AS 4276.17.1:2016 pdf free
AS 4276.17.1:2016 pdf free.Water microbiology Method 17.1: Spores of Clostridium perfringens – Membrane filtration method
The procedure shall be as follows:
(a) For confirmation, select all target colonies for counts of 1 to 10, and select at least 10 target colonies at random for counts above 10.
NOTE: The requirement to select up to 10 colonies for confirmation contrasts with other AS 4276 Standards where up to only 5 is the requirement. This is because this method is typified by somewhat variable confirmation rates where low rates may be seen,due to interfering sulfite reducing Clostridia other than C. perfringens. Increasing the number of colonies selected for confirmation reduces the measurement uncertainty associated with the practice of partial confirmation.
(b) The selected colonies are subcultured onto Columbia blood agar or a suitable nutrient rich agar with or without blood (e.g. Columbia agar base, tryptone soya agar). For waters with high background counts or where other sulfite reducing bacteria may make it difficult to isolate C. perfringens (e.g. spreading colonies) the use of Columbia blood agar (or a suitable nutrient rich agar containing blood) with neomycin (0.01%) may be beneficial.
(c) Incubate anaerobically at 44 ±1°C for 21 ±3 h.
NOTE: Non-selective media are preferred when undertaking confirmation testing. Generally,there are some strains of a target microorganism that are inhibited by a given selective agent.The procedure shall be as follows: Pre-warm acid phosphatase reagent to approximately 36°C for 30- 60 minutes prior to use. Add 2 to 3 drops of the acid phosphatase reagent onto filter paper and spread colonies, grown anaerobically on Columbia blood or a suitable nutrient rich agar plate, onto the phosphate reagent soaked paper. A purplish colour developing within 3 to 4 min is considered as a positive reaction.
Since the black colour of the colonies rapidly fades and finally disappears under aerobic conditions, the plates have to be counted within 30 min after completion of the anaerobic incubation. If a number of anaerobic jars are used, the plates should be checked jar by jar or in portions if the incubation was performed in an anaerobic incubator.AS 4276.17.1 pdf free download.
