Screening Antibacterial Photodynamic Effect of Monascus Red Yeast Rice (Hong-Qu) and Mycelium Extracts.

The fungus Monascus is a well-known source of secondary metabolites with interesting pharmaceutical and nutraceutical applications. In particular, Monascus pigments possess a wide range of biological activities (e.g. antimicrobial, antioxidant, anti-inflammatory or antitumoral). To broaden the scope of their possible application, this study focused on testing Monascus pigment extracts as potential photosensitizing agents efficient in antimicrobial photodynamic therapy (aPDT) against bacteria. For this purpose, eight different extracts of secondary metabolites from the liquid- and solid-state fermentation of Monascus purpureus DBM 4360 and Monascus sp. DBM 4361 were tested against Gram-positive and Gram-negative model bacteria, Bacillus subtilis and Escherichia coli and further screened for ESKAPE pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. To the bacterial culture, increasing concentration of extracts was added and it was found that all extracts showed varying antimicrobial activity against Gram-positive bacteria in dark, which was further increased after irradiation. Gram-negative bacteria were tolerant to the extracts' exposure in the dark but sensitivity to almost all extracts that occurred after irradiation. The Monascus sp. DBM 4361 extracts seemed to be the best potential candidate for aPDT against Gram-positive bacteria, being efficient at low doses, i.e. the lowest total concentration of Monascus pigments exhibiting aPDT effect was 3.92 ± 1.36 mg/L for E. coli. Our results indicate that Monascus spp., forming monascuspiloin as the major yellow pigment and not-forming mycotoxin citrinin, is a promising source of antimicrobials and photoantimicrobials.

Mathematical Modeling for Evaluating Inherent Parameters Affecting UVC Decontamination of Indicator Bacteria.

UV light is a tool associated with the denaturation of cellular components, DNA damage, and cell disruption. UV treatment is widely used in the decontamination process; however, predicting a sufficient UV dose by using traditional methods is doubtful. In this study, an in-house UVC apparatus was designed to investigate the process of the inactivation of five indicator bacteria when the initial cell concentrations and irradiation intensities varied. Both linear and nonlinear mathematical models were applied to predict the inactivation kinetics. In comparison with the Weibull and modified Chick-Watson models, the Chick-Watson model provided a good fit of the experimental data for five bacteria, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus faecalis, and Bacillus subtilis. The specific death rate (kd) significantly increased when the irradiation intensity (I) increased from 1.41 W/m2 to 3.02 W/m2 and 4.83 W/m2 (P < 0.05). Statistical analysis revealed no significant difference in the kd values among the groups of tested Gram-positive bacteria, Gram-negative bacteria, and B. subtilis spores, but the kd values differed among groups (P < 0.05). The death rate coefficient (k) varied from species to species. The k values of the tested Gram-positive bacteria were higher than those of the Gram-negative bacteria. The thick peptidoglycan layer in the Gram-positive membrane was responsible for UVC resistance. The high guanine-cytosine (GC) content in bacteria also contributed to UV resistance due to the less photoreactive sites on the nucleotides. This investigation provides a good understanding of bacterial inactivation induced by UVC treatment. IMPORTANCE Prevention and control measures for microbial pathogens have attracted worldwide attention due to the recent coronavirus disease 2019 pandemic. UV treatments are used as a commercial control to prevent microbial contamination in diverse applications. Microorganisms exhibit different UV sensitivities, which are often measured by the UV doses required for decreasing the number of microbial contaminants in the logarithmic order. The maximum efficacy of UV is usually observed at 254 nm (residing in the UVC range of the light spectrum). UV technology is a nonthermal physical decontamination measure that does not require any chemicals and consumes low levels of energy while leaving insignificant amounts of chemical residues or toxic compounds. Therefore, obtaining the microbial death kinetics and their intrinsic parameters provided in this study together with the UV photoreaction rate enables advancement in the design of UV treatment systems.

Synergistic bactericidal effects of pairs of photosensitizer molecules activated by ultraviolet A light against bacteria in plasma.

BACKGROUND: The current approach to reducing bacterial contamination in blood transfusion products is through detection or pathogen reduction methods, some of which utilize ultraviolet (UV) light photosensitizers. A small number of photosensitizers are being used as single agents in combination with UV light, but their efficacy can be limited against some pathogens. Benzophenone (BP) and vitamins B1, B6, and K3 have been identified as effective UVA photosensitizers for inactivation of bacteria. We evaluated whether combining pairs of photosensitizers in this group would have synergistic bactericidal effects on Gram-negative and Gram-positive bacteria. STUDY DESIGN AND METHODS: Bacteria species of Escherichia coli, Bacillus cereus, Staphylococcus aureus, and Klebsiella pneumoniae were mixed with 0 to 100 mM concentrations of photosensitizers and exposed to UVA irradiation at 18 J/cm2 to assess their bactericidal effects. RESULTS: Single photosensitizers irradiated with UVA produced a range of bactericidal activity. When combined in pairs, all demonstrated some synergistic bactericidal effects with up to 4-log reduction above the sum of activities of individual molecules in the pair against bacteria in plasma. Photosensitizer pairs with BP had the highest synergism across all bacteria. With vitamin K3 in the pair, synergism was evident for Gram-positive but not for Gram-negative bacteria. Vitamin B1 and vitamin B6 had the least synergism. These results indicate that a combination approach with multiple photosensitizers may extend effectiveness of pathogen reduction in plasma. CONCLUSIONS: Combining photosensitizers in pathogen reduction methods could improve bactericidal efficacy and lead to use of lower concentrations of photosensitizers to reduce toxicities and unwanted side effects.

Efficient Photodynamic Killing of Gram-Positive Bacteria by Synthetic Curcuminoids.

In our previous study, we have demonstrated that curcumin can efficiently kill the anaerobic bacterium Propionibacterium acnes by irradiation with low-dose blue light. The curcuminoids present in natural plant turmeric mainly include curcumin, demethoxycurcumin, and bisdemethoxycurcumin. However, only curcumin is commercially available. Eighteen different curcumin analogs, including demethoxycurcumin and bisdemethoxycurcumin, were synthesized in this study. Their antibacterial activity against Gram-positive aerobic bacteria Staphylococcus aureus and Staphylococcus epidermidis was investigated using the photodynamic inactivation method. Among the three compounds in turmeric, curcumin activity is the weakest, and bisdemethoxycurcumin possesses the strongest activity. However, two synthetic compounds, (1E,6E)-1,7-bis(5-methylthiophen-2-yl)hepta-1,6-diene-3,5-dione and (1E,6E)-1,7-di(thiophen-2-yl)hepta-1,6-diene-3,5-dione, possess the best antibacterial activity among all compounds examined in this study. Their chemical stability is also better than that of bisdemethoxycurcumin, and thus has potential for future clinical applications.

Photodynamic Inactivation of Bacteria with Porphyrin Derivatives: Effect of Charge, Lipophilicity, ROS Generation, and Cellular Uptake on Their Biological Activity In Vitro.

Resistance of microorganisms to antibiotics has led to research on various therapeutic strategies with different mechanisms of action, including photodynamic inactivation (PDI). In this work, we evaluated a cationic, neutral, and anionic meso-tetraphenylporphyrin derivative's ability to inactivate the Gram-negative and Gram-positive bacteria in a planktonic suspension under blue light irradiation. The spectroscopic, physicochemical, redox properties, as well as reactive oxygen species (ROS) generation capacity by a set of photosensitizers varying in lipophilicity were investigated. The theoretical calculations were performed to explain the distribution of the molecular charges in the evaluated compounds. Moreover, logP partition coefficients, cellular uptake, and phototoxicity of the photosensitizers towards bacteria were determined. The role of a specific microbial efflux pump inhibitor, verapamil hydrochloride, in PDI was also studied. The results showed that E. coli exhibited higher resistance to PDI than S. aureus (3-5 logs) with low light doses (1-10 J/cm2). In turn, the prolongation of irradiation (up to 100 J/cm2) remarkably improved the inactivation of pathogens (up to 7 logs) and revealed the importance of photosensitizer photostability. The PDI potentiation occurs after the addition of KI (more than 3 logs extra killing). Verapamil increased the uptake of photosensitizers (especially in E. coli) due to efflux pump inhibition. This effect suggests that PDI is mediated by ROS, the electrostatic charge interaction, and the efflux of photosensitizers (PSs) regulated by multidrug-resistance (MDR) systems. Thus, MDR inhibition combined with PDI gives opportunities to treat more resistant bacteria.

Evaluation of Structure-Function Relationships of Aggregation-Induced Emission Luminogens for Simultaneous Dual Applications of Specific Discrimination and Efficient Photodynamic Killing of Gram-Positive Bacteria.

Bacterial infectious diseases, especially those caused by Gram-positive bacteria, have been seriously threatening human health. Preparation of a multifunctional system bearing both rapid bacterial differentiation and effective antibacterial effects is highly in demand, but remains a severe challenge. Herein, we rationally designed and successfully developed a sequence of aggregation-induced emission luminogens (AIEgens) with orderly enhanced D-A strength. Evaluation of structure-function relationships reveals that AIEgens having intrinsic positive charge and proper ClogP value are able to stain Gram-positive bacteria. Meanwhile, one of the presented AIEgens (TTPy) can generate reactive oxygen species (ROS) in extraordinarily high efficiency under white light irradiation due to the smaller singlet-triplet energy gap. Thanks to the NIR emission, excellent specificity to Gram-positive bacteria, and effective ROS generation efficiency, TTPy has been proved to perform well in selective photodynamic killing of Gram-positive bacteria in vitro, such as S. aureus and S. epidermidis, even in S. aureus-infected rat wounds.

Characterizing the Antimicrobial Properties of 405 nm Light and the Corning® Light-Diffusing Fiber Delivery System.

BACKGROUND AND OBJECTIVES: Hospital-acquired infections (HAIs) and multidrug resistant bacteria pose a significant threat to the U.S. healthcare system. With a dearth of new antibiotic approvals, novel antimicrobial strategies are required to help solve this problem. Violet-blue visible light (400-470 nm) has been shown to elicit strong antimicrobial effects toward many pathogens, including representatives of the ESKAPE bacterial pathogens, which have a high propensity to cause HAIs. However, phototherapeutic solutions to prevention or treating infections are currently limited by efficient and nonobtrusive light-delivery mechanisms. STUDY DESIGN/MATERIALS AND METHODS: Here, we investigate the in vitro antimicrobial properties of flexible Corning® light-diffusing fiber (LDF) toward members of the ESKAPE pathogens in a variety of growth states and in the context of biological materials. Bacteria were grown on agar surfaces, in liquid culture and on abiotic surfaces. We also explored the effects of 405 nm light within the presence of lung surfactant, human serum, and on eukaryotic cells. Pathogens tested include Enterococcus spp, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., Staphylococcus epidermidis, Streptococcus pyogenes, Candida albicans, and Escherichia coli. RESULTS: Overall, the LDF delivery of 405 nm violet-blue light exerted a significant degree of microbicidal activity against a wide range of pathogens under diverse experimental conditions. CONCLUSIONS: The results exemplify the fiber's promise as a non-traditional approach for the prevention and/or therapeutic intervention of HAIs. Lasers Surg. Med. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Comparison of Anti-Microbial Effects of Low-Level Laser Irradiation and Microwave Diathermy on Gram-Positive and Gram-Negative Bacteria in an In Vitro Model.

Background and Objectives: The aim of this study was to compare the effects of low-level laser therapy and continuous microwave diathermy on the growth of Gram-negative and Gram-positive bacteria and to establish their efficacy as an alternative therapeutic modality. MATERIALS AND METHODS: Laser fluence of 13 Joules (J)/cm2, 18 J/cm2 and 30 J/cm2 were used against several bacterial strains. Microwave dosages of 25, 50 and 100 watts (W) were used, respectively. RESULTS: A significant difference between the three groups was observed using repeated analysis of variance (RANOVA) (F value: 0.74, and p value: 0.001). The Greenhouse-Geisser correction (GG) revealed significant results for laser irradiation alone. However, effect size calculation showed effects with microwave diathermy as well as laser fluence. CONCLUSIONS: Low-level laser therapy appears to be an effective modality of treatment when compared with continuous microwave diathermy on the Gram-negative and the Gram-positive bacterial strains tested. Microwave diathermy revealed large and medium effects on the bacterial cell counts with dominant effects on Gram-negative strains.

Effect of Laser Irradiation on Cell Function and Its Implications in Raman Spectroscopy.

Lasers are instrumental in advanced bioimaging and Raman spectroscopy. However, they are also well known for their destructive effects on living organisms, leading to concerns about the adverse effects of laser technologies. To implement Raman spectroscopy for cell analysis and manipulation, such as Raman-activated cell sorting, it is crucial to identify nondestructive conditions for living cells. Here, we evaluated quantitatively the effect of 532-nm laser irradiation on bacterial cell fate and growth at the single-cell level. Using a purpose-built microfluidic platform, we were able to quantify the growth characteristics, i.e., specific growth rates and lag times of individual cells, as well as the survival rate of a population in conjunction with Raman spectroscopy. Representative Gram-negative and Gram-positive species show similar trends in response to a laser irradiation dose. Laser irradiation could compromise the physiological function of cells, and the degree of destruction is both dose and strain dependent, ranging from reduced cell growth to a complete loss of cell metabolic activity and finally to physical disintegration. Gram-positive bacterial cells are more susceptible than Gram-negative bacterial strains to irradiation-induced damage. By directly correlating Raman acquisition with single-cell growth characteristics, we provide evidence of nondestructive characteristics of Raman spectroscopy on individual bacterial cells. However, while strong Raman signals can be obtained without causing cell death, the variety of responses from different strains and from individual cells justifies careful evaluation of Raman acquisition conditions if cell viability is critical.IMPORTANCE In Raman spectroscopy, the use of powerful monochromatic light in laser-based systems facilitates the detection of inherently weak signals. This allows environmentally and clinically relevant microorganisms to be measured at the single-cell level. The significance of being able to perform Raman measurement is that, unlike label-based fluorescence techniques, it provides a "fingerprint" that is specific to the identity and state of any (unlabeled) sample. Thus, it has emerged as a powerful method for studying living cells under physiological and environmental conditions. However, the laser's high power also has the potential to kill bacteria, which leads to concerns. The research presented here is a quantitative evaluation that provides a generic platform and methodology to evaluate the effects of laser irradiation on individual bacterial cells. Furthermore, it illustrates this by determining the conditions required to nondestructively measure the spectra of representative bacteria from several different groups.

Can microbial cells develop resistance to oxidative stress in antimicrobial photodynamic inactivation?

Infections have been a major cause of disease throughout the history of humans on earth. With the introduction of antibiotics, it was thought that infections had been conquered. However, bacteria have been able to develop resistance to antibiotics at an exponentially increasing rate. The growing threat from multi-drug resistant organisms calls for intensive action to prevent the emergence of totally resistant and untreatable infections. Novel, non-invasive, non-antibiotic strategies are needed that act more efficiently and faster than current antibiotics. One promising alternative is antimicrobial photodynamic inactivation (APDI), an approach that produces reactive oxygen species when dyes and light are combined. So far, it has been questionable if bacteria can develop resistance against APDI. This review paper gives an overview of recent studies concerning the susceptibility of bacteria towards oxidative stress, and suggests possible mechanisms of the development of APDI-resistance that should at least be addressed. Some ways to potentiate APDI and also to overcome future resistance are suggested.

Effects of gamma irradiation on the physico-chemical and biological properties of levofloxacin.

The aim of the present study was to examine the effect of gamma radiation on levofloxacin. Powder form of levofloxacin was subjected to different radiation doses (25, 50, 75, 100 and 125kGy) of Cobalt-60 source in a Gammacell-220 at a rate of 8.5 Gray/hr. The effect of radiation has been investigated with the aid of different spectroscopic techniques (UV-Vis, FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and by antibacterial activities. UV data did not reveal significant changes in the structure of levofloxacin which is supported by scanning electron microscopy. However, X-rays diffraction shows a change in crystallinity of levofloxacin to an amorphous structure and this has been reflected on the morphology of this compound as indicated by SEM images. The antibacterial activities, on the other hand, reveal resistance of irradiated levofloxacin against bacteria, where some bacteria were highly affected by the irradiated drug. Similarly, FT-IR data show some changes in the functional groups principal absorption bands, in the IR spectrum, at frequencies 3286, 2846, 1716 and 1620 cm-1 for the O-H stretching band of quinolone, C-H stretching band, and C=O stretching band of carboxylic and pyridine. In addition, new peaks appeared which were not seen in the non-irradiated spectrum. In conclusion, some changes occurred in levofloxacin drug with the passage of radiation but the drug was chemically stable.

Parietin: an efficient photo-screening pigment in vivo with good photosensitizing and photodynamic antibacterial effects in vitro.

The photophysical, photoinduced pro-oxidant and antibacterial properties in vitro of the natural occurring parietin (PTN; 1,8-dihydroxy-3-methoxy-6-methyl-9,10-anthraquinone) were evaluated. PTN was extracted from the lichen identified as Teloschistes flavicans (Sw.) Norm. (Telochistaceae). Results indicate that in chloroform solution, PTN presents spectroscopic features corresponding to an excited-state intramolecular proton-transfer (ESIPT) state with partial keto-enol tautomerization. In argon-saturated solutions, the singlet excited state is poorly fluorescent (ΦF = 0.03), decaying by efficient intersystem crossing to an excited triplet state 3PTN*, as detected by laser-flash photolysis experiments. In the presence of triplet molecular oxygen, the 3PTN* was fully quenched producing singlet molecular oxygen (1O2) with a quantum yield of 0.69. In addition, in buffer solutions, PTN has the ability to also generate a superoxide radical anion (O2˙-) in a human leukocyte model and its production was enhanced under UVA-Vis irradiation. Finally, the in vitro antibacterial capability of PTN in the dark and under UVA-Vis illumination was compared in microbial cultures of both Gram positive and negative bacteria. As a result, PTN showed promising photo-induced antibacterial activity through the efficient photosensitized generation of both 1O2 and O2˙- species. Thus, we have demonstrated that PTN, an efficient photo-screening pigment in lichens, is also a good photosensitizer in solution with promising applications in antibacterial photodynamic therapy.

Broad-Spectrum Antimicrobial Effects of Photocatalysis Using Titanium Dioxide Nanoparticles Are Strongly Potentiated by Addition of Potassium Iodide.

Photocatalysis describes the excitation of titanium dioxide nanoparticles (a wide-band gap semiconductor) by UVA light to produce reactive oxygen species (ROS) that can destroy many organic molecules. This photocatalysis process is used for environmental remediation, while antimicrobial photocatalysis can kill many classes of microorganisms and can be used to sterilize water and surfaces and possibly to treat infections. Here we show that addition of the nontoxic inorganic salt potassium iodide to TiO2 (P25) excited by UVA potentiated the killing of Gram-positive bacteria, Gram-negative bacteria, and fungi by up to 6 logs. The microbial killing depended on the concentration of TiO2, the fluence of UVA light, and the concentration of KI (the best effect was at 100 mM). There was formation of long-lived antimicrobial species (probably hypoiodite and iodine) in the reaction mixture (detected by adding bacteria after light), but short-lived antibacterial reactive species (bacteria present during light) produced more killing. Fluorescent probes for ROS (hydroxyl radical and singlet oxygen) were quenched by iodide. Tri-iodide (which has a peak at 350 nm and a blue product with starch) was produced by TiO2-UVA-KI but was much reduced when methicillin-resistant Staphylococcus aureus (MRSA) cells were also present. The model tyrosine substrate N-acetyl tyrosine ethyl ester was iodinated in a light dose-dependent manner. We conclude that UVA-excited TiO2 in the presence of iodide produces reactive iodine intermediates during illumination that kill microbial cells and long-lived oxidized iodine products that kill after light has ended.

Efficacy of Ultraviolet (UV-C) Light in a Thin-Film Turbulent Flow for the Reduction of Milkborne Pathogens.

Nonthermal technologies are being investigated as viable alternatives to, or supplemental utilization, with thermal pasteurization in the food-processing industry. In this study, the effect of ultraviolet (UV)-C light on the inactivation of seven milkborne pathogens (Listeria monocytogenes, Serratia marcescens, Salmonella Senftenberg, Yersinia enterocolitica, Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus) was evaluated. The pathogens were suspended in ultra-high-temperature whole milk and treated at UV doses between 0 and 5000 J/L at a flow rate of 4300 L/h in a thin-film turbulent flow-through pilot system. Of the seven milkborne pathogens tested, L. monocytogenes was the most UV resistant, requiring 2000 J/L of UV-C exposure to reach a 5-log reduction. The most sensitive bacterium was S. aureus, requiring only 1450 J/L to reach a 5-log reduction. This study demonstrated that the survival curves were nonlinear. Sigmoidal inactivation curves were observed for all tested bacterial strains. Nonlinear modeling of the inactivation data was a better fit than the traditional log-linear approach. Results obtained from this study indicate that UV illumination has the potential to be used as a nonthermal method to reduce microorganism populations in milk.

Diversity of ionizing radiation-resistant bacteria obtained from the Taklimakan Desert.

So far, little is known about the diversity of the radiation-resistant microbes of the hyperarid Taklimakan Desert. In this study, ionizing radiation (IR)-resistant bacteria from two sites in Xinjiang were investigated. After exposing the arid (water content of 0.8 ± 0.3%) and non-arid (water content of 21.3 ± 0.9%) sediment samples to IR of 3000 Gy using a (60)Co source, a total of 52 γ-radiation-resistant bacteria were isolated from the desert sample. The 16S rRNA genes of all isolates were sequenced. The phylogenetic tree places these isolates into five groups: Cytophaga-Flavobacterium-Bacteroides, Proteobacteria, Deinococcus-Thermus, Firmicutes, and Actinobacteria. Interestingly, this is the first report of radiation-resistant bacteria belonging to the genera Knoellia, Lysobacter, Nocardioides, Paracoccus, Pontibacter, Rufibacter and Microvirga. The 16s rRNA genes of four isolates showed low sequence similarities to those of the published species. Phenotypic analysis showed that all bacteria in this study are able to produce catalase, suggesting that these bacteria possess reactive oxygen species (ROS)-scavenging enzymes. These radiation-resistant bacteria also displayed diverse metabolic properties. Moreover, their radiation resistances were found to differ. The diversity of the radiation-resistant bacteria in the desert provides further ecological support for the hypothesis that the ionizing-radiation resistance phenotype is a consequence of the evolution of ROS-scavenging systems that protect cells against oxidative damage caused by desiccation.

[Antibiotic Resistance of Microbial Isolates from Long-Term Healing Wounds Exposed to Light of Various Wave Lengths].

The data on inhibition of the growth of microorganisms of a characteristic spectrum and antibiotic resistance isolated from long-term healing wounds by light of various wave ranges are presented. The growing cultures on blood agar were exposed to polarized light, red and infrared, ultraviolet of medium- and short-wave continuous modes accustomed in physiotherapy of wounds.The effect of light in some way induced inhibition of the growth, but complete recovery was stated only after the use of ultraviolet light when confirmed quantitatively in terms of the CFU.

Influence of external bacterial structures on the efficiency of photodynamic inactivation by a cationic porphyrin.

The main targets of photodynamic inactivation (PDI) are the external bacterial structures, cytoplasmic membrane and cell wall. In this work it was evaluated how the external bacterial structures influence the PDI efficiency. To reach this objective 8 bacteria with distinct external structures were selected; 4 Gram-negative bacteria (Escherichia coli, with typical Gram-negative external structures; Aeromonas salmonicida, Aeromonas hydrophila both with an S-layer and Rhodopirellula sp., with a peptidoglycan-less proteinaceous cell wall and with cytoplasm compartmentalization) and 4 Gram-positive bacteria (Staphylococcus aureus, with typical Gram-positive external structures; Truepera radiovictrix, Deinococcus geothermalis and Deinococcus radiodurans, all with thick cell walls that give them Gram-positive stains, but including a second complex multi-layered membrane and structurally analogous to that of Gram-negative bacteria). The studies were performed in the presence of 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetraiodide (Tetra-Py(+)-Me) at 5.0 µM with white light (40 W m(-2)). The susceptibility of each bacteria to PDI by Tetra-Py(+)-Me was dependent on bacteria external structures. Although all Gram-positive bacteria were inactivated to the detection limit (reduction of ∼8 log) after 60-180 min of irradiation, the inactivation followed distinct patterns. Among the Gram-negative bacteria, E. coli was the only species to be inactivated to the detection limit (∼8 log after 180 min). The efficiency of inactivation of the two species of Aeromonas was similar (reduction of ∼5-6 log after 270 min). Rhodopirellula was less susceptible (reduction of ∼4 log after 270 min). As previously observed, the Gram-positive bacteria are more easily inactivated than Gram-negative strains, and this is even true for T. radiovictrix, D. geothermalis and D. radiodurans, which have a complex multi-layered cell wall. The results support the theory that the outer cell structures are major bacterial targets for PDI. Moreover, the chemical composition of the external structures has a stronger effect on PDI efficiency than complexity and the number of layers of the external coating, and lipids seem to be an important target of PDI.

Photoinactivation of Gram positive and Gram negative bacteria with the antimicrobial peptide (KLAKLAK)(2) conjugated to the hydrophilic photosensitizer eosin Y.

We test the hypothesis that the antimicrobial peptide (KLAKLAK)(2) enhances the photodynamic activity of the photosensitizer eosin Y upon conjugation. The conjugate eosin-(KLAKLAK)(2) was obtained by solid-phase peptide synthesis. Photoinactivation assays were performed against the Gram-negative bacteria Escherichia coli , Pseudomonas aeruginosa , and multidrug resistant Acinetobacter baumannii AYE, as well as the Gram-positive bacteria Staphylococcus aureus , and Staphylococcus epidermidis . Partitioning assays were performed with E. coli and S. aureus . Photohemolysis and photokilling assays were also performed to assess the photodynamic activity of the conjugate toward mammalian cells. Eosin-(KLAKLAK)(2) photoinactivates 99.999% of 10(8) CFU/mL of most bacteria tested at a concentration of 1 µM or below. In contrast, neither eosin Y nor (KLAKLAK)(2) cause any significant photoinactivation under similar conditions. The increase in photodynamic activity of the photosensitizer conferred by the antimicrobial peptide is in part due to the fact that (KLAKLAK)(2) promotes the association of eosin Y to bacteria. Eosin-(KLAKLAK)(2) does not significantly associate with red blood cells or the cultured mammalian cell lines HaCaT, COS-7, and COLO 316. Consequently, little photodamage or photokilling is observed with these cells under conditions for which bacterial photoinactivation is achieved. The peptide (KLAKLAK)(2) therefore significantly enhances the photodynamic activity of eosin Y toward both Gram-positive and Gram-negative bacteria while interacting minimally with human cells. Overall, our results suggest that antimicrobial peptides such as (KLAKLAK)(2) might serve as attractive agents that can target photosensitizers to bacteria specifically.

[Study of the state of parietal microflora and wall of the large intestine of mice under the influence of anomalous magnetic field].

AIM: Study the possible qualitative and quantitative changes of microbial community of the parietal mucin of the large intestine and the state of the wall of the large intestine in experimental animals underbackground and anomalous influence of geomagnetic field. MATERIALS AND METHODS: CBA mice were put under the influence of anomalous magnetic field comparable to its intensity in Zheleznogorsk (3 Oe) for 1 and 2 weeks. Quantitative and qualitative study of mucous microflora of the large intestine of the mice was performed by bacteriological method. Identification of the microorganisms was performed by microbiological analyzer "Multiskan-Ascent" and commercial test-systems "Lachema-Czech Republic": ENTHEROtest-16, STAPHYtest-16, Streptotest-16, En-COCCUStest-16; for lactobacilli and bifidobacteria identification - API 50 CHL (bioMerieux). Bacteria content in 1 g of material was calculated by the number of microorganism colonies grown. RESULTS: A pattern of changes of mucous microflora of the intestine and the state of the wall of the large intestine of the experimental animals that had been put under the influence of anomalous magnetic field is shown. During evaluation of qualitative and quantitative diversity of microbial community of parietal mucin of the large intestine of the mice under the influence of magnetic field on the background and anomalous levels changes not only in quantity and frequency of detection of obligate, transitory flora but also cell elements of mucous membrane of the wall of the large intestine were established. CONCLUSION: The results of the study allow to make a conclusion about the presence of reactivity of the parietal microflora of the intestine of the mice to the influence of the anomalous magnetic field. This leads to changes in cell elements in the mucous membrane of the wall that manifest by infiltration of the connective tissue stroma by leucocytes and reconstruction of epithelium, that are features of dysbiosis.

[The impact of UV radiation B and C in vitro on different of bacteria strains isolated from patients hospitalized in the Warsaw Medical University Clinics]. / Wplyw promieniowania uv w zakresie dlugosci b i C, w warunkach in vitro, na rózne szczepy bakterii izolowanych od pacjentów hospitalizowanych w klinikach Warszawskiego Uniwersytetu Medycznego.

INTRODUCTION: Infections in human body caused by various microbes are a significant problem in modern medicine. Special attention is put to infections of wounds, which are a significant threat to the life of patients. Attempts to treat these wounds base mainly on the application of various chemical preparations (locally) and systematic antibiotic treatment. UV radiation, because of its anti-bacterial activity, appear a complementary issue in therapy. AIM OF THE SURVEY: The aim of this study was an examination of the sensitivity of bacteria strains isolated from patients hospitalised in the Warsaw Medical University clinics, and prove that antibiotics and operation of UV B and C radiation with Endolamp 474 may become a complementary or alternative method of treatment. MATERIAL AND METHODOLOGY: The study used 65 strains grown aerobically (15 strains of Escherichia coli, 20 strains of Pseudomonas aeruginosa, 15 strains of Staphylococcus aureus, 15 strains of Streptococcus and Enterococcus sp). The same strains were planted on different excipients and were subjected to UV radiation using Endolamp 474. Correctly prepared strains were radiated from a 25 cm distance in various durations (from 5 seconds to 105 seconds). RESULTS AND CONCLUSIONS: As a result of UV irradiation of microorganisms studied B and C using 474 Endolampy received varied, but the great sensitivity to the effects of this radiation, in all tested bacterial strains. UV radiation on microorganisms requires further study, also in vivo.