Site-specific ubiquitination of MLKL targets it to endosomes and targets Listeria and Yersinia to the lysosomes

Phosphorylation of the pseudokinase mixed lineage kinase domain-like protein (MLKL) by the protein kinase RIPK3 targets MLKL to the cell membrane, where it triggers necroptotic cell death. We report that conjugation of K63-linked polyubiquitin chains to distinct lysine residues in the N-terminal HeLo domain of phosphorylated MLKL (facilitated by the ubiquitin ligase ITCH that binds MLKL via a WW domain) targets MLKL instead to endosomes. This results in the release of phosphorylated MLKL within extracellular vesicles. It also prompts enhanced endosomal trafficking of intracellular bacteria such as Listeria monocytogenes and Yersinia enterocolitica to the lysosomes, resulting in decreased bacterial yield. Thus, MLKL can be directed by specific covalent modifications to differing subcellular sites, whence it signals either for cell death or for non-deadly defense mechanisms.

The role of organic matter and bacterial physiology on river metabolism at low flow

<p>Development of accurate water quality modelling tools is necessary for integrated water quality management of river systems. The existing water quality models can simulate dissolved oxygen (DO) concentration quite well in rivers, however, there are discrepancies during summer low flow season which are assumed to be due to the heterotrophic bacterial decomposition of organic matter (OM) (Wang, 2019). Therefore, we used the C-RIVE biogeochemical model in order to evaluate the influence of controlling parameters on the DO simulations at low flow.</p><p>Four Sobol’ sensitivity analyses (SA) were carried out based on an evolving strategy of reduction in the number of parameters and hiding the inter-parameter interactions. The studied parameters are bacterial (such as growth rate of bacteria), OM-related (repartition and degradation of OM into constituent fractions) and physical (for instance reaeration of river due to navigation and wind) whose variation ranges are selected based on a detailed literature review.</p><p>Bacterial growth and mortality rates are by far the two most influential parameters followed by bacterial yield and the share of biodegradable dissolved organic matter (BDOM). More refined SA results indicate that depending on the net bacterial growth (=growth – mortality) being low or high, the bacterial yield and BDOM concentration are the most influential parameters, respectively. Reaeration constant due to navigation and the bacterial uptake of substrate are the other two influential parameters identified in this work. </p><p>The results of this study highlight the importance of accurate in-situ sampling and measurement of these influential parameters in order to reduce modelling uncertainties, as well as the necessity for a suitable sampling frequency in order to characterize potential bacterial community switch during transient events such as combined sewer overflows. </p><p>References:</p><p>Wang, S. (2019). Simulation Du Métabolisme de La Seine Par Assimilation de Données En Continu. These de doctorat, Paris Sciences et Lettres</p>

Improving the recovery and detection of bloodstream pathogens from blood culture

Introduction. Bloodstream infections (BSI) are growing in incidence and present a serious health threat. Most patients wait up to 48 h before microbiological cultures can confirm a diagnosis. Low numbers of circulating bacteria in patients with BSI mean we need to develop new methods and optimize current methods to facilitate efficient recovery of bacteria from the bloodstream. This will allow detection of positive blood cultures in a more clinically useful timeframe. Many bacterial blood recovery methods are available and usually include a combination of techniques such as centrifugation, filtration, serum separation or lysis treatment. Here, we evaluate nine different bacteria recovery methods performed directly from blood culture. Aim. We sought to identify a bacterial recovery method that would allow for a cost-effective and efficient recovery of common BSI pathogens directly from blood culture. Methods. Simulated E. coli ATCC 25922 blood culture was used as a model system to evaluate nine different bacteria recovery methods. Each method was assessed on recovery yield, cost, hands-on time, risk of contamination and ease of use. The highest scoring recovery method was further evaluated using simulated blood cultures spiked with seven of the most frequently occurring bloodstream pathogens. The recovery yield was calculated based on c.f.u. count before and after each recovery method. Independent t-tests were performed to determine if the recovery methods evaluated were significantly different based on c.f.u. ml−1 log recovery. Results. All nine methods evaluated successfully recovered E. coli ATCC 25922 from simulated blood cultures although the bacterial yield differed significantly. The MALDI-TOF intact cell method offered the poorest recovery with a mean loss of 2.94±0.37 log c.f.u. ml−1. In contrast, a method developed by Bio-Rad achieved the greatest bacterial yield with a mean bacteria loss of 0.27±0.013 log c.f.u. ml−1. Overall, a low-speed serum-separation method was demonstrated to be the most efficient method in terms of time, cost and recovery efficiency and successfully recovered seven of the most frequent BSI pathogens with a mean bacteria loss of 0.717±0.18 log c.f.u. ml−1. Conclusion. The efficiency of bacterial recovery can vary significantly between different methods and thereby can have a critical impact on downstream analysis. The low-speed serum-separation method offered a simple and effective means of recovering common BSI pathogens from blood culture and will be further investigated for use in the rapid detection of bacteraemia and susceptibility testing in clinical practice.

Implication of Proteus spp in the Pathology of Nosocomial Wound Infection in Northeastern Nigeria

Aims: To determine the infection rate and antibiogram of Proteus spp among hospitalised patients suffering from wound infection in Maiduguri. Methodology: A total of 320 wound swab samples were collected from August 2016 to June 2017, and processed via microscopy, culture and further confirmed by biochemical tests. Kirby bauer disc diffusion test was used to determine the antimicrobial susceptibility pattern of Proteus spp isolated. Results: Twenty eight (28) samples yielded Proteus spp, giving a prevalence rate of 8.75%. Male patients were more affected (60.71%) compared to females (39.29%). Difference in sex in relation to rate of infection was statistically not significant (X2 =3.963, p<.01). Patients within the age group of 21-30 years (28.57%) recorded the highest bacterial yield while those of 61-70 years and >70 years (3.57% respectively) recorded the least. Patients suffering from Wound Sepsis and Burns recorded the most significant infection rate (28.57% respectively). Proteus mirabilis (53.57%) was the most isolated Proteus specie while Proteus penneri (7.14%) was the least. Proteus spp isolates demonstrated a marked resistance against Augmentin (89.29%) and Nalidixic Acid (85.71%) but high sensitivity was observed towards Ciprofloxacin (85.71%) and Streptomycin (78.57%). Conclusion: We establish that Proteus spp actually contribute to the pathology of wounds infection among hospitalised patients, and the Proteus specie most implicated in the aetiology of wound infection is Proteus mirabilis. Ciprofloxacin and Streptomycin are the drugs of choice for the treatment of patients with Proteus spp wound infection in the study area, and the use of Nalidixic acid and Augmentin is highly discouraged due to high resistance.

Prospective study of bedside inoculation of blood culture bottles with ascitic fluid versus delayed inoculation for the detection of spontaneous bacterial peritonitis

Background: Spontaneous bacterial peritonitis (SBP) is the most common bacterial infection in cirrhosis, accounting for 10%-30% of all reported bacterial infections in the patients admitted to hospital. Spontaneous bacterial peritonitis (SBP) is the most frequent and life-threatening infection in patients with liver cirrhosis. All forms of cirrhosis have been reported to be complicated by SBP. A delay in the time period between the collection of the ascitic fluid sample, and its inoculation into the blood culture media, has been one of the reasons implicated to account for low-test positivity. There was lack of studies for comparing the bacterial yield between bedside inoculated blood culture bottles with ascitic fluid over delayed inoculation in the detection of SBP. Hence this study is done to compare the bacterial yield between bedside inoculated blood culture bottles with ascitic fluid over delayed inoculation for the detection of SBP.Methods: Cross sectional study.Results: Maximum number of cases of cirrhosis with ascites with SBP was seen in the age group of 31-40years (54.4%) with mean age of study population being 39.66years, more common in males, bed side inoculation yielded more positive culture reports compared to delayed inoculation and E. coli and klebsilla being the common organisms.Conclusions: Difference between 2 culture methods in isolating organism in SBP cases was not statically significant. But, among culture positive cases, this study demonstrates that bedside inoculation of blood culture bottles is superior to delayed laboratory inoculation.

Comparison of Incision and Drainage against Needle Aspiration for the Treatment of Breast Abscess

We aim to compare the incision and drainage against ultrasound-guided aspiration for the treatment of breast abscesses. Sixty-four patients were randomly allocated to Group A (incision and drainage) and Group B (needle aspiration). Incision and drainage was done under general, whereas aspiration was done under local anesthesia with antibiotic coverage after the pus sample was taken for cultures. Time taken to resolve symptoms including point tenderness, erythema and hyperthermia, recurrence of breast abscess, and healing time was recorded. Patients were followed until 8 weeks. Culture and sensitivity of the pus were done. Data were analyzed in SPSS 16.0. The mean difference of healing time was significant ( P = 0.001). A total of 93.3 per cent were healed in Group B and 76.6 per cent in Group A ( P = 0.033). Twenty-two samples (34.37%) had no bacterial yield and the remaining 42 samples (65.6%) yielded 11 anaerobic cultures (17.18%) and 31 aerobic cultures (48.4%). Ultrasound-guided aspiration of breast abscesses with the judicious use of antibiotics is a better treatment modality than incision and drainage.

Activated carbon as a better habitat for water and wastewater treatment microorganisms

Effects of PAC on bacterial activity were evaluated by sequencing batch cultures (20 hours each) of E.coli K-12 on synthetic medium containing glucose as a sole carbon source. Four suspended sequencing batch culture systems were operated; CP: cultures supplemented with PAC, CR: cultures with removal of metabolites by PAC at the end of each batch culture, CD: cultures supplemented with PAC in dialysis tubing to separate from E.coli, and CC: cultures without PAC (control). The supernatant of each batch culture was filtered through a membrane filter (0.2 μm) and was mixed with the same volume of fresh medium to be used as the medium for the next batch culture. The sequencing batch cultures were repeated three times for all the systems. The bacterial growth in CC was inhibited with the increase in the number of batch cultures. Although a significant amount of metabolites was accumulated in the 3rd batch culture of CC, little accumulation was noted in the 3rd batch culture of CP. No growth inhibition was noted in CP for all the batch cultures. The little differences in the bacterial yield and metabolite accumulation between CR and CD suggested that adsorption/desorption of metabolites with PAC did not play a major role in bacterial growth. PAC addition may partly stimulate the growth by the removal of growth inhibiting metabolites. However, the fact that CP showed higher yield than CR and CD indicated that the contact between bacteria and PAC plays a significant role in the growth of bacteria.