Summary of Results - gov.uk...Summary of Results External Quality Assessment of Water Microbiology...

Summary of ResultsExternal Quality Assessment of Water Microbiology

Bottled and Mineral Water Scheme

Sample Numbers: BMW21A, BMW21BDistribution Number: BMW21

Distribution Date:

Results Due:

Report Date:

Data analysed by:

Report compiled by:

January 2019

22 February 2019

06 March 2019

Joanna Donn

Manchari Rajkumar

Joanna Donn

Manchari Rajkumar

This report must not be reproduced without permission of the organisers.

Authorised by: Nita Patel

Samples prepared and

quality control tested by:Angela Appea

Richard Borrill

Thomas Harper

Margaret Njenga

Zak Prior

Lili Tsegaye

Vanessa Waite

Public Health England

Food and Environmental Proficiency Testing Unit (FEPTU)

61 Colindale Avenue

London

NW9 5EQ

Tel: +44 (0)20 8327 7119

Fax: +44 (0)20 8200 8264

Email: [email protected]

Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential of 11


For further information about the scheme please refer to:

Scheme Guide:

Guide to Scoring and Statistics:

General guidance for z-scores:

Participants' enumeration results are converted into z-scores using the following formula:

The σpt-value expresses the acceptable difference between the individual participant 's result and the participants'

consensus median. The σpt-value used for calculating z-scores for all parameters in the Bottled and Mineral

Water Scheme is 0.35. A guide to interpreting z-scores follows, although laboratories must interpret their scores

in the context of their own laboratory situation.

z = -1.99 to +1.99 satisfactory

z = -2 to -2.99 or +2 to +2.99 questionable

z= < -3.00 or > + 3.00 unsatisfactory

It is usually recommended that z-scores exceeding +/-2 are investigated to establish the possible cause. As a

general rule, PHE recommends that all questionable and unsatisfactory results are investigated.

FEPTU Quality Control: To demonstrate homogeneity of the sample, a minimum of 10 LENTICULE® discs ,

selected randomly from a batch, are tested in duplicate for parameters requiring enumeration.

To demonstrate stability of the sample, a minimum of six LENTICULE discs, selected randomly from a batch, are

examined throughout the distribution period for enumeration parameters.

Public Health England uses methods stipulated in The Natural Mineral Water, Spring Water and Bottled Drinking

Water (England) Regulations (2018).

The FEPTU results are used for guidance in the preliminary intended results notification, letters are posted on the

website immediately after every distribution; electronic notification of their availability is sent to all participants.

Refer to section 17.0 of the Scheme Guide if you have experienced difficulties with any of the examinations .

Participants are reminded that reporting an incorrect or false negative results could have serious public health

implications.

Results as summarised in the performance assessment sheet included in this report, provide a more

effective indication of on-going problems with the enumeration of low levels of indicator organisms in

bottled and mineral water samples. Performance assessment cannot be undertaken as effectively if

laboratories do not participate in all distributions for the Bottled and Mineral Water Scheme.

Please contact FEPTU staff for advice and information:

Accreditation: PHE Water EQA Scheme for Bottled and Mineral Water is accredited by the United Kingdom

Accreditation Service (UKAS) to ISO/IEC 17043:2010.

Carmen Gomes or Kermin DaruwallaRepeat samples

Data Analysis

Microbiological advice

General comments and complaints

Scheme consultants

Manchari Rajkumar or Nita Patel

Nita Patel or Zak Prior

Nita Patel or Zak Prior

Julie E. Russell

Tel: +44 (0)20 8327 7119

Fax: +44 (0)20 8200 8264

Email: [email protected]

0006

https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide

https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scoring-systems-and-statistics

= participants' result expressed (expressed as a log 10 value)

= assigned value (participants' consensus median (expressed as a log 10 value))

= the fixed standard deviation for the examination (calculated by FEPTU)

Scheme Co-ordinator Nita Patel


σpt

Xpt

xi

Z = (xi-Xpt)

σpt

FEPTU's website


https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scoring-systems-and-statistics


https://www.gov.uk/government/collections/external-quality-assessment-eqa-and-proficiency-testing-pt-for-food-water-and-environmental-microbiology


Sample: BMW21A

Escherichia coli (wild strain), Klebsiella pneumoniae (wild strain), Enterococcus faecium (wild strain),

Pseudomonas aeruginosa (NCTC 10332), Clostridium perfringens (wild strain)

Contents:

Expected Results:

All counts are expressed as colony forming units (cfu) in 250mL except sporulated sulphite-reducing anaerobes which is in 50 mL and the

colony counts at 37ºC/24h and 22ºC/72h which are cfu per mL.

The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.

Parameter Coliform

bacteria

E.coli Enterococci P.aeruginosa Sporulated

sulphite-reducing

anaerobes

Colony

count

37ºC/24h

Colony

count

22ºC/72h

11473143FEPTU median 2538

4650405050No. results returned 5050

11502238Assigned value

(Participants

median all results)

2332

00.080.030.030.02Uncertainty of

assigned value*

0.040.04

00452239Participants mean

(all results)

2331

N/AN/AN/AN/AN/AParticipants median

(MPN only)

N/AN/A


(MF only)

23 (n=42)32 (n=42)

0 - 30 - 37 - 1575 - 681 - 120Expected Range 1 - 7310 - 100

00.450.150.190.11Standard

deviation**

0.230.25

34457No of outlying

counts

25

N/AN/AN/AN/AN/AFalse positives N/AN/A

00027False negatives 21

Your result

Score for

performance

assessment

Z-score

* U (Xpt) is based on results transformed to a log₁₀ scale

** Robust S* based on median absolute deviation about the participants' median (MADe)

Total sent samples 52

Not examined 1

Non returns 0


Sample: BMW21B

Enterobacter cloacae (wild strain), Enterococcus faecalis (wild strain), Pseudomonas aeruginosa (wild

strain), Clostridium bifermentans (wild strain), Kocuria kristinae (NCTC 11038)

Contents:

Expected Results:

All counts are expressed as colony forming units (cfu) in 250mL except sporulated sulphite-reducing anaerobes which is in 50 mL and the

colony counts at 37ºC/24h and 22ºC/72h which are cfu per mL.

The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.

Parameter Coliform

bacteria

E.coli Enterococci P.aeruginosa Sporulated

sulphite-reducing

anaerobes

Colony

count

37ºC/24h

Colony

count

22ºC/72h

1211142019103FEPTU median 018

4650404950No. results returned 5050

10910420894Assigned value

(Participants

median all results)

014

0.010.020.050.070.01Uncertainty of

assigned value*

N/A0.03

107101201192Participants mean

(all results)

014


(MPN only)

N/AN/A


(MF only)

N/A14 (n=42)

34 - 34533 - 3274 - 621 - 2530 - 297Expected Range N/A4 - 44

0.080.090.270.260.07Standard

deviation**

N/A0.2

02501No of outlying

counts

N/A3

N/AN/AN/AN/AN/AFalse positives 0N/A

005170False negatives N/A1

Your result

Score for

performance

assessment

Z-score

* U (Xpt) is based on results transformed to a log₁₀ scale

** Robust S* based on median absolute deviation about the participants' median (MADe)

Total sent samples 52

Not examined 1

Non returns 0


Distribution Sample Escherichia coli

score

Coliform bacteria

score

Enterococci

score

Pseudomonas

aeruginosa

score

Sporulated

sulphite-reducing

anaerobes

Colony Count

37ºC/24 h

score

Colony Count

22ºC/72 h

score

BMW21 BMW21A

BMW21B

BMW20 BMW20A

BMW20B

BMW19 BMW19A

BMW19B

Total maximum

possible score

Total percentage

Performance Assessment Sheet

Overall Performance Assessment for Distributions

BMW19, BMW20, BMW21

0

10

20

30

0

1-9

10

-19

20

-29

30

-39

40

-49

50

-59

60

-69

70

-79

80

-89

90

-99

10

0

Num

ber

of part

icip

ants

Percentage achieved of max possible

score for stipulated distributions

Performance Assessment Comment:

Participants are reminded that to take advantage of the performance

assessment overtime tool provided in the reports they need to take

part in more than one distribution a year.

Performance assessments are designed to alert participants to

on-going problems with their examinations and are provided after

every distribution. Scores are allocated to results reported for every

parameter, for every sample to help assess performance.

Cumulative scores are calculated for the current and the previous two

distributions for the Bottled and Mineral Water Scheme. Participants'

cummulative scores for each of the examinations are compared with

the maximum possible scores after every distribution.

Your overall performance with the enumerations of low levels of

indicator organisms in Bottled and Mineral Water proficiency testing

samples for the current and the previous two distributions are collated

in the chart to the right.

Performance Assessment Comment:

Laboratories that achieve less than 70% of the maximum possible score are likely to be experiencing significant problems

with their examinations and are advised to:

a) refer to the relevant distribution reports for sample-specific comments

b) refer to the website guidance documents:

c) contact the organisers for advice

https://www.gov.uk/government/collections/external-quality-assessment-eqa-and-proficiency-testing-pt-for-food-water-and-environ

mental-microbiology

https://www.gov.uk/government/collections/external-quality-assessment-eqa-and-proficiency-testing-pt-for-food-water-and-environmental-microbiology


0

5

10

15

20

<1

1-9

10-1

4

15-1

9

20-2

4

25-2

9

30-3

4

35-3

9

40-4

4

45-4

9

50-5

4

55-5

9

60-6

4

65-6

9

70-7

4

75-7

9

80-8

4

85-8

9

90-9

9

>99

No

. o

f R

esu

lts

Ou

tlyi

ng

re

su

lts

Ou

tlyi

ng

re

su

lts

BMW21A: Coliform bacteria

Ou

tlyi

ng

re

su

lts

0210

Count per 250mL

PHE score

32 Participant Median

38 FEPTU Median

0

5

10

15

20

<1

1-3

4-6

7-9

10-1

2

13-1

6

17-2

0

21-2

4

25-2

8

29-3

2

33-3

6

37-4

0

41-4

4

45-4

8

49-5

2

53-5

6

57-6

0

61-6

4

65-7

2

>72

No

. o

f R

esu

lts

Ou

tlyi

ng

re

su

lts

Ou

tlyi

ng

re

su

lts

BMW21A: Escherichia coli020

Count per 250mL

PHE score


25 FEPTU Median

0

5

10

15

20

25

30

<1

1-6

7-1

2

13-1

8

19-2

4

25-3

0

31-3

6

37-4

2

43-4

8

49-5

4

55-6

0

61-6

6

67-7

2

73-7

8

79-8

5

86-9

2

93-9

9

100-1

06

107-1

20

>120

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21A: Enterococci020

Count per 250mL

PHE score


43 FEPTU Median

0

5

10

15

20

<1

1-4

5-7

8-1

0

11-1

3

14-1

6

17-1

9

20-2

2

23-2

5

26-2

8

29-3

1

32-3

5

36-3

9

40-4

3

44-4

7

48-5

1

52-5

5

56-5

9

60-6

7

>67

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21A: Pseudomonas aeruginosa

Ou

tlyin

g r

esu

lts

0210

Count per 250mL

PHE score


31 FEPTU Median

0

5

10

15

20

25

30

<4

4-6

7-1

4

15-2

2

23-3

0

31-3

8

39-4

6

47-5

4

55-6

2

63-7

0

71-7

8

79-8

6

87-9

4

95-1

02

103-1

11

112-1

20

121-1

29

130-1

38

139-1

56

>156

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21A: Sporulated sulphite-reducing anaerobes

Ou

tlyin

g r

esu

lts

0210

Count per 50mL

PHE score


47 FEPTU Median

No data for graph

BMW21A: Colony Count 37ºC/24 h


No data for graph

BMW21A: Colony Count 22ºC/72 h


0

5

10

15

20

<1

1-3

4-6

7-8

9-1

0

11-1

2

13-1

4

15-1

6

17-1

8

19-2

0

21-2

2

23-2

4

25-2

6

27-2

8

29-3

0

31-3

2

33-3

5

36-3

8

39-4

4

>44

No

. o

f R

esu

lts

Ou

tlyi

ng

re

su

lts

Ou

tlyi

ng

re

su

lts

BMW21B: Coliform bacteria

Ou

tlyi

ng

re

su

lts

0210

Count per 250mL

PHE score


18 FEPTU Median

No data for graph

BMW21B: Escherichia coli

0

5

10

15

20

25

30

<30

30-4

3

44-5

7

58-7

1

72-8

5

86-9

9

100-1

13

114-1

27

128-1

41

142-1

55

156-1

69

170-1

83

184-1

97

198-2

11

212-2

25

226-2

39

240-2

53

254-2

67

268-2

97

>297

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21B: Enterococci020

Count per 250mL

PHE score


103 FEPTU Median

0

5

10

15

20

25

30

<1

1-1

2-2

3-3

4-4

5-5

6-6

7-7

8-8

9-9

10-1

0

11-1

1

12-1

2

13-1

3

14-1

5

16-1

7

18-1

9

20-2

1

22-2

5

>25

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21B: Pseudomonas aeruginosa020

Count per 250mL

PHE score


19 FEPTU Median

0

5

10

15

20

<1

1-3

4-6

7-9

10-1

2

13-1

5

16-1

8

19-2

1

22-2

4

25-2

7

28-3

0

31-3

3

34-3

6

37-3

9

40-4

2

43-4

5

46-4

9

50-5

3

54-6

1

>61

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21B: Sporulated sulphite-reducing anaerobes

Ou

tlyin

g r

esu

lts

0210

Count per 50mL

PHE score


20 FEPTU Median

0

5

10

15

20

25

30

<33

33-4

8

49-6

3

64-7

8

79-9

3

94-1

08

109-1

23

124-1

38

139-1

53

154-1

68

169-1

83

184-1

99

200-2

15

216-2

31

232-2

47

248-2

63

264-2

79

280-2

95

296-3

27

>327

No

. o

f R

esu

lts

Ou

tlyin

g r

esu

lts

Ou

tlyin

g r

esu

lts

BMW21B: Colony Count 37ºC/24 h020

Count per mL

PHE score


114 FEPTU Median


0

5

10

15

20

25

30

<34

34-5

0

51-6

6

67-8

2

83-9

8

99-1

14

115-1

30

131-1

46

147-1

62

163-1

78

179-1

94

195-2

10

211-2

26

227-2

42

243-2

59

260-2

76

277-2

93

294-3

10

311-3

44

>344

No

. o

f R

esu

lts

Ou

tlyi

ng

re

su

lts

Ou

tlyi

ng

re

su

lts

BMW21B: Colony Count 22ºC/72 h020

Count per mL

PHE score


121 FEPTU Median

Summary of Results - gov.uk...Summary of Results External Quality Assessment of Water Microbiology...

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