The effect of free chlorine on Burkholderia pseudomallei in potable water

Abstract

Chlorine is widely used in public water supplies to provide a disinfection barrier. The effect of chlorine disinfection on the water-borne pathogen Burkholderia pseudomallei was assessed using multiple techniques. After exposure to chlorine viable bacteria were undetectable by conventional plate count techniques, however persistence of B. pseudomallei was verified by flow cytometry and bacteria were recoverable following a simple one step broth procedure. The minimum residual chlorine concentration and contact time as prescribed by potable water providers in Australia was insufficient to reduce a B. pseudomallei population by more than 2 log 10 . Chlorine had a bacteriostatic effect only on B. pseudomallei; viable bacteria were recovered from water containing up to 1000 ppm free chlorine. This finding has practical implications for water treatment in regions where B. pseudomallei is endemic. Future work to assess the effect of alternative water disinfection processes either singly or in sequence is necessary.

Disinfection of Burkholderia pseudomallei in potable water

“…This is in agreement with the findings of Kim et al (2002) who showed that, in general, oxidising disinfectants (chlorine and monochloramine in this study) were more effective than non-oxidising ones against Legionella in water systems. The reduction by chlorine calculated by MPN in this study is greater than those estimates produced by flow cytometry (Howard and Inglis, 2003a), however flow cytometry was not used due to the lower detection limit of 10 4 CFU/mL.…”

“…Survival of groups of chlorine "tolerant", chlorine "sensitive" and mucoid strains from the earlier study (Howard and Inglis, 2003a) showed a difference between the three disinfecting agents used in this study. When exposed to chlorine the mucoid strains were as resistant to chlorine as the tolerant group.…”

“…(Howard and Inglis, 2003a). Using flow cytometry to estimate viable bacteria and a recovery procedure to determine survival of chlorine-treated B. pseudomallei suspensions, the recovery of viable bacteria from water containing up to 1000 mg/L free chlorine indicated that chlorine had a bacteriostatic effect on B. pseudomallei (Howard and Inglis, 2003a). This study highlighted the need for assessment of alternative water disinfection processes for B. pseudomallei.…”

“…pseudomallei strains for this study were selected from a group of 45 isolates previously tested for tolerance to chlorine (Howard and Inglis, 2003a). Three of the most tolerant strains (NCTC 13177, NCTC 10276 and BCC11) were selected for most of the experiments.…”

“…Endamebic bacterial survival of B. pseudomallei has recently been observed in Acanthamoeba (Inglis et al, 2000). (Howard and Inglis, 2003a). Using flow cytometry to estimate viable bacteria and a recovery procedure to determine survival of chlorine-treated B. pseudomallei suspensions, the recovery of viable bacteria from water containing up to 1000 mg/L free chlorine indicated that chlorine had a bacteriostatic effect on B. pseudomallei (Howard and Inglis, 2003a).…”