Oxygen restriction increases the infective potential of Listeria monocytogenes in vitro in Caco-2 cells and in vivo in guinea pigs

<p>Abstract</p> <p>Background</p> <p>Listeria monocytogenes has been implicated in several food borne outbreaks as well as sporadic cases of disease. Increased understanding of the biology of this organism is important in the prevention of food borne listeriosis.</p> <p>The infectivity of <it>Listeria monocytogenes </it>ScottA, cultivated with and without oxygen restriction, was compared in <it>vitro </it>and <it>in vivo</it>. Fluorescent protein labels were applied to allow certain identification of <it>Listeria </it>cells from untagged bacteria in <it>in vivo </it>samples, and to distinguish between cells grown under different conditions in mixed infection experiments.</p> <p>Results</p> <p>Infection of Caco-2 cells revealed that <it>Listeria </it>cultivated under oxygen-restricted conditions were approximately 100 fold more invasive than similar cultures grown without oxygen restriction. This was observed for exponentially growing bacteria, as well as for stationary-phase cultures.</p> <p>Oral dosage of guinea pigs with <it>Listeria </it>resulted in a significantly higher prevalence (p < 0.05) of these bacteria in jejunum, liver and spleen four and seven days after challenge, when the bacterial cultures had been grown under oxygen-restricted conditions prior to dosage. Additionally, a 10–100 fold higher concentration of <it>Listeria </it>in fecal samples was observed after dosage with oxygen-restricted bacteria. These differences were seen after challenge with single <it>Listeria </it>cultures, as well as with a mixture of two cultures grown with and without oxygen restriction.</p> <p>Conclusion</p> <p>Our results show for the first time that the environmental conditions to which <it>L. monocytogenes </it>is exposed prior to ingestion are decisive for its <it>in vivo </it>infective potential in the gastrointestinal tract after passage of the gastric barrier. This is highly relevant for safety assessment of this organism in food.</p

Municipality screening of citizens with suspicion of chronic obstructive pulmonary disease

Up to 436,000 adult Danes suffer from chronic obstructive pulmonary disease (COPD), with only one third diagnosed at this time. The Danish National Board of Health recommends early detection of COPD, focusing on smokers/ex-smokers over 35 years of age with at least one lung symptom. A governmental prevention committee has suggested that the municipalities, in addition to general practice, should be a potential arena responsible for early detection of COPD. We undertook a pilot study to investigate the feasibility and effectiveness of early detection of COPD in municipalities following the recommendations of the Danish National Board of Health

C-di-GMP regulates <i>Pseudomonas aeruginosa</i> stress response to tellurite during both planktonic and biofilm modes of growth

Stress response plays an important role on microbial adaptation under hostile environmental conditions. It is generally unclear how the signaling transduction pathway mediates a stress response in planktonic and biofilm modes of microbial communities simultaneously. Here, we showed that metalloid tellurite (TeO(3)(2–)) exposure induced the intracellular content of the secondary messenger cyclic di-GMP (c-di-GMP) of Pseudomonas aeruginosa. Two diguanylate cyclases (DGCs), SadC and SiaD, were responsible for the increased intracellular content of c-di-GMP. Enhanced c-di-GMP levels by TeO(3)(2–) further increased P. aeruginosa biofilm formation and resistance to TeO(3)(2–). P. aeruginosa ΔsadCΔsiaD and PAO1/p(lac)-yhjH mutants with low intracellular c-di-GMP content were more sensitive to TeO(3)(2–) exposure and had low relative fitness compared to the wild-type PAO1 planktonic and biofilm cultures exposed to TeO(3)(2–). Our study provided evidence that c-di-GMP level can play an important role in mediating stress response in microbial communities during both planktonic and biofilm modes of growth

Kidney oxygenation, perfusion and blood flow in people with and without type 1 diabetes

Background We used magnetic resonance imaging (MRI) to study kidney energetics in persons with and without type 1 diabetes (T1D). Methods In a cross-sectional study, 15 persons with T1D and albuminuria and 15 non-diabetic controls (CONs) underwent multiparametric MRI (3 Tesla Philips Scanner) to quantify renal cortical and medullary oxygenation (R-2*, higher values correspond to higher deoxyhaemoglobin concentration), renal perfusion (arterial spin labelling) and renal artery blood flow (phase contrast). Analyses were adjusted for age, sex, systolic blood pressure, plasma haemoglobin, body mass index and estimated glomerular filtration rate (eGFR). Results Participants with T1D had a higher median (Q1; Q3) urine albumin creatinine ratio (UACR) than CONs [46 (21; 58) versus 4 (3; 6) mg/g; P < .0001] and a lower mean +/- SD eGFR (73 +/- 32 mL/min/1.73 m(2) versus 88 +/- 15 mL/min/1.73 m(2); P = .12), although not significantly. Mean medullary R-2* was lower in T1D (34 +/- 6/s versus 38 +/- 5/s; P < .01) corresponding to a higher oxygenation. R-2* was not different in the cortex. Cortical perfusion was lower in T1D (163 +/- 40 versus 224 +/- 49 mL/100 g/min; P < .001). Renal artery blood flow was lower in T1D than in CONs (360 +/- 130 versus 430 +/- 113 mL/min; P = .05). In T1D, lower cortical oxygenation and renal artery blood flow were both associated with higher UACR and lower eGFR (P < .05). Conclusions Participants with T1D and albuminuria exhibited higher medullary oxygenation than CONs, despite lower cortical perfusion and renal artery blood flow. This might reflect perturbed kidney energetics leading to a higher setpoint of medullary oxygenation in T1D. Lower cortical oxygenation and renal artery blood flow were associated with higher UACR and lower eGFR in T1D.Peer reviewe

The role of individual exopolysaccharides in antibiotic tolerance of Pseudomonas aeruginosa aggregates

The bacterium Pseudomonas aeruginosa is involved in chronic infections of cystic fibrosis lungs and chronic wounds. In these infections the bacteria are present as aggregates suspended in host secretions. During the course of the infections there is a selection for mutants that overproduce exopolysaccharides, suggesting that the exopolysaccharides play a role in the persistence and antibiotic tolerance of the aggregated bacteria. Here, we investigated the role of individual P. aeruginosa exopolysaccharides in aggregate-associated antibiotic tolerance. We employed an aggregate-based antibiotic tolerance assay on a set of P. aeruginosa strains that were genetically engineered to over-produce a single, none, or all of the three exopolysaccharides Pel, Psl, and alginate. The antibiotic tolerance assays were conducted with the clinically relevant antibiotics tobramycin, ciprofloxacin and meropenem. Our study suggests that alginate plays a role in the tolerance of P. aeruginosa aggregates toward tobramycin and meropenem, but not ciprofloxacin. However, contrary to previous studies we did not observe a role for Psl or Pel in the tolerance of P. aeruginosa aggregates toward tobramycin, ciprofloxacin, and meropenem