Evaluation of the occurrence of sporulating and nonsporulating pathogenic bacteria in manure and in digestate of five agricultural biogas plants

Abstract

The number of agricultural biogas plants has been increasing in the past decades in some European countries. Digestates obtained after anaerobic digestion (AD) of manure are usually spread on agricultural land; however, their hygiene status regarding pathogens posing public health and/or animal health challenges has been poorly characterized up to now in France. In this study, three replicates of manure and digestate were collected from five farm biogas plants receiving animal manure in order to assess the occurrence and concentrations of sporulating (Clostridium botulinum, Clostridioides difficile, Clostridium perfringens) and nonsporulating (Listeria monocytogenes, thermotolerant Campylobacter spp., Salmonella, Escherichia coli, enterococci) bacteria. Concentrations of E. coli, enterococci, and C. perfringens in digestates ranged from 102 to 104, 104 to 105, and <103 to 7 × 105 CFU/g, respectively. Salmonella and C. difficile were detected in manure and digestate from the five biogas plants at concentrations ranging from <1.3 to >7 × 102 MPN/g and from 1.3 to 3 × 102 MPN/g, respectively. Thermotolerant Campylobacter, detected in all the manures, was only found in two digestates at a concentration of cells ranging from <10 to 2.6 × 102 CFU/g. Listeria monocytogenes and C. botulinum were detected in three manures and four digestates. The bacterial counts of L. monocytogenes and C. botulinum did not exceed 3 × 102 and 14 MPN/g, respectively. C. botulinum type B was detected at very low level in both the manure and digestate of farm biogas plants with no botulism history. The levels of pathogenic bacteria in both manure and digestate suggested that some bacteria can persist throughout AD.

Characterization of Clostridium Perfringens Isolates Collected from Three Agricultural Biogas Plants over a One-Year Period

“…Although digestates from biogas plants fed with manure contain high levels of C. perfringens (ca. 10 4 CFU/g) [32][33][34][35][36][37], no information is available on the range of toxin genes and the antimicrobial profiles of this pathogenic bacterium in agricultural digestate that is intended for land application. This is the first study to assess digestate as a potential carrier of virulent and multiresistant C. perfringens.…”

“…Soge et al [8] also reported that the tetA(P) gene was common in isolates in water and soil. Despite the ability of C. perfringens to transfer antibiotic resistance via bacterial conjugation [7] and its ability to survive under conditions found in mesophilic anaerobic digesters (MAD) [31,32], information is lacking on the antimicrobial susceptibility of resistant C. perfringens isolates in digestate intended for land application.…”

Does Mycobacterium tuberculosis var. bovis Survival in the Environment Confound Bovine Tuberculosis Control and Eradication? A Literature Review

“…paratuberculosis , showed survival for up to 2 months in mesophilic ADs. To date, it is unclear to what extent the products of AD can be rendered safe and much depends on the survival structures (such as sporulation) and strategies (such as dormancy) used by different pathogens [ 115 ].…”

Conventional and Innovative Hygienization of Feedstock for Biogas Production: Resistance of Indicator Bacteria to Thermal Pasteurization, Pulsed Electric Field Treatment, and Anaerobic Digestion

“…The mechanisms behind these phenomena are to be discussed in Section 4. 3 TAD: Thermophilic anaerobic digestion, 4 MSW: Municipal solid waste, 5 By default, numbers provided in this column mean microbial reduction, 6 "-" means reduction in target microorganisms, 7 "+" means increase in target microorganisms. [65,66].…”

“…Contamination of feedstock by various pathogens, such as Salmonella spp., Listeria spp., Giardia spp., Cryptosporidium parvum, and Campylobacter spp. [2,3] and other emerging contaminants like antibiotic resistance genes (ARG) [4], could be transmitted to the environment through waste and digestate land application if they are not properly handled [5]. In 2002, the United States Environmental Protection Agency (US EPA) disclosed that the spreading of biosolids (sewage sludge) on farm lands might cause health problem to nearby local habitants [6].…”