THE USE OF PASSIVE SAMPLERS FOR THE DETECTION OF E. COLI IN WASTEWATER

Abstract

Wastewater surveillance of antibiotic resistant bacteria and genes has been a useful epidemiology tool in monitoring antibiotic resistance within populations. These monitoring approaches are frequently reliant on composite samples from automatic samplers. These samplers can be expensive and require infrastructure modifications. Passive sampling could be a practical and affordable approach to wastewater surveillance in certain situations where automatic samplers cannot be implemented. However, their use in the detection of bacteria within wastewater is limited. The overall objective of this study was to assess the detection capacity of various passive materials for E. coli in wastewater. The casing used to house the passive materials was a torpedo shaped passive sampler. The passive materials placed in the sampler are gauze, cotton buds, and either a nylon or polyvinylidene fluoride (pvdf) membrane filter. The first aim of the study was to develop an effective protocol for the detachment of E. coli from different passive materials placed in wastewater. We determined that the use of peptone physiological salt and vortexing provided an effective approach for the detachment of E. coli from the materials. Also, in this study, passive samplers were placed once a week for a 24-h continuous sampling in effluent wastewater for 8 weeks. The highest quantity of E. coli was detected on gauze with mean concentrations of 4.9 log cfu / passive material, followed by bud (3.7 log cfu / passive material) while nylon and pvdf membranes had similar mean concentrations (2.3 log cfu/ passive material). Furthermore, buds (R2 = 0.88) showed the strongest relationship when compared with the 24-h effluent composite samples collected from automated samplers, while gauze had the weakest relationship (R2 = 0.48). The passive materials also showed that they could detect E. coli during exposure to varying concentration and time-duration. These results have demonstrated that the samplers can be used for passive sampling of bacteria within wastewater, however the type of passive material to be used is dependent on the research aims to be achieved.