Investigation of the suitability of aquatic invertebrates as biological indicators for detecting the presence of Campylobacter spp. in recreational water supplies.
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Campylobacter species, the most frequent cause of acute bacterial gastroenteritis in humans, are of worldwide significance. Drinking and recreational surface waters have been identified as a major vehicle of pathogenic Campylobacter spp. transmission to humans. Outbreaks of campylobacteriosis as well as sporadic cases have been reported both locally and internationally. However, in only a small proportion of cases has the responsible organism been isolated from the implicated water source. The inherent difficulties with isolation of Campylobacter spp. from environmental water sources make the development of more reliable, alternative isolation and detection methods a preferred option. In this study, the potential for aquatic invertebrates to act as biological indicators for detecting Campylobacter spp. from recreational water was investigated. The suspension and filter feeding strategies of aquatic invertebrates allowing them to concentrate Campylobacter cells to readily detectable levels within their tissues was explored. Sampling of water, mussels, cockles and snails from the Avon-Heathcote rivers and estuary revealed low isolation rates with no apparent correlation between Campylobacter presence in water and the invertebrates. Placement of freshwater mussels in the Avon and Heathcote rivers proved successful for isolation of Campylobacter spp., while marine mussels, cockles and snails routinely tested negative. Hence, the freshwater mussel was chosen as a candidate bio-indicator. In vitro (tank) experiments showed close correlation between Campylobacter detection in mussels and water. However, isolation of Campylobacter from mussels was deemed to be no better than testing the water itself. Environmental Campylobacter isolates were analysed by resistotyping, flaA PCR-RFLP typing and PFGE to determine relationships between isolates. Although very few isolates were found to be clonal, a high level of genetic relatedness was determined between isolates from the Avon and Heathcote rivers. This indicates a common source of input between these rivers, most likely to be from birds. A validation study for the use of the cadF virulence gene as a marker for PCR detection of pathogenic Campylobacter species was under taken. Although useful for distinguishing Campylobacter spp. in pure culture, this system was found to show a degree of unreliability for specific detection from environmental samples.