Campylobacter Survival In Groundwater: Comparison Of Two Strain Types And Two Groundwater Types

Following the Campylobacter outbreak in Havelock North it was recognised that there was a lack of data on the survival of Campylobacter in groundwater. In particular, there is a lack of information on the survival of Campylobacter in different groundwater in terms of oxygen status. To close this knowledge gap we designed an experiment to measure the survival of an outbreak strain of Campylobacter and the type strain in an oxic and an anoxic groundwater.

A laboratory scale system was set up to investigate the survival of one of the Havelock North outbreak strains (HN16) and the laboratory type strain of Campylobacter jejuni (NCTC11351) in both an oxic and anoxic groundwater. The two groundwater types were held at 12°C (average temperature of local groundwater (Daughney and Reeves, 2002)) and the dissolved oxygen was maintained in both systems throughout the experiment. Samples were taken at specific time intervals over the period and analysed for Campylobacter using selective media.

The results show that Campylobacter can survive in groundwater for over two weeks. Differences were observed in the rate of die off between the two strains of Campylobacter studied. The outbreak strain of Campylobacter showed higher survival rate compared with the type strain of Campylobacter in anoxic groundwater. Initially (first 6 days), the two strains of Campylobacter died off at different rates, and were not significantly different between the types of groundwater, with die-off rates calculated as 0.055 – 0.084 days for HN16 and 0.288 – 0.289 days for NCTC 11351. After 6 days, the type of groundwater appeared to have an effect on the survival of both strains of Campylobacter. The outbreak strain continued to survive well in anoxic groundwater and showed a 1 log-drop in concentration after 16 days, die-off date of 0.0873 days. The type strain NCTC 11351 also showed slower die off in anoxic groundwater over days 6 to 16. It is interesting to note that there appeared to be a plateauing of the die off occurring in both strains of Campylobacter occurring in oxic groundwater. Looking at the overall survival rates for Campylobacter higher survival occurred in anoxic groundwater for both strains. Campylobacter is a microaerophillic microorganism which grows optimally in low oxygen levels. The low oxygen concentration (maintained at less than 2 mg/L) could play a role in the survival of Campylobacter in groundwater.

Comparative die off rates will be presented in anoxic and oxic groundwater for both strains. Implications for public health will be discussed.