Cephalosporin-3’-diazeniumdiolate NO-donor prodrug PYRRO-C3D enhances azithromycin susceptibility of non-typeable Haemophilus influenzae biofilms

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Objectives: PYRRO-C3D is a cephalosporin-3-diazeniumdiolate nitric oxide (NO)-donor prodrug designed to selectively deliver NO to bacterial infection sites. The objective of this study was to assess the activity of PYRRO-C3D against non-typeable Haemophilus influenzae (NTHi) biofilms and examine the role of NO in reducing biofilm-associated antibiotic tolerance. Methods: The activity of PYRRO-C3D on in vitro NTHi biofilms was assessed through CFU enumeration and confocal microscopy. NO release measurements were performed using an ISO-NO probe. NTHi biofilms grown on primary ciliated respiratory epithelia at an air-liquid interface were used to investigate the effects of PYRRO-C3D in the presence of host tissue. Label-free LC/MS proteomic analyses were performed to identify differentially expressed proteins following NO treatment. Results: PYRRO-C3D specifically released NO in the presence of NTHi, while no evidence of spontaneous NO release was observed when the compound was exposed to primary epithelial cells. NTHi lacking β-lactamase activity failed to trigger NO release. Treatment significantly increased the susceptibility of in vitro NTHi biofilms to azithromycin, causing a log-fold reduction in viability (p<0.05) relative to azithromycin alone. The response was more pronounced for biofilms grown on primary respiratory epithelia, where a 2-log reduction was observed (p<0.01). Label-free proteomics showed that NO increased expression of sixteen proteins involved in metabolic and transcriptional/translational functions. Conclusions: NO release from PYRRO-C3D enhances the efficacy of azithromycin against NTHi biofilms, putatively via modulation of NTHi metabolic activity. Adjunctive therapy with NO mediated through PYRRO-C3D represents a promising approach for reducing biofilm associated antibiotic tolerance

New approaches to the treatment of biofilm-related infections

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Bacteria causing chronic infections predominately grow as surface-attached, sessile communities known as biofilms. Biofilm-related infections including cystic fibrosis lung infection, chronic and recurrent otitis media, chronic wounds and implant- and catheter-associated infections, are a significant cause of morbidity and mortality at great financial cost. Chronic biofilm-based infections are recalcitrant to conventional antibiotic therapy and are often unperturbed by host immune responses such as phagocytosis, despite a sustained presence of host inflammation. The diagnosis of clinically important biofilm infections is often difficult as Koch’s postulates are rarely met. If treatment is required, surgical removal of the infected implant, or debridement of wound or bone, is the most efficient means of eradicating a clinically significant biofilm. New approaches to treatment are under investigation

How to diagnose the cause of sudden cardiac arrest

Sudden cardiac death or sudden cardiac arrest (SCA) is defined as natural death that occurs within an hour of the onset of acute symptoms or during sleep due to a primary cardiac cause. Most cases of SCA are attributable to coronary artery disease, with occult cardiomyopathy or inheritable arrhythmic syndromes accounting for a minority of SCA. Diagnosing the cause of SCA has potential implications for the patient and the family, and demands a comprehensive approach. This review summarizes the potential causes of SCA and outlines a systematic diagnostic approach to the SCA survivor. (Cardiol J 2011; 18, 2: 210-216

Parallel evolution in streptococcus pneumoniae biofilms

Streptococcus pneumoniae is a commensal human pathogen and the causative agent of various invasive and noninvasive diseases. Carriage of the pneumococcus in the nasopharynx is thought to be mediated by biofilm formation, an environment where isogenic populations frequently give rise to morphological colony variants, including small colony variant (SCV) phenotypes. We employed metabolic characterization and whole-genome sequencing of biofilm-derived S. pneumoniae serotype 22F pneumococcal SCVs to investigate diversification during biofilm formation. Phenotypic profiling revealed that SCVs exhibit reduced growth rates, reduced capsule expression, altered metabolic profiles, and increased biofilm formation compared to the ancestral strain. Whole-genome sequencing of 12 SCVs from independent biofilm experiments revealed that all SCVs studied had mutations within the DNA-directed RNA polymerase delta subunit (RpoE). Mutations included four large-scale deletions ranging from 51 to 264 bp, one insertion resulting in a coding frameshift, and seven nonsense single-nucleotide substitutions that result in a truncated gene product. This work links mutations in the rpoE gene to SCV formation and enhanced biofilm development in S. pneumoniae and therefore may have important implications for colonization, carriage, and persistence of the organism. Furthermore, recurrent mutation of the pneumococcal rpoE gene presents an unprecedented level of parallel evolution in pneumococcal biofilm development

Systematic Study of Electron Localization in an Amorphous Semiconductor

We investigate the electronic structure of gap and band tail states in amorphous silicon. Starting with two 216-atom models of amorphous silicon with defect concentration close to the experiments, we systematically study the dependence of electron localization on basis set, density functional and spin polarization using the first principles density functional code Siesta. We briefly compare three different schemes for characterizing localization: information entropy, inverse participation ratio and spatial variance. Our results show that to accurately describe defect structures within self consistent density functional theory, a rich basis set is necessary. Our study revealed that the localization of the wave function associated with the defect states decreases with larger basis sets and there is some enhancement of localization from GGA relative to LDA. Spin localization results obtained via LSDA calculations, are in reasonable agreement with experiment and with previous LSDA calculations on a-Si:H models.Comment: 16 pages, 11 Postscript figures, To appear in Phys. Rev.

An integrated model system to gain mechanistic insights into biofilm-associated antimicrobial resistance in Pseudomonas aeruginosa MPAO1

open access articlePseudomonas aeruginosa MPAO1 is the parental strain of the widely utilized transposon mutant collection for this important clinical pathogen. Here, we validate a model system to identify genes involved in biofilm growth and biofilm-associated antibiotic resistance. Our model employs a genomics-driven workflow to assemble the complete MPAO1 genome, identify unique and conserved genes by comparative genomics with the PAO1 reference strain and genes missed within existing assemblies by proteogenomics. Among over 200 unique MPAO1 genes, we identified six general essential genes that were overlooked when mapping public Tn-seq data sets against PAO1, including an antitoxin. Genomic data were integrated with phenotypic data from an experimental workflow using a user-friendly, soft lithography-based microfluidic flow chamber for biofilm growth and a screen with the Tn-mutant library in microtiter plates. The screen identified hitherto unknown genes involved in biofilm growth and antibiotic resistance. Experiments conducted with the flow chamber across three laboratories delivered reproducible data on P. aeruginosa biofilms and validated the function of both known genes and genes identified in the Tn-mutant screens. Differential protein abundance data from planktonic cells versus biofilm confirmed the upregulation of candidates known to affect biofilm formation, of structural and secreted proteins of type VI secretion systems, and provided proteogenomic evidence for some missed MPAO1 genes. This integrated, broadly applicable model promises to improve the mechanistic understanding of biofilm formation, antimicrobial tolerance, and resistance evolution in biofilms

Low concentrations of nitric oxide modulate Streptococcus pneumoniae biofilm metabolism and antibiotic tolerance

Streptococcus pneumoniae is one of the key pathogens responsible for otitis media (OM), the most common infection in children and the largest cause of childhood antibiotic prescription. Novel therapeutic strategies that reduce the overall antibiotic consumption due to OM are required because although widespread pneumococcal conjugate immunization has controlled invasive pneumococcal disease, overall OM incidence has not decreased. Biofilm formation represents an important phenotype contributing to the antibiotic tolerance and persistence of S. pneumoniae in chronic or recurrent OM. We investigated the treatment of pneumococcal biofilms with nitric oxide (NO), an endogenous signaling molecule and therapeutic agent that has been demonstrated to trigger biofilm dispersal in other bacterial species. We hypothesised that addition of low concentrations of NO to pneumococcal biofilms would improve antibiotic efficacy and higher concentrations exert direct antibacterial effects. Unlike in many other bacterial species, low concentrations of NO, did not result in S. pneumoniae biofilm dispersal. Instead, treatment of both in vitro biofilms and ex vivo adenoid tissue samples (a reservoir for S. pneumoniae biofilms) with low concentrations of NO enhanced pneumococcal killing when combined with amoxicillin-clavulanic acid, an antibiotic commonly used to treat chronic OM. Quantitative proteomic analysis using iTRAQ (isobaric tag for relative and absolute quantitation) identified 13 proteins that were differentially expressed following low-concentration NO treatment, 85% of which function in metabolism or translation. Treatment with low-concentration NO therefore appears to modulate pneumococcal metabolism and may represent a novel therapeutic approach to reduce antibiotic tolerance in pneumococcal biofilms

Invasive Propionibacterium acnes infections in a non-selective patient cohort: clinical manifestations, management and outcome

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Purpose An increasing number of reports suggest that Propionibacterium acnes can cause serious invasive infections. Currently only limited data exist regarding the spectrum of invasive P. acnes infections. Methods Non-selective cohort study at a tertiary hospital in the UK over a nine-year-period (2003-2012) investigating clinical manifestations, risk factors, management and outcome of invasive P. acnes infections. Results Forty-nine cases were identified; the majority were neurosurgical infections and orthopaedic infections (n=28 and n=15, respectively). Only two cases had no predisposing factors; all neurosurgical and 93.3% of orthopaedic cases had a history of previous surgery and/or trauma. Foreign material was in situ at the infection site in 59.3% and 80.0% of neurosurgical and orthopaedic cases, respectively. All neurosurgical and orthopaedic cases required one or more surgical interventions to treat P. acnes infection, with or without concomitant antibiotic therapy; the duration of antibiotic therapy was significantly longer in the group of orthopaedic cases (median 53 versus 19 days; p=0.0025). All tested P. acnes isolates were susceptible to penicillin, ampicillin and chloramphenicol; only one was clindamycin-resistant. Conclusions Neurosurgical and orthopaedic infections account for the majority of invasive P. acnes infections. The majority of cases have predisposing factors, including previous surgery and/or trauma; spontaneous infections are rare. Foreign material is commonly present at the site of infection, indicating that the pathogenesis of invasive P. acnes infections likely involves biofilm formation. Since invasive P. acnes infections are associated with considerable morbidity, further studies are needed to establish effective prevention and optimal treatment strategies