Monitoring of β-d-Galactosidase Activity as a Surrogate Parameter for Rapid Detection of Sewage Contamination in Urban Recreational Water

Abstract

Simple, automated methods are required for rapid detection of wastewater contamination in urban recreational water. The activity of the enzyme β-D-galactosidase (GAL) can rapidly (<2 h) be measured by field instruments, or a fully automated instrument, and was evaluated as a potential surrogate parameter for estimating the level of fecal contamination in urban waters. The GAL-activity in rivers, affected by combined sewer overflows, increased significantly during heavy rainfall, and the increase in GAL-activity correlated well with the increase in fecal indicator bacteria. The GAL activity in human feces (n = 14) was high (mean activity 7ˆ10 7 ppb MU/hour) and stable (1 LOG 10 variation), while the numbers of Escherichia coli and intestinal enterococci varied by >5 LOG 10 . Furthermore, the GAL-activity per gram feces from birds, sheep and cattle was 2-3 LOG 10 lower than the activity from human feces, indicating that high GAL-activity in water may reflect human fecal pollution more than the total fecal pollution. The rapid method can only be used to quantify high levels of human fecal pollution, corresponding to about 0.1 mg human feces/liter (or 10 3 E. coli/100 mL), since below this limit GAL-activity from non-fecal environmental sources may interfere.

Early detection and classification of live bacteria using time-lapse coherent imaging and deep learning

“…Overall, there is a strong and urgent need for an automated method that can achieve rapid and high-throughput colony detection with high sensitivity (routinely achieving, e.g., 1 CFU per 100–1000 mL in less than 12 h) to provide a powerful alternative to the currently available EPA-approved gold-standard analytical methods that (1) are slow, take ~24–48 h and (2) require experts to read and quantify samples. To address this important need, various other approaches 18 – 20 have been investigated for the detection of total coliform bacteria and E. coli in water samples, including solid phase cytometry 21 , droplet-based micro-optical lens array measurements 22 , fluorimetry 23 , luminometry 24 , and fluorescence microscopy 25 . Despite the fact that these methods provide high sensitivity and some time savings, they cannot handle large sample sizes (e.g., ≥100 mL) or cannot perform the automated classification of bacterial colonies.…”

Transcriptional Response of Staphylococcus aureus to Sunlight in Oxic and Anoxic Conditions

“…However, FIB concentrations are known to fluctuate on short timescales due to factors such as sunlight exposure and tides (Boehm et al, 2009 ; Russell et al, 2013 ; Corsi et al, 2016 ), calling into question the utility of FIB measurements that require long processing times. To address this issue, rapid detection methods and water quality modeling techniques have begun to be applied in recreational water quality monitoring (Wade et al, 2008 ; Thoe et al, 2015 ; He et al, 2016 ; Tryland et al, 2016 ). However, an incomplete understanding of the mechanisms leading to bacterial decay in coastal environments limits our ability to include these factors in water quality models and points to a need for improved understanding of these mechanisms.…”

Monitoring Approaches for Faecal Indicator Bacteria in Water: Visioning a Remote Real-Time Sensor for E. coli and Enterococci

“…Enzyme activity assays [7,22,26,28,[42][43][44]77,82,[99][100][101][102][103][144][145][146][147][148][149][150] The assays use enzyme chemistry and are used within biosensors and find results through fluorescence. Additionally, used in portable field kits, automated instruments, and traditional laboratory techniques.…”

“…The results are typically gathered through external measurement devices but can be viewed by eye in some circumstances. Processing typically involves sample filtration, lysing, and incubations of β-d-glucuronidase (GUS) activity for viable culturable (VC) and VBNC E. coli and glucosidase activity for enterococci [42,99,100]. However, GUS activity is the most specific, being present in 94-97% of the E. coli strains tested [99].…”

“…Similarly, the portable Colifast field kit contains the equipment required to perform any of the three available instrumental analyses; the kit includes the Colifast growth medium, sample vials, utensils, an incubator, and a fluorimeter (the Colifast measuring device), allowing portable detection of E. coli. A 10 mL sample is manually tested, for results between 15 min and 2 h, detecting down to 1 CFU/100 mL [100,107]. On the other hand, some field kits under development offer very promising result times; one such system is the handheld fluorimeter device by Ferrero et al [79].…”