Sanitary status of 47 pig manures in Brittany: comparison of the effectiveness of manure treatments on the levels of indicator bacteria and two pathogenic bacteria

The hygienic performance of three manure treatment systems (simple storage, biological treatment or thermal treatment) was evaluated for effluents collected from 47 piggeries across Brittany, France. Microbial analyses were carried out on raw manure, on the sludge stored in a tank after biological treatment and on the liquid phase stored in a lagoon after sludge settling or after thermal treatment. The effect of the treatments on E. coli, enterococci, Salmonella and Listeria monocytogenes was evaluated. The concentrations of indicator bacteria were highly variable regardless of the farm or the manure management

VBNC state and ‘regrowth’ during waste treatment: factors playing a role in loss of culturability of pathogenic bacteria seeded in digestates from agricultural biogas plants

During treatment of organic waste by anaerobic digestion, composting or in wastewater treatment plants, pathogenic bacteria are submitted to various biotic and abiotic stress. In treated wastes (digestates, composts…) increase of bacterial counts obtained by culture for indicators (E. coli) and pathogenic bacteria (Salmonella sp., Shigella sp., Listeria monocytogenes) are sometimes recorded, but the underlying mechanisms remain unknown. Some recent studies indicate that this may be due to the induction of Viable but Non-Culturable (VBNC) state during treatment, followed by ‘resuscitation’ during storage of treated products. Here, a microcosm approach was used to evaluate the persistence of three pathogenic bacteria (Salmonella Derby, Campylobacter coli and Listeria monocytogenes) in digestates from agricultural wastes, stored for later land spreading. Nine samples, including raw digestates, liquid fractions of digestate and composted digestates, were inoculated with each pathogen and maintained for 40 days at 24°C. Concentrations of pathogens were monitored using culture and qPCR methods. In some digestates, the concentration of the pathogens by qPCR assay was several orders of magnitude higher than the concentration of culturable cells, suggesting a potential loss of culturability and induction of VBNC state. The potential VBNC state which was generally not observed in the same digestate for the three pathogens, occurred more frequently for C. coli and L. monocytogenes than for Salmonella Derby. The effect of NH4+/NH3 on the culturability of C. coli and Salmonella Derby was also shown. Our results underline the importance of considering VBNC cells when evaluating the sanitary effect of an anaerobic digestion process and the persistence of pathogens during the storage of digestates and subsequent land spreading

VBNC state and ‘regrowth’ during waste treatment: factors playing a role in loss of culturability of pathogenic bacteria seeded in digestates from agricultural biogas plants

International audienceDuring treatment of organic waste by anaerobic digestion, composting or in wastewater treatment plants, pathogenic bacteria are submitted to various biotic and abiotic stress. In treated wastes (digestates, composts…) increase of bacterial counts obtained by culture for indicators (E. coli) and pathogenic bacteria (Salmonella sp., Shigella sp., Listeria monocytogenes) are sometimes recorded, but the underlying mechanisms remain unknown. Some recent studies indicate that this may be due to the induction of Viable but Non-Culturable (VBNC) state during treatment, followed by ‘resuscitation’ during storage of treated products. Here, a microcosm approach was used to evaluate the persistence of three pathogenic bacteria (Salmonella Derby, Campylobacter coli and Listeria monocytogenes) in digestates from agricultural wastes, stored for later land spreading. Nine samples, including raw digestates, liquid fractions of digestate and composted digestates, were inoculated with each pathogen and maintained for 40 days at 24°C. Concentrations of pathogens were monitored using culture and qPCR methods. In some digestates, the concentration of the pathogens by qPCR assay was several orders of magnitude higher than the concentration of culturable cells, suggesting a potential loss of culturability and induction of VBNC state. The potential VBNC state which was generally not observed in the same digestate for the three pathogens, occurred more frequently for C. coli and L. monocytogenes than for Salmonella Derby. The effect of NH4+/NH3 on the culturability of C. coli and Salmonella Derby was also shown. Our results underline the importance of considering VBNC cells when evaluating the sanitary effect of an anaerobic digestion process and the persistence of pathogens during the storage of digestates and subsequent land spreading

Evaluation of Lactobacillus sobrius/L. amylovorus as a New Microbial Marker of Pig Manure▿

Based on a comparison of the dominant microbial populations in 17 pig manure samples and using a molecular typing method, we identified a species, Lactobacillus sobrius and Lactobacillus amylovorus (which now are considered a single species and are designated L. sobrius/amylovorus here), that was consistently found in manure. The aim of the present study was to confirm by real-time PCR the relevance of this species as a marker of pig fecal contamination. The specificity of L. sobrius/amylovorus was evaluated in human and animal DNA extracted from feces. The real-time PCR assay then was applied to water samples, including effluents from urban wastewater treatment plants, runoff water, and rivers. L. sobrius/amylovorus was consistently present in all samples of swine origin: 48 fecal samples, 18 from raw manure and 10 from biologically treated manure at mean concentrations of 7.2, 5.9, and 5.0 log10 cells/g, respectively. The species was not detected in any of the other livestock feces (38 samples from cattle and 16 from sheep), in the 27 human fecal samples, or in the 13 effluent samples from urban wastewater treatment plants. Finally, L. sobrius/amylovorus was not detected in runoff water contaminated by cattle slurry, but it was quantified at concentrations ranging from 3.7 to 6.5 log10 cells/100 ml in runoff water collected after pig manure was spread on soil. Among the stream water samples in which cultured Escherichia coli was detected, 23% tested positive for L. sobrius/amylovorus. The results of this study indicate that the quantification of L. sobrius/amylovorus using real-time PCR will be useful for identifying pig fecal contamination in surface waters

Sanitary status of 47 pig manures in Brittany: comparison of the effectiveness of manure treatments on the levels of indicator bacteria and two pathogenic bacteria

The hygienic performance of three manure treatment systems (simple storage, biological treatment or thermal treatment) was evaluated for effluents collected from 47 piggeries across Brittany, France. Microbial analyses were carried out on raw manure, on the sludge stored in a tank after biological treatment and on the liquid phase stored in a lagoon after sludge settling or after thermal treatment. The effect of the treatments on E. coli, enterococci, Salmonella and Listeria monocytogenes was evaluated. The concentrations of indicator bacteria were highly variable regardless of the farm or the manure management.</p

Dynamique des pathogènes lors du stockage des digestats

Dynamique des pathogènes lors du stockage des digestats. Journées de la Méthanisation : Applications Agricoles et Industrielle

Dynamique des pathogènes lors du stockage de digestats issus de la méthanisation

communication oraleDynamique des pathogènes lors du stockage de digestats issus de la méthanisation. 7. Colloque AFE

Microalgae process design for nutrient extraction from digestate through laboratory tests and model

International audienceEvery year the knowledge about the microbial ecology of anaerobic digestion increases but despite that, the inoculation step of anaerobic digesters still remains empirical. Anaerobic digestion remains a microbial process without any microbial engineering. In this review we try to understand why putting in practice this knowledge remains difficult by identifying bottlenecks of this unsuccessful story

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

International audienceDigestate produced by agricultural biogas plants (BGPs) may contain pathogenic bacteria. Among them,Clostridium perfringensdeserves particular attention due to its ability to grow under anaerobic conditions and persist in amended soil. The aim of this study was to examine the potential pathogenicity and the antimicrobial resistance ofC. perfringensin manure and digestate collected from three agricultural biogas plants (BGPs). A total of 157 isolates (92 from manure, 65 from digestate) were screened for genes encoding seven toxins (cpa,cpb,etx,iapcpe,netB, andcpb2). The 138cpapositive isolates were then screened fortetA(P),tetB(P),tet(M), anderm(Q) genes and tested for antimicrobial susceptibility. The toxinotypes identified in both manure and digestate were type A (78.3% of the isolates), type G (16.7%), type C (3.6%), and type D (1.4%), whereas none of the isolates were type F. Moreover, half of the isolates carried thecpb2gene. The overall prevalence oftetA(P) gene alone,tetA(P)-tetB(P) genes, anderm(Q) gene was 31.9, 34.8, and 6.5%, respectively. None of the isolates harbored thetet(M) gene. Multiple antimicrobial resistant isolates were found in samples that were collected from all the manure and digestates. Among them, 12.3% were highly resistant to some of the antibiotics tested, especially to clindamycin (MIC >= 16 mu g/mL) and tilmicosin (MIC > 64 mu g/mL). Some isolates were highly resistant to antibiotics used in human medicine, including vancomycin (MIC > 8 mu g/mL) and imipenem (MIC > 64 mu g/mL). These results suggest that digestate may be a carrier of the virulent and multidrug resistant C. perfringens

Microalgae process design for nutrient extraction from digestate through laboratory tests and model

International audienceEvery year the knowledge about the microbial ecology of anaerobic digestion increases but despite that, the inoculation step of anaerobic digesters still remains empirical. Anaerobic digestion remains a microbial process without any microbial engineering. In this review we try to understand why putting in practice this knowledge remains difficult by identifying bottlenecks of this unsuccessful story