Improving the aseptic transfer procedures in hospital pharmacies part A: methods for the determination of the surface bioburden on ampoules and vials.

Objectives: To develop methods for surface bioburden determination of ampoules and vials to be used in the validation of the disinfection procedures and in routine monitoring of ampoules and vials.

Methods: The surface bioburdens of ampoules and vials are determined before and after disinfection by contact plates and total immersion.

Results: The mean surface bioburdens of non-disinfected ampoules and vials taken straight from the original boxes are 2.4 and 5.01 cfu (total immersion; n = 20), and 0.97 and 0.94 cfu (contact plates; n = 60). The mean surface bioburdens of ampules and vials after disinfection by wiping are 1.15 and 7.50 cfu (total immersion; n = 20), and 0.12 and 0.10 cfu (contact plates; n = 60). The high number of cfu on vials (total immersion) indicate hidden cfu around the neck not removable by wiping and not detected by contact plates. Total immersion needs special laboratory facilities and is expensive (about €50 a sample). Therefore, it is less appropriate for use in routine monitoring. However, because of the high recovery, it is the method of choice for the validation of the disinfection procedure. Surface bioburden determination by contact plates is relatively simple. Non-flat surfaces cannot be reached, but the recovery from the touched flat part of the surface is high (around 50%). The recovery from swabs is low (around 10%). Another disadvantage of swabs is the laboratory work after sampling. We therefore advise contact plates for routine monitoring. To get a reliable value of the mean surface bioburden at least 30 samples need to be examined.

Conclusion: Total immersion is the method of choice for the determination of the effectiveness of a disinfection procedure for ampoules and vials. Contact plate is the method of choice for routine monitoring of the surfaces of ampoules and vials.