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cWe previously demonstrated that some Escherichia coli strains with uropathogenic properties survived treatment stages of sewage treatment plants (STPs), suggesting that they may be released into the environment. We investigated the presence of such strains in the surrounding environmental waters of four STPs from which these persistent strains were isolated. In all, 264 E. coli isolates were collected from 129 receiving water sites in a 20-km radius surrounding STPs. We also included 93 E. coli strains collected from 18 animal species for comparison. Isolates were typed using a high-resolution biochemical fingerprinting method (the PhPlate system), and grouped into common (C) types. One hundred forty-seven (56%) environmental isolates were identical to strains found in STPs' final effluents. Of these, 140 (95%) carried virulence genes (VGs) associated with intestinal pathogenic E. coli (IPEC) or uropathogenic E. coli (UPEC) and were found in a variety of sites within areas sampled. Of the remaining 117 environmental strains not identical to STP strains, 105 belonged to 18 C types and 102 of them carried VGs found among IPEC or UPEC strains. These strains belonged mainly to phylogenetic groups A (A0 and A1) and B1 and to a lesser extent B2 2 , B2 3 , D1, and D2. Eight of 18 environmental C types, comprising 50 isolates, were also identical to bird strains. The presence of a high percentage of environmental E. coli in waters near STPs carrying VGs associated with IPEC and UPEC suggests that they may have derived from STP effluents and other nonpoint sources.

"Candidatus Microthrix parvicella" is a filamentous bacterium that grows with great difficulty in cultures from the mixed liquor of activated sludge sewage treatment plants. It is gram positive, and the ultrastructure of its cell walls has been determined to be of the gram-positive type by electron microscopical examination. Phylogenetically, it is a deep-branching member of the subphylum actinomycetes within the gram-positive phylum of the domain Bacteria. As for phenotypic features, it is known that the organism contains polyphosphate inclusions and that it is catalase positive. In mixed cultures in activated sludge plants and in pure culture in the laboratory, it has a characteristic and distinctive winding filamentous morphology, with filaments hundreds of micrometers long."Microthrix pawicella" is a filamentous bacterium found in activated sludge sewage treatment plants, where it causes solids separation problems known as foaming and bulking (7). It is found in these plants throughout the world, and when surveys of the solids separation problems are carried out, this bacterium features near the top of the list of causative organisms. "M. pawicella" is notorious in the wastewater industry because of its problem-causing properties. Although some researchers isolated it with apparent ease (4,5,15,17), in recent years it has eluded many, as evidenced by active discussion at the International Association on Water Quality conference on Microorganisms in Activated Sludge and Biofilm Processes (Paris, France [12]) and the workshop on Microbial Ecology in Wastewater (Stuttgart, Germany [9]).For a summary of the information on "M. pawicella", the work of Blackall et al. (2) should be consulted. However, much information on the attempts to isolate this organism is not included in that publication. We have attempted to obtain "M. pawicella" in axenic culture for 12 years. During this time it is estimated that more than 700 "M. pawicella" filaments have been micromanipulated. A wide range of media which were incubated in a range of atmospheres and temperatures was evaluated. In our experience, the "M. pawicel1a"-specific, chemically defined medium of Slijkhuis (14) has never supported the growth of any micromanipulated filaments nor that of any isolates of "M. pawicella" obtained from other media. Of all the media reported to support the growth of filamentous bacteria from activated sludge, only freshly prepared R2A (13) and modified NTM (2, 8) have been able to sustain "M. parvicella" growth, and these media are not universally successful. Atmospheres tested with a range of media included 90% CO, plus 10% H, and the microaerophilic conditions generated by so-called candle jars. Neither condition increased isolation success, nor did either accelerate the growth rates of isolates. Filaments of "M. pawicella" were manipulated to other media and incubated at natural atmosphere and 20 to 22°C. These media included (i) liquid and solid (1.5% agar) media based on activated sludge (autoclaved, filtered mixed liquor; autoclaved...

Aims:  To see if the compositions of the microbial communities in full scale enhanced biological phosphorus removal activated sludge systems were the same as those from laboratory scale sequencing batch reactors fed a synthetic sewage. Methods:  Biomass samples taken from nine full scale enhanced biological phosphate removal (EBPR) activated sludge plants in the eastern states of Australia were analysed for their populations of polyphosphate (polyP)‐accumulating organisms (PAO) using semi‐quantitative fluorescence in situ hybridization (FISH) in combination with DAPI (4′‐6‐diamidino‐2‐phenylindole) staining for polyP. Results:  Very few betaproteobacterial Rhodocyclus related organisms could be detected by FISH in most of the plants examined, and even where present, not all these cells even within a single cluster, stained positively for polyP with DAPI. In some plants in samples from aerobic reactors the Actinobacteria dominated populations containing polyP. Conclusions:  The PAO populations in full‐scale EBPR systems often differ to those seen in laboratory scale reactors fed artificial sewage, and Rhodocyclus related organisms, dominating these latter communities may not be as important in full‐scale systems. Instead Actinobacteria may be the major PAO. Significance and Impact of the Study:  These findings illustrate how little is still known about the microbial ecology of EBPR processes and that more emphasis should now be placed on analysis of full‐scale plants if microbiological methods are to be applied to monitoring their performances.

We investigated the prevalence and persistence of Escherichia coli strains in four sewage treatment plants (STPs) in a subtropical region of Queensland, Australia. In all, 264 E. coli strains were typed using a high-resolution biochemical fingerprinting method and grouped into either a single or a common biochemical phenotype (S-BPT and C-BPT, respectively). These strains were also tested for their phylogenetic groups and 12 virulence genes associated with intestinal and extraintestinal E. coli strains. Comparison of BPTs at various treatment stages indicated that certain BPTs were found in two or all treatment stages. These BPTs constituted the highest proportion of E. coli strains in each STP and belonged mainly to phylogenetic group B2 and, to a lesser extent, group D. No virulence genes associated with intestinal E. coli were found among the strains, but 157 (59.5%) strains belonging to 14 C-BPTs carried one or more virulence genes associated with uropathogenic strains. Of these, 120 (76.4%) strains belonged to seven persistent C-BPTs and were found in all four STPs. Our results indicate that certain clonal groups of E. coli with virulence characteristics of uropathogenic strains can survive the treatment processes of STPs. These strains were common to all STPs and constituted the highest proportion of the strains in different treatment tanks of each STP.

Aims: To investigate the presence of methicillin-resistant Staphylococcus aureus (MRSA) in untreated hospital wastewaters (UHWW), their transmission into the receiving sewage treatment plant (STP) and survival through the STP treatment. Methods and Results: Over eight consecutive weeks of sampling, we isolated 224 Staph. aureus strains from UHWW-1, UHWW-2 and its receiving STP inlet (SI) and post-treatment outlet (SO). These strains were typed using the PhP typing method and RAPD-PCR and tested for their antibiotic resistance patterns. Resistance to cefoxitin and the presence of mecA gene identified MRSA isolates. In all, 11 common (C) and 156 single (S) PhP-RAPD types were found among isolates, with two multidrug resistant (MDR) C-types found in H2, SI and SO. These C-type strains also showed resistance to cefoxitin and vancomycin. The mean number of antibiotics to which the strains from UHWW were resistant (5Á14 ± 2) was significantly higher than the STP isolates (2Á9 ± 1Á9) (P < 0Á0001). Among the 131 (68%) MRSA strains, 24 were also vancomycin resistant. MDR strains (including MRSA) were more prevalent in hospital wastewaters than in the STP. Conclusion: This study provides evidence of the survival of MRSA strains in UHWWs and their transit to the STP and then through to the final treated effluent and chlorination stage. Significance and Impact of the Study: This preliminary study identifies the need to further investigate the load of MRSA in hospitals' wastewaters and possible their survival in STPs. From a public health point of view, this potential route of hospital MRSA dissemination is of great importance.

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