Cytotoxicity analysis of pre- and post-hurricane harvey soil samples collected from greater houston bayous.

Rapid urbanization, anthropogenic pollution and frequent flooding events are affecting the soil and water quality along the streams and bayous of Houston. Soil acts as sink and reservoir of heavy metals and nutrients affecting human and animal health. The objectives of the study are 1) to analyze the effects of the metal and nutrient concentration of bayou flood plain surface soil samples on the gut cell cytotoxicity and 2) to evaluate the spatial and temporal difference in soil contamination on cell viability of colon cancer (HT-29) and normal colon epithelial (CCD 841 CoN) cell lines. To evaluate soil contamination between pre- and post-hurricane (Summer and Fall) conditions in six Bayous (Brays, Buffalo, Halls, Hunting, Greens and White Oak Bayous) of Harris County, Texas, in vitro bioassay analysis was applied to soil extracts. The MTT assay determined that, with increase in concentration of Bayou soil from 12.5% to 100%, the viability of CCD 841 CoN and HT-29 cells decreased significantly, across all sampling locations during both summer and fall seasons. Among all the bayous, the viability of CCD 841 CoN cells in summer and fall followed the pattern of White Oak > Greens > Halls > Brays Bayou, where the viability of cells exposed to White Oak soils was 3-4 times higher than cells exposed to Brays Bayou soil at 100% soil concentration. The viability of HT-29 cells in both seasons followed the pattern of Greens > White Oak > Halls > Brays Bayou, where the viability of cells exposed to Greens Bayou soil was more than 3-4 times higher than the cells exposed to Brays Bayou soil at 100% concentration. The higher concentration of metals and nutrients such as P, Zn, Cd, and Cu might have contributed to the significant cell lethality in Brays Bayou samples compared to other locations.

Mixed bacterial responses to dust exposure in an A549 eukaryotic co-culture.

Recent studies evaluated the impact of dust exposure on pure and mixed cultures of Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, and Pseudomonas aeruginosa, revealing increased biofilm formation and altered sensitivities to H2O2. In this study, we examined the impact of lead (Pb), house, road, and combined dust on K. pneumoniae and P. aeruginosa in pure, mixed, or eukaryotic co-culture with human alveolar basal epithelial (A549) cells. Although no impact on pure or mixed culture growth was observed when bacteria were exposed to Pb, house, or road dust, increased biofilm was produced by P. aeruginosa in the presence of 0.8 µg/mL of Pb, while P. aeruginosa and K. pneumoniae both exhibited increased biofilm production in the presence of 100 µg/mL of house, road, and combined dust. When co-cultured with eukaryotic A549 cells, both bacteria demonstrated increased proliferation 6 h post-infection when challenged with house, road, or combined dust. However, when mixed bacteria were co-cultured with A549 cells, P. aeruginosa exhibited a significant ~ 1.5-fold increased proliferation in the presence of 100 µg/mL house, road, or combined dust. In sharp contrast, K. pneumoniae exhibited significantly reduced proliferation, when in mixed (with P. aeruginosa) A-549 co-culture, following exposure to 100 µg/mL house, road, or combined dust. To evaluate whether a host cell inflammatory response contributed to this disparity, NF-κB activation was evaluated in each co-culture infection. K. pneumoniae-A-549 co-culture, treated with 100 µg/mL of combined dust, exhibited no alterations in NF-κB translocation to the nucleus. Further, no differences in cytokine production were observed in the K. pneumoniae A-549 co-culture treated with 100 µg/mL of house dust. Taken together, these data suggest that within the lung environment, mixed infections exposed to dust or dust contaminants could benefit one organism at the expense of the other, independent of the activation of inflammatory pathways.