Review of Methods Suitable for Environmental Surveillance of Salmonella Typhi and Paratyphi.

Typhoid fever is an enteric disease caused by the pathogens Salmonella Typhi and Salmonella Paratyphi. Clinical surveillance networks are lacking in many affected areas, thus presenting a need to understand transmission and population prevalence. Environmental surveillance (ES) has been suggested as a potentially effective method in the absence of (or in supplement to) clinical surveillance. This review summarizes methods identified in the literature for sampling and detection of typhoidal Salmonella from environmental samples including drinking water, wastewater, irrigation water, and surface waters. Methods described use a trap or grab sampling approach combined with various selective culture and molecular methods. The level to which the performance of identified methods is characterized for ES in the literature is variable, thus arguing for the optimization and standardization of ES techniques.

A Review of the Most Commonly Used Methods for Sample Collection in Environmental Surveillance of Poliovirus.

We performed a review of the environmental surveillance methods commonly used to collect and concentrate poliovirus (PV) from water samples. We compared the sampling approaches (trap vs grab), the process methods (precipitation vs filtration), and the various tools and chemical reagents used to separate PV from other viruses and pathogens in water samples (microporous glass, pads, polyethylene glycol [PEG]/dextran, PEG/sodium chloride, NanoCeram/ViroCap, and ester membranes). The advantages and disadvantages of each method are considered, and the geographical areas where they are currently used are discussed. Several methods have demonstrated the ability to concentrate and recover PVs from environmental samples. The details of the particular sampling conditions and locations should be considered carefully in method selection.

Evaluation of the bag-mediated filtration system as a novel tool for poliovirus environmental surveillance: Results from a comparative field study in Pakistan.

Poliovirus (PV) environmental surveillance (ES) plays an important role in the global eradication program and is crucial for monitoring silent PV circulation especially as clinical cases decrease. This study compared ES results using the novel bag-mediated filtration system (BMFS) with the current two-phase separation method. From February to November 2016, BMFS and two-phase samples were collected concurrently from twelve sites in Pakistan (n = 117). Detection was higher in BMFS than two-phase samples for each Sabin-like (SL) PV serotype (p<0.001) and wild PV type 1 (WPV1) (p = 0.065). Seventeen sampling events were positive for WPV1, with eight discordant in favor of BMFS and two in favor of two-phase. A vaccine-derived PV type 2 was detected in one BMFS sample but not the matched two-phase. After the removal of SL PV type 2 (SL2) from the oral polio vaccine in April 2016, BMFS samples detected SL2 more frequently than two-phase (p = 0.016), with the last detection by either method occurring June 12, 2016. More frequent PV detection in BMFS compared to two-phase samples is likely due to the greater effective volume assayed (1620 mL vs. 150 mL). This study demonstrated that the BMFS achieves enhanced ES for all PV serotypes in an endemic country.

Organics captured from comet 81P/Wild 2 by the Stardust spacecraft.

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

Isotopic compositions of cometary matter returned by Stardust.

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.

Infrared spectroscopy of comet 81P/Wild 2 samples returned by Stardust.

Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.

Elemental compositions of comet 81P/Wild 2 samples collected by Stardust.

We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ( approximately 180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

Mineralogy and petrology of comet 81P/Wild 2 nucleus samples.

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.