Evaluation of an Inexpensive Growth Medium for Direct Detection of Escherichia coli in Temperate and Sub-Tropical Waters.
The cost and complexity of traditional methods for the detection of faecal indicator bacteria, including E. coli, hinder widespread monitoring of drinking water quality, especially in low-income countries and outside controlled laboratory settings. In these settings the problem is exacerbated by the lack of inexpensive media for the detection of E. coli in drinking water. We developed a new low-cost growth medium, aquatest (AT), and validated its use for the direct detection of E. coli in temperate and sub-tropical drinking waters using IDEXX Quanti-Tray®. AT was compared with IDEXX Colilert-18® and either EC-MUG or MLSB for detecting low levels of E. coli from water samples from temperate (n = 140; Bristol, UK) and subtropical regions (n = 50, Pretoria/Tshwane, South Africa). Confirmatory testing (n = 418 and 588, respectively) and the comparison of quantitative results were used to assess performance. Sensitivity of AT was higher than Colilert-18® for water samples in the UK [98.0% vs. 86.9%; p<0.0001] and South Africa [99.5% vs. 93.2%; p = 0.0030]. There was no significant difference in specificity, which was high for both media (>95% in both settings). Quantitative results were comparable and within expected limits. AT is reliable and accurate for the detection of E. coli in temperate and subtropical drinking water. The composition of the new medium is reported herein and can be used freely.
UNICEF, New York, United States of America.
Robert E S
RE
Bain
School of Chemistry, University of Bristol, Bristol, United Kingdom.
Claire
C
Woodall
Department of Civil and Environmental Engineering, University of Surrey, Guildford, United Kingdom.
John
J
Elliott
Division of Epidemiology, School of Public Health, University of California, Berkeley, United States of America.
Benjamin F
BF
Arnold
CPI International, Santa Rosa, CA, United States of America.
Rosalind
R
Tung
Public Health England, Bristol, United Kingdom.
Robert
R
Morley
Council for Scientific and Industrial Research, Pretoria, South Africa.
Martella
M
du Preez
The Water Institute, University of North Carolina, Chapel Hill, NC, United States of America.
Jamie K
JK
Bartram
School of Chemistry, University of Bristol, Bristol, United Kingdom.
Anthony P
AP
Davis
Brightwater Diagnostics Limited, Bath, United Kingdom.
Stephen W
SW
Gundry
Department of Civil and Environmental Engineering, University of Surrey, Guildford, United Kingdom.
Stephen
S
Pedley
D003470:Culture Media / Q000737:chemistry / Q000191:economics; D060766:Drinking Water / Q000382:microbiology*; D004784:Environmental Monitoring / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D004926:Escherichia coli / Q000254:growth & development / Q000302:isolation & purification*; D006801:Humans; D012680:Sensitivity and Specificity; D013019:South Africa; D006113:United Kingdom; D014871:Water Microbiology; D060753:Water Quality
D003470:Culture Media; D060766:Drinking Water