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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 Page 1 of 11
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 2 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
https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide
σpt
Xpt
xi
Z = (xi-Xpt)
σpt
FEPTU's website
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 3 of 11
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
N/AN/AN/AN/AN/AParticipants median
(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
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 4 of 11
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
N/AN/AN/AN/AN/AParticipants median
(MPN only)
N/AN/A
N/AN/AN/AN/AN/AParticipants median
(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
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 5 of 11
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
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 6 of 11
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
23 Participant Median
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
38 Participant Median
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
22 Participant Median
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
50 Participant Median
47 FEPTU Median
No data for graph
BMW21A: Colony Count 37ºC/24 h
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 7 of 11
No data for graph
BMW21A: Colony Count 22ºC/72 h
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 8 of 11
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
14 Participant Median
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
94 Participant Median
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
8 Participant Median
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 Participant Median
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
104 Participant Median
114 FEPTU Median
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 9 of 11
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
109 Participant Median
121 FEPTU Median
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 10 of 11
Printed at 14:24 on Wednesday, 6 March, 2019The data in FEPTU reports is confidential Page 11 of 11