CAGE PROCESSING in Animal Facilities - Felasa

surfaces stay soil free. For an evenly spread of test soiling on the surface, the test strip must be thoroughlydegreased (the use of alcohol alone is not sufficient; it is recommended to use fat solvents or laboratory detergents,or to process the test strip in an automated washer at approximately 60 °C). 0.1 ml of the test soilingis applied evenly to each contaminated area and dried for 24 hours at 22 °C ± 1 °C and a relative air humidityof 50% ± 10% (temperature and air humidity must be recorded in the test report). The testing must be donewithin 10 days after the test strip was produced. It is recommended to store the test strip at room temperaturefree of contamination (e.g. in aluminium foil or glass tubes). The number of organisms per contaminated piecemust be high enough, considering the detection limit, to allow for evaluation of the reduction factor (at least 1x10 7 CFU/test strip). Contaminated pieces can be acquired at, for example, SGS Germany GmbH, Hamburg.7.2.3.4 Evaluation of test stripsAfter the washer finished its cycle the test strips are detached under aseptic conditions (e.g. by moving eachwith sterilised tweezers). Each piece is then examined visually for residues of test soiling before being transferredinto a 10 ml phosphate buffer solution (PBS), with inactivating substances, where applicable.Composition of the phosphate buffer solution (PBS)Solution A:16 g NaCl,0.4 g KCl,0.4 g KH 2PO 4To dissolve in 1600 ml distilled waterSolution B: 0.2 g CaCl 2To dissolve in 200 ml distilled waterSolution C: 0.2 g MgSO 4To dissolve in 200 ml distilled waterSolutions A to C require a separate Steam sterilisation. After cooling down completely, they should be mixedunder sterile conditions, by adding the inactivating substance, where applicable.The test organisms are recovered by extracting them from the test strips that were transferred into test tubes.The extraction is done by putting the test tube racks on shaking devices with a frequency of approximately 500rpm for at least 20 minutes. After that, the number of organisms can be determined from the shaken liquid. Itmust be indicated what method was used.Parallel to that, the transport controls are equally transferred into 10 ml PBS and analysed, without being treatedin the washer.Valid methods for determining the number of organisms are:• dilution series and surface culture,• spiral plater.A suitable selective culture medium (e.g. Kanamycin Esculin Acid Agar) can help suppress the growing ofother organisms. The incubation time of the spiked culture media at 36 ± 1 °C is 48 hours. It must be indicatedwhat methods were used for determining the number of organisms as well as what culture solutions and culturemedia were used.The reduction of organisms count results from the difference of the number of detected CFU of test organismson the treated test strips and from the average value of the three untreated test strips (transport controls). Thereduction factor must at least add up to 5 lg levels with 90% of the used test strips.7.3 Test procedures for washing and decontamination of water bottlesWith water bottles, the washing performance is assessed by means of test soiling directly contaminating thebottle surface.Cage Processing in Animal Facilities · 4th issue · 2013 53