Gail M. Brion

F-specific RNA coliphages: occurrence, types, and survival in natural waters

A small, well-defined watershed was investigated over a 2-year period to determine the prevalence of F-specific RNA coliphage (F + RNA) serotypes as indicators of animal fecal contamination. Sampling sites collected runoff from areas of urban and agricultural land use patterns. F-specific coliphages were concentrated from 2-L freshwater samples by polyethylene glycol precipitation, isolated using the double agar layer (DAL) method, confirmed as F + RNA by RNAse suppression, and serotyped. A subset of serotyped F + RNA were confirmed by genotyping. To determine relative survival, 10 confirmed F + RNA field isolates and 5 prototypic F + RNA were spiked into surface water and incubated at 25 degrees C for 36 days. F-specific coliphage isolation was strongly associated with rainfall events and was infrequent from primarily animal impacted surface waters. Field isolates were predoffiinantly Type I F + RNA (81%) and raw sewage isolates were predominantly Type III F + RNA (57%). Genotyping from either the watershed or raw sewage samples never positively identified Type IV F + RNA. Results from laboratory studies showed that F + RNA differ in their survival in water and that Type IV strains were the least persistent. Type III F + RNA were found to be reliably related to the release of uncontrolled human fecal material in the watershed, but the results of this study suggest that further study is required before utilizing for fecal source identification in natural waters.

A neural network approach to identifying non-point sources of microbial contamination

Commonly measured fecal bacteria concentrations in water and rainfall data were utilized as inputs for training a neural network model to distinguish between urban and agricultural fecal contamination present in inputs to a drinking water reservoir. Seven sites were selected that represented differing degrees of fecal contamination arising from agricultural, urban, or a blend of both land use activities. The absence of human sewage at the inlet sites to the reservoir was determined by analysis for coprostannol and serotyping of male-specific coliphage. Analyses for fecal coliform (FC), fecal streptococci (FS), total coliform (TC) and coliphage were conducted over 2 years from weekly samples collected from these sites during dry and rainy times during warm seasons. The average concentrations of microorganisms measured were highly variable and analysis of FC/FS ratios was not able to differentiate between urban or agriculturally impacted sites. A neural network model was written that used bacterial and weather data to differentiate between three site classifications: urban, agricultural and a mixture of these. The validity of the source identification, neural network model was verified through case study.

A neural-network-based classification scheme for sorting sources and ages of fecal contamination in water

Artificial neural networks (ANNs) were successfully applied to data observations from a small watershed consisting of commonly measured indicator bacteria, weather conditions, and turbidity to distinguish between human sewage and animal-impacted runoff, fresh runoff from aged, and agricultural land-use-associated fresh runoff from that of suburban land-use-associated-fresh runoff. The ANNs were applied in a cascading, or hierarchical scheme. ANN performance was measured in two ways: (1) training and (2) testing. An ANN was able to sort sewage from runoff with < 1% error. Turbidity was found to be relatively unimportant for sorting sewage from runoff, while gross measurements of gram-negative and gram-positive bacteria were required. Predictions clustered tightly around the known values. ANN classification of aged suburban runoff from fresh, and agricultural runoff from suburban was accomplished with > 90% accuracy.

Iodine disinfection of a model bacteriophage, MS2, demonstrating apparent rebound

Abstract MS2 coliphage viruses suspended in buffered distilled water were rapidly inactivated by

Mortality patterns among Paducah Gaseous Diffusion Plant workers.

Objective: To determine whether Paducah Gaseous Diffusion Plant workers had mortality patterns that differed from the general US population and to investigate whether mortality patterns were associated with job title or workplace exposures. Methods: A retrospective occupational cohort mortality study was conducted on 6759 workers. Standardized mortality ratio analyses compared the cohort with the referent US population. Internal comparisons producing standardized rate ratios were conducted by job title, metal exposure, and cumulative internal and external radiation exposures. Results: Overall mortality and cancer rates were lower than the referent population, reflecting a strong healthy worker effect. Individual not significant standardized mortality ratios and standardized rate ratios were noted for cancers of the lymphatic and hematopoietic tissue. Conclusions: Although relatively low exposures to radiation and metals did not produce statistically significant health effects, no significant elevations for lymphatic and hematopoietic cancers were consistent with previous studies of nuclear workers.

Occupational exposure to trichloroethylene and cancer risk for workers at the Paducah Gaseous Diffusion Plant.

ObjectiveThe Paducah Gaseous Diffusion Plant (PGDP) became operational in 1952; it is located in the western part of Kentucky. We conducted a mortality study for adverse health effects that workers may have suffered while working at the plant, including exposures to chemicals.Materials and MethodsWe studied a cohort of 6820 workers at the PGDP for the period 1953 to 2003; there were a total of 1672 deaths to cohort members. Trichloroethylene (TCE) is a specific concern for this workforce; exposure to TCE occurred primarily in departments that clean the process equipment. The Life Table Analysis System (LTAS) program developed by NIOSH was used to calculate the standardized mortality ratios for the worker cohort and standardized rate ratio relative to exposure to TCE (the U.S. population is the referent for ageadjustment). LTAS calculated a significantly low overall SMR for these workers of 0.76 (95% CI: 0.72–0.79). A further review of three major cancers of interest to Kentucky produced significantly low SMR for trachea, bronchus, lung cancer (0.75, 95% CI: 0.72–0.79) and high SMR for Non-Hodgkin’s lymphoma (NHL) (1.49, 95% CI: 1.02–2.10).ResultsNo significant SMR was observed for leukemia and no significant SRRs were observed for any disease. Both the leukemia and lung cancer results were examined and determined to reflect regional mortality patterns. However, the Non-Hodgkin’s Lymphoma finding suggests a curious amplification when living cases are included with the mortality experience.ConclusionsFurther examination is recommended of this recurrent finding from all three U.S. Gaseous Diffusion plants.

Artificial neural network prediction of viruses in shellfish.

ABSTRACT A database was probed with artificial neural network (ANN) and multivariate logistic regression (MLR) models to investigate the efficacy of predicting PCR-identified human adenovirus (ADV), Norwalk-like virus (NLV), and enterovirus (EV) presence or absence in shellfish harvested from diverse countries in Europe (Spain, Sweden, Greece, and the United Kingdom). The relative importance of numerical and heuristic input variables to the ANN model for each country and for the combined data was analyzed with a newly defined relative strength effect, which illuminated the importance of bacteriophages as potential viral indicators. The results of this analysis showed that ANN models predicted all types of viral presence and absence in shellfish with better precision than MLR models for a multicountry database. For overall presence/absence classification accuracy, ANN modeling had a performance rate of 95.9%, 98.9%, and 95.7% versus 60.5%, 75.0%, and 64.6% for the MLR for ADV, NLV, and EV, respectively. The selectivity (prediction of viral negatives) was greater than the sensitivity (prediction of viral positives) for both models and with all virus types, with the ANN model performing with greater sensitivity than the MLR. ANN models were able to illuminate site-specific relationships between microbial indicators chosen as model inputs and human virus presence. A validation study on ADV demonstrated that the MLR and ANN models differed in sensitivity and selectivity, with the ANN model correctly identifying ADV presence with greater precision.

Effect of microgravity on Escherichia coli and MS-2 bacteriophage disinfection by iodinated resins☆

Experiments on chemical disinfection by iodinated resins were conducted on STS 50 (USML-1), which flew a 13 day mission during 1992. Fluid processing apparatus containing microorganisms and iodinated resins was assembled in either Manhattan, Kansas, or Boulder, Colorado, and loaded on-board the Space Shuttle for the mission. Pentaiodide resin was more effective than the triiodide resin against Escherichia coli. Both resins were more effective bactericides at unit gravity than microgravity because of cosedimentation of bacteria and iodinated resin beads. In bacteriophage experiments, the triiodide resin reduced the viable titer of MS-2 by nine logs. The few viable phage surviving chemical disinfection were associated with precipitant formation in the fluid processing apparatus.

Multivariate Logistic Regression for Predicting Total Culturable Virus Presence at the Intake of a Potable-Water Treatment Plant: Novel Application of the Atypical Coliform/Total Coliform Ratio

ABSTRACT Predicting the presence of enteric viruses in surface waters is a complex modeling problem. Multiple water quality parameters that indicate the presence of human fecal material, the load of fecal material, and the amount of time fecal material has been in the environment are needed. This paper presents the results of a multiyear study of raw-water quality at the inlet of a potable-water plant that related 17 physical, chemical, and biological indices to the presence of enteric viruses as indicated by cytopathic changes in cell cultures. It was found that several simple, multivariate logistic regression models that could reliably identify observations of the presence or absence of total culturable virus could be fitted. The best models developed combined a fecal age indicator (the atypical coliform [AC]/total coliform [TC] ratio), the detectable presence of a human-associated sterol (epicoprostanol) to indicate the fecal source, and one of several fecal load indicators (the levels of Giardia species cysts, coliform bacteria, and coprostanol). The best fit to the data was found when the AC/TC ratio, the presence of epicoprostanol, and the density of fecal coliform bacteria were input into a simple, multivariate logistic regression equation, resulting in 84.5% and 78.6% accuracies for the identification of the presence and absence of total culturable virus, respectively. The AC/TC ratio was the most influential input variable in all of the models generated, but producing the best prediction required additional input related to the fecal source and the fecal load. The potential for replacing microbial indicators of fecal load with levels of coprostanol was proposed and evaluated by multivariate logistic regression modeling for the presence and absence of virus.

Effects of RH on Glass Microfiber Filtration Efficiency for Airborne Bacteria and Bacteriophage Over Time

This study investigated the removal efficiency of viable signals of aerosolized bacteria and viruses, stabilized with respect to relative humidity, by simple glass microfiber filters. When examined over an extended time period, relative humidity affected both the size distribution of the stabilized aerosols and the removal efficiency of aerosolized microorganisms by simple glass microfiber filters. The size distribution of the generated humidity stabilized aerosol particles differed, with 50% relative humidity having a greater number of small diameter particles ( < .02 microns) than aerosols generated at 23% relative humidity, and 23% relative humidity having more particles in the range between .02 and .3 microns than 50%. The removal efficiency of aerosols containing viable bacteria (E. coli) and bacterial viruses (MS2) initially showed greater than 5 logs of removal (99.999%) at both 23% and 50% RHs for both aerosolized microorganisms. Increased RH was related to improved removal of viable aerosolized bacteria and viruses at all timepoints measured over a 60-minute test period. RH had more impact upon removal efficiencies for MS2 bacteriophages than E. coli bacteria, with removal efficiencies for MS2 at 50% RH declining after 30 minutes to levels seen at 23% RH. Some interesting findings of this study were that the two microorganisms that were mixed into a single cocktail at similar concentrations to generate the aerosol apparently did not associate, to a large extent, in the same aerosol particles, as inferred by significant differences in their removal behavior at higher RH of 50%. This study shows that the relative humidity of an aerosol-containing stream should be considered as an important experimental control variable, and that the removal of aerosolized viruses cannot be predicted from bacteria.