Potable Water
ABL scientists, in collaboration with academic and industry partners, have developed an automated system for concentrating particulates, including pathogens of interest, from potable water. The prototype system was successfully field-tested at a local water utility. In this series of tests, the Automated Concentration System (ACS) was paired with a microarray biosensor for completely autonomous concentration-detection. The ACS is water pressure-driven when hooked to a pressurized line and uses a hollow fiber ultrafilter to concentrate particles from the water stream. Alternatively, water can be pumped through the filter, making monitoring of non-pressurized liquid streams possible. The ACS operates in a dead-end filtration configuration and the filter is backflushed with buffer to recover the collected particulates. At the end of each concentration-recovery cycle, the filter is automatically cleaned and backflushed to prepare it for the next cycle. All concentrator functions needed for water pressure-driven operation are programmable using a script imbedded in the concentrator software permitting complete automation of concentration and recovery. In addition, the ACS programming includes a command to send a signal to a receptive biosensor to initiate automated detection. 
The ACS is currently being tested with an improved filter and other modifications that will improve the filtration rate and target recovery. These modifications will extend the range of targets that can be concentrated and recovered from water to include viruses and possibly some larger biological toxins and also reduce the size and weight of the unit. Projects to develop additional detection technologies, including automated biosensors, to identify targets of interest in the retentate matrix are also underway. Additionally, simple secondary concentration methods are being studied that further lower the limit of detection by concentrating target in the ACS retentate prior to analysis.
Recreational Water 
Microbial fecal indicator organisms have been used for over a century as sentinels for the presence of fecal contamination and to warn of the increased risk for enteric pathogens. They are found in the gastrointestinal tract of humans and other warm-blooded animals. Fecal indicator organisms, along with the pathogens (viruses, bacteria, and protozoa), are shed in fecal material and can contaminate surface waters. Levels of enterococci in bathing waters have been correlated with the incidence of gastrointestinal illness. Enterococci are used as indicators of fecal contamination in marine waters.
Currently, enterococci are detected by membrane filtration followed by incubation on mEI agar for 24 hours (Environmental Protection Agency Method 1600). Potential public exposure to enteric pathogens continues during the incubation period. ABL researchers have developed methods to speed the detection of enterococci by concentrating the organisms present in large volumes of marine water through dead-end hollow fiber ultrafiltration. Concentrated samples are analyzed on a fiber optic biosensor in an indirect assay format using a polyclonal anti-Streptococcus Group D antibody (American Research Products, Belmont, MA) as the primary antibody. The process can detect enterococci within 2.5 hours versus the 24-hour minimum required for EPA Method 1600. Rapid detection of other fecal indicator organisms and enteric pathogens is possible with the ultrafiltration system. One limitation of using microbial fecal indicators to warn of the presence of human pathogens 
is their presence in the fecal material of warm-blooded animals other than humans. Human-associated microbes are found exclusively in the gastrointestinal tracts of humans. They are indicative of the presence of fecally-transmitted human pathogens in surface waters. These microbes are present at much lower levels than fecal indicator organisms however. ABL researchers are developing assays for detection of human-associated microorganisms using the ultrafiltration system coupled to PCR.
Produce Wash
Pathogens in the local food supply have become a serious health concern as the result of several contamination events that have occurred during recent years. ABL scientists are developing methods to assay foods for these pathogens. Initial testing has focused on samples of unwashed lettuce, spinach and other produce acquired from local markets. The produce samples are “washed” in 20 L carboys and the wash water is tested for indicator organisms and select pathogens using both FDA standard (Bacteriological Analytical Manual) 
and rapid detection methods. One goal is to determine if lateral flow assay technology is useful for screening produce wash water and meat samples for E. coli O157:H7. Initial results suggest detection limits for E. coli O157:H7 and Salmonella typhimurium of 105 to 106 CFU/ml for the commercially-available assay strips tested. Since levels in the wash water are expected to be lower, ABL researchers are also developing an automated concentration procedure for the wash water based on the ACS technology developed for potable water. The ultimate goal is to develop a rapid concentration-detection procedure that can sensitively detect and identify pathogens in the wash water in only a few hours. This will facilitate mitigation procedures for contaminated produce and potentially prevent its distribution to the public.