Traditional copper water storage vessels and sub-lethal injury of Salmonella enterica serovar Typhi and Vibrio cholerae

Recent studies on Escherichia coli have demonstrated sub-lethal injury-sensitivity to oxygen and selective agents prior to irreversible inactivation when kept in water in a brass vessel. The present study was carried out to investigate whether equivalent responses occur in copper vessels using the pathogens Salmonella enterica serovar Typhi and Vibrio cholerae. Bacterial suspensions were stored in water in a traditional copper vessel for up to 24 h at 30 °C. Samples were withdrawn and plated on selective and non-selective media, then incubated under (a) aerobic conditions and (b) conditions where reactive oxygen species were neutralized to enumerate injured bacteria. Short-term incubation in water kept in a copper vessel caused a greater decrease in counts for both pathogens on selective media, compared to non-selective media with greater differences between aerobic and reactive oxygen species-neutralized counts using selective media compared to non-selective nutrient agar. These findings have practical implications for the short-term storage of water samples in copper storage vessel as the possibility of bacterial injury is high, hence enumeration under conventional aerobic conditions may not be sufficient to give a count of all viable bacteria.