),
. This level is 10 -1, Ten to the
minus one meaning one microbe per 10 items. A
log of reduction to 10-2 therefore means one microbe per 100 items, etc. A log of
might survive on a million items
presuming that the original
microbial load was one million microbes or less. This is what is
called a Sterility Assurance Level (SAL) 10-6 = One
microbe per million items. That's it.
This is the level that your sterilizer must produce to be acceptable
as "sterile," a log of 10-6.
The level of disinfection-sterilization varies according to the
appropriate use of the item.
Topically applied "sterile" products,
a log of 10-3 is considered suitable.
Implantables require a SAL of 10-6 Log.
Normal saturated steam processing produces one log of reduction
(90% "kill") every
1 to 2 minutes at 15 Lbs. psi. and 250°F.
"Sterility" under the conditions of saturated steam can be reached
in about 12 to 15 minutes and an additional 5 minutes is considered
precautionary for "overkill."
A holding time of 15 to 20
minutes at temperature and pressure is considered adequate
It would be un-reasonable to extend this
time or leave the sterilizer run longer than 20 minutes
without known and good reason. In tattoo and piercing non-hospital environment.
can certainly give your clients the greatest confidence that the
products you are using are sterile.
The importance of cleaning
is to reduce the
original microbial load so that you can be sure of this SAL of
10-6. If you started with 10 billion microbes ( a
quantity of 1010) you can see that
to reach a probability of 1
in a million items (10-6) will require
a longer cycle per minute time or higher
temperatures. (Sterilization Technology)
Items should be cleaned, dried and placed into sterilization
pouches. Though air is a source of microbes to possibly contaminate
items after washing and before bagging, even hospital air has been
measured to only an estimated load of 128 microbes per cubic meter, so
air is not of great concern unless you live in areas that have
a heavy soil particle air count. Soils are the predominant source
Overkill is a term referring to the additional time a
sterilizer operates beyond the time necessary to reach the kill
level of sterilization. The common reference is the bacterial
spore G. Stearolthermphilus which is used for biological
monitoring of the sterilization process, which is usually in your
spore test that you send for testing.
sterilization of the BI can usually be achieved in 6 minutes with the rest of
the time considered "overkill." A holding time of 15
to 20 minutes at temperature and pressure is considered adequate
"overkill." Tests may show adverse indicators if the
test is held at either a much higher temperature or much longer
Higher temperatre and longer dwell may be evaluated as a failed
Sterilizatio: fast, higher temperature, is not
designed for routine sterilization.