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Chapter 8*: SANITARY INSPECTION AND MICROBIOLOGICAL WATER QUALITY - page 21 / 52

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MF

Membrane filtration

APHA American Public Health Association

TTC

Triphenyl-tetrazolium chloride

ISO 9308-1 is under revision. Only one culture medium (a) has been chosen and is proposed under the same ISO reference in Table 8.7 1

Table 8.6 Standard methods for the determination of faecal streptococci (enterococci) - MF methods

ISO 7899-2 (ISO, 1984b)1

APHA

Isolation media

a) KF streptococcus agar with 1% sterile solution of TTC added to cooled basal medium b) Slanetz-Bartley agar2 with 1% sterile solution of TTC added to cooled basal medium

a) m-E agar for enterococci, or b) m-Enterococcus agar2 for faecal streptococci

Incubation conditions

Incubation conditions

44 ± 4 h at 35 ± 1 °C or 37 ± 1 °C; however, if other types of micro-organisms are expected use 5 ± 1 h at 37 ± 1 °C followed by 44 ± 0.5°C until 48 h

a) 48 h at 41 ± 0.5 °C; transfer membrane fil- to esculin iron agar for 20 min ± 2 h at 41 ± 0.5 °C b) 48 h at 35 ± 0.5 °C

Reaction a) and b) Colonies: red, brown or pink (+)

Reaction a) and b) Colonies: pink to red (+)

Confirmatory media tests

Verify a representative number of colonies by two tests:

Verify at least 10 well-isolated typical colonies by sub-culturing on:

1. BEAA Incubation conditions 48 h at 44 ± 0.5 °C 2. Catalase Reaction

BHIA Incubation conditions 24-48 h at 35 ± 0.5 °C Transfer a loop-full of growth to: BHIB Incubation conditions

Dark brown to black colonies surrounded by black halos are (+) BEAA, with a (-) catalase test = faecal streptococci

24 h at 35 ± 0.5 °C

A series of five tests are recommended for confirmation:

1. Catalase 2. Gram 3. BEA Incubation conditions 48 h at 35 ± 0.5 °C Reaction Growth = (+)

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