Maxim Sheludchenko

Acinetobacter baumannii survives for prolonged periods under a wide range of environmental conditions. In a larger study investigating the efficacy of pathogen removal in a waste stabilization ponds (WSP), we cultivated microbes from wastewater samples on mCCDA agar containing selective and recommended supplements for the growth of Campylobacter . This bacterium is a recommended reference pathogen for the verification and validation of water recycling schemes in Australia and other parts of the world. A high number of colonies characteristic of Campylobacter grew on the selective media but this did not correlate with qPCR data. Using primers targeting the16S rRNA gene, and additional confirmatory tests such as detection of VS1, omp A, bla _OXA-51-like , bla _OXA-23-like genes, we tested eight random colonies from eight samples (64 colonies in total) and identified them as A. baumannii . Wastewater grab samples taken three times over 6 months throughout the WSP system showed removal of A. baumannii in the WSP atrates similar to E. coli . In contrast, further intensive sampling from the inlet and the outlet of the WSP using a refrigerated auto-sampler showed that the number of A. baumannii in most sampling rounds did not differ significantly between the inlet and outlet of the WSP and that there was high variation between replicates at the outlet only. Resistance genes were detected in most A. baumannii isolated from the waste stabilisation pond and may potentially be a source of antibiotic resistance for environmental strains.

Maturation ponds are used in rural and regional areas in Australia to remove the microbial loads of sewage wastewater, however, they have not been studied intensively until present. Using a combination of culture-based methods and quantitative real-time PCR, we assessed microbial removal rates in maturation ponds at four waste stabilization ponds (WSP) with (n = 1) and without (n = 3) baffles in rural and remote communities in Australia. Concentrations of total coliforms, E. coli, enterococci, Campylobacter spp., Salmonella spp., F+ RNA coliphage, adenovirus, Cryptosporidium spp. and Giardia (oo) cysts in maturation ponds were measured at the inlet and outlet. Only the baffled pond demonstrated a significant removal of most of the pathogens tested and therefore was subjected to further study by analyzing E. coli and enterococci concentrations at six points along the baffles over five sampling rounds. Using culture-based methods, we found a decrease in the number of E. coli and enterococci from the initial values of 100,000 CFU per 100 mL in the inlet samples to approximately 1000 CFU per 100 mL in the outlet samples for both bacterial groups. Giardia cysts removal was relatively higher than fecal indicators reduction possibly due to sedimentation.