Summary
Pseudomonas bacteria are widespread and are found in soil and water, as well as pathogens of both plants and animals. The ability of Pseudomonas to colonize many different environments is ...facilitated by the multiple signaling systems these bacteria contain that allow Pseudomonas to adapt to changing circumstances by generating specific responses. Among others, signaling through extracytoplasmic function σ (σECF) factors is extensively present in Pseudomonas. σECF factors trigger expression of functions required under particular conditions in response to specific signals. This manuscript reviews the phylogeny and biological roles of σECF factors in Pseudomonas, and highlights the diversity of σECF‐signaling pathways of this genus in terms of function and activation. We show that Pseudomonas σECF factors belong to 16 different phylogenetic groups. Most of them are included within the iron starvation group and are mainly involved in iron acquisition. The second most abundant group is formed by RpoE‐like σECF factors, which regulate the responses to cell envelope stress. Other groups controlling solvent tolerance, biofilm formation and the response to oxidative stress, among other functions, are present in lower frequency. The role of σECF factors in the virulence of Pseudomonas pathogenic species is described.
This manuscript reviews the phylogeny and biological roles of σECF factors in Pseudomonas and highlights the diversity of ECF‐signaling pathways of this genus in terms of function and activation.
Summary
Pathogens have developed several strategies to obtain iron during infection, including the use of iron‐containing molecules from the host. Haem accounts for the vast majority of the iron pool ...in vertebrates and thus represents an important source of iron for pathogens. Using a proteomic approach, we have identified in this work a previously uncharacterized system, which we name Hxu, that together with the known Has and Phu systems, is used by the human pathogen Pseudomonas aeruginosa to respond to haem. We show that the Has and Hxu systems are functional signal transduction pathways of the cell‐surface signalling class and report the mechanism triggering the activation of these signalling systems. Both signalling cascades involve an outer membrane receptor (HasR and HxuA respectively) that upon sensing haem in the extracellular medium produces the activation of an σECF factor in the cytosol. HxuA has a major role in signalling and a minor role in haem acquisition in conditions in which the HasR and PhuR receptors or other sources of iron are present. Remarkably, P. aeruginosa compensates the lack of the HasR receptor by increasing the production of HxuA, which underscores the importance of haem signalling for this pathogen.
A total of 183 patients were colonized or infected with multidrug-resistant Pseudomonas aeruginosa isolates at a hospital in Spain during 2007-2010; prevalence increased over this period from 2.8% to ...15.3%. To characterize these isolates, we performed molecular epidemiologic and drug resistance analysis. Genotyping showed that 104 (56.8%) isolates belonged to a single major clone (clone B), which was identified by multilocus sequence typing as sequence type (ST) 175. This clone was initially isolated from 5 patients in 2008, and then isolated from 23 patients in 2009 and 76 patients in 2010. PCR analysis of clone B isolates identified the bla(VIM-2) gene in all but 1 isolate, which harbored bla(IMP-22). ST175 isolates were susceptible to only amikacin (75%) and colistin (100%). Emergence of the ST175 clone represents a major health problem because it compromises therapy for treatment of P. aeruginosa nosocomial infections.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In February 2006, a patient colonized with a multidrug-resistant sequence type 56 Acinetobacter baumannii strain was admitted to a hospital in Madrid, Spain. This strain spread rapidly and caused a ...large outbreak in the hospital. Clinicians should be alert for this strain because its spread would have serious health consequences.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
Cell‐surface signalling (CSS) enables Gram‐negative bacteria to transduce an environmental signal into a cytosolic response. This regulatory cascade involves an outer membrane receptor that ...transmits the signal to an anti‐sigma factor in the cytoplasmic membrane, allowing the activation of an extracytoplasmic function (ECF) sigma factor. Recent studies have demonstrated that RseP‐mediated proteolysis of the anti‐sigma factors is key to σECF activation. Using the Pseudomonas aeruginosa FoxR anti‐sigma factor, we show here that RseP is responsible for the generation of an N‐terminal tail that likely contains pro‐sigma activity. Furthermore, it has been reported previously that this anti‐sigma factor is processed in two separate domains prior to signal recognition. Here, we demonstrate that this process is common in these types of proteins and that the processing event is probably due to autoproteolytic activity. The resulting domains interact and function together to transduce the CSS signal. However, our results also indicate that this processing event is not essential for activity. In fact, we have identified functional CSS anti‐sigma factors that are not cleaved prior to signal perception. Together, our results indicate that CSS regulation can occur through both complete and initially processed anti‐sigma factors.
The influence of acute graft pyelonephritis (AGPN) on graft outcome in renal transplant recipients still remains controversial.
We retrospectively analysed 189 patients (113 males; mean age: 49.7 ± ...13.1 years) undergoing renal transplantation at the University Hospital 12 de Octubre (Madrid, Spain) from January 2002 to December 2004, with a minimum follow-up of 36 months. Factors associated with AGPN were assessed by logistic regression analysis. Long-term graft function was compared according to the occurrence of this complication during follow-up. 'Decline in renal graft function' was defined as the increase in serum creatinine (SC) levels > 0.33 mg/dL between Month 3 and Year 1 after transplantation.
Nineteen patients (10.0%) were diagnosed with 25 episodes of AGPN (incidence rate: 4.4 episodes per 100 patient-years). The presence of glomerulonephritis as the underlying disease odds ratio (OR) 4.2; 95% confidence interval (95%CI): 1.3-14.1 and the previous occurrence of two to five (OR 9.4; 95%CI: 1.5-56.8) or more than five episodes of asymptomatic bacteriuria after transplantation (OR 19.8; 95%CI: 2.4-160.2) emerged as independent predictors for AGPN. A near-significant association was found for cytomegalovirus infection (OR 4.2; 95%CI: 0.9-18.4), whereas receiving a single-kidney transplant (vs. double-kidney) showed a protective effect (OR 0.2; 95%CI: 0.0-0.8). During the 36-month follow-up, levels of SC, creatinine clearance and 24-h proteinuria did not differ significantly between patients with or without AGPN, and this complication did not exert any effect on the risk for decline in renal graft function.
AGPN does not impair long-term graft function in renal transplant recipients.
Limited data exist regarding the role of agr dysfunction in reducing susceptibility to vancomycin in methicillin-susceptible Staphylococcus aureus (MSSA). This study investigated the clinical and ...molecular epidemiology of MSSA causing bacteraemia, with emphasis on the reduced susceptibility to vancomycin (RSV) phenotype (MIC ≥ 1.5 mg/L) and its relationship with agr dysfunction.
All MSSA bloodstream isolates obtained at our hospital during 2010 were analysed. Antimicrobial susceptibility was determined and time-kill experiments were performed for oxacillin. Multilocus sequence type and agr genotype were determined and DNA microarray analysis of virulence factors was performed. agr dysfunction was assessed phenotypically and by RT-PCR quantification of RNAIII.
Of 84 MSSA, 55 (65.5%) exhibited the RSV phenotype, comprising 13 clonal complexes. agr II polymorphism was more prevalent in RSV than non-RSV isolates (41.8% versus 17.2%, P = 0.023) and average levels of RNAIII gene expression were higher in RSV than non-RSV isolates (ΔCt 4.05 ± 3.29 versus 1.5 ± 2.11, P = 0.005), implying greater agr dysfunction in RSV MSSA.
We demonstrated a correlation between RSV phenotype in MSSA and reduced agr expression, particularly in association with the agr II genotype. These results may help to understand the role of agr dysfunction in the increased mortality in MSSA infections.
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