Karin Meinike Jørgensen

Chemical and biochemical variation in animal manure solids separated using different commercial separation technologies.

Chemical and biochemical properties were investigated in 47 solids collected from commercial solids separation plants separating liquid manure into a nutrient-rich solid fraction and a nutrient-poor liquid fraction. The samples originated from five different types of separation technologies, separating primarily swine manure and anaerobically digested manure. The largest variations in measured chemical and biochemical characteristics between samples from the five different separation technologies were found for ash, total P, total C, DM and C distribution in the biochemical fractions (neutral detergent solubles (NDS), hemicellulose, cellulose and lignin). Principal component analysis (PCA) of the data obtained showed that the chemical and biochemical characteristics of the solids were dependent on the type of technology used for separation.

Sublethal Ciprofloxacin Treatment Leads to Rapid Development of High-Level Ciprofloxacin Resistance during Long-Term Experimental Evolution of Pseudomonas aeruginosa

ABSTRACT The dynamics of occurrence and the genetic basis of ciprofloxacin resistance were studied in a long-term evolution experiment (940 generations) in wild-type, reference strain (PAO1) and hypermutable (PAOΔmutS and PAOMY-Mgm) P. aeruginosa populations continuously exposed to sub-MICs (1/4) of ciprofloxacin. A rapid occurrence of ciprofloxacin-resistant mutants (MIC of ≥12 μg/ml, representing 100 times the MIC of the original population) were observed in all ciprofloxacin-exposed lineages of PAOΔmutS and PAOMY-Mgm populations after 100 and 170 generations, respectively, and in one of the PAO1 lineages after 240 generations. The genetic basis of resistance was mutations in gyrA (C248T and G259T) and gyrB (C1397A). Cross-resistance to beta-lactam antibiotics was observed in the bacterial populations that evolved during exposure to sublethal concentrations of ciprofloxacin. Our study shows that mutants with high-level ciprofloxacin resistance are selected in P. aeruginosa bacterial populations exposed to sub-MICs of ciprofloxacin. This can have implications for the long-term persistence of resistant bacteria and spread of antibiotic resistance by exposure of commensal bacterial flora to low antibiotic concentrations.

Phosphorus distribution in untreated and composted solid fractions from slurry separation.

The distribution of phosphorus (P) (water-soluble inorganic P [P(i)], acid-soluble P(i), and residual P) was determined in 40 samples of solids from solid-liquid separated slurry. These were collected from separation plants using different technologies, separating by simple mechanical means, by flocculation as pre-treatment before mechanical separation or by anaerobic digestion followed by separation and centrifugation. Simple mechanical separation yielded a low solid TP content (8-9 g P kg(-1) dry matter [DM]) compared with separation by flocculation (26 g P kg(-1) DM) or by anaerobic digestion-centrifugation (33.4 g P kg(-1) DM). Acid-soluble P(i) predominated in the high P-yielding solids, whereas organic-bound or residual P was a minor component in all slurry solids. Acid-soluble P(i) and residual P were significantly correlated with total phosphorus (TP) content (R(2) = 0.855 and R(2) = 0.584), but water-soluble P(i) was uncorrelated (R(2) = 0.077). The relative distribution of P(i) to TP in the solids showed a high proportion of water-soluble P(i) in solids from simple mechanical separation, whereas the absolute concentrations were highest in solids from separation by flocculation and anaerobic digestion-centrifugation. Three solid fractions, representing the range of solids variability produced by the separation techniques, were composted for 30 d, and the P distribution was compared before and after composting. Total mass of P was conserved during composting, but water-soluble P(i) as a proportion of TP decreased in most cases. The most pronounced decrease in water-soluble P(i) was observed during composting of the solids separated using flocculation. However, changes in short- to medium-term bioavailability of P were modest, and thus the potential benefits of composting regarding storage and handling can presumably be realized without seriously compromising the P fertilization quality.

Diversity of metabolic profiles of cystic fibrosis Pseudomonas aeruginosa during the early stages of lung infection

Pseudomonas aeruginosa is the dominant pathogen infecting the airways of cystic fibrosis (CF) patients. During the intermittent colonization phase, P. aeruginosa resembles environmental strains but later evolves to the chronic adapted phenotype characterized by resistance to antibiotics and mutations in the global regulator genes mucA, lasR and rpoN. Our aim was to understand the metabolic changes occurring over time and between niches of the CF airways. By applying Phenotype MicroArrays, we investigated changes in the carbon and nitrogen catabolism of subsequently clonally related mucoid and non-mucoid (NM) lung and sinus P. aeruginosa isolates from 10 CF patients (five intermittently colonized/five chronically infected). We found the most pronounced catabolic changes for the early/late NM isolate comparisons, with respiratory reduction seen for all chronically infecting isolates and two intermittently colonizing isolates. Fewer differences were observed between sinus and lung isolates, showing a higher degree of isolate similarity between these two niches. Modest respiratory changes were seen for the early isolate/PAO1 comparisons, indicating colonization with environmental isolates. Assignment of metabolic pathways via the KEGG database showed a prevalence of substrates involved in the metabolism of Ala, Asp and Glu, d-Ala, and Arg and Pro. In conclusion, extensive heterogeneity in the metabolic profiles of the P. aeruginosa isolates was observed from the initial stages of the infection, showing a rapid diversification of the bacteria in the heterogeneous environment of the lung. Metabolic reduction seems to be a common trait and therefore an adaptive phenotype, though it can be reached via multiple metabolic pathways.