title: Wastewater irrigation increases the abundance of potentially harmful gammaproteobacteria in soils in Mezquital Valley, Mexico.
abstract: Wastewater contains large amounts of pharmaceuticals, pathogens, and antimicrobial resistance determinants. Only a little is known about the dissemination of resistance determinants and changes in soil microbial communities affected by wastewater irrigation. Community DNAs from Mezquital Valley soils under irrigation with untreated wastewater for 0 to 100 years were analyzed by quantitative real-time PCR for the presence of sul genes, encoding resistance to sulfonamides. Amplicon sequencing of bacterial 16S rRNA genes from community DNAs from soils irrigated for 0, 8, 10, 85, and 100 years was performed and revealed a 14% increase of the relative abundance of Proteobacteria in rainy season soils and a 26.7% increase in dry season soils for soils irrigated for 100 years with wastewater. In particular, Gammaproteobacteria, including potential pathogens, such as Pseudomonas, Stenotrophomonas, and Acinetobacter spp., were found in wastewater-irrigated fields. 16S rRNA gene sequencing of 96 isolates from soils irrigated with wastewater for 100 years (48 from dry and 48 from rainy season soils) revealed that 46% were affiliated with the Gammaproteobacteria (mainly potentially pathogenic Stenotrophomonas strains) and 50% with the Bacilli, whereas all 96 isolates from rain-fed soils (48 from dry and 48 from rainy season soils) were affiliated with the Bacilli. Up to six types of antibiotic resistance were found in isolates from wastewater-irrigated soils; sulfamethoxazole resistance was the most abundant (33.3% of the isolates), followed by oxacillin resistance (21.9% of the isolates). In summary, we detected an increase of potentially harmful bacteria and a larger incidence of resistance determinants in wastewater-irrigated soils, which might result in health risks for farm workers and consumers of wastewater-irrigated crops.
authors.affiliation: University Medical Centre Freiburg, Division of Infectious Diseases, Freiburg, Germany Albert Ludwigs University Freiburg, Institute for Biology II, Microbiology, Freiburg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Broszat
authors.affiliation: Georg August University Göttingen, Institute of Microbiology and Genetics, Göttingen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Nacke
authors.affiliation: University Medical Centre Freiburg, Division of Infectious Diseases, Freiburg, Germany Albert Ludwigs University Freiburg, Institute for Biology II, Microbiology, Freiburg, Germany.
authors.forename: Ronja
authors.initials: R
authors.lastname: Blasi
authors.affiliation: Universidad Nacional Autónoma de México, Instituto de Geología, Ciudad Universitaria, Mexico City, Mexico.
authors.forename: Christina
authors.initials: C
authors.lastname: Siebe
authors.affiliation: University Medical Centre Freiburg, Division of Infectious Diseases, Freiburg, Germany Hauner Children's Hospital, Division of Pediatric Infectious Diseases, Ludwig Maximilians University Munich, Munich, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Huebner
authors.affiliation: Georg August University Göttingen, Institute of Microbiology and Genetics, Göttingen, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Daniel
authors.affiliation: University Medical Centre Freiburg, Division of Infectious Diseases, Freiburg, Germany Albert Ludwigs University Freiburg, Institute for Biology II, Microbiology, Freiburg, Germany elisabeth.grohmann@uniklinik-freiburg.de.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Grohmann
mesh_terms: D057914:Agricultural Irrigation / Q000379:methods*; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D058448:Biota; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial; D008800:Mexico; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D062065:Wastewater
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D062065:Wastewater