certification of an irradiation facility

Radiat. Phys. Chem. Vol.]5, pp.l]5-]20. Pergamon Press Ltd. 1980. Printed in Great Britain.

VALIDATION/CERTIFICATION OP AN IRRADIATION FACILITY

Paul M. Borick, Ph.D. Box 54, Lakeville, Pa 18438

INTRODUCTION The present need for pharmaceutical and medical device manufacturers to utilize radiation for sterilization of their products necessitates that certain parameters be fulfilled to assure validation of the process. Some of these factors will be discussed within the scope of this paper. Sterilization by radiation is now gaining wider acceptance in the health care field. A prior review (2) indicated the two general types employed commercially - electron accelerators and the use of radioactive isotopes, e.g. - Cobalt 60. The latter process has gained wider acceptance as there is a constant emmission of penetrating gamma rays with a continuous batch process maintained. On the other hand, electron accelerators produce an instantaneous result from high energy electrons with low penetrating ability, consequently, their use requires control of those variables which affect the sterilization process. These variables include electron current, scan width and exposure time. Although the time required for sterilization by Cobalt 60 or Cesium 137 is dependent upon the concentration of curies in the source, the continuous process is maintained by setting the through-put on the conveyor system. Once these variables are placed under control and the systems validated, a highly efficient means for sterilization of a wide variety of medical products can be achieved. As with other processes, to validate and certify a radiation facility, a four step approach can be taken, to assure that the operation is. accomplishing its intended purpose. This general concept of certification consists of a four part scientific approach. These include: (I) the Installation Qualification IQ, (2) the Operational Qualification OQ, (5) the Validation and (4) the Certification phases of the process. The Installation Qualification (IQ) involves the proper installation of the equipment and its suitability to perform its intended function. Such items as proper connection to the utilities, spare parts, the existence of operating and sanitizing standard operating procedures, etc are covered. Any discrepancies in the condition of the equipment or related items are noted for corrective action to be taken. The Operational Qualification (OQ) follows next. During this phase, operating parameters of the equipment are examined and compared with a set of approved acceptance criteria with approval from various departments, i.e. - Engineering, Manufacturing, Quality Assurance and Research and Development. Parameters such as speed of operation, product handling, functioning of safety interlocks, operating controls to minimize product contamination, environmental profile tests and any and all factors which will influence the intended purpose of the

unit(s). The V a l i d a t i o n process i s i n i t i a t e d

a f t e r successful completion o f the IQ and OQ phases.

a b i l i t y o f t h e e q u i p m e n t , s y s t e m and p r o c e s s i s c h a l l e n g e d t o a s s u r e i t s i n t e n d e d within the process variable limits set forth in the protocol. It further assures identity, purity, quantity and quality of the product is maintained. A c c e p t a b l e microbial and particulate contamination levels, bioburden, tolerances "~' values, If5

function that the limits of etc. are

The

If6

P.M.

Borick

specified. The equipment is operated under these prescribed conditions for a specified time during which samples of the product are collected, examined and analyzed. These tests must prove that the equipment is capable of consistently meeting the acceptance criteria when operated in accordance with standard operating procedures. A minimum of three consecutive successful runs are usually accepted for this purpose. Once the IQ, OQ and Validation are completed, i.e. have met the acceptance criteria specified and have received final approval by representatives of management, a final Certification Document is completed. This is the means by which management expresses agreement with the test procedures, data collection, background knowledge and experience and capability of those envolved in the Validation Process. As with other processes, to assure that the radiation facility is effecting proper sterilization, various parameters must be established. The dosimetry pattern needs to be determined. Since electron accelerators have very limited penetrating ability whereas gamma rays from radioactive Cobalt are extremely penetrating, the thickness or type of material to be sterilized must he evaluated in both areas. Accelerators are quite complicated in design and construction and these electronic components are subject to breakdown, assurance thus must be given that the unit is working effectively. Since emission of gamma rays from radioactive Cobalt is a natural phenomenom, one need be more concerned with the auxiliary equipment such as the conveyor system and validate the fact that the through speed is maintained in accordance with the desired standard. ~ T H O D S AND RESULTS When bioburden studies are to be performed, one should determine the microbial count of the products to he subjected to radiation. The microbial count of various types of medical devises was determined by using the Rodac plate method of contact with the surface of the product to be tested. Various representative samples as shown in Table I were selected. The results obtained indicate that various microorganisms per square inch were obtained from a wide list of medical products. These, however, were relatively low counts. Although 2.5 Mrads is generally accepted as the sterilizing dose, lower doses may be used to sterilize those items with a low bioburden. Note that in Table If, latex surgeon's gloves were readily sterilized at the lower dose rate of 1.2 Mrads and the microbial count diminished to that point as the radiation dose was increased. Although there were no detectable changes in the texture or feel of the gloves, darkening was progressively more noticeable with higher doses of irradiation. Where the sterilization process has an undesirable effect on the item to be sterilized, such as alteration in the chemical or biological properties, a loss in tensile strength or a notable color change, it may be necessary to use an alternate sterilization process. One of the key factors in challenging a sterilization facility is through the use of biological indicators. These contain resistant microbial spores in or on various materials. Bacillus pumilus and Clostridium tetani were shown to have a high degree of resistance to radiation. Since B. pumilus is a relatively inniocuous microorganism and is readily available, it has been ~ccepted as the organism of choice for challenging the sterilization capacity of the radiation facility. As reported in a previous paper (6), it is the responsibility of the individual laboratory to determine the optimum conditions for each biological indicator as such factors as temperature, pH, or media may have an influencing effect on the microorganism used. Tests conducted showed that biological indicators containing 2.0 x 104 spores of B. pumilus ATCC #27142 irradiated with 0.45 Mrad of Cobalt 60 provided a sensitive metho~ of evaluating spore germination of outgrowth parameters. From the data shown in Table III, it was determined that 25°C and 32°C provide similar outgrowth and both showed greater positive growth than the 37oc temperature for this strain of B. pumilus. The germination of spores was influenced by pH as can be seen in Figure 1 as ~here was a significant difference between pH 6 and that of pH 7 or 8 when Difco Columbia medium was employed for growth and recovery of this biological indicator. A similar result was obtained with soybean casein digest broth as shown in Figure 2. It should he borne in mind that other factors may affect outgrowth. As an example, since B pumilus is a strict

Validation/Certification of an Irradiation Facility

]17

aerobe, oxygen made readily available to the spore will affect outgrowth. The use o f t i s s u e c u l t u r e as r e p o r t e d p r e v i o u s l y (1) (2) has g a i n e d a c c e p t a n c e as a method o f b i o l o g i c a l e v a l u a t i o n . The c e l l c u l t u r e method i s a s e n s i t i v e and r a p i d means f o r d e t e c t i n g t h e p r e s e n c e o f c y t o t o x i c a g e n t s . Table IV shows t h a t "U' c e l l s 1 were u n a f f e c t e d when v a r i o u s p o l y m e r i c m a t e r i a l s were e x p o s e d t o Cobalt 60 i r r a d i a t i o n and s u b s e q u e n t l y t e s t e d i n tissue culture. I t can be s e e n from t h e d a t a shown t h a t an e x p o s u r e o f v a r i o u s polymers t o an i r r a d i a t i o n dose o f 2.5 Mrads were no d i f f e r e n t t h a n t h e u n s t e r i l i z e d s a m p l e s . The effects of the cell culture method can be microscopically observed by the presence or absence of zones of inhibition in close proximity to the test material as shown in Illustration I. A toxic response will initiate a wide zone of inhibition adjacent to the test material. DISCUSSION The p r e s e n t c o n c e r n by t h e U.S. Food and Drug A d m i n i s t r a t i o n and t h e E n v i r o n m e n t a l P r o t e c t i o n Agency r e g a r d i n g some o f t h e h a z a r d s i n v o l v e d i n e t h y l e n e o x i d e s t e r i l i z a t i o n has g i v e n g r e a t e r impetus t o m a n u f a c t u r e r s f o r use o f r a d i a t i o n s t e r i l i z a t i o n . A major advantage of r a d i a t i o n is that it is considered a cold process which makes it attractive for heat sensitive materials. Although there is no need for concern regarding heat or humidification, other parameters must be considered in the validation of a radiation facility. Electron accelerators with their low penetrating ability require control of those variables which can affect the sterilization process. These variables include electron current, scan width and exposure time. In an earlier experience with this system, sterility failure occurred when the scan width narrowed due to a malfunction of the unit. Those items at the far end of the carrier tray did not receive an adequate dose and were shown to contain positive microorganisms after sterility testing. Since the constant emission of gamma rays from radioactive Cobalt is a natural phenomenon, one need be more concerned with the auxiliary equipment such as the conveyor system and validation of the through speed, has to be accomplished to assure that this is maintained in accordance with the desired standard. Cobalt 60 sources are now being designed to meet the demands of future increased production. This too must be validated as the size of the source is increased. Where output capacity is increased b~yond the limits of the accelerator, it may be necessary to purchase an additional unit, consequently, it too must be validated to assure proper operation. It is extremely important in challenging a sterilization facility that biological indicators be employed using the radiation resistant B. pumilus. For a further review regarding their preparation and use in various sterilization processes, one is referred to the publication by Borick and Borick (5). Where possible, the product should be inoculated with a recognized microbial strain to give assurance to the process. If this is not possible, spore strips may be substituted in determining the microbial flora of the product to be sterilized, subsequently followed by the use of biological indicators, one can gain sufficient evidence to assure oneself that the process is indeed effective. Monitoring of the sterilization process must be performed and certain assumptions cannot be made. It was shown in a prior publication (4) that less relevant vegetative microbial cells i.e. Micrococci, embedded as part of the normal flora of unprepared dehydrated culture media, could not be totally destroyed when exposed to the normally accepted radiation dose of 2.5 Mrads. In t h e USP c o l l a b o r a t i v e s t u d y p r e v i o u s l y r e p o r t e d ( 3 ) , a l t h o u g h B. pumilus s p o r e s on p a p e r s t r i p s were r e a d i l y k i l l e d a t r e l a t i v e l y low d o s e s , two o f t h e l a b o r a t o r i e s i n v o l v e d i n t h e s t u d y were u n a b l e t o d e s t r o y t h e B. pumilus s p o r e s a t 1 x 108 i n d r i e d b l o o d serum a t dose l e v e l s o f 2.5 Mrads. This would i n d i c a t e t h a t u n d e r v e r y d i f f i c u l t c i r c u m s t a n c e s , p r e c a u t i o n s h o u l d be e x e r c i s e d t o a s s u r e s t e r i l i t y o f t h e p r o d u c t . This can o n l y be a c c o m p l i s h e d t h r o u g h an effective validation~certification program.

iFootnote, mouse cells of fibreplastic origin capable of forming colonies in vitro

118

P.M.

Borick

SUMMARY The present need to utilize radiation for the sterilization of a wide variety of products and packaging materials necessitates that certain parameters be fulfilled to assure validation of the process. Those variables which can have an affect on the sterility of the product must be challenged to assure that they are maintained in accordance with prescribed standard operating procedures. As with other processes, these must be established with physical and biological challenges to the system to assure its effectiveness. TABLE 1

Numbers and Types of Microorganisms Present on Various Non-Sterile Devices

Product

Avg. Count/ Sq. In.

Surgeon's Gloves Vinyl Exam Gloves Latex Exam Gloves Nursery D i ~ e r s Adhesive Bandages Surgical Drapes Surgical Dressings (polyurethane) Surgical Dressings (gauze) Sanitary Napkins Elastic Bandages Drape Towels Drape Sheets Leggings

Type Organisms


cocci, bacilli cocci, bacilli cocci, bacilli cocci cocci, bacilli cocci mold, cocci, bacilli cocci cocci, bacilli cocci, bacilli cocci, bacilli mold, cocci, bacilli cocci

TABLE II Radiation Sterilization of Specially Formulated Latex Surgeon's Glove

Dose Mrad

Biological Indicator

Count

9.5 x 105

5.3 x 105

0.25

9.1 x 104

6.3 x 104

0.50

3.1 x 103

3.1 x 103

0.80 1.20 i. 80

4.0 x 102 0 0

2.0 x 102 0 0

0

TABLE I I I E f f e c t o f T e m p e r a t u r e on E x t e n t o f B i o l o g i c a l I n d i c a t o r * Outgrowth A f t e r 0.45 Mrad o f C o b a l t 60

Positive Growth Samples After Incubation temperature

Seven Days Number

Percent

Fourteen Days Number

Percent

25°C

226

78.5

242

84.0

32°C

235

81.6

240

83.3

37°C

219

76.0

221

76.7

* 2 x 104 B. pumilus ATCC #27142 on cotton sutures.

Validation/Certification

TABLE IV Effects of Materials

of an Irradiation

on L Cells a f t e r E x p o s u r e

Polymer

Facility

to Cobalt-60

Unsterilized

*Polyester Polyurethane * Polyethylene - low density Polymethyl Pentene Nylon 6,6 Polycarbonate Polyvinylidene Chloride *Styrene Acrylonitrile Polydimethyl Siloxane Polytetrafluoroethylene Cellulose Acetate Ethylene Vinyl Acetate Polyvinyl Chloride

1|9

Irradiation

2.5 M.R.

-

-

-

-

+ -

+ -

+ Indicates potential toxicity * Visual discoloration of p o l y m e r n o t e d

lllustration

I.

Effects of polymers o n tissue cell culture. Clear zone of inhibition - indicates no growth (potential toxicitv). I00 "pH8

/

• pH7 8o

E

~

~°

~

40

/-

: pH6

E

Time, days Fig.

1.

Effect o f pH on o u t g r o w t h spores. Columbia broth.

of

irradiated

B.~u8

ATCC 27142

]20

P . M . Borick

B IB LI OGRAPHY i.

Abodeely, R.A. and P.M. Borick Tissue Culture as a method for the evaluation of biomedical materials. Proc. 24th Ann. Meeting Tissue Culture Assoc., Boston, Mass., JLme 4-7, 1973.

2.

Borick, Paul M, Biological, Chemical and physical effect of radiation on various products. Proc. Cosmetics, Toiletries and Fragrance Assoc., Technology Seminar, Saddlebrook, N.J., April 10-11, 1978.

3.

Borick, Paul M., The appplicability of sterility of various devises utilized in the medical-surgical field. Bul Parenteral Drug Assoc., 1976, 30 247-254.

4.

Borick, Paul M., A.N. Parisi and I.T. Zuk, Use of biological indicators to affect a seven day sterility release. Proc. Technical Symposum Health Industries Assoc., Washington, D.C., 1973, pp. 112-122.

5.

Borick, Paul, M and J.A. Borick, Sterility testing of pharmaceuticals, cosmetics and medical devises in Quality Control in the Pharmaceutical Industry, 1977, Vol. I, pp. 1-38, Academic Press Inc., New York.

6.

Zuk, I.T., A.N. Parisi and P.M. Borick, Optimization of biological indicator outgrowth and recovery conditions, 72nd Ann. Mtg. Amer. Soc. Microbiol,, Philadelphia, Pa. April 23, 1972. I00

/

......

801

pH?

pH8

I 60

~----

pHr~

40

u

20

o

2

~

L

~

,'o

Growth, doys

,'2

,~

Fig.2. Effect of pH on growth irradiated B. pumilus ~pores. Soybean casein digest broth.