Enterococci vs coliforms as a possible fecal contamination indicator: baseline data for Karachi

Area of Science:

• Environmental microbiology
• Water quality assessment
• Public health

Background:

• Fecal contamination of drinking water causes waterborne diseases.
• Coliforms, traditional indicators, have low survival rates under stress.
• Assessing alternative indicators like enterococci is crucial for Karachi.

Purpose of the Study:

• Compare coliform and enterococci loads in Karachi sewage.
• Evaluate bacterial indicator variability across different locations and times.
• Determine the suitability of enterococci as a fecal contamination indicator.

Main Methods:

• Collected sewage samples from 18 towns in Karachi (June, Aug, Nov 2006).
• Used selective media to quantify colony-forming units (CFU) for coliforms and enterococci.
• Identified bacteria using conventional microbiological methods and statistical analysis.

Main Results:

• Enterococci load ranged from 1.27-8.47 X 10(7) CFU/ml.
• Coliform load ranged from 3.03-13.9 X 10(7) CFU/ml.
• Both indicators showed significant inter-town and temporal variability, with enterococci exhibiting lower variability.

Conclusions:

• Enterococci demonstrate higher survival rates and lower variability compared to coliforms.
• Enterococci show potential as a more reliable fecal contamination indicator in Karachi.
• Local data supports the potential shift from coliforms to enterococci for water quality monitoring.