Enumeration and Identification of Coliform Bacteria Injured by Chlorine or Fungicide Mixed with Agricultural Water

Abstract

Chemical sanitizers may induce no injury (bacteria survive), sublethal injury (bacteria are injured), or lethal injury (bacteria die). The proportion of coliform bacteria that were injured sublethally by chlorine and fungicide mixed with agricultural water (pond water), which was used to dilute the pesticide solution, was evaluated using the thin agar layer (TAL) method. In pure cultures of Enterobacter cloacae , Escherichia coli , and E. coli O157:H7 (representing a human pathogen), the percentage of chlorine-injured cells was 69 to 77% for dilute electrolyzed water containing an available chlorine level of 2 ppm. When agricultural water was mixed with electrolyzed water, the percentage of injured coliforms in agricultural water was 75%. The isolation and identification of bacteria on TAL and selective media suggested that the chlorine stress caused injury to Enterobacter kobei . Of the four fungicide products tested, diluted to their recommended concentrations, Topsin-M, Sumilex, and Oxirane caused injury to coliform bacteria in pure cultures and in agricultural water following their mixture with each pesticide, whereas Streptomycin did not induce any injury to the bacteria. The percentage of injury was 45 to 97% for Topsin-M, 80 to 87% for Sumilex, and 50 to 97% for Oxirane. A comparison of the coliforms isolated from the pesticide solutions and then grown on either TAL or selective media indicated the possibility of fungicide-injured Rahnella aquatilis , Yersinia mollaretii , and E. coli . These results suggest the importance of selecting a suitable sanitizer and the necessity of adjusting the sanitizer concentration to a level that will kill the coliforms rather than cause sanitizer-induced cell injury that can result in the recovery of the coliforms.

Formation of Sublethally Injured Yersinia enterocolitica, Escherichia coli O157:H7, and Salmonella enterica Serovar Enteritidis Cells after Neutral Electrolyzed Oxidizing Water Treatments

“…The percentage of the injured population was 45 to 97% for thiophanate-methyl-treated cells, 80 to 87% for procymidone-treated cells, and 50 to 97% for ethylene oxide-treated cells. These results demonstrate the importance of choosing not only the right sanitizer but also the right sanitizer concentrations so that the treatment kills target microorganisms completely rather than just injures the cells (58).…”

“…However, limited information is available in the literature about the conditions under which sublethally injured cells are formed and the characteristics of these sublethally injured cells. In a study conducted by Izumi et al (58), the proportion of chlorine-injured Enterobacter cloacae, E. coli, and E. coli O157:H7 cells in pure culture was shown to be between 69 and 77%. Fungicides, including thiophanate-methyl (Topsin-M), procymidone (Sumilex), and ethylene oxide (Oxirane), also caused the formation of injured cells.…”

Research progress on the injury mechanism and detection method of disinfectant-injured Escherichia coli in the drinking water system

“…In another study, Hou et al (2017) found that drug-resistant bacteria accounted for 51.72% among 58 injured non-fastidious bacteria isolated from drinking water, and 80% of them had obvious multi-drug resistance. Besides, Izumi et al (2016) showed that chlorine-injured bacterial cells accounted for 69-77% in diluted electrolyzed water containing 2 mg/L available chlorine. When agricultural water was mixed with electrolyzed water, the injury rate of coliforms was about 75%, and the bactericidal products diluted to the recommended concentration could also cause injury to the coliforms in agricultural water.…”

Viability of Chlorine-injured <i>Escherichia Coli</i> O157:H7 on Fresh-cut Cabbage during Cold Storage in High CO₂ Atmospheres

“…Since we previously reported that electrolyzed water containing chlorine caused chlorine-injury to a pure culture of E. coli Izumi et al, 2016a , E coli O157:H7 was injured sublethally by using electrolyzed water. Electrolyzed strongly acidic water pH 2.7, 25 ppm available chlorine was generated using a water electrolyzer -Light Amano, Yokohama, Japan , and then diluted to the concentration of 0.5, 1, 2, 3, and 4 ppm of available chlorine with sterile distilled water.…”