Biological indicators of steam sterilization processes with Geobacillus stearothermophilus (ATCC 7953) spores self-contained

DESCRIPTION
USP (United States Pharmacopoeia) and EP (European Pharmacopoeia) standards, recommend to use bioindicators during steam sterilization processes of pharmaceuticals, drugs in vials, culture media, medical instruments and more . STERILtest GST E6/E5 self-contained are made of a thermoplastic tube, with a cup permeable to steam , that contains an ampoule with a nutrient broth with a pH indicator and a disc impregnated with Geobacillus stearothermophilus (ATCC 7953) spores in predefined concentrations (E6 = 1-5 x 10⁶ UFC/disc; E5 =1-5 x 10⁵ UFC/disc). These bioindicators are used for regular control of steam sterilization cycles (for ie. 15 minutes at 121 °C) and control of any steam autoclave functionality. Biological indicators STERILtest GST E6/E5 self-contained are produced under strictly controlled conditions in order to satisfy the requirements indicated in the USP current edition and in accordance with ISO 11138 and EN 866 standards.

PRINCIPLE
STERILtest GST E6/E5 self-contained contains, inside a thermoplastic tube, a paper disc impregnated with Geobacillus stearothermophilus (ATCC 7953) spores in predefined concentrations (E6= 1-5 x 10⁶ UFC/disc; E5 = 1-5 x 10⁵ UFC/disc). The tube contains also a small glass ampoule with nutrient broth with a pH indicator. Spores are completely killed off after 15 minutes of sterilization at 121 °C and therefore during the following incubation in the culture medium contained inside the ampoule, they are not able to grow and to modify the medium’s colour. At a lower temperature or at a shorter sterilization time, spores partially survive and therefore during the incubation are able to grow and to modify the medium’s colour.

INSTRUCTION FOR USE

1. Take one or more STERILtest GST E6/E5 self-contained from the package.
2. Put the STERILtest GST E6/E5 self-contained on the bottom, in the centre, inner sides and on the critical points of the autoclave or in positions decided by user.
3. For autoclaves with capacity up to 250 litres put two STERILtest GST E6/E5 self-contained for each selected point of the autoclave. For autoclaves with capacity higher than 250 litres put six or more STERILtest GST E6/E5 self-contained in each selected point.
4. Remove the STERILtest GST E6/E5 self-contained after sterilization cycle, and activate them by breaking the glass ampoule through pressure to permit contact between culture medium and spores.
5. Incubate the activated STERILtest GST E6/E5 self-contained at 55-60 °C (131-140 °F) for at least 48 hours or for a different time validated by user.
6. Incubate, at the same conditions of time and temperature, a STERILtest GST E6/E5 self-contained, activated by breaking the glass ampoule through pressure, not submitted to the sterilization cycle and belonging to the same batch, as spore growth control (positive control).
7. Examine STERILtest GST E6/E5 self-contained colour and interpret results as per evalutation TABLE: a change of medium’s colour from violet/clear to yellow/turbid indicates a microbial growth and therefore an unsuccessful sterilization. On the contrary, the persistence of the medium’s initial colour (violet/clear) indicates absence of microbial growth and therefore a successful sterilization.

EVALUATION
Geobacillus stearothermophilus (ATCC 7953) spores are killed off if the sterilization cycle has been efficient: in this case the broth contained in STERILtest GST E6/E5 self-contained remains violet/clear even after incubation at 55-60 °C (131-140 °F) for at least 48 hours or for the selected time. If the sterilization cycle has not been efficient, spores partially survive and the broth contained in STERILtest GST E6/E5 self-contained turns yellow/turbid after incubation at 55-60 °C (131-140 °F) for at least 48 hours or for the selected time. The broth contained in STERILtest GST E6/E5 self-contained not submitted to the sterilization cycle and used as spore growth control has to turn yellow/turbid after incubation. On the contrary, the test must be repeated after having investigated the causes of the negative result.

VIALS TREATMENT AFTER USE
After use, sterilize the positive STERILtest GST E6/E5 self-contained (yellow/turbid) in autoclave at 121 °C for at least 30 minutes and eliminate them in accordance with the procedures of the laboratory.

STORAGE
Store the product at 2-8 °C: in these conditions it maintains its validity until the expiry date indicated on the label.

BIBLIOGRAPHY
1. United States Pharmacopoeia latest edition.
2. European Pharmacopoeia latest edition.
3. ISO 11138 EN 866 latest edition.

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