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Blood agar to detect virulence factors in tap water heterotrophic bacteria
P Payment1, E Coffin, G Paquette
1Institut Armand-Frappier, Université du Québec, Laval, Canada.
Abstract:
Cytolytic colonies were found in 57% of tap water samples, and up to 6% of samples were found to contain bacteria having three or more virulence factors. The factors evaluated were cytotoxicity, hemolysis, cell adherence, and cell invasiveness. Overall, 17% of the samples contained cytolytic colonies that were adherent and hemolytic. Among the media tested, tryptic soy agar with sheep blood (incubated at 35 degrees C for 48 h) was the best medium for the detection of cytolytic colonies. Of the colonies growing on this medium, 13% were cytolytic, whereas on medium R2A, less than 3% were cytolytic. Furthermore, when tryptic soy agar with blood was used, 24% of the samples contained colonies with at least three virulence factors whereas only 5% were positive with R2A. Routine monitoring by using tryptic soy agar with sheep blood is suggested as an appropriate procedure for the detection of bacteria with pathogenic potential in drinking water.
Insights
Tap water samples frequently contained cytolytic bacteria with virulence factors. Tryptic soy agar with sheep blood is recommended for detecting potentially pathogenic bacteria in drinking water.
Area of Science:
- Microbiology
- Environmental Science
- Public Health
Background:
- Tap water can harbor bacteria with pathogenic potential.
- Assessing bacterial virulence factors in drinking water is crucial for public health.
- Previous methods may not optimally detect these bacteria.
Purpose of the Study:
- To evaluate the prevalence of cytolytic bacteria and virulence factors in tap water.
- To compare the efficacy of different culture media for detecting these bacteria.
- To recommend an optimal method for routine monitoring.
Main Methods:
- Analysis of tap water samples for cytolytic colonies and bacterial virulence factors (cytotoxicity, hemolysis, adherence, invasiveness).
- Comparison of tryptic soy agar with sheep blood and R2A medium for bacterial culture.
- Incubation at 35°C for 48 hours for optimal detection.
Main Results:
- Cytolytic colonies were detected in 57% of tap water samples.
- Up to 6% of samples contained bacteria with three or more virulence factors.
- Tryptic soy agar with sheep blood was superior to R2A for detecting cytolytic colonies and bacteria with multiple virulence factors.
Conclusions:
- Tryptic soy agar with sheep blood is an effective medium for detecting bacteria with pathogenic potential in drinking water.
- Routine monitoring using this method is recommended to ensure water safety.
- The study highlights the presence of potentially harmful bacteria in tap water systems.
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