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

Aim: 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. Methods: Bacterial suspensions were stored in water in a traditional copper vessel for up to 24 h at 30ºC. Samples were withdrawn and plated on selective and non-selective media, then incubated under (a) aerobic conditions and (b) conditions where reactive oxygen species were neutralized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. Results: 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 ROS-n counts using selective media compared to non-selective nutrient agar. Conclusion: 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.