7 research outputs found
Rapid MPN-Qpcr Screening for Pathogens in Air, Soil, Water, and Agricultural Produce
A sensitive, high-throughput, and cost-effective method for screening bacterial pathogens in the environment was developed. A variety of environmental samples, including aerosols, soil of various types (sand, sand/clay mix, and clay), wastewater, and vegetable surface (modeled by tomato), were concomitantly spiked with Salmonella enterica and/or Pseudomonas aeruginosa to determine recovery rates and limits of detection. The various matrices were first enriched with a general pre-enrichment broth in a dilution series and then enumerated by most probable number (MPN) estimation using quantitative PCR for rapid screening of amplicon presence. Soil and aerosols were then tested in non-spiked environmental samples, as these matrices are prone to large experimental variation. Limit of detection in the various soil types was 1–3 colony-forming units (CFU) g[superscript −1]; on vegetable surface, 5 CFU per tomato; in treated wastewater, 5 CFU L[superscript −1]; and in aerosols, >300 CFU mL[superscript −1]. Our method accurately identified S. enterica in non-spiked environmental soil samples within a day, while traditional methods took 4 to 5 days and required sorting through biochemically and morphologically similar species. Likewise, our method successfully identified P. aeruginosa in non-spiked aerosols generated by a domestic wastewater treatment system. The obtained results suggest that the developed method presents a broad approach for the rapid, efficient, and reliable detection of relatively low densities of pathogenic organisms in challenging environmental samples.United States-Israel Binational Agricultural Research and Development Fund (Grant No. CP-9033-09)MIT International Science and Technology InitiativesKraft Foods Compan
Adapting Enzyme-Based Microbial Water Quality Analysis to Remote Areas in Low-Income Countries
Enzyme–substrate
microbial water tests, originally developed for efficiency gains
in laboratory settings, are potentially useful for on-site analysis
in remote settings. This is especially relevant in developing countries
where water quality is a pressing concern and qualified laboratories
are rare. We investigated one such method, Colisure, first for sensitivity
to incubation temperatures in order to explore
alternative incubation techniques appropriate for remote areas, and
then in a remote community of Zambia for detection of total coliforms
and Escherichia coli in drinking-water
samples. We sampled and analyzed 352 water samples from source, transport
containers and point-of-use from 164 random households. Both internal
validity (96–100%) and laboratory trials (zero false negatives
or positives at incubation
between 30 and 40 °C) established reliability under field conditions.
We therefore recommend the use of this and other enzyme-based methods
for remote applications. We also found that most water samples from
wells accessing groundwater were free of E. coli whereas most samples from surface sources were fecally contaminated.
We further found very low awareness among the population of the high
levels of recontamination in household storage containers, suggesting
the need for monitoring and treatment beyond the water source itself
Antifouling Properties of a Self-Assembling Glutamic Acid-Lysine Zwitterionic Polymer Surface Coating
There
is a need for the development of antifouling materials to
resist adsorption of biomacromolecules. Here we describe the preparation
of a novel zwitterionic block copolymer with the potential to prevent
or delay the formation of microbial biofilms. The block copolymer
comprised a zwitterionic (hydrophilic) section of alternating glutamic
acid (negatively charged) and lysine (positively charged) units and
a hydrophobic polystyrene section. Cryo-TEM and dynamic-light-scattering
(DLS) results showed that, on average, the block copolymer self-assembled
into 7-nm-diameter micelles in aqueous solutions (0 to 100 mM NaCl,
pH 6). Quartz crystal microbalance with dissipation monitoring (QCM-D),
atomic force microscopy (AFM), and contact angle measurements demonstrated
that the block copolymer self-assembled into a brush-like monolayer
on polystyrene surfaces. The brush-like monolayer produced from a
100 mg/L block copolymer solution exhibited an average distance, <i>d</i>, of approximately 4–8 nm between each block copolymer
molecule (center to center). Once the brush-like monolayer self-assembled,
it reduced EPS adsorption onto the polystyrene surface by ∼70%
(mass), reduced the rate of bacterial attachment by >80%, and inhibited
the development of thick biofilms. QCM-D results revealed that the
EPS molecules penetrate between the chains of the brush and adsorb
onto the polystyrene surface. Additionally, AFM analyses showed that
the brush-like monolayer prevents the adhesion of large (><i>d</i>) hydrophilic colloids onto the surface via hydration repulsion;
however, molecules or colloids small enough to fit between the brush
polymers (<<i>d</i>) were able to be adsorbed onto the
surface via van der Waals interactions. Overall, we found that the
penetration of extracellular organelles, as well as biopolymers through
the brush, is critical for the failure of the antifouling coating,
and likely could be prevented through tuning of the brush density.
Stability and biofilm development testing on multiple surfaces (polypropylene,
glass, and stainless steel) support practical applications of this
novel block copolymer