Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia colicells that were exposed to ultraviolet C (UVC) radiation. Exponential and stationary wild-type and uvrA-deficientE. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC). Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out.

Treated domestic sewage: kinetics of Escherichia coli and total coliform inactivation by oxidation with hydrogen peroxide

Hydrogen peroxide has been used for decades in developed countries as an oxidizing agent in the treatment of water, domestic sewage and industrial effluents. This study evaluated the influence of the concentration of H2O2 and pH on the inactivation of Escherichia coli cells and the disinfection of sewage treated. The results showed that the inactivation rate increased with pH and H2O2. The presence of other contaminants dissolved in the effluent is probably the cause of these differences, because E. coli inactivation in synthetic wastewater was found to be much faster than in the real treated domestic sewage.

Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures

Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.

Recognition of enteroinvasive Escherichia coli and Shigella flexneri by dendritic cells: distinct dendritic cell activation states

The innate and adaptive immune responses of dendritic cells (DCs) to enteroinvasive Escherichia coli (EIEC) infection were compared with DC responses to Shigella flexneri infection. EIEC triggered DCs to produce interleukin (IL)-10, IL-12 and tumour necrosis factor (TNF)-α, whereas S. flexneri induced only the production of TNF-α. Unlike S. flexneri, EIEC strongly increased the expression of toll like receptor (TLR)-4 and TLR-5 in DCs and diminished the expression of co-stimulatory molecules that may cooperate to inhibit CD4+ T-lymphocyte proliferation. The inflammation elicited by EIEC seems to be related to innate immunity both because of the aforementioned results and because only EIEC were able to stimulate DC transmigration across polarised Caco-2 cell monolayers, a mechanism likely to be associated with the secretion of CC chemokine ligands (CCL)20 and TNF-α. Understanding intestinal DC biology is critical to unravelling the infection strategies of EIEC and may aid in the design of treatments for infectious diseases.

Human sepsis-associated Escherichia coli (SEPEC) is able to adhere to and invade kidney epithelial cells in culture

The adhesins of extraintestinal pathogenic Escherichia coli are essential for mediating direct interactions between the microbes and the host cell surfaces that they infect. Using fluorescence microscopy and gentamycin protection assays, we observed that 49 sepsis-associated E. coli (SEPEC) strains isolated from human adults adhered to and invaded Vero cells in the presence of D-mannose (100%). In addition, bacteria concentrations of approximately 2 x 10(7) CFU/mL were recovered from Vero cells following an invasion assay. Furthermore, PCR analysis of adhesin genes showed that 98.0% of these SEPEC strains tested positive for fimH, 69.4% for flu, 53.1% for csgA, 38.8% for mat, and 32.7% for iha. Analysis of the invasin genes showed that 16.3% of the SEPEC strains were positive for tia, 12.3% for gimB, and 10.2% for ibeA. Therefore, these data suggest that SEPEC adhesion to cell surfaces occurs through non-fimH mechanisms. Scanning electron microscopy showed the formation of microcolonies on the Vero cell surface. SEPEC invasiveness was also confirmed by the presence of intracellular bacteria, and ultrastructural analysis using electron transmission microscopy revealed bacteria inside the Vero cells. Taken together, these results demonstrate that these SEPEC strains had the ability to adhere to and invade Vero cells. Moreover, these data support the theory that renal cells may be the predominant pathway through which SEPEC enters human blood vessels.

Purification and parcial characterization of a hemagglutinating factor (HAF): a possible adhesive factor of the diffuse adherent of Escherichia coli (DAEC)

The mannose-resistant hemagglutinating factor (HAF) was extracted and purified from a diffuse adherent Escherichia coli (DAEC) strain belonging to the classic enteropathogenic E. coli (EPEC) serotype (0128). The molecular weight of HAF was estimated to be 18 KDa by SDS-PAGE and 66 KDa by Sephadex G100, suggesting that the native form of HAF consists of 3-4 monomeric HAF. Gold immunolabeling with specific HAF antiserum revealed that the HAF is not a rigid structure like fimbriae on the bacterial surface. The immunofluorescence test using purified HAF on HeLa cells, in addition to the fact that the HAF is distributed among serotypes of EPEC, suggests that HAF is a possible adhesive factor of DAEC strains

Biological and genetic characteristics of uropathogenic Escherichia coli strains

The aim of the present study was to determine biological characteristics such as expression of fimbriae, Congo red binding, production of hemolysin and aerobactin, adhesion to HeLa and uroepithelial cells and invasion of HeLa cells by Escherichia coli isolates obtained from patients showing clinical signs of urinary tract infection (UTI). Also, the presence of genes (apa, afa, spa) for fimbria expression and cytotoxic necrotizing factors (CNF1, CNF2) was assayed using specific primers in PCR. The data obtained were compared with the clonal relationships obtained by analysis of multilocus enzyme electrophoresis (MLEE), restriction fragment length polymorphism (RFLP) of the rDNA (ribotyping) and enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). All isolates but one presented a combination of at least two of the characteristics studied, a fact suggesting the presence of pathogenicity islands (PAIs). Diffuse adherence type to HeLa cells was observed to occur in most of the strains, but adhesion to uroepithelial cells seems to be a more reliable test to verify pathogenicity. Although four strains seemed to be able to invade HeLa cells when assayed by light microscopy, electron microscopy studies demonstrated that these strains were not invasive. MLEE, RFLP and ERIC-PCR were able to group the isolates differently into main clusters that were not correlated with the presence of pathogenic traits.

Endocytosis-inducer adhesins produced by enteropathogenic serogroups of Escherichia coli participate on bacterial attachment to infant enterocytes

Enteropathogenic E. coli (EPEC) infection of Hep-2 cells preoceeds through bacterial attachment to cell surface and internalization of adhered bacteria. EPEC attachment is a prerequisite for cell infection and is mediated by adhesins that recognize carbohydrate-containing receptors on cell membrane. Such endocytosis-inducer adhesins (EIA) also promote EPEC binding to infant enterocytes, suggesting that EIA may have an important role on EPEC gastroenteritis.

Localized, diffuse, and aggregative-adhering Escherichia coli from infants with acute diarrhea and matched-controls

Of 126 infants under 2 years, enrolled in a study on the etiology of acute diarrhea in Recife, Brazil, we selected 37 from whom no recognized enteropathogens, except classic enteropathogenic Escherichia coli, were identified. For comparison, we also examined 37 matched-control infants without diarrhea seen at the same hospital setting. This paper had the purpose to determine the prevalence of localized, diffuse, and aggregative-adhering E. coli strains in both groups. Three to five fecal E. coli colonies, of each case and control, were tested individually for adherence to HeLa cells by using the one step 3-h incubation assay. Strains of E. coli showing localized adherence were found significantly more often in patients (37.8%) than in controls (13.5%), p < 0.02, and they were pratically confined to EPEC serovars 055:H-, 0111:H2, and 119:H6. In contrast, E. coli isolates exhibiting the diffuse or aggregative patterns of adherence were restricted to non-EPEC serogroups and were more frequently encountred among controls.

A Preliminary Investigation on the Chemical Composition of the Cell Surface of Five Enteropathogenic Escherichia coli Serotypes

The cell surfaces of five enteropathogenic Escherichia coli serotypes (O111:H2; O111:H12; O125:H9; O119:H6; O26:H11) were assayed by chemical methods, lectin agglutination tests and spectroscopy associated to transmission electron microscopy. Results of lectin agglutination assays showed that all strains reacted with mannosebinding lectins. Strains belonging to serotype O125:H9 also agglutinated with lectins which recognize galactose and Nacetylgalactosamine residues. The bacterial cells were treated with 0.01M phosphate buffered saline (pH 7.0) at 100oC for 2 hr and the extracts were submitted to precipitation and fractionated by Cetavlon. Phosphate, total sugar and protein contents were determined. Gas liquid chomatography-mass spectrometry analysis of alditol acetates showed the presence of galactose, mannose, fucose, glucose and traces of ribose. Spectroscopic analysis of intact cells showed the presence of a capsule-like structure which was not totally preserved after extraction. Some cells were still surrounded by an amorphous capsular-like material after polysaccharide extraction.

Production of cytolethal distending toxin and other virulence characteristics of Escherichia coli strains of serogroup O86

Genetic and phenotypic virulence markers of different categories of diarrhoeagenic Escherichia coli were investigated in 106 strains of enteropathogenic E. coli (EPEC) serogroup O86. The most frequent serotype found was O86:H34 (86%). Strains of this serotype and the non motile ones behaved as EPEC i.e., carried eae, bfpA and EAF DNA sequences and presented localised adherence to HeLa cells. Serotypes O86:H2, O86:H6, O86:H10, O86:H18, O86:H27 and O86:H non determined, belonged to other categories. The majority of the strains of serotype O86:H34 and non motile strains produced cytolethal-distending toxin (CDT). The ribotyping analysis showed a correlation among ribotypes, virulence markers and serotypes, thus suggesting that CDT production might be a property associated with a universal clone represented by the O86:H34 serotype.

Expression of bacterial virulence factors and cytokines during in vitro macrophage infection by enteroinvasive Escherichia coli and Shigella flexneri: a comparative study

Enteroinvasive Escherichia coli (EIEC) and Shigellaspp cause bacillary dysentery in humans by invading and multiplying within epithelial cells of the colonic mucosa. Although EIEC and Shigellashare many genetic and biochemical similarities, the illness caused by Shigellais more severe. Thus, genomic and structure-function molecular studies on the biological interactions of these invasive enterobacteria with eukaryotic cells have focused on Shigella rather than EIEC. Here we comparatively studied the interactions of EIEC and of Shigella flexneriwith cultured J774 macrophage-like cells. We evaluated several phenotypes: (i) bacterial escape from macrophages after phagocytosis, (ii) macrophage death induced by EIEC and S. flexneri, (iii) macrophage cytokine expression in response to infection and (iv) expression of plasmidial (pINV) virulence genes. The results showed thatS. flexneri caused macrophage killing earlier and more intensely than EIEC. Both pathogens induced significant macrophage production of TNF, IL-1 and IL-10 after 7 h of infection. Transcription levels of the gene invasion plasmid antigen-C were lower in EIEC than in S. flexneri throughout the course of the infection; this could explain the diminished virulence of EIEC compared to S. flexneri.

The ability of haemolysins expressed by atypical enteropathogenic Escherichia coli to bind to extracellular matrix components

Typical and atypical enteropathogenic Escherichia coli (EPEC) are considered important bacterial causes of diarrhoea. Considering the repertoire of virulence genes, atypical EPEC (aEPEC) is a heterogeneous group, harbouring genes that are found in other diarrheagenic E. coli pathotypes, such as those encoding haemolysins. Haemolysins are cytolytic toxins that lyse host cells disrupting the function of the plasma membrane. In addition, these cytolysins mediate a connection to vascular tissue and/or blood components, such as plasma and cellular fibronectin. Therefore, we investigated the haemolytic activity of 72 aEPEC isolates and determined the correlation of this phenotype with the presence of genes encoding enterohaemolysins (Ehly) and cytolysin A (ClyA). In addition, the correlation between the expression of haemolysins and the ability of these secreted proteins to adhere to extracellular matrix (ECM) components was also assessed in this study. Our findings demonstrate that a subset of aEPEC presents haemolytic activity due to the expression of Ehlys and/or ClyA and that this activity is closely related to the ability of these isolates to bind to ECM components.

Estudos de QSAR baseados em dados de atividade biológica obtidos por microcalorimetria: III interação de m-alcoxifenóis e p-hidroxibenzoatos de alquila com Escherichia coli

QSAR studies based on flow microcalorimetric bioassay data for interaction of homologous series of m-alkoxyphenols and p-hydroxybenzoates with E. coli cells were carried out applying factorial design. Results for both series showed a linear relationship between log(dose)max and log Po/w. Analysis of these data allows the identification of contributions toward the derived bioactivity from the parent structures (the molecule minus n-CH2 groups present in the side-chain) and the lipophilic groups, CH2. These results are discussed with respect to drug quantitative structure-relationship.

Inativação por oxidação fotocatalítica de Escherichia coli e Pseudomonas sp.

This study presents the bactericidal activity of titanium dioxide photocatalysis, using as model Escherichia coli and Pseudomonas sp. cells. It was observed that the process efficiency is related to initial cell concentration, light intensity, UV irradiation exposure time, TiO2 concentration increase. The ultimate removal efficiency was above 99.9%.