The application of TiO2 photocatalysis for disinfection of water contaminated with pathogenic micro-organisms: a review

The use of semiconductor photocatalysis for treatment of water and air has been the topic of intense research activity over the past 20 years. This powerful process has also been extended to the disinfection of environments contaminated with pathogenic micro-organisms. This review summarizes recent developments concerned with the photocatalytic treatment of water contaminated with pathogenic micro-organisms presenting a potential hazard to animals and human beings.

Antibiotic Management of Lung Infections in Cystic Fibrosis. I. The Microbiome, Methicillin-Resistant Staphylococcus aureus, Gram-Negative Bacteria, and Multiple Infections

Despite significant advances in treatment strategies targeting the underlying defect in cystic fibrosis (CF), airway infection remains an important cause of lung disease. In this two-part series, we review recent evidence related to the complexity of CF airway infection, explore data suggesting the relevance of individual microbial species, and discuss current and future treatment options. In Part I, the evidence with respect to the spectrum of bacteria present in the CF airway, known as the lung microbiome is discussed. Subsequently, the current approach to treat methicillin-resistant Staphylococcus aureus, gram-negative bacteria, as well as multiple coinfections is reviewed. Newer molecular techniques have demonstrated that the airway microbiome consists of a large number of microbes, and the balance between microbes, rather than the mere presence of a single species, may be relevant for disease pathophysiology. A better understanding of this complex environment could help define optimal treatment regimens that target pathogens without affecting others. Although relevance of these organisms is unclear, the pathologic consequences of methicillin-resistant S. aureus infection in patients with CF have been recently determined. New strategies for eradication and treatment of both acute and chronic infections are discussed. Pseudomonas aeruginosa plays a prominent role in CF lung disease, butmany other nonfermenting gram-negative bacteria are also found in the CF airway. Many new inhaled antibiotics specifically targeting P. aeruginosa have become available with the hope that they will improve the quality of life for patients. Part I concludes with a discussion of how best to treat patients with multiple coinfections.

Genome analysis of a simultaneously predatory and prey-independent, novel Bdellovibrio bacteriovorus from the River Tiber, supports in silico predictions of both ancient and recent lateral gene transfer from diverse bacteria

BACKGROUND: Evolution equipped Bdellovibrio bacteriovorus predatory bacteria to invade other bacteria, digesting and replicating, sealed within them thus preventing nutrient-sharing with organisms in the surrounding environment. Bdellovibrio were previously described as "obligate predators" because only by mutations, often in gene bd0108, are 1 in ~1x10(7) of predatory lab strains of Bdellovibrio converted to prey-independent growth. A previous genomic analysis of B. bacteriovorus strain HD100 suggested that predatory consumption of prey DNA by lytic enzymes made Bdellovibrio less likely than other bacteria to acquire DNA by lateral gene transfer (LGT). However the Doolittle and Pan groups predicted, in silico, both ancient and recent lateral gene transfer into the B. bacteriovorus HD100 genome.

RESULTS: To test these predictions, we isolated a predatory bacterium from the River Tiber- a good potential source of LGT as it is rich in diverse bacteria and organic pollutants- by enrichment culturing with E. coli prey cells. The isolate was identified as B. bacteriovorus and named as strain Tiberius. Unusually, this Tiberius strain showed simultaneous prey-independent growth on organic nutrients and predatory growth on live prey. Despite the prey-independent growth, the homolog of bd0108 did not have typical prey-independent-type mutations. The dual growth mode may reflect the high carbon content of the river, and gives B. bacteriovorus Tiberius extended non-predatory contact with the other bacteria present. The HD100 and Tiberius genomes were extensively syntenic despite their different cultured-terrestrial/freshly-isolated aquatic histories; but there were significant differences in gene content indicative of genomic flux and LGT. Gene content comparisons support previously published in silico predictions for LGT in strain HD100 with substantial conservation of genes predicted to have ancient LGT origins but little conservation of AT-rich genes predicted to be recently acquired.

CONCLUSIONS: The natural niche and dual predatory, and prey-independent growth of the B. bacteriovorus Tiberius strain afforded it extensive non-predatory contact with other marine and freshwater bacteria from which LGT is evident in its genome. Thus despite their arsenal of DNA-lytic enzymes; Bdellovibrio are not always predatory in natural niches and their genomes are shaped by acquiring whole genes from other bacteria.

Predatory Bdellovibrio bacteria use gliding motility to scout for prey on surfaces

Bdellovibrio bacteriovorus is a famously fast, flagellate predatory bacterium, preying upon Gram-negative bacteria in liquids; how it interacts with prey on surfaces such as in medical biofilms is unknown. Here we report that Bdellovibrio bacteria "scout" for prey bacteria on solid surfaces, using slow gliding motility that is present in flagellum-negative and pilus-negative strains.

Reduced Bacterial Colony Count of Anaerobic Bacteria Is Associated with a Worsening in Lung Clearance Index and Inflammation in Cystic Fibrosis

Anaerobic bacteria have been identified in abundance in the airways of cystic fibrosis (CF) subjects. The impact their presence and abundance has on lung function and inflammation is unclear. The aim of this study was to investigate the relationship between the colony count of aerobic and anaerobic bacteria, lung clearance index (LCI), spirometry and C-Reactive Protein (CRP) in patients with CF. Sputum and blood were collected from CF patients at a single cross-sectional visit when clinically stable. Community composition and bacterial colony counts were analysed using extended aerobic and anaerobic culture. Patients completed spirometry and a multiple breath washout (MBW) test to obtain LCI. An inverse correlation between colony count of aerobic bacteria (n = 41, r = -0.35; p = 0.02), anaerobic bacteria (n = 41, r = -0.44, p = 0.004) and LCI was observed. There was an inverse correlation between colony count of anaerobic bacteria and CRP (n = 25, r = -0.44, p = 0.03) only. The results of this study demonstrate that a lower colony count of aerobic and anaerobic bacteria correlated with a worse LCI. A lower colony count of anaerobic bacteria also correlated with higher CRP levels. These results indicate that lower abundance of aerobic and anaerobic bacteria may reflect microbiota disruption and disease progression in the CF lung.

Bacteria microarrays as sensitive tools for exploring pathogen surface epitopes and recognition by host receptors

We describe a protocol for the generation and validation of bacteria microarrays and their application to the study of specific features of the pathogen's surface and interactions with host receptors. Bacteria were directly printed on nitrocellulose-coated glass slides, using either manual or robotic arrayers, and printing quality, immobilization efficiency and stability of the arrays were rigorously controlled by incorporating a fluorescent dye into the bacteria. A panel of wild type and mutant strains of the human pathogen Klebsiella pneumoniae, responsible for nosocomial and community-acquired infections, was selected as model bacteria, and SYTO-13 was used as dye. Fluorescence signals of the printed bacteria were found to exhibit a linear concentration-dependence in the range of 1 x 10(8) to 1 x 10(9) bacteria per ml. Similar results were obtained with Pseudomonas aeruginosa and Acinetobacter baumannii, two other human pathogens. Successful validation of the quality and applicability of the established microarrays was accomplished by testing the capacity of the bacteria array to detect recognition by anti-Klebsiella antibodies and by the complement subcomponent C1q, which binds K. pneumoniae in an antibody-independent manner. The biotin/AlexaFluor-647-streptavidin system was used for monitoring binding, yielding strain-and dose-dependent signals, distinctive for each protein. Furthermore, the potential of the bacteria microarray for investigating specific features, e.g. glycosylation patterns, of the cell surface was confirmed by examining the binding behaviour of a panel of plant lectins with diverse carbohydrate-binding specificities. This and other possible applications of the newly developed arrays, as e.g. screening/evaluation of compounds to identify inhibitors of host-pathogen interactions, make bacteria microarrays a useful and sensitive tool for both basic and applied research in microbiology, biomedicine and biotechnology.

The influence of microbial factors on the susceptibility of bacteria to photocatalytic destruction

The role that bacterial factors play in determining how bacteria respond to photocatalytic degradation is becoming increasingly recognised. Fimbriae which are thin, proteinaceous cell surface structures produced by many enterobacteria are generally considered to be important bacterial virulence determinants in the host. Recent studies, however, suggest that their expression may be increased during times of environmental stress to protect them against factors such as nutrient depletion and oxidation. In this study bacteria were grown under defined culture conditions to promote the expression of type 1 fimbriae and subjected to photocatalytic treatment. Results showed that Escherichia coli grown under conditions to express type 1 fimbriae were more resistant to photocatalytic destruction than control cultures, taking 75 min longer to be destroyed. Curli fimbriae are also known to play a role in environmental protection of bacteria and they are associated with biofilm production. The ability of the E. coli strain to produce curli fimbriae was confirmed and biofilms were grown and subjected to photocatalytic treatment. Biofilm destruction by photocatalysis was assessed using a resazurin viability assay and a loss of cell viability was demonstrated within 30 min treatment time. This study suggests that intrinsic bacterial factors may play a role in determining an organism’s response to photocatalytic treatment and highlights their importance in this disinfection process.

Identification of lactic acid bacteria strains modulating incretin hormone secretion and gene expression in enteroendocrine cells

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones released from intestinal enteroendocrine (EE) cells and have well-established glucose-lowering actions. Lactic acid bacteria (LAB) colonise the human intestine, but it is unknown whether LAB and EE cells interact. Acute co-culture of LAB with EE cells showed that certain LAB strains elicit GLP-1 and GIP secretion (13-194-fold) and upregulate their gene expression. LAB-induced incretin hormone secretion did not appear to involve nutrient mechanisms, nor was there any evidence of cytolysis. Instead PCR array studies implicated signalling agents of the toll-like receptor system, e.g. adaptor protein MyD88 was decreased 23-fold and cell surface antigen CD14 was increased 17-fold. Mechanistic studies found that blockade of MyD88 triggered significant GLP-1 secretion. Furthermore, blocking of CD14 completely attenuated LAB-induced secretion. A recent clinical trial clearly shows that LAB have potential for alleviating type 2 diabetes, and further characterisation of this bioactivity is warranted.

Ultrashort self-assembling peptidomimetic nanomaterials target resistant pathogenic infections

The impending and increasing threat of antimicrobial resistance has led to a greater focus into developing alternative therapies as substitutes for traditional antibiotics for the treatment of multi-drug resistant infections.1 Our group has developed a library of short, cost-effective, diphenylalanine-based peptides (X1-FF-X2) which selective eradicate (viability reduced >90% in 24 hours) the most resistant biofilm forms of a range of Gram-positive and negative pathogens including: methicillin resistant and sensitive Staphyloccoccus aureus and Staphyloccoccus epidermidis; Pseudomonas aeruginosa, Proteus mirabilis and Escherichia coli. They demonstrate a reduced cell cytotoxic profile (NCTC929 murine fibroblast) and limited haemolysis.2 Our molecules have the ability respond to subtle changes in pH, associated with bacterial infection, self-assembling to form β-sheet secondary structures and supramolecular hydrogels at low concentrations (~0.5%w/v). Conjugation of variety of aromatic-based drugs at the X1 position, including non-steroidal anti-inflammatories (NSAIDs), confer further pharmacological properties to the peptide motif enhancing their therapeutic potential. In vivo studies using waxworms (Galleria mellonella) provide promising preliminary results demonstrating the low toxicity and high antimicrobial activity of these low molecular weight gelators in animal models. This work shows biofunctional peptide-based nanomaterials hold great promise for future translation to patients as antimicrobial drug delivery and biomaterial platforms.3 [1] G. Laverty, S.P. Gorman and B.F. Gilmore. Int.J.Mol.Sci. 2011, 12, 6566-6596. [2] G. Laverty, A.P. McCloskey, B.F. Gilmore, D.S. Jones, J Zhou, B Xu. Biomacromolecules. 2014, 15, 9, 3429-3439. [3] A.P. McCloskey, B.F. Gilmore and G.Laverty. Pathogens. 2014, 3, 791-821.

The role of antimicrobial peptides in periodontal disease.

Objectives Fibroblasts play a significant role as regulators of the host response in periodontal disease, responding to bacterial stimulation by producing an array of inflammatory cytokines and chemokines. LL-37, a host defence peptide, inhibits LPS-induced cytokine signalling in macrophages, suggesting an immunomodulatory role. The objective was to investigate the interaction between LL-37 and gingival fibroblasts – both its direct regulation of fibroblast activity and its effect on fibroblast response to LPS activation. Methods Human gingival fibroblasts (HGFs) were incubated for 24 hours in the presence of either P. gingivalis LPS (10µg/ml) or E. coli LPS (10ng/ml) along with LL-37 (0-50 µg/ml). IL-6 and IL-8 production by HGFs in the conditioned medium was determined by ELISA. Western blot was performed to determine the effect of LL-37 on LPS -induced IκBα degradation in HGFs following LPS stimulation over 2 hours. DNA microarray analysis was performed on cell populations incubated for 6 hr in the presence or absence of the peptide. Confirmation of LL-37 effects on specific gene expression was obtained by QPCR. Results At low concentrations (≤ 5 µg/ml) LL-37 significantly inhibited LPS-induced cytokine production by HGFs. At higher concentrations LL37 induced IL-8 production independent of LPS. Addition of LL-37 blocked LPS-induced IκBα degradation in HGFs. Microarray analysis revealed that LL-37 (50µg/ml) upregulated a significant number of cytokines and chemokines by > 5 fold. Upregulation of five of these, CXCL1, CXCL2, CXCL3, IL-24 and IL-8 was confirmed by Q-PCR. Conclusion The host defence peptide LL-37, the only known human cathelicidin, appears to have pleiotrophic effects in innate immunity. At least some of these are mediated through cytokine and chemokine signalling networks. The ability of LL-37 to reduce bacterial LPS-induced cytokine production in gingival fibroblasts, at low concentrations, suggests a potential therapeutic role in the management of periodontal disease.