Improved virus concentration methods for wash waters from decontamination of permeable and non-permeable surfaces.

Surface decontamination is a method of using wash water to decontaminated surfaces preventing transmission of biological contaminants that can pose potential health risks to responders and the public. However, the risks associated with handling used wash water are largely unknown due to the lack of effective methodology to screen for pathogenic microorganisms present in these samples, especially viral pathogens. This study adapted the dead-end hollow-fiber ultrafiltration (D-HFUF) system to wash waters, including a separate procedure for recovering particle attached viruses. Simulated wash water was created using dechlorinated tap water containing a mild surfactant (0.05 % Tween 80). To determine virus recovery efficiencies, measured amounts of somatic and F+ coliphage were spiked into 2-liter volumes of wash water under the following scenarios: (1) wash water was amended with a measured amount of sterile river sediment with no sediment separation prior to filter concentration; or (2) sediment added to wash water was allowed to settle prior to filter concentrating clarified liquid portions, while precipitated sediment was subjected to viral extraction techniques to recover particle attached virus; and (3) the optimized method was deployed on non-porous and porous surfaces to simulate a decontamination clean-up event. Separation of sediment prior to D-HFUF significantly increased recovery of coliphages, (P = <0.0001) versus filtration of sediment and liquids simultaneously. A tryptic soy broth (TSB) elution solution was significantly more effective (P = ≤0.010) for recovery of both somatic and F+ coliphage, (108 ± 9 % and 92 ± 9 %, respectively), compared to elution buffers containing various surfactants (sodium hexametaphosphate, Tween 80) for recovering particle attached virus. Simulating a biocontaminate clean-up event (using the optimized sediment separation and elution protocol) resulted in coliphage recoveries of 75-96 % (permeable surface) and 71-92 % (non-permeable surface). This procedure can be used to effectively detect viruses in used wash waters aiding in reducing risks to human health during site decontamination.

Assessment of two volumetrically different concentration approaches to improve sensitivities for SARS-CoV-2 detection during wastewater monitoring.

Wastewater monitoring for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the virus responsible for the global coronavirus disease 2019 (COVID-19) pandemic, has highlighted the need for methodologies capable of assessing viral prevalence during periods of low population infection. To address this need, two volumetrically different, methodologically similar concentration approaches were compared for their abilities to detect viral nucleic acid and infectious SARS-CoV-2 signal from primary influent samples. For Method 1, 2 L of SARS-CoV-2 seeded wastewater was evaluated using a dead-end hollow fiber ultrafilter (D-HFUF) for primary concentration, followed by the CP Select™ for secondary concentration. For Method 2, 100 mL of SARS-CoV-2 seeded wastewater was evaluated using the CP Select™ procedure. Following D-HFUF concentration (Method 1), significantly lower levels of infectious SARS-CoV-2 were lost (P value range: 0.0398-0.0027) compared to viral gene copy (GC) levels detected by the US Centers for Disease Control (CDC) N1 and N2 reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) assays. Subsamples at different steps in the concentration process were also taken to better characterize the losses of SARS-CoV-2 during the concentration process. During the centrifugation step (prior to CP Select™ concentration), significantly higher losses (P value range: 0.0003 to <0.0001) occurred for SARS-CoV-2 GC levels compared to infectious virus for Method 1, while between the methods, significantly higher infectious viral losses were observed for Method 2 (P = 0.0002). When analyzing overall recovery of endogenous SARS-CoV-2 in wastewater samples, application of Method 1 improved assay sensitivities (P = <0.0001) compared with Method 2; this was especially evident during periods of lower COVID-19 case rates within the sewershed. This study describes a method which can successfully concentrate infectious SARS-CoV-2 and viral RNA from wastewater. Moreover, we demonstrated that large volume wastewater concentration provides additional sensitivity needed to improve SARS-CoV-2 detection, especially during low levels of community disease prevalence.

Performance evaluation of a dead-end hollowfiber ultrafiltration method for enumeration of somatic and F+ coliphage from recreational waters.

Dead-end hollow fiber ultrafiltration combined with a single agar layer assay (D-HFUF-SAL) has potential use in the assessment of sanitary quality of recreational waters through enumeration of coliphage counts as measures of fecal contamination. However, information on applicability across a broad range of sites and water types is limited. Here, we tested the performance of D-HFUF-SAL on 49 marine and freshwater samples. Effect of method used to titer the spiking suspension (SAL versus double agar layer [DAL]) on percent recovery was also evaluated. Average somatic coliphage recovery (72 % ± 27) was significantly higher (p < 0.0001) compared to F+ (53 % ± 19). This was more pronounced for marine (p ≤ 0.0001) compared to freshwaters (p = 0.0134). Neither method affected somatic coliphage, but DAL (28 % ± 12) significantly (p < 0.0001) underestimated F + coliphage recoveries compared to SAL (53 % ± 19). Overall, results indicate that, while D-HFUF-SAL performed well over a wide variety of water types, F + coliphage recoveries were significantly reduced for marine waters suggesting that some components unique to this habitat may interfere with the assay performance. More importantly, our findings indicate that choice of spike titer method merits careful consideration since it may under-estimate method percent recovery.

Development of a large volume concentration method for recovery of coronavirus from wastewater.

Levels of severe acute respiratory coronavirus type 2 (SARS CoV 2) RNA in wastewater could act as an effective means to monitor coronavirus disease 2019 (COVID-19) within communities. However, current methods used to detect SARS CoV 2 RNA in wastewater are limited in their ability to process sufficient volumes of source material, inhibiting our ability to assess viral load. Typically, viruses are concentrated from large liquid volumes using two stage concentration, primary and secondary. Here, we evaluated a dead-end hollow fiber ultrafilter (D-HFUF) for primary concentration, followed by the CP Select™ for secondary concentration from 2 L volumes of primary treated wastewater. Various amendments to each concentration procedure were investigated to optimally recover seeded OC43 (betacoronavirus) from wastewater. During primary concentration, the D-HFUF recovered 69 ± 18% (n = 29) of spiked OC43 from 2 L of wastewater. For secondary concentration, the CP Select™ system using the Wastewater Application settings was capable of processing 100 mL volumes of primary filter eluates in <25 min. A hand-driven syringe elution proved to be significantly superior (p = 0.0299) to the CP Select™ elution for recovering OC43 from filter eluates, 48 ± 2% compared to 31 ± 3%, respectively. For the complete method (primary and secondary concentration combined), the D-HFUF and CP select/syringe elution achieved overall 22 ± 4% recovery of spiked OC43 through (n = 8) replicate filters. Given the lack of available standardized methodology confounded by the inherent limitations of relying on viral RNA for wastewater surveillance of SARS CoV 2, it is important to acknowledge these challenges when interpreting this data to estimate community infection rates. However, the development of methods that can substantially increase sample volumes will likely allow for reporting of quantifiable viral data for wastewater surveillance, equipping public health officials with information necessary to better estimate community infection rates.

Draft Genome Sequences of Seven Legionella pneumophila Isolates from a Hot Water System of a Large Building.

Public health data show that a significant fraction of the nation's waterborne disease outbreaks are attributable to premise plumbing. We report the draft genome sequences of seven Legionella pneumophila serogroup 1 isolates from hot water lines of a large building. Genomic analysis identified the isolates as belonging to sequence type 1.

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil.

Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.

A Method Detection Limit for Bacillus anthracis Spores in Water Using an Automated Waterborne Pathogen Concentrator.

The method detection limit (MDL, 99% chance of detecting a positive result in a single replicate), as per the United States Code of Federal Regulations, was determined for a protocol using an ultrafiltration based automated waterborne pathogen concentration device. Bacillus anthracis Sterne strain spores were seeded at low levels into 100 L reagent water samples. Suspect colonies were confirmed through morphological, chemical, and genetic tests. Samples of 100 L (n=14) of reagent water were seeded with five B. anthracis CFUs each. To confirm the estimated detection limit, a second set (n=19) of 100 L reagent water samples were seeded at a higher level (7 CFUs). The second estimate of the MDL could not be pooled with the first, due to significant difference in variance. A third trial (n=7) seeded with 10 CFUs produced an estimate of the MDL that could be pooled with the higher previous estimate. Another trial consisting of eight 100 L samples of tap water were seeded with approximately 7 CFUs. Recovery in these samples was not significantly different from the pooled MDL. Theoretically a concentration of 4.6 spores/100 L would be required for detection 95% of the time, based on a Poisson distribution. The calculated pooled MDL, based on experimental data was approximately 6 B. anthracis CFU/100 L (95% confidence interval 4.8 to 8.4). Detection at this level was achieved in municipal water samples.

Construction and characterization of stable, constitutively expressed, chromosomal green and red fluorescent transcriptional fusions in the select agents, Bacillus anthracis, Yersinia pestis, Burkholderia mallei, and Burkholderia pseudomallei.

Here, we constructed stable, chromosomal, constitutively expressed, green and red fluorescent protein (GFP and RFP) as reporters in the select agents, Bacillus anthracis, Yersinia pestis, Burkholderia mallei, and Burkholderia pseudomallei. Using bioinformatic approaches and other experimental analyses, we identified P0253 and P1 as potent promoters that drive the optimal expression of fluorescent reporters in single copy in B. anthracis and Burkholderia spp. as well as their surrogate strains, respectively. In comparison, Y. pestis and its surrogate strain need two chromosomal copies of cysZK promoter (P2cysZK) for optimal fluorescence. The P0253-, P2cysZK-, and P1-driven GFP and RFP fusions were first cloned into the vectors pRP1028, pUC18R6KT-mini-Tn7T-Km, pmini-Tn7-gat, or their derivatives. The resultant constructs were delivered into the respective surrogates and subsequently into the select agent strains. The chromosomal GFP- and RFP-tagged strains exhibited bright fluorescence at an exposure time of less than 200 msec and displayed the same virulence traits as their wild-type parental strains. The utility of the tagged strains was proven by the macrophage infection assays and lactate dehydrogenase release analysis. Such strains will be extremely useful in high-throughput screens for novel compounds that could either kill these organisms, or interfere with critical virulence processes in these important bioweapon agents and during infection of alveolar macrophages.

Rapid targeted gene disruption in Bacillus anthracis.

BACKGROUND: Anthrax is a zoonotic disease recognized to affect herbivores since Biblical times and has the widest range of susceptible host species of any known pathogen. The ease with which the bacterium can be weaponized and its recent deliberate use as an agent of terror, have highlighted the importance of gaining a deeper understanding and effective countermeasures for this important pathogen. High quality sequence data has opened the possibility of systematic dissection of how genes distributed on both the bacterial chromosome and associated plasmids have made it such a successful pathogen. However, low transformation efficiency and relatively few genetic tools for chromosomal manipulation have hampered full interrogation of its genome. RESULTS: Group II introns have been developed into an efficient tool for site-specific gene inactivation in several organisms. We have adapted group II intron targeting technology for application in Bacillus anthracis and generated vectors that permit gene inactivation through group II intron insertion. The vectors developed permit screening for the desired insertion through PCR or direct selection of intron insertions using a selection scheme that activates a kanamycin resistance marker upon successful intron insertion. CONCLUSIONS: The design and vector construction described here provides a useful tool for high throughput experimental interrogation of the Bacillus anthracis genome and will benefit efforts to develop improved vaccines and therapeutics.

Characterization of stable, constitutively expressed, chromosomal green and red fluorescent transcriptional fusions in the select agent bacterium, Francisella tularensis Schu S4 and the surrogate type B live vaccine strain (LVS).

Here, we constructed stable, constitutively expressed, chromosomal green (GFP) and red fluorescent (RFP) reporters in the genome of the surrogate strain, Francisella tularensis spp. holarctica LVS (herein LVS), and the select agent, F. tularensis Schu S4. A bioinformatic approach was used to identify constitutively expressed genes. Two promoter regions upstream of the FTT1794 and rpsF(FTT1062) genes were selected and fused with GFP and RFP reporter genes in pMP815, respectively. While the LVS strains with chromosomally integrated reporter fusions exhibited fluorescence, we were unable to deliver the same fusions into Schu S4. Neither a temperature-sensitive Francisella replicon nor a pBBR replicon in the modified pMP815 derivatives facilitated integration. However, a mini-Tn7 integration system was successful at integrating the reporter fusions into the Schu S4 genome. Finally, fluorescent F. tularensis LVS and a mutant lacking MglA were assessed for growth in monocyte-derived macrophages (MDMs). As expected, when compared to wild-type bacteria, replication of an mglA mutant was significantly diminished, and the overall level of fluorescence dramatically decreased with infection time. The utility of the fluorescent Schu S4 strain was also examined within infected MDMs treated with clarithromycin and enrofloxacin. Taken together, this study describes the development of an important reagent for F. tularensis research, especially since the likelihood of engineered antibiotic resistant strains will emerge with time. Such strains will be extremely useful in high-throughput screens for novel compounds that could interfere with critical virulence processes in this important bioweapons agent and during infection of alveolar macrophages.

Identification of bacterial populations in drinking water using 16S rRNA-based sequence analyses.

Intracellular RNA is rapidly degraded in stressed cells and is more unstable outside of the cell than DNA. As a result, RNA-based methods have been suggested to study the active microbial fraction in environmental matrices. The aim of this study was to identify bacterial populations in drinking water by analyzing 16S rRNA-based clone libraries. Hollow-fiber ultrafiltration was used to concentrate bacterial communities from 40l of tap water collected at 12 different times during three different summer months from a single point-of-use. Total RNA was extracted from the microbial concentrates and used to develop 16S rRNA-based clone libraries. Phylogenetic analyses of 1231 partial 16S rRNA gene sequences showed that difficult-to-classify bacterial sequences were the most predominant clones, representing 57.6% of the sequences analyzed. Within these unclassified clades, most sequences were closely related to sequences retrieved from previous DNA- and RNA-based drinking water studies. Other bacterial groups represented in this study included Proteobacteria, cyanobacteria, Actinobacteria, Bacteroidetes, and Planctomycetes. Overall, the results suggest that these bacterial groups are amongst potentially active bacteria in drinking water. Diversity analyses of clones generated show that while overall diversity is similar amongst the different months, membership changes with respect to time. The results from this study further improve our understanding of the molecular diversity and bacterial population dynamics of drinking water microbial communities. Moreover, these results provide the sequence foundation for the development of molecular assays that target active drinking water bacteria.