Identification and significance of Gram-negative bacteria in municipal solid waste landfill leachate from Vojvodina region

Landfill leachate is a medium affected by a considerable number of factors, both within the landfill body (landfill age, the morphological composition of waste, temperature and moisture content, landfill fluid migration, waste treatment technologies before disposal, landfill body thickness, waste decomposition phases), and outside (meteorological parameters, with an emphasis on annual precipitation). The variable and almost unpredictable qualitative composition of leachate from municipal solid waste landfills, that often includes emerging substances, such as antibiotics and endocrine disruptors, as well as heavy metals, significantly affects the structure and diversity of the present microbiological communities. By implementing leachate sampling campaigns in the winter, spring, and autumn in 2019 at three non-sanitary (L1, L2, L3) and one sanitary (L4) municipal solid waste landfills in the region of Vojvodina, the presence of microorganisms Escherichia coli, Klebsiella pneumoniae and Citrobacter freundii, Gram-negative bacteria from the family of Enterobacteriaceae, in the phylum Proteobacteria, were detected. Due to the frequent causing of urinary, extraintestinal, diarrheal, and respiratory infections, meningitis, colitis, sepsis, as well as high resistance to a range of antibiotics, Gram-negative bacteria may represent a potential risk to human and animal health, under specific exposure circumstances. In addition to the use of Gram-negative bacteria Escherichia coli, Klebsiella pneumonia, and Citrobacter freundii as indicators of fecal contamination, the potential of the use of the mentioned bacteria as indicators of contamination of leachate with heavy metals and organic compounds, as well as the functionality and condition of municipal solid waste landfills.