Automated dead-end ultrafiltration of large volume water samples to enable detection of low-level targets and reduce sample variability.

AIMS: A Portable Multi-use Automated Concentration System (PMACS) concentrates micro-organisms from large volumes of water through automated dead-end ultrafiltration and backflushing. The ability to detect microbial targets from ground, surface and cooling tower waters collected using standard methods was compared with samples from the PMACS in this study. METHODS AND RESULTS: PMACS (100 l) and standard grab samples (100-500 ml) were collected from sites in Florida and South Carolina, USA. Samples were analysed for the presence of faecal indicator bacteria (FIB; ground and surface water) or Legionella pneumophila (Lp; cooling tower water). FIB were enumerated by growth on selective media following membrane filtration or in IDEXX defined substrate media. Lp cells were detected by direct fluorescence immunoassay using FITC-labelled monoclonal antibodies targeting serogroups 1, 2, 4 and 6. FIB were found in PMACS samples from ground and surface waters when their concentrations were below detection limits in grab samples. The concentrations of Lp in cooling tower samples collected over 5 months were more consistent in PMACS samples than grab samples. CONCLUSIONS: These data demonstrate that PMACS concentration is advantageous for water monitoring. FIB were detected in PMACS samples when their concentrations were below the detection limits of the standard methods used. PMACS processing provided more representative samples of cooling tower waters reducing sample variability during long-term monitoring. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the utility of PMACS processing for enhanced monitoring of water for low-level microbial targets and for reducing sample variability in long-term monitoring programmes.

Automated concentration and recovery of micro-organisms from drinking water using dead-end ultrafiltration.

AIMS: Concentration of pathogens diluted in large volumes of water is necessary for their detection. An automated concentration system placed online in drinking water distribution systems would facilitate detection and mitigate the risk to public health. METHODS AND RESULTS: A prototype concentrator based on dead-end hollow fibre ultrafiltration was used to concentrate Bacillus atrophaeus spores directly from tap water. Backflush was used to recover accumulated particulates for analysis. In field tests conducted on a water utility distribution system, 3.2 x 10(4)-1.4 x 10(6) CFU ml(-1) (6.1 x 10(6)-3.0 x 10(8) CFU) were recovered from the filter when 2.9 x 10(7)-1.0 x 10(9) CFU were spiked into the system. Per cent recovery ranged from 21% to 68% for flow volumes of 15-21 l. Tests using spore influent levels <10 CFU l(-1) (spike < 1000 CFU) yielded 23-40% recovery for volumes >100 l. CONCLUSIONS: B. atrophaeus spores at levels <10 CFU l(-1) were concentrated directly from tap water using an automated dead-end hollow-fibre ultrafiltration system. SIGNIFICANCE AND IMPACT OF THE STUDY: The prototype concentrator represents a critical step towards an autonomous system that could be installed in drinking water distribution lines or other critical water lines to facilitate monitoring. Recovered samples can be analysed using standard or rapid biosensor methods.

Characterization of monoclonal antibodies to two Treponema denticola serotypes by the indirect fluorescent-antibody assay.

Members of the genus Treponema have been implicated as possible aetiologic agents of periodontal disease. Previously developed murine monoclonal antibodies (MAbs) to two Treponema denticola strains were characterized by an indirect fluorescent-antibody (IFA) technique. Fifteen T. denticola strains and 32 other bacteria commonly isolated from periodontal pockets were used in the screening process. Two monoclonal antibodies to T. denticola ATCC 33521, serotype B, reacted with five T. denticola isolates, and one monoclonal antibody to T. denticola ATCC 33520, serotype c, reacted with two T. denticola isolates. There was no cross-reactivity between MAbs to the two serotypes. Preliminary tests of the MAbs on human periodontal samples show that they are useful in detecting these bacteria in clinical samples.

Measurement of biological activity in materially closed microbial ecosystems.

Gas phase oxygen concentrations of materially closed, energetically open miniature microbial ecosystems were measured periodically. Our results indicate: (i) closed systems remain biologically active for at least 9 years, (ii) Po2 values might serve as an indicator of stability, (iii) each closed ecosystem seems to seek its own unique final Po2 state, and (iv) ecosystem response to experimentally depleted Po2 suggests the presence of positive feedback control.

A survey of attitudes of obstetric patients to a new-old concept of postnatal care.

One hundred and thirty six mothers who were patients in a low dependency postnatal maternity unit were surveyed to assess their attitudes to this kind of care, and whether they preferred it to the more traditional acute care maternity unit. Their confidence in caring for their babies was also assessed. A three month follow-up study sought a retrospective opinion of the unit and measured the incidence of breast feeding. The findings indicated an overwhelming support for this kind of unit.