An Approach Using Non‐Conventional Indicators for Detecting Microbial Water Pollution

Abstract

The present study aims to investigate the suitability of the genus Aeromonas as a nonconventional microbial indicator of water quality in different Egyptian water resources; River Nile, drainage wastewater, and chlorinated drinking water. Aeromonas was detected in 71.2% of examined samples, being maximum in drainage water and minimum in River Nile and drinking water. Several positive significant relationships between Aeromonas and the corresponding heterotrophic plate count, total coliforms, fecal coliforms, and fecal streptococci were recorded, particularly in drainage water and River Nile. 81.4% of presumptive Aeromonas species were identified as A. hydrophila. The effect of seasonal variation showed maximum recovery in summer (61.5%) and spring (28.9%) compared to autumn (5.8%) and winter (3.8%). The time needed to reduce the population by 90% (T 90 ) was 55 h and the calculated decay coefficient was 0.018 h À1 .The residual chlorine efficient to inactivate A. hydrophila in drinking water supplies should be maintained at levels not less than 0.7 mg L À1 . Susceptibility of 72 isolates to 20 different antibiotics revealed recognizable multiple antibiotic resistance phenomenon toward eight (40%) of the tested antibiotics. Sensitivity was mostly directed to norfloxacin, ofloxacin, ceftriaxone, and cefotaxime. The study concluded that, supplementing the traditional indicators index of water quality with Aeromonas levels could be a simple, reliable, and inexpensive valid tool for better microbiological characterization of water.