Enumeration of coliform bacteria and Escherichia coli

soake 

HPA STANDARD METHOD 

ENUMERATION OF 

COLIFORM BACTERIA 

AND 

ESCHERICHIA COLI 

BY MEMBRANE FILTRATION 

W 2 

Issued by Standards Unit, Evaluations and Standards Laboratory 

Centre for Infections 

ENUMERATION OF COLIFORM BACTERIA AND ESCHERICHIA COLI BY MEMBRANE FILTRATION 

Issue no: 4.1 Issue date: 03.10.07 Issued by Standards Unit, Evaluations and Standards Laboratory in conjunction with the 

Regional Food, Water and Environmental Coordinators Forum Page 1 of 15 

Reference no: W 2i4.1 

This SOP should be used in conjunction with the series of SOPs from the Health Protection Agency 

www.evaluations-standards.org.uk 

Email: standards@hpa.org.uk

STATUS OF NATIONAL STANDARD METHODS 

National Standard Methods, which include standard operating procedures (SOPs), algorithms and 

guidance notes, promote high quality practices and help to assure the comparability of diagnostic 

information obtained in different laboratories. This in turn facilitates standardisation of surveillance 

underpinned by research, development and audit and promotes public health and patient confidence 

in their healthcare services. The methods are well referenced and represent a good minimum 

standard for clinical and public health microbiology. However, in using National Standard Methods, 

laboratories should take account of local requirements and may need to undertake additional 

investigations. The methods also provide a reference point for method development. 

National Standard Methods are developed, reviewed and updated through an open and wide 

consultation process where the views of all participants are considered and the resulting documents 

reflect the majority agreement of contributors. 

Representatives of several professional organisations, including those whose logos appear on the 

front cover, are members of the working groups which develop National Standard Methods. Inclusion 

of an organisation’s logo on the front cover implies support for the objectives and process of preparing 

standard methods. The representatives participate in the development of the National Standard 

Methods but their views are not necessarily those of the entire organisation of which they are a 

member. The current list of participating organisations can be obtained by emailing 

standards@hpa.org.uk. 

The performance of standard methods depends on the quality of reagents, equipment, commercial 

and in-house test procedures. Laboratories should ensure that these have been validated and shown 

to be fit for purpose. Internal and external quality assurance procedures should also be in place. 

Whereas every care has been taken in the preparation of this publication, the Health Protection 

Agency or any supporting organisation cannot be responsible for the accuracy of any statement or 

representation made or the consequences arising from the use of or alteration to any information 

contained in it. These procedures are intended solely as a general resource for practising 

professionals in the field, operating in the UK, and specialist advice should be obtained where 

necessary. If you make any changes to this publication, it must be made clear where changes have 

been made to the original document. The Health Protection Agency (HPA) should at all times be 

acknowledged. 

The HPA is an independent organisation dedicated to protecting people’s health. It brings together 

the expertise formerly in a number of official organisations. More information about the HPA can be 

found at www.hpa.org.uk. 

The HPA aims to be a fully Caldicott compliant organisation. It seeks to take every possible 

precaution to prevent unauthorised disclosure of patient details and to ensure that patient-related 

records are kept under secure conditions 1 . 

More details can be found on the website at www.evaluations-standards.org.uk. Contributions to the 

development of the documents can be made by contacting standards@hpa.org.uk. 

Please note the references are now formatted using Reference Manager software. If you alter or delete text without 

Reference Manager installed on your computer, the references will not be updated automatically. 

Suggested citation for this document: 

Health Protection Agency (2007). Enumeration of coliform bacteria and Escherichia coli by membrane 

filtration. National Standard Method W 2 Issue 4. 

http://www.hpa-standardmethods.org.uk/pdf_sops.asp. 








INDEX 

STATUS OF NATIONAL STANDARD METHODS ................................................................................2 

INDEX......................................................................................................................................................3 

AMENDMENT PROCEDURE .................................................................................................................4 

SCOPE OF DOCUMENT ........................................................................................................................5 

INTRODUCTION .....................................................................................................................................5 

BACKGROUND........................................................................................................................................5 

1 DEFINITIONS ...................................................................................................................................6 

2 PRINCIPLE.......................................................................................................................................6 

3 SAFETY CONSIDERATIONS ..........................................................................................................6 

3.1 SAMPLE TRANSPORT AND STORAGE .............................................................................................6 

3.2 SAMPLE PROCESSING..................................................................................................................6 

4 EQUIPMENT.....................................................................................................................................7 

5 CULTURE MEDIA AND REAGENTS ..............................................................................................7 

6 SAMPLE PROCESSING ..................................................................................................................8 

6.1 SAMPLE PREPARATION AND DILUTIONS .........................................................................................8 

6.2 FILTRATION AND INCUBATION .......................................................................................................9 

6.3 COUNTING OF COLONIES..............................................................................................................9 

6.4 CONFIRMATORY TESTS ................................................................................................................9 

7 CALCULATION OF RESULTS ......................................................................................................10 

8 REPORTING...................................................................................................................................10 

9 QUALITY CONTROL .....................................................................................................................11 

9.1 MEMBRANE FILTRATION .............................................................................................................11 

9.2 CONFIRMATORY TESTS ..............................................................................................................11 

10 REFERENCE FACILITIES .............................................................................................................12 

11 ACKNOWLEDGEMENTS AND CONTACTS ................................................................................12 

FLOWCHART SHOWING THE PROCESS FOR THE ENUMERATION OF COLIFORM BACTERIA 

AND ESCHERICHIA COLI BY MEMBRANE FILTRATION ...............................................................13 

REFERENCES ......................................................................................................................................14 








AMENDMENT PROCEDURE 

Controlled document 

reference 

Controlled document title 

W 2 

Enumeration of coliform bacteria and Escherichia coli by membrane 

filtration 

Each National Standard Method has an individual record of amendments. The current amendments 

are listed on this page. The amendment history is available from standards@hpa.org.uk. 

On issue of revised or new pages each controlled document should be updated by the copyholder in 

the laboratory. 

Amendment 

Number/ 

Date 

7/ 

04.10.07 

Issue no. 

Discarded 

Insert 

Issue 

no. 

Page Section(s) involved Amendment 

4 4.1 9 6.2 Filtration and 

incubation 

Corrected the temperature 

tolerance from 44°C ± 1°C to 

44°C ± 0.5°C in line with MDW 

2002. 








ENUMERATION OF COLIFORM BACTERIA AND 

ESCHERICHIA COLI BY MEMBRANE 

FILTRATION 

SCOPE OF DOCUMENT 

The method described is applicable to the enumeration of coliform bacteria and Escherichia coli in 

water samples intended for human consumption and in pool waters by the membrane filtration 

technique. It may be used for environmental and recreational water samples but not for designated 

bathing waters sampled under the bathing water regulations 2 . These samples are analysed using 

methods detailed by the Environment Agency. 

INTRODUCTION 

Background 

Coliform bacteria are widely regarded as the most reliable microbiological indicator of water quality. 

They are found in the human and animal intestine and may serve as indicators of potential faecal 

pollution but may also be environmental in origin. ‘Faecal coliform bacteria’ and E. coli are only found in 

human and animal intestines and tests for their presence in water are necessary to confirm that pollution 

is of human and/or animal origin. The term ‘faecal coliform’ is not precise and is consequently not used 

in this National Standard Method (NSM). In the context of water microbiology in the United Kingdom 

faecal coliform bacteria are regarded as being E. coli. 

Coliform bacteria and E. coli are sensitive to the disinfection processes used in water treatment and do 

not usually multiply in water particularly in temperate zones. These organisms should not be present in 

a 250 mL sample of mineral waters or drinking waters in bottles and containers or 100 mL for other 

waters of potable quality 3-11 . 

This method is based on the method described in the Microbiology of Drinking Water 2002 document 12 . 








1 DEFINITIONS 

In the context of this method the following definitions apply: 

Presumptive coliform bacteria 

Organisms which produce acid from lactose and form all shades and sizes of yellow colonies on 

membranes soaked in membrane lauryl sulphate broth (MLSB) after incubation at 30°C for 4 

hours followed by 37°C for 14 hours. 

Presumptive E. coli 

Organisms which produce acid from lactose and form all shades and sizes of yellow colonies 

on membranes soaked in MLSB after incubation at 30°C for 4 hours followed by incubation at 

44°C for 14 hours. 

Coliform bacteria (total coliforms) 

Presumptive coliform bacteria which produce acid from lactose at 37°C within 48 hours, are 

oxidase negative and possess β-galactosidase. 

E. coli 

Presumptive E. coli which also produce indole from tryptophan after incubation at 44°C for 24 

hours. Most strains produce β-glucuronidase. 

2 PRINCIPLE 

A measured volume of the sample or a dilution of the sample is filtered through a membrane 

that is capable of retaining the organisms. The membrane is incubated on an absorbent pad 

saturated with a selective differential broth medium. Colonies of the target organisms are 

counted, confirmatory tests carried out and the result calculated as the colony count per 

100 mL or 250 mL of sample. 

3 SAFETY CONSIDERATIONS 13-18 

Normal microbiology laboratory precautions apply. 

Care should be taken where manual lifting of large volumes of water is required. 

3.1 SAMPLE TRANSPORT AND STORAGE 

Compliance with current postal and transportation regulations as stated in the Advisory 

Committee on Dangerous Pathogens 2005 19 is essential. 

3.2 SAMPLE PROCESSING 

Care must be taken when using a boiling waterbath (National Standard Method: W1 Section 

2) 20 . 

• Amyl alcohol and concentrated hydrochloric acid used in the preparation of Kovacs reagent 

must be handled with care 

• Acid protective gloves are to be worn when performing the indole test 

The above guidance should be supplemented with local COSHH and risk assessments 








4 EQUIPMENT 

Usual laboratory equipment and in addition: 

• Membrane filtration manifold 

• Filter funnels graduated to 50 mL and 100 mL 

• Pyrex vacuum flask with protective jacket or equivalent: large volume eg 5 L 

• Vacuum pump with moisture trap or protective filter, or alternative vacuum source 

• Stainless steel flat tipped forceps or sterilisable equivalent 

• Boiling waterbath (instrument steriliser) 

• Cycling incubator: 30°C ± 1.0°C and 37°C ± 1.0°C 

• Cycling incubator: 30°C ± 1.0°C and 44°C ± 0.5°C 

• Incubator: 37°C ± 1.0°C 

• Water bath: 44°C ± 0.5°C 

• Petri dishes 

• Sterile absorbent pads 

• Cellulose ester 0.45 µm gridded filters 

• Automatic pipettors and associated sterile pipette tips capable of delivering up to10 mL 

and 1 mL volumes (optional) 

• Pipettes / (sterile total delivery) 10 mL and 1 mL, graduated in 0.1 mL (optional) 

• Pastettes 

5 CULTURE MEDIA AND REAGENTS 

Media with the following formulations should be used. Follow MDW 2002 12 

preparation and shelf-life times. 

for in-house 

Equivalent commercial media may be used; follow the manufacturer’s instructions. 

Peptone saline diluent (Maximum recovery diluent) 

Peptone 

Sodium chloride 

Water 

pH 7.0 ± 0.2 at 25°C 

1.0 g 

8.5 g 

1 L 

Membrane lauryl sulphate broth (MLSB) 

Peptone 

Yeast extract 

Lactose 

Phenol red 

Sodium lauryl sulphate 

Water 

pH 7.4 ± 0.2 at 25°C 

40.0 g 

6.0 g 

30.0 g 

0.2 g 

1.0 g 

1 L 

Lactose peptone water (LPW) 

Peptone 


Lactose 

Andrades indicator 

Water 

10.0 g 

5.0 g 

10.0 g 

10 mL 

1 L 








pH 7.5 ± 0.2 at 25°C 

2% Tryptone water (TW) 

Tryptone 


Water 

pH 7.5 ± 0.2 at 25°C 

20.0 g 

5.0 g 

1 L 

MacConkey agar (MA) 

Bile Salts 

Peptone 

Lactose 


Neutral red 

Agar 

Water 

pH 7.4 ± 0.2 at 25°C 

5.0 g 

20.0 g 

10.0 g 

5.0 g 

0.05 g 

12.0 g 

1 L 

Nutrient agar (NA) 

Meat extract 

Peptone 


Agar 

Water 

pH 7.5 ± 0.2 at 25°C 

10.0 g 

10.0 g 

5.0 g 

15.0 g 

1 L 

Kovacs reagent 21 

p – Dimethylaminobenzaldehyde 

Amyl alcohol (analytical grade reagent, 

free from organic bases) 

Hydrochloric acid (concentrated) 

5.0 g 

75 mL 

25 mL 

Oxidase reagent (prepare fresh or use commercially prepared strips etc) 

Tetramethyl – p – phenylenediamine 

Hydrochloride 

Water 

0.1 g 

10 mL 

6 SAMPLE PROCESSING 

6.1 SAMPLE PREPARATION AND DILUTIONS 

The nature of the request and condition of the sample should be noted on arrival. 

Water samples should be received and handled as described in National Standard Method: 

W 1 Section 5 20 . 

The sample should be stored and transported at 2°C – 8°C. Samples should be analysed as 

soon as is practicable on the day of collection. In exceptional circumstances, if there is a 

delay, storage under the above conditions should not exceed 24 hours before the 

commencement of analysis. 

Following the procedures laid down in National Standard Method: W 1 Section 6 20 , select 

suitable volumes for analysis and prepare any necessary dilutions. 








6.2 FILTRATION AND INCUBATION 

Place an absorbent pad in each Petri dish and add sufficient MLSB to saturate the pad 

(usually 2.5 mL depending on the brand of pad) and soak for at least 5 minutes. If 

necessary, remove any excess medium from the saturated pad using, for example, a sterile 

pipette / pastette, before the membrane is placed on the pad. For each brand of pad it is 

important to check the amount of medium that is to be added and the time necessary for 

soaking in order to prevent drying out during incubation. 

Following the procedures laid down in National Standard Method: W 1 Section 6 20 : 

Filter a measured volume of sample through the membrane. For bottled mineral waters use 250 

mL water, for other potable quality waters use volumes of 100 mL. For surface waters use 100 

mL and, if expected to be highly polluted, use 10 mL and 1 mL volumes. Use two filters for each 

sample, one for coliform bacteria and one for E. coli. For mains drinking water and pool waters 

it is acceptable to use a single membrane where the result is likely or expected to be negative, 

incubated at 37°C, for both coliform bacteria and E. coli. 

Place the membrane on a pad soaked in MLSB. Put the membranes and pads in a sealed 

container and place in an incubator as follows: 

For coliform bacteria: 30°C ± 1°C for 4 hours ± 1 hour followed by 37°C ± 1°C for 14 hours ± 1 

hour. 

For E. coli: 30°C ± 1°C for 4 hours ± 1 hour followed by 44°C ± 0.5°C for 14 hours ± 1 hour. 

6.3 COUNTING OF COLONIES 

After a minimum total incubation period of 18 hours, enumerate the presumptive coliform 

bacteria and presumptive E. coli by counting and recording all yellow colonies irrespective of 

size. As colony colours are liable to change on cooling and standing, it is necessary to perform 

the count within 15 minutes of removing from the incubator 12 . It is important to note factors 

affecting the result eg when pink colonies are present in high numbers they may interfere with 

the growth or count of lactose fermenting colonies. 

6.4 CONFIRMATORY TESTS 

Select colonies for confirmation as described in National Standard Method: W 1 Section 6.3 20 . 

Sub-culture colonies from both the 37°C and 44°C membranes for confirmation as coliform 

bacteria and E. coli. Presumptive coliform bacteria isolated at 37°C may confirm as 

E. coli and presumptive E. coli colonies isolated at 44°C may confirm as coliform bacteria but 

not E. coli. Also, colonies may be isolated on only one of the two membranes. When only 

one membrane has been used and incubated at 37°C, colonies should be confirmed for both 

coliform bacteria and E. coli. If the confirmed count for E. coli from the 44°C membrane filter 

is greater than the confirmed count for coliform bacteria from the 37°C membrane filter, then 

the higher count must be recorded as the confirmed count for coliform bacteria disregarding 

the colonies on the 37°C membrane. For example, if zero coliform bacteria have been 

isolated at 37°C but two E. coli isolated at 44°C, then the results should be reported as two 

coliform bacteria and two E. coli 12 . 

Coliform bacteria 

Sub-culture selected yellow colonies to lactose peptone water (LPW), MacConkey agar (MA) 

and nutrient agar (NA). Spread the MA and NA plates in a manner to give isolated colonies. 

Place the LPW in an incubator at 37°C. Examine for acid production after 20 ± 4 hours and if 

results are negative examine after further 20 ± 4 hours incubation. Place the MA and NA in an 

incubator at 37°C for 20 hours ± 4 hours. Coliform bacteria produce colonies on MA that are 

usually circular in shape, convex with a smooth surface and an entire edge. They are various 








shades of red in colour. If the growth on MA/NA is not pure then LPW should be repeated with 

a pure culture obtained from the MA/NA. 

Perform an oxidase test on colonies from the NA plate. Pure cultures are essential for this test 

and it may be necessary to make further sub-cultures from characteristic colonies on the MA to 

NA. Moisten a piece of filter paper in a Petri dish with 2 – 3 drops of freshly prepared oxidase 

reagent or equivalent. Using a stick, glass rod or platinum/plastic (not nichrome) loop transfer a 

colony of the test organism to the filter paper and rub it on the moistened area. A positive 

reaction is indicated by the appearance of a dark purple colour within 10 seconds. No colour 

change or a purplish colour which develops later are both negative reactions. 

Coliform bacteria are oxidase negative and produce acid from lactose. 

E. coli 

Sub-culture the same colonies selected for confirmation as coliform bacteria to LPW and TW. 

Place in a waterbath at 44°C for 20 hours ± 4 hours. 

Perform an indole test on the TW culture as follows: 

Add approximately 0.2 mL Kovacs reagent and shake gently. A deep red colour developing 

almost immediately in the upper layer indicates a positive result (indole production). E. coli is 

indole positive, produces acid in LPW and is oxidase negative. 

7 CALCULATION OF RESULTS 

Calculate the presumptive count of the test organisms as follows: 

Presumptive count / 100 mL = Number of colonies counted x 100 

Volume tested 

Following the procedures described in National Standard Method: W 1 Section 7 20 , calculate 

the number of confirmed coliform bacteria and E. coli present in the specified volume of the 

original sample. 

8 REPORTING 

Report the results using the procedure described in National Standard Method: W 1 Section 

9 20 . Interpretation of results should follow QSOP 57 – The microbiological examination of water 

samples 22 . 

If coliform bacteria or E. coli are not detected, report as: 

‘Not detected in 100 mL’ 

If the test organisms are detected report as: 

‘a per 100 mL’ 

where a is the confirmed count 

When E. coli has been confirmed from both the 37°C and 44°C membrane, report the higher 

count. If E. coli or other coliform bacteria are detected at 44°C and when there are no colonies 

at 37°C be sure to report the colonies at 44°C as coliform bacteria. It is illogical to report for 

example: 

E. coli: “2 per 100 mL” and 

coliform bacteria: “Not detected in 100 mL” from the same sample. 








For natural mineral waters, bottled waters or waters in containers, the result is reported as the 

count per 250 mL. 

9 QUALITY CONTROL 

9.1 MEMBRANE FILTRATION 

When the membrane filtration technique is used, internal quality control procedures must be 

carried out at least once daily depending on the workload of the laboratory. If more than one 

batch of media is used it is necessary to repeat the quality control for each batch (see National 

Standard Method W 1 Section 10) 20 . 

The quantitative internal quality controls are performed using suspensions of positive and 

negative control organisms known to contain less than 100 colony forming units in the volume 

filtered. 

Positive controls 

Escherichia coli NCTC 9001 for incubation at 37°C (coliform bacteria positive) or 44°C (E. coli 

positive) 

Klebsiella aerogenes NCTC 9528 for incubation at 37°C (coliform bacteria positive) 

Negative controls 

Klebsiella aerogenes NCTC 9528 for incubation at 44°C 

Pseudomonas aeruginosa NCTC 10662 

Blank control 

Filter 100 mL of sterile distilled water or peptone saline diluent using the same funnel as used for 

the positive control following disinfection. 

Incubate all quality control tests in parallel with routine tests, proceed with confirmatory tests and 

determine the counts. 

9.2 CONFIRMATORY TESTS 

For each batch of confirmatory tests inoculate known positive and negative controls as shown 

below: 

Lactose peptone water 

Test strains 

37°C 44°C 

24 or 48 hours 24 hours 

E. coli NCTC 9001 Not necessary Acid 

Klebsiella aerogenes NCTC 9528 Acid No growth 

Pseudomonas aeruginosa NCTC 10662 No acid No acid 








Oxidase test 

Test strains 


Positive (purple) 

E. coli NCTC 9001 Negative (colourless) 

Indole production in tryptone water 44°C/24 hours 

Test strains 

E. coli NCTC 9001 Positive (red) 

Klebsiella aerogenes NCTC 9528 Negative (colourless) 


Negative (colourless) 

10 REFERENCE FACILITIES 

N/A 

11 ACKNOWLEDGEMENTS AND CONTACTS 

This National Standard Method has been developed, reviewed and revised by the Water 

Working Group for Standard Methods (http://www.hpastandardmethods.org.uk/wg_water.asp). 

The contributions of many individuals in Food, 

Water and Environmental laboratories, reference laboratories and specialist organisations 

who have provided information and comment during the development of this document are 

acknowledged. 

The National Standard Methods are issued by Standards Unit, Evaluations and Standards 

Laboratory, Centre for Infections, Health Protection Agency London. 

For further information please contact us at: 

Standards Unit 

Evaluations and Standards Laboratory 

Centre for Infections 

Health Protection Agency 

Colindale 

London 

NW9 5EQ 

E-mail: standards@hpa.org.uk 








FLOWCHART SHOWING THE PROCESS FOR THE 

ENUMERATION OF COLIFORM BACTERIA AND 

ESCHERICHIA COLI BY MEMBRANE FILTRATION 

Transport to laboratory at 2°C – 8°C out of direct sunlight 

in suitable containers 

 

Store at 2°C – 8°C in the dark and analyse as soon as is practicable on the day of collection, 

otherwise within 24 hours of collection 

 

Mix sample well and make any necessary dilutions 

 

Filter 

 

Place filter on pad soaked in MLSB 

 

Incubate at 30°C ± 1°C for 4 hours ± 1 hour and 

37°C for 14hours ± 1 hour 

 

Incubate at 30°C ± 1°C for 4 hours ± 1 hour 

and 44°C for 14 hours ± 1 hour 

 

Count yellow colonies 

within 15 minutes of removal from incubator 

 

 

Count yellow colonies 

within 15 minutes of removal from incubator 

Sub-culture to LPW, MA, and NA (oxidase test) 

for incubation at 37°C (coliform bacteria) and to LPW and TW at 44°C (E. coli) 

 

Perform biochemical tests and calculate counts of coliform bacteria and E. coli 

 

Report and interpret using QSOP 57 – The microbiological examination of water samples 22 








REFERENCES 

1. Department of Health NHS Executive: The Caldicott Committee. Report on the review of patientidentifiable 

information. London. December 1997. 

2. The Bathing Waters (Classification) Regulations 1991: Statutory Instrument No. 1597. HMSO. 

http://www.opsi.gov.uk/si/si1991/Uksi_19911597_en_1.htm. 

3. The Natural Mineral Water, Spring Water and Bottled Drinking Water Regulations (Statutory 

Instrument No. 666). London: HMSO; 2003. 

4. The Private Water Supplies Regulations (Statutory Instrument No. 2790). London: HMSO; 1991. 

5. The Water Supply (Water Quality) (Amendment) Regulations (Statutory Instrument No. 2885). 

London: HMSO; 2001. 

6. The Drinking Water in Containers Regulations (Statutory Instrument No. 743). London: HMSO; 

1994. 

7. PHLS. Hygiene for Hydrotherapy Pools. 2 nd ed. London: PHLS; 1999. 

8. Health and Safety Executive, Health Protection Agency. Management of Spa Pools - Controlling 

the Risks of Infection. http://www.hpa.org.uk/publications/2006/spa_pools/spa_pools.pdf. 

9. Pool Water Treatment Advisory group, editor. Swimming Pool Water - Treatment and Quality 

Standards. Greenhouse Publishing; 1999. 

10. Industry Guide to Good Hygiene Practice: Vending and Dispensing Guide Supplement (to the 

Catering Guide). Chadwick House Group ; 2000. 

11. Council Directive 98/83/EC: Relating to the Quality of Water Intended for Human Consumption. 

Official Journal of the European Communities; 1998. p. L330-32-L330/53. 

12. Standing Committee of Analysts. Environment Agency. The Microbiology of Drinking Water 

(2002). Methods for the Examination of Waters and Associated Materials - Part 4: Methods for the 

isolation and enumeration of coliform bacteria and Escherichia coli (including E. coli 0157:H7). 

London. www.environment-agency.gov.uk/commondata/acrobat/mdwpart4.pdf . 

13. Public Health Laboratory Service Standing Advisory Committee on Laboratory Safety. Safety 

Precautions: Notes for Guidance. 4 th ed. London: Public Health Laboratory Service (PHLS); 1993. 

14. Control of Substances Hazardous to Health Regulations 2002. General COSHH. Approved Code 

of Practice and Guidance, L5. Suffolk: HSE Books; 2002. 

15. Health and Safety Executive. 5 steps to risk assessment: a step by step guide to a safer and 

healthier workplace, IND (G) 163 (REVL). Suffolk: HSE Books; 2002. 

16. Health and Safety Executive. A guide to risk assessment requirements: common provisions in 

health and safety law, IND (G) 218 (L). Suffolk: HSE Books; 2002. 

17. NHS Estates. Health Building Note 15. Facilities for pathology services. 2nd ed. London: The 

Stationary Office; 2005. 

18. Advisory Committee on Dangerous Pathogens. The management, design and operation of 

microbiological containment laboratories. Suffolk: HSE Books; 2001. 








19. Advisory Committee on Dangerous Pathogens. Biological agents: Managing the risks in 

laboratories and healthcare premises. HSE. 

http://www.advisorybodies.doh.gov.uk/acdp/publications.htm#1. 

20. National Standard Method W 1 - General technique for the detection of bacteria by membrane 

filtration. London: Health Protection Agency; 2007. 

21. Barrow GI, Feltham R K A, editors. Cowan and Steel's Manual for the Identification of Medical 

Bacteria. 3rd ed. Cambridge: Cambridge University Press; 1993. 

22. National Standard Method QSOP 57 - The microbiological examination of water samples. London: 

Health Protection Agency; 2005.

Enumeration of coliform bacteria and Escherichia coli

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?