cdrh - cber tse instrument decontamination project stanley brown, katharine merritt, terry woods,...
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CDRH - CBER TSE INSTRUMENT DECONTAMINATION PROJECT
Stanley Brown, Katharine Merritt,
Terry Woods, Scott McNamee and Deanna Busick
CDRH/ OST / DMMS & DLS
David Asher, Kitty Pomeroy, Rolf Taffs
CBER / OBRR / DETTD
with funding from
FDA, Office of Science & Health Coordination
TSEAC 17 July 03
INSTRUMENTS
• Surgical – primarily reusable.
but also “Single” Use Devices, SUDs
exposed to contaminated human tissues
• tissue processing
exposed to animal tissues
Disclaimer• The methods used were selected by the
research teams, as reasonably inexpensive approaches, within the constraints of the FDA lab facilities and manpower, to:
1. provide an understanding of the issues 2. examine the feasibility of decontamination
protocols recommended by WHO
• These presentations do not constitute regulatory endorsement as methods to validate decontamination protocols.
WHO protocols1. autoclave in 1 N NaOH, 121°C, 30 min2. immerse 1 hr in: 2a. 1 N NaOH, or 2b. sodium hypochlorite (20,000 ppm Cl) --- then autoclave in water 121°C, 1 hr3. soak in NaOH or Bleach, rinse then steam autoclave, 1 hr
*** all followed by routine (ultrasonic) cleaning, rinsing, and sterilization
CDC website notes & warnings
1. autoclaving in NaOH
can wreck autoclave and operators
2b. soaking in bleach
can wreck instruments
• these are based on CDRH studies
CDRH / OST TSE Decontamination Research
Issues based on WHO recommendations
1. safety of autoclaving in NaOH
2. effects of protocols 1 & 2 on instruments
3. develop pins as model “instruments”
4. Protein & Microbial decontamination
1. Use of Containment Pans and Lids for Autoclaving
Caustic Solutions
Stanley A. Brown, Katharine Merritt
Am J. Infection Control
31: 257-260, 2003.
The problem• WHO method #1:
• place instruments in 1 N NaOH
and autoclave at 121°C.
• Some autoclave manufacturers have said:
“do that and you have no warranty”
• Note: must use gravity displacement autoclaves, with liquid (no vacuum) cycles.
MethodsA. 1 L of NaOH in a pan & cover
B. 10 ml NaOH in beaker in a pan & cover
1. Place in table top
gravity displacement autoclave
2. repeat 1 hr sterilization cycles
3. measure pH inside and out of pan & lid
4. measure pH of autoclave
6 liter water reservoir
somepansandlids
Lid (F) Pan (4), Nalgene Instrument pipet sterilizing pan
filled with 1 liter of NaOH
note gutter drain slot
lid contained inside pan lip
Lid (D) Pan (2), NaOH in an open beaker in the pan
Results – autoclaving in NaOH• No pH changes outside the containment • Condensate inside container was caustic• No pH change in water reservoir
• Conclusion: Autoclaving in NaOH can be done without damage to autoclave interior
• Caution: handle hot caustic with care• Note: can not be done in Central Services • Note: may require larger (approved) pans
2. The Effects on the instruments of the WHO protocols
for TSE decontamination
manuscript in preparation
Questions:
1. Will protocols cause corrosion?
2. Are certain instruments more at risk?
3. Does corrosion affect function?
Methods
• Bought a bunch of instruments “surgical” from Roboz “Lab” from V W R some “Germany” some “Pakistan”• Repeated 1 hr cycles: autoclave in 1 N (3.9%) NaOH soak in 1 N (3.9%) NaOH soak in 6% NaOCl (28,500 ppm Cl) autoclave in water
1 hr bleach –vs- 5x autoclave in NaOHNeedle holder carbide jaws
1x bleach -vs- 5x autoclave in NaOHneedle holder gold handles
Germany –vs- Pakistan 5x autoclave in NaOH
Germany –vs- Pakistan 5x soak in bleach
Results – Instrument Corrosion
• Autoclaving in NaOH – darkening in some box joints titanium gets very dark
• soaking in NaOH – no changes
• soaking in NaOCl bleach – “good” instruments do OK exception: gold handles, carbide jaws “not so good” corrode, esp. welds & finger rings
BUT: if it’s going to corrode, it will do it first try; no need for long experiments
3. Pins for “instruments”
Needed a model “instrument”
1. like 25g needle & 1/2 cc syringe
used in CBER hamster model
2. suspend over 96 well plates
for serial dilutions of:
bacteria, viruses, brain homogenate
3. autoclavable
0.5 x 15 mm SS wire glued in Eppendorf tip
pins over 96 well plate
4. CDRH PIN STUDY THREE QUESTIONS TO BE ANSWERED
1. Will blood and tissue adhere to the pins?
2. Will the WHO cleaning protocols remove the blood and tissue?
3. Does damage to the instruments affect blood and tissue adherence and cleaning? (Stainless steel vs piano wire)
blood and tissue adherence
• Pins placed in a rack and immersed in slab of liver for 1 hr, left to dry for 24 hrs
• Pins in rack and into 96 well plate with sheep blood 1 hr, left to dry for 24 hours
1. US clean: 60°C, 30 min Klenzyme, then DW
2. autoclave: 1 hr in NaOH, then US clean
3. bleach 1 hr: then US clean
4. uncleaned controls
Results – blood and tissue
• Uncleaned controls: More protein adhered to the pins from liver than from blood
• Damaged pins not more adherent
• Repeat exposure and US cleaning (5 times)
did not result in increase of protein adherence
• All cleaning protocols removed the protein as detected by Bradfords (less than 1 ul of blood)
Bacterial Adherence
• Pins placed in a suspension of (S. epidermidis)
incubated for 24 hours
then left to dry
• Then U.S. cleaning or WHO
• Then they were inserted into agar in a test tube and incubated for 24 hours
Results - Bacterial Adherence (1)
• autoclaving and bleach killed them all
• tried “modified” WHO protocols:
Dropped autoclave in 1N NaOH
All US cleaning done at room temperature
Bacteria Results (2)with modified WHO Approach
• Only the pins treated with bleach
showed no growth
??? killed or cleaned??
• The other procedures had fewer bacteria
than the untreated control,
but bacteria were present
SEM of microbes on uncleaned pin
CDRH Studies’ Conclusions
• Some WHO protocols can damage
some surgical instruments
• The discoloration from NaOH does not seem to impair function or cleaning
• Question: if bacteria were removed in the cleaning protocols? The final sterilization procedure would kill them.
• Question: can prions be removed – CBER
Now turn the podium over to Dr. David Asher from CBER