Chemical and in vitro bioanalytical assessment of drinking water quality in Manhiça, Mozambique

BACKGROUND

The chemical quality of drinking water is widely unknown in low-income countries.

OBJECTIVE

We conducted an exploratory study in Manhiça district (Mozambique) to evaluate drinking water quality using chemical analyses and cell-based assays.

METHODS

We measured nitrate, fluoride, metals, pesticides, disinfection by-products, and industrial organochlorinated chemicals, and conducted the bioassays Ames test for mutagenicity, micronuclei assay (MN-FACS), ER-CALUX, and antiAR-CALUX in 20 water samples from protected and unprotected sources.

RESULTS

Nitrate was present in all samples (median 7.5 mg/L). Manganese, cobalt, chromium, aluminium, and barium were present in 90-100% of the samples, with median values of 32, 0.6, 2.0, 61, 250 μg/l, respectively. Manganese was above 50 μg/l (EU guideline) in eight samples. Arsenic, lead, nickel, iron, and selenium median values were below the quantification limit. Antimony, cadmium, copper, mercury, zinc and silver were not present. Trihalomethanes, haloacetic acids, haloacetonitriles and haloketones were present in 5-28% samples at levels ≤4.6 μg/l. DDT, dieldrin, diuron, and pirimiphos-methyl were quantified in 2, 3, 3, and 1 sample, respectively (range 12-60 ng/L). Fluoride was present in one sample (0.11 mg/l). Trichloroethene and tetrachloroethene were not present. Samples were negative in the in vitro assays.

SIGNIFICANCE

Results suggest low exposure to chemicals, mutagenicity, genotoxicity and endocrine disruption through drinking water in Manhiça population. High concentration of manganese in some samples warrants confirmatory studies, given the potential link to impaired neurodevelopment.

DNA vaccination regimes against Schmallenberg virus infection in IFNAR-/- mice suggest two targets for immunization

Schmallenberg virus (SBV) is an RNA virus of the Bunyaviridae family, genus Orthobunyavirus that infects wild and livestock species of ruminants. While inactivated and attenuated vaccines have been shown to prevent SBV infection, little is known about their mode of immunity; specifically, which components of the virus are responsible for inducing immunological responses in the host. As previous DNA vaccination experiments on other bunyaviruses have found that glycoproteins, as well as modified (i.e. ubiquitinated) nucleoproteins (N) can confer immunity against virulent viral challenge, constructs encoding for fragments of SBV glycoproteins G_N and G_C, as well as ubiquitinated and non-ubiquitinated N were cloned in mammalian expression vectors, and vaccinated intramuscularly in IFNAR^-/- mice. Upon viral challenge with virulent SBV, disease progression was monitored. Both the ubiquitinated and non-ubiquitinated nucleoprotein candidates elicited high titers of antibodies against SBV, but only the non-ubiquitinated candidate induced statistically significant protection of the vaccinated mice from viral challenge. Another construct encoding for a putative ectodomain of glycoprotein G_C (segment aa. 678-947) also reduced the SBV-viremia in mice after SBV challenge. When compared to other experimental groups, both the nucleoprotein and G_C-ectodomain vaccinated groups displayed significantly reduced viremia, as well as exhibiting no clinical signs of SBV infection. These results show that both the nucleoprotein and the putative G_C-ectodomain can serve as protective immunological targets against SBV infection, highlighting that viral glycoproteins, as well as nucleoproteins are potent targets in vaccination strategies against bunyaviruses.

Double staining (CTC-DAPI) for detection and enumeration of viable but non-culturable Campylobacter jejuni cells

Direct microscopic enumeration of viable Campylobacter jejuni cells (ie, respiring bacteria) were performed in both culturable and non-culturable states. Five different C jejuni strains were used, including a reference strain, ATCC 33291. Cells from all five strains were incubated alone with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), a redox dye. It was reduced by an electron transport chain to an insoluble red fluorescent CTC formazan salt, which accumulated intracellularly. The presence of these red CTC crystals in the bacteria cells was indicative of cellular respiratory activity. Counterstaining with 4'-6 diamino-2 phenylindole (DAPI), which fluoresces in blue, made a suitable contrast and allowed simultaneous enumeration of total and viable bacteria on a single filter. Four hours of incubation with 5 mM CTC under a microaerobic atmosphere was found to be the optimal condition yielding the maximum number of respiring cells (both culturable and non-culturable). When used in combination with standard culture techniques, double staining makes it possible to monitor the viable but non-culturable cells of jejuni obtained by starvation more easily than with the direct viable count procedure.