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Heterotrophic Plate Counts and Drinking-water Safety

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Heterotrophic Plate Counts and Drinking-water Safety

Jamie Bartram | J. A. Cotruvo | M. Exner | C. Fricker | A. Glasmacher

(2003)

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Additional Information

Book Details

ISBN
978-1-78040-594-0
Edition
1
Language
English
Pages
272
Subjects
The environment
Environmental science, engineering & technology
Water supply & treatment

Abstract

Heterotrophic Plate Counts and Drinking-water Safety provides a critical assessment of the role of the Heterotrophic Plate Count (HPC) measurement in drinking water quality management. It was developed from an Expert workshop of 32 scientists convened by the World Health Organization and the WHO/NSF International Collaborating Centre for Drinking Water Safety and Treatment in Geneva, Switzerland. Heterotrophs are organisms, including bacteria, yeasts and moulds, that require an external source of organic carbon for growth. The HPC test (or Standard Plate Count), applied in many variants, is the internationally accepted test for measuring the hetrotrophic microorganism population in drinking water, and also other media. It measures only a fraction of the microorganisms actually present and does not distinguish between pathogens and non-pathogens. High levels of microbial growth can affect the taste and odor of drinking water and may  indicate the presence of nutrients and biofilms which could harbor pathogens, as well as the possibility that some event has interfered with the normal production of the drinking water. HPC counts also routinely increase in water that has been treated by an in-line device such as a carbon filter or softener, in water-dispensing devices and in bottled waters and indeed in all water that has suitable nutrients, does not have a residual disinfectant, and is kept under sufficient conditions. There is debate among health professionals as to the need, utility or quantitative basis for health-based standards or guidelines relating to HPC-measured regrowth in drinking water.   The issues that were addressed in this work include: the relationship between HPC in drinking water (including that derived from in-line treatment systems, dispensers and bottled water) and health risks for the general public                          the role of HPC as an indirect indicator or index for pathogens of concern in drinking water                         the role of HPC in assessing the efficacy and proper functioning of water treatment and supply processes                         the relationship between HPC and the aesthetic acceptability of drinking water. Heterotrophic Plate Counts and Drinking-water Safety provides valuable information on the utility and the limitations of HPC data in the management and operation of piped water systems as well as other means of providing drinking water to the public. It is of particular value to piped public water suppliers and bottled water suppliers, manufacturers and users of water treatment and transmission equipment and inline treatment devices, water engineers, sanitary and clinical microbiologists, and national and local public health officials and regulators of drinking water quality.

Table of Contents

Section Title Page Action Price
Cover\r Cover
Contents v
Foreword vii
Acknowledgements ix
List of acronyms and abbreviations xi
Robert Koch xiv
1:\rExpert consensus 1
1.1 DEFINITIONS AND SCOPE\r 1
1.1.1 Drinking-water 1
1.1.2 Heterotrophic plate count 2
1.1.3 Microbial growth in water 2
1.1.4 Use of HPC in water management 3
1.2 USES IN PIPED WATER SUPPLIES\r 3
1.2.1 Water safety plans 3
1.2.2 Water quality targets 4
1.2.3 Validation and verification 4
1.2.4 Aesthetic quality 5
1.3 USES IN NON-PIPED AND OTHER WATER SUPPLIES\r 6
1.3.1 Bottled water 6
1.3.2 Plumbed-in devices 6
1.3.3 Conveyances 6
1.3.4 Other water exposure media 7
1.4 HEALTH ASPECTS\r 7
1.4.1 Exposure 7
1.4.2 Epidemiology 7
1.4.3 Health effects — specific organisms 8
1.4.4 Populations at increased risk (including sensitivity through life stages) 8
1.4.5 Health care facilities 9
1.5 OUTSTANDING QUESTIONS AND RESEARCH 9
1.6 REFERENCES 10
2: Public health aspects of the role of\rHPC — an introduction 12
2.1 INTRODUCTION 12
2.2 HISTORICAL ASPECTS 13
2.3 RECENT DEVELOPMENTS 14
2.3.1 New procedure for determining colony counts 15
2.3.2 Biofilms 15
2.3.3 Risks from bacteria detected in water 15
2.4 ALTERED BASIC CONDITIONS 17
2.4.1 The scope of national drinking-water regulations 17
2.4.2 Regulations for water quality in high-risk areas 18
2.4.3 Changes in sociodemographic conditions 18
2.5 REFERENCES 18
3:\rThe history and use of HPC in drinking-water quality management 20
3.1 INTRODUCTION 20
3.2 GERMS AND DISEASE: FROM DISCOVERY TO CULTIVATION 21
3.3 KOCH: ASSESSING FILTER EFFICIENCY AND SETTING LIMITS 22
3.4 WATER MICROBIOLOGY: THE UNITED KINGDOM EXAMPLE\r 23
3.4.1 Early water microbiology 23
3.4.2 Early use of heterotrophic plate counts (HPC) 25
3.4.3 Guidance on the use of HPC 26
3.4.4 Interpretation of HPC levels 26
3.4.5 Current use of HPC in the United Kingdom 28
3.5 THE AMERICAN PERSPECTIVE ON THE PLATE COUNT\r 29
3.5.1 Early water bacteriology in the USA 29
3.5.2 Measuring HPC microorganisms in the USA 33
3.5.3 Interference with the total coliform assay 34
3.6 OPPORTUNISTIC PATHOGENS AND HEALTH EFFECTS 35
3.7 HEALTH EFFECTS: EPIDEMIOLOGICAL STUDY 38
3.8 HPC BACTERIA IN FOOD 39
3.9 MANDATORY OR GUIDELINE HPC VALUES IN THE 1970S AND 1980S 41
3.10 STANDARDS AND GUIDELINES IN THE 1990S 42
3.11 CONCLUSIONS 42
3.12 REFERENCES 45
4:\rThe presence of bacteria in water after regrowth 49
4.1 INTRODUCTION 49
4.2 DETECTION OF BACTERIA IN WATER 50
4.3 THE “VIABLE BUT NON-CULTURABLE” STATE 51
4.4 MICROBIOLOGICAL REGROWTH 51
4.5 MICROBIAL PATHOGENS IN WATER 52
4.5.1 Aeromonas spp. 53
4.5.2 Pseudomonas 54
4.5.3 Mycobacterium avium complex (MAC) 54
4.5.4 Other microorganisms 54
4.6 REGROWTH OF BACTERIA IN POINT-OF-USE AND POINT-OF-ENTRY DEVICES 55
4.7 POTENTIAL BENEFICIAL EFFECTS OF REGROWTH 56
4.8 THE EFFECT OF AUTO-DISINFECTION OF POU DEVICES 57
4.9 CONCLUSIONS 58
4.10 REFERENCES 58
5:\rBacteria of potential health concern 61
5.1 INTRODUCTION 61
5.2 COMMENSAL BACTERIA 62
5.2.1 Aeromonas 62
5.2.2 Yersinia 64
5.2.3 Klebsiella 64
5.2.4 Pseudomonas 65
5.2.5 Virulence factors 65
5.2.6 Hospital-acquired infection 66
5.3 RECOGNIZED WATERBORNE PATHOGENS 66
5.3.1 Campylobacter 68
5.3.2 Escherichia coli 69
5.3.3 Salmonella 70
5.3.4 Shigella 71
5.3.5 Vibrio 71
5.4 EMERGING PATHOGENS 72
5.4.1 Helicobacter pylori 72
5.4.2 Mycobacterium 73
5.4.3 Burkholderia pseudomallei 74
5.4.4 Francisella tularensis 74
5.5 BIOTERRORISM THREAT AGENTS 75
5.6 CONCLUSIONS 75
5.7 REFERENCES 77
6:\rRelationships between common water bacteria and pathogens in drinking-water 80
6.1 INTRODUCTION 80
6.2 HETEROTROPHIC BACTERIA AS INHABITANTS OF A DRINKING-WATER ECOSYSTEM 81
6.2.1 Biofilm 82
6.2.2 Starvation-survival lifestyle 84
6.2.3 The viable but non-culturable state 86
6.3 WHAT IS A PATHOGEN IN DRINKING-WATER? 86
6.3.1 Pseudomonas aeruginosa\r 90
6.3.2 Aeromonas\r 91
6.3.3 Legionella 92
6.3.4 Mycobacterium avium complex (MAC) 93
6.3.5 Helicobacter pylori 94
6.4 HETEROTROPHIC BACTERIA IN DISTRIBUTION SYSTEMS AND PATHOGENS 94
6.4.1 Spatial and temporal heterogeneity in the pipe network 94
6.4.2 Biological heterogeneity and instability 95
6.4.3 Diversity of bacterial stresses 97
6.4.4 Interactions between heterotrophic bacteria and pathogens 97
6.4.4.1 E. coli as a model of enteric bacteria 98
6.4.4.2 Pathogens growing in water 99
6.5 HETEROTROPHIC BACTERIA IN NATURAL MINERAL WATER AND PATHOGENS 100
6.5.1 Bottle habitat 101
6.5.1.1 The bottle effect 101
6.5.1.2 Attached versus unattached bacteria 102
6.5.1.3 Growth or resuscitation 102
6.5.2 Microbial community 103
6.5.2.1 Gram-negative bacteria 103
6.5.2.2 Gram-positive bacteria 105
6.5.2.3 Identified bacteria by rRNA-targeted oligonucleotide probes 106
6.5.2.4 Bacterial microdiversity 106
6.5.3 Fate of pathogens in natural mineral water 106
6.5.3.1 Enteric bacteria 107
6.5.3.2 Pathogenic bacteria growing in water 107
6.5.4 Assessing health risk from autochthonous bacteria 109
6.5.4.1 Animal model system 110
6.5.4.2 Randomized trial in infants 110
6.5.4.3 Virulence characteristics of bacteria 110
6.6 CONCLUSIONS 111
6.7 REFERENCES 113
7:\rEpidemiological and riskassessment evidence of diseaselinked to HPC bacteria 119
7.1 INTRODUCTION 119
7.2 EPIDEMIOLOGICAL STUDIES OF HUMAN ILLNESS AND HPC 121
7.3 EPIDEMIOLOGICAL STUDIES OF DISEASE DUE TO BACTERIA THAT MAY BE PART OF THE HPC FLORA 122
7.3.1 Mycobacteria 123
7.3.2 Aeromonas 124
7.3.3 Pseudomonas aeruginosa 125
7.3.4 Legionella 127
7.3.5 Other HPC bacteria 127
7.4 RISK ASSESSMENT 128
7.4.1 Hazard identification 129
7.4.2 Exposure assessment 130
7.4.3 Dose–response assessment 130
7.4.4 Risk categorization 131
7.5 CONCLUSIONS 132
7.6 REFERENCES 133
8:\rInfections from HPC organisms in drinking-water amongst the immunocompromised 137
8.1 INTRODUCTION 137
8.2 EPIDEMIOLOGY AND PATHOPHYSIOLOGY OF IMMUNODEFICIENCY 138
8.3 THE SETTING OF CARE FOR IMMUNOCOMPROMISED PATIENTS 139
8.4 INFECTIOUS RISKS FOR AMBULATORY IMMUNOCOMPROMISED PATIENTS 140
8.5 FUNGAL INFECTIONS FROM WATER SYSTEMS 140
8.6 RISK ASSESSMENT OF OPPORTUNISTIC BACTERIAL PATHOGENS 141
8.7 RISK ASSESSMENT FOR INFECTION FROM WATER 142
8.8 STAGES OF IMMUNOSUPPRESSION AND APPROPRIATE PROTECTION MEASURES 143
8.9 THE PRECAUTIONARY PRINCIPLE 144
8.10 REFERENCES 144
9:\rMethods to identify and enumerate frank and opportunistic bacterial pathogens in water and biofilms 146
9.1 INTRODUCTION 146
9.2 WATER OR BIOFILM SAMPLING FOR PATHOGENS 149
9.3 CULTURE-BASED (TRADITIONAL) METHODS 150
9.4 CONCENTRATION OF TARGET BACTERIA 150
9.5 GROWTH AND DETECTION WITH CHROMOGENIC SUBSTANCES 153
9.6 IMMUNOLOGICAL AND NUCLEIC ACID-BASED METHODS 153
9.6.1 Antibody-based methods 153
9.6.2 Immunomagnetic separation 154
9.6.3 Gene sequence-based methods 155
9.6.4 Polymerase chain reaction 155
9.6.5 Fluorescence 158
9.7 FINGERPRINTING METHODS 159
9.7.1 Ribotyping 159
9.7.2 Profiling of low-molecular-weight RNA 160
9.7.3 Restriction fragment length polymorphism 161
9.7.4 Amplified fragment length polymorphisms and arbitrarily primed PCR 162
9.7.5 Repetitive gene PCR 163
9.7.6 Denaturing and temperature gradient gel electrophoresis 163
9.7.7 Single-strand conformation polymorphism 164
9.8 EMERGING METHODS 165
9.9 CONCLUSIONS 167
9.10 REFERENCES 168
10:\rConditions favouring coliform and HPC bacterial growth in drinkingwater and on water contact surfaces 177
10.1 INTRODUCTION 177
10.2 GROWTH OF COLIFORM AND HPC BACTERIA IN WATER 179
10.2.1 Filtration 179
10.2.2 Temperature 179
10.2.3 Disinfectant residual and disinfectant level 179
10.2.4 AOC and BDOC levels 181
10.2.5 Corrosion control and pipe materials 184
10.2.6 Residence time 189
10.3:\rBIOFILM CONTROL FOR BACTERIA OF POTENTIAL PUBLIC HEALTH SIGNIFICANCE 189
10.3.1 Mycobacterium avium complex\r 189
10.3.2 Legionella 193
10.3.3 Other organisms 193
10.4 CONCLUSIONS 193
10.5 REFERENCES 194
11:\rManaging regrowth in drinkingwater distribution systems 199
11.1 INTRODUCTION 199
11.2 PROBLEMS RELATED TO MICROBIAL ACTIVITY\r 200
11.2.1 Regrowth, biofilms and microbial activity 200
11.2.2 Coliforms 201
11.2.3 Opportunistic pathogens 201
11.2.4 Increased HPC values 203
11.2.5 Nuisance organisms 204
11.3 ASSESSMENT OF MICROBIAL ACTIVITY\r 205
11.3.1 Monitoring tools needed 205
11.3.2 Heterotrophic plate counts 206
11.3.3 Total direct counts 206
11.3.4 Adenosine triphosphate 207
11.3.5 Other methods 208
11.3.6 Suite of methods 209
11.4 FACTORS PROMOTING MICROBIAL ACTIVITY\r 210
11.4.1 Energy sources in water 210
11.4.1.1 Power of multiplication 210
11.4.1.2 Assimilable organic carbon 211
11.4.1.3 Biodegradable dissolved organic carbon 212
11.4.1.4 Biofilm formation rate 213
11.4.2 Materials and sediments 213
11.4.2.1 Materials 213
11.4.2.2 Sediments and corrosion products 214
11.4.3 Temperature and hydraulic conditions 214
11.4.4 Models 215
11.4.5 Biological stability 215
11.4.6 Suite of tools 217
11.5 CONTROLLING MICROBIAL ACTIVITY\r 217
11.5.1 General 217
11.5.2 Biological stability 217
11.5.2.1 Water treatment 217
11.5.2.2 Materials 219
11.5.3 Disinfection 219
11.5.3.1 Chlorine 219
11.5.3.2 Monochloramine 220
11.5.4 Distribution system configuration and maintenance 221
11.5.5 Multiple barriers against microbial activity in distribution systems 221
11.6 REFERENCES 222
12:\rThe role of HPC in managing the treatment and distribution of drinking-water 233
12.1 INTRODUCTION 233
12.2 HPC BACTERIA IN WATER TREATMENT PLANTS 234
12.3 HPC BACTERIA IN WATER DISTRIBUTION SYSTEMS 235
12.4 HPC BACTERIA IN WATER TREATMENT DEVICES 236
12.5 HPC BACTERIA IN BOTTLED WATER 237
12.6 STANDARDS AND GUIDELINES 238
12.6.1 World Health Organization (WHO) guidelines 238
12.6.2 European guidelines 239
12.6.3 United Kingdom regulations 239
12.6.4 German regulations 240
12.6.5 Canadian guidelines 240
12.6.6 Regulations in the USA 241
12.6.7 Australian guidelines 242
12.6.8 Regulations in other countries 242
12.7 CONCLUSIONS 242
12.8 REFERENCES 243
Index 245

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