Quantification and molecular characterization of intact rotavirus species A (RVA) in municipal solid waste leachate

AIMS

Leachate comprises a solid waste decomposition product found fresh in collection trucks or as an effluent in landfills. This study aimed to assess the occurrence, concentrations, and genetic diversity of intact rotavirus species A (RVA) in solid waste leachate.

METHODS AND RESULTS

Leachate samples were concentrated by ultracentrifugation, treated with propidium monoazide (PMA), and exposed to LED photolysis. Treated and untread samples were extracted using the QIAamp Fast DNA Stool mini kit, and nucleic acids were screened for RVA employing a Taqman® Real-time PCR. The PMA RT-qPCR method detected RVA in eight out of nine truck samples and in 15.40% (2/13) of the landfill leachate samples. The RVA concentrations in the PMA-treated samples ranged from 4.57 × 103 to 2.15 × 107 genomic copies (GC) 100 mL-1 in truck leachate and from 7.83 × 103 to 1.42 × 104 GC 100 mL-1 in landfill samples. Six truck leachate samples were characterized as RVA VP6 genogroup I2 by partial nucleotide sequencing.

CONCLUSIONS

The high intact RVA detection rates and concentrations in truck leachate samples indicate potential infectivity and comprise a warning for solid waste collectors concerning hand-to-mouth contact and the splash route.

Human adenovirus in municipal solid waste leachate and quantitative risk assessment of gastrointestinal illness to waste collectors

Leachate is a variable effluent from waste management systems generated during waste collection and on landfills. Twenty-two leachate samples from waste collection trucks and a landfill were collected from March to December 2019 in the municipality of Rio de Janeiro (Brazil) and were analyzed for Human Adenovirus (HAdV), bacterial indicators and physico-chemical parameters. For viral analysis, samples were concentrated by ultracentrifugation and processed for molecular analysis using QIAamp Fast DNA Stool mini kit® for DNA extraction followed by nested-PCR and qPCR/PMA-qPCR TaqMan® system. HAdV was detected by nested-PCR in 100% (9/9) and 83.33% (12/13) of the truck and landfill leachate samples, respectively. Viral concentrations ranged from 8.31 × 10¹ to 6.68 × 10⁷ genomic copies per 100 ml by qPCR and PMA-qPCR. HAdV species A, B, C, and F were characterized using nucleotide sequencing. HAdV were isolated in A549 culture cells in 100% (9/9) and 46.2% (6/13) from truck and landfill leachate samples, respectively. Regardless of the detection methods, HAdV concentration was predicted by the quantity of total suspended solids. A quantitative microbial risk assessment was performed to measure the probability of gastrointestinal (GI) illness attributable to inadvertent oral ingestion of truck leachate, revealing the higher probability of disease for the direct splashing into the oral cavity (58%) than for the gloved hand-to-mouth (33%). In a scenario where waste collectors do not wear gloves as protective personal equipment, the risk increases to 67%. This is the first study revealing infectious HAdV in solid waste leachate and indicates a potential health risk for waste collectors.

Evaluation of Viral Recovery Methodologies from Solid Waste Landfill Leachate

Leachate from solid waste landfill is a dark liquid of variable composition and possible source of contamination of groundwater and surface waters. This study aims to assess skimmed milk flocculation and ultracentrifugation as viral concentration methods associated to different nucleic acid extraction protocols in order to establish a methodology for virus recovery from sanitary landfill leachate. Spiking experiments using human adenovirus (HAdV) and bacteriophage PP7 revealed the association of QIAamp Fast DNA Stool mini kit® nucleic acid extraction and ultracentrifugation as an effective method for recovering HAdV (346.18%) and PP7 (523.97%) when compared to organic flocculation method (162.64% for HAdV and 0.61% for PP7) that presented PCR inhibition in all undiluted samples. Ultracentrifugation applied in three landfill samples confirm efficiency of the methodology detecting HAdV in all samples with a mean of 3.44E + 06 ± 1.56E + 06 genomic copies/mL. Nucleotide sequencing characterized HAdV as belonging to group B and F. JC polyomavirus (JCPyV) was also investigated in those samples; however, detection was not observed. Methodologies for detection of viruses in leachate can be useful to generate data for future health risk analysis of workers who have contact with solid urban waste, as well as populations exposed to different environmental matrices contaminated by these effluents.