Viable Particle Monitoring in Aseptic Processing Area

In pharmaceutical companies products are manufactured in classified area. Different guidelines use different terms for classification of area. Basically four classes are there in pharmaceuticals. These are class A,B,C and D as per EU GMP and Drug and cosmetic act (schedule M) and class 5,6,7,8 as per ISO guideline. For environment monitoring most of the companies follow EU GMP guidelines because this guideline has most stringent limits for viable count. In these classified area different product like injections, tablets, capsules, dry syrups, liquid syrups, ointments are manufactured. Product manufacturing and related activities performed in a particular class of area depending upon the criticality of the product. For example if sterile product are manufactured then filling operations must be performed under class A environment surrounded by class B and class B surrounded by C and then C by class D and if other less critical products are being manufactured like liquid syrups, tablets and capsules then class C and D area are suitable. Guidelines have defined different limits for viable particles for different classes. So, control over the environment is very important and critical. Any deviation from the specified limits could results in failure of the product hence rejection of batch which would be a big loss for the company. So, to prevent contamination in the product, control over the manufacturing environment is critical factor. We can't perform manufacturing activities if viable count in the area is not with in the specified limit. Different microbiological methods are used in pharmaceuticals to check viable contamination as per different guidelines and regulatory authorities as mentioned below.

1. Settle Plate exposure ( Passive air sampling)

2. Volumetric Air Sampling (Active air sampling)

3. Surface monitoring

4. Personnel monitoring

1. Settle Plate exposure ( Passive air sampling): Settle plate exposure method is also called passive air sampling because in this method no mechanical means are used for the sampling of air. In this method 90 mm soyabean casein digest agar (SCDA) media plates are used with addition of glycerol depending upon the validation study. Glycerol prevent dehydration of the media during exposure. In this method SCDA media plates are prepared and after pre-incubation of media plates are exposed in the classified area for 4 hours as per EU GMP. After completion of exposure time, plates are collected form the particular area and incubated for total 5 days at 20-25° C for 72 hours and 30-35° C for further 48 hours. After completion of 5 days incubated plates are monitored for viable count. In aseptic processing areas where sterile products are manufactured continuous monitoring should be preferred as per different guidelines in which if filling time is extended then fresh plates should be exposed to cover the whole filling time. The positive point of this method is that viable contamination could be checked for long hours. But drawback is also there with this method as it could only check viable contamination which collect or deposit over the media plate during exposure hours. So, locations for plate exposure should be properly selected and justified based on the risk assessment studies.

2. Volumetric Air Sampling (Active air sampling): This is also called active air sampling because in this monitoring method an instrument (air sampler) is used to sample the air. As per guidelines 1 m3 or 1000 litres air should be sampled per location for volumetric air sampling. Pre-incubated SCDA media plates are used for air sampling and after completion of sample plates are incubated for 5 days at 20-25° C for 72 hours and 30-35° C for further 48 hours. The positive point of this method is that it can give more accurate data of viable count as compare to settle plates exposure because air is forcefully sucked by the air sampler during sampling. But sample duration time of this method is very less and can not be used for continuous hours like settle plate method.

3. Surface monitoring: Surface monitoring is performed by two methods. 

(a) Surface monitoring by swab

(b) Surface monitoring by contact plates

In surface monitoring different surface of the manufacturing area and equipments are sampled by using swab sticks and 55 mm contact plates. If surface is irregular then swab sticks are preferred. Most commonly 25 cm² area is sampled by swab stick and if surface is flat then 55 mm contact plates are preferred for monitoring. To cover 25 cm² area we can use templates for accuracy and one more thing should be considered during surface monitoring by swab is that whole sampling area should be covered during sampling.

4. Personnel monitoring: Personnel monitoring is very critical in aseptic area. Personnels are the main source of contamination in aseptic area. Contact plates of SCDA media are used for the monitoring of personnels working in aseptic area. Depend upon the criticality and handling of products personnels are monitored for different locations like finger dabs, forehead, chest, armpits, elbows, abdomen, booties. etc. For personnel monitoring 55 mm contact plates are used but for finger dab monitoring 90 mm  SCDA plates can be used because 55 mm plates are small to cover five finger dabs properly on single plate. Personnel monitoring locations should be finalised wisely based on the product handling and criticality. All personnels should be monitored during the exit from the aseptic area.

Below is the table showing viable count limits by different methods in different grades of areas as per EU GMP guideline.

Recommended limits for microbial contamination (a)
Grade	Settle Plate cfu/4 hours (b)	Air Sampling (cfu/m3)	Surface monitoring (cfu/plate)	Personnel monitoring
A	<1	<1	<1	<1
B	5	10	5	5
C	50	100	25	-
D	100	200	50	-

Notes

(a) These are average values.

(b) Individual settle plates may be exposed for less than 4 hours.

We can see that different methods are used to check microbial contamination in manufacturing area. Each method has its own positive points and limitations. A sound environment monitoring plan to check viable contamination should include all these methods to have proper control over the manufacturing area.

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