The role of drinking water as a source of transmission of

antimicrobial resistant Escherichia coli

Brenda L. Coleman, Allison McGeer, Marina Salvadori, Ian Johnson, Iris Gutmanis,

Sue Bondy, Norm Neuman, Marie Louis,Scott McEwen, Fran Jamieson, & Rebecca Irwin

Antimicrobial Resistance

• What is it?

• Why do we care?

• How does it occur?– Selective pressure– Transmission

Escherichia coli

• Human colonization

• Human infection

• Water as a vehicle for transmission

• E. coli indicator of contamination

Private drinking water

• 10-50% of Canadian households

• 30-50% test water

• 2-20% contaminated with E. coli

Objectives

1. Measure the proportion of E. coli positive water samples that are antimicrobial resistant (AR)

2. Measure the prevalence of human carriage of AR E. coli

3. Determine whether the use of water contaminated with AR E. coli is associated with human carriage

SamplingPublic health labs

(Water samples)

Standard testing for bacterial contaminationat participating laboratories

E. coli - positiveNo bacterial

contamination

Surveillance(Water samples)

E. coli susceptibility tested sample

Resistant Susceptible

Case-control(Households)

Eligible & non-replicate householdsHousehold questionnaire

Case Control A Control B

Cross-sectional(Individuals)

Eligible individualsPersonal questionnaire & rectal swab

Resistant Susceptible

Water samples

340,009 tested

15,238 E. coli (4.5%)

6,492 susceptibility tested

645 resistant (9.9%)

Proportion of E. coli positive water samples that were antimicrobial resistantOntario May 2005-September 2006

0%

2%

4%

6%

8%

10%

12%

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Proportion of E. coli- positive water samples and proportion of antimicrobial resistant E. coli- positive isolates

Ontario, May 1, 2005 - September 30, 2006

0%

5%

10%

15%

20%

25%

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E. coli

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Human samples1,710 households eligible

↓

831 household questionnaires

↓

655 households →985 personal

questionnaires

↓

488 households ← 699 rectal swabs

Households & Subjects

488 households• 108 with AR E. coli water source

– 69 with untreated AR E. coli

699 subjects• 12 to 87 years old• Males = females• 433 (62%) used tap water only• 376 (54%) travelled outside Canada• 185 (27%) had direct livestock contact• 85 (12%) used antibiotic

Proportion of rectal swabs with AR E. coliOntario, 2005-2007

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10%

20%

30%

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Theorized relationship between human carriage & consumption of antimicrobial

resistant E. coliPotential effect modifier:

Bottled water

Primary predictor: Outcome:

Water used Carriage of antimicrobial resistant E. coli

Potential confounders:

Age Antibiotic use

Sex Hospitalization

Household education Child in day care

Household income Household size

Laboratory region Contact with livestock

Mode of data collection Farming property

Days between water sample Contact with dog/cat

& interview Contact with raw meatTravel

Final multivariable model

Predictor RR 95% Conf. interval

Water used (contaminated & not treated) 1.4 1.1, 1.7

Travel outside Canada 1.3 1.1, 1.6

Contact with cattle 1.3 1.0, 1.5

Sex (male) 1.2 1.0, 1.5

Limitations

• Convenience sample

• Age of subjects

• Lack of exposure dose/treatment of water

• Causation

Conclusions

• Private drinking water sources are contaminated with AR E. coli

• Relatively high prevalence of AR E. coli carriage in non-institutionalized residents

• Carriage of AR E. coli is associated with the use of contaminated water