Surface Of Agar Plates Research Articles

Isolation of Secondary Metabolites From Marine Actinobacterium of Microbispora sp.T3S11 and Their Antibacterial Activities.

Introduction Marine actinobacteria are promising sources of novel bioactive compounds due to their distinct ecological niches and diverse secondary metabolite production capabilities. Among these,Microbisporasp. T3S11 is notable for its unique spore chain structure, which allows for both morphological and genetic identification. Despite its potential, little is understood about the secondary metabolites produced by this strain. In this study, we hope to fill this gap by extracting and analyzing the antibacterial activities of secondary metabolites fromMicrobisporasp. T3S11, which will be the first time its bioactive compound profile is investigated. Aim To evaluate the antibacterial activity of secondary metabolites isolated from the marine actinobacteriumMicrobisporasp. T3S11. Materials and methods The antibacterial assays were carried out on agar plates containing the appropriate media for each pathogen. Sterile filter paper disks were impregnated with secondary metabolites extracted fromMicrobisporasp. T3S11 and placed on the surface of agar plates inoculated with the appropriate pathogens. Similarly, disks containing tetracycline were used as a positive control. The plates were then incubated at the appropriate temperature for each pathogen, and the zones of inhibition around the disks were measured to determine the extracted metabolites' antibacterial activity. Result Secondary metabolites had antimicrobial activity againstStreptococcus mutans,Klebsiella pneumonia, and methicillin-resistantStaphylococcus aureus(MRSA). The inhibition ofS. mutanswas 7.5 mm and 8.5 mm at 75 μg/mL and 100 μg/mL, respectively.Klebsiella pneumoniazones measured 7 mm and 7.5 mm, while MRSA zones measured 7.6 mm and 8.5 mm at the same concentrations. Tetracycline, the standard antibiotic, had larger inhibition zones: 22 mm forS. mutansandKlebsiella pneumoniaand 16 mm for MRSA, indicating variable susceptibility. Conclusion We conclude that the secondary metabolites extracted fromMicrobisporasp. T3S11exhibits high antibacterial activity. This could be attributed to the presence of various active compounds.

Towards the isolation of more robust next generation probiotics: The first aerotolerant Bifidobacterium bifidum strain

This work reports on the first described aerotolerant Bifidobacterium bifidum strain, Bifidobacterium bifidum IPLA60003, which has the ability to form colonies on the surface of agar plates under aerobic conditions, a weird phenotype that to our knowledge has never been observed in B. bifidum. The strain IPLA60003 was generated after random UV mutagenesis from an intestinal isolate. It incorporates 26 single nucleotide polymorphisms that activate the expression of native oxidative-defense mechanisms such as the alkyl hydroxyperoxide reductase, the glycolytic pathway and several genes coding for enzymes involved in redox reactions. In the present work, we discuss the molecular mechanisms underlying the aerotolerance phenotype of B. bifidum IPLA60003, which will open new strategies for the selection and inclusion of probiotic gut strains and next generation probiotics into functional foods.

Impact of local and systemic antimicrobials on leukocyte- and platelet rich fibrin: an in vitro study

The aim of this study was to evaluate the effect of local and systemic administration of antimicrobials to leukocyte- and platelet-rich fibrin (L-PRF). For part A, 16 tubes of venous blood were collected from each of eight systemically healthy subjects. Prior to blood centrifugation, 12 of the 16 tubes were injected with 0.125 ml, 0.25 ml or 0.50 ml metronidazole solution. One set of L-PRF membranes was used to assess the release of vascular endothelial growth factor AB, platelet-derived growth factor, transforming growth factor beta 1, and bone morphogenetic protein 2 at indicated time points. The metronidazole release over time by L-PRF membranes was also evaluated. The remaining L-PRF membranes were placed on the surface of agar plates inoculated with three different periodontal pathogens to determine their antibacterial activity. For part B, another six subjects were enrolled with three subjects taking 2 g amoxicillin and three subjects 500 mg metronidazole as prophylaxis prior to a periodontal treatment. Before and 2 h after consuming one of the prescribed antimicrobials, three tubes of blood were collected for preparing L-PRF membranes. These membranes were used to measure the antibacterial activity against periodontal pathogens. No statistically significant difference could be found in the release of growth factors between L-PRF membranes with and without incorporation of metronidazole solution. The release of metronidazole could be detected up to day 3, however with the highest concentration during the first 4 h. This concentration was dose dependent. The antibacterial capacity of L-PRF membranes increased significantly for both the systemic intake, and after the addition of metronidazole solution to the blood tubes before centrifugation, the latter again dose dependent. The antibacterial capacity of L-PRF against the periodontal pathogens tested can significantly be enhanced by the addition of antimicrobials, without disadvantage for the release of growth factors.

Study of the Microbiological Quality of Groundwater in the Don Bosco District of Mimboman in the City of Yaoundé, Cameroon

Groundwater is a precious and essential natural resource for many uses. Its use for food or hygiene purposes requires an excellent microbiological quality to avoid waterborne diseases. The study objective as to investigate the bacteriological quality of groundwater in the “Don Bosco’’, area located at Mimboman in the city of Yaoundé. Household surveys were conducted to identify the main source of drinking water supply. After identification of the different boreholes, water samples were taken from 10 boreholes. Bacteria were isolated after filtering 100 ml of the sample from each borehole through a 0.45 µm microporosity membrane. This membrane was then deposited on the surface of agar plates incubated at 37°C and 44°C for 24 +/- 2h. After subculturing on different media, the pure bacterial isolates were identified by their cultural and biochemical characteristics. A total of 95 households were surveyed and it was found that the main source of drinking water was boreholes (65.5%). The probable sources of pollution were latrines located above the boreholes (8/10), followed by a lack of disinfection after 6 months (7/10). Bacteriological analyses showed that the borehole water consumed by the population of Don Bosco does not meet WHO standards with a non-conformity of 50% for total flora, 38.8% for total coliforms, 31.5% for faecal coliforms and 31.5% for faecal streptococci. Six (06) general and bacterial species were isolated: group D streptococci (30%), <i>Escherichia coli</i> (30%), <i>Shigella</i> (5%), <i>Salmonella</i> (5%), <i>Yersinia enterocolitica</i> (5%) and <i>Aeromonas</i> (5%). In this study, the detection of a variety of germs in ground water indicates that these waters are unfit for consumption. As a result, there is an urgent need to move the latrines in question and to proceed with regular and appropriate disinfection of the wells in the Don Bosco area in Mimboman district, to guarantee a life quality for the population that consumes this water.

"Smart" Polylactic Acid Films with Ceftriaxone Loaded Microchamber Arrays for Personalized Antibiotic Therapy.

Bacterial infections are a severe medical problem, especially in traumatology, orthopedics, and surgery. The local use of antibiotics-elution materials has made it possible to increase the effectiveness of acute infections treatment. However, the infection prevention problem remains unresolved. Here, we demonstrate the fabrication of polylactic acid (PLA) “smart” films with microchamber arrays. These microchambers contain ceftriaxone as a payload in concentrations ranging from 12 ± 1 μg/cm2 to 38 ± 8 μg/cm2, depending on the patterned film thickness formed by the different PLA concentrations in chloroform. In addition, the release profile of the antibiotic can be prolonged up to 72 h in saline. At the same time, on the surface of agar plates, the antibiotic release time increases up to 96 h, which has been confirmed by the growth suppression of the Staphylococcus aureus bacteria. The efficient loading and optimal release rate are obtained for patterned films formed by the 1.5 wt % PLA in chloroform. The films produced from 1.5 and 2 wt % PLA solutions (thickness—0.42 ± 0.12 and 0.68 ± 0.16 µm, respectively) show an accelerated ceftriaxone release upon the trigger of the therapeutic ultrasound, which impacted as an expansion of the bacterial growth inhibition zone around the samples. Combining prolonged drug elution with the on-demand release ability of large cargo amount opens up new approaches for personalized and custom-tunable antibacterial therapy.

The effectiveness of a three-step sterilization method for Goldmann tonometer prism: A cross-sectional study.

Purpose:To propose a three-step sterilization method for Goldmann tonometer prism (GTP) and to analyze the sterilization effects of each step.Methods:120 patients (240 eyes) who underwent Goldmann applanation tonometer (GAT) IOP measurement were enrolled in this study. GTPs were used individually for each patient and wiped by swabs soaked with 75% ethyl alcohol, ofloxacin eye drops, and 75% ethyl alcohol for at least 5 s. GTPs were directly pressed onto the surface of agar plates before (W0) and after three-step sterilization (W1, W2, and W3). All the agars were sent to the laboratory in 2 h and incubated at 37°C for 48 h. Subsequently, the growth of microbial species was assessed through visual inspection of the colonies at the inoculation points on the agar surface.Results:Staphylococcus. epidermidis was the most frequently isolated bacterium and was observed in 23.33% of all prisms. Most of the bacteria were eliminated at W3 except Staphylococcus. epidermidis and Kocuria roseus in one case. The isolation rates of Staphylococcus genus and Staphylococcus. epidermidis were significantly decreased (both with P < 0.001). The number of bacteria types isolated from prisms at time point W2 and W3 had a statistically significant difference compared with W1 and W (both with P < 0.05), while W2 and W3 exhibited no significant difference.Conclusion:This three-step sterilization method for GTP proved to be effective and safe for repeated use. We recommend using ofloxacin to prevent the transmission of pathogens based on ethyl alcohol, which could also bring some economic benefits.

Antimicrobial Efficacy of Nanopropolis Coated Vs Silver-Curcumin Nanoparticles Coated Gutta-Percha Points on Various Microbial Species. A Comparative In Vitro Study

Introduction: Nanopropolis, nanosilver and curcumin have a wide antimicrobial action range. They are to be tested as a gutta-percha coating. Objectives: Comparing the antimicrobial efficacy of silver-curcumin nanoparticles versus nanopropolis coated gutta-percha against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Candida albicans and assessing the continuity of both coatings. Materials and Methods: Suspensions of both materials were loaded on filter discs, placed on the surface of agar plates inoculated with tested microbes and incubated for 24 hours. Gutta-percha cones were inserted in Eppendorf tubes containing the tested materials for 24 hours, placed on the surface of agar plates inoculated with the tested microbes and incubated for 24 hours. The antimicrobial activity of the discs was determined by measuring the diameter of the inhibition zone whereas it was measured by positive response and its degree around gutta-percha. Coated gutta-percha cones were scanned under scanning electron microscope to assess the continuity of the coating. Results: Mean and Standard Deviation of the inhibition zone diameter for Silver-curcumin nanoparticles around discs were 12.35±0.71mm for E.faecalis, 20.6±0.39mm for S.aureus, 14.6±0.61mm for E.coli and 18.2±0.67mm for C.albicans. For nanopropolis they were 8.95±0.69mm for E.faecalis, 15.4±0.7mm for S.aureus, 9.75±0.86mm for E.coli and 14.8±0.63mm for Candida. The inhibition zones around gutta-percha were more pronounced for Silver-curcumin nanoparticles. Statistically significant difference was found between the inhibitory effect of silver-curcumin nanoparticles and nanopropolis against all tested microorganisms P

Screening Bacterial Colonies Using X-Gal and IPTG: α-Complementation.

Many plasmid vectors (e.g., the pUC series, Bluescript, pGem, and their derivatives) carry a short segment of Escherichia coli DNA containing the regulatory sequences and the coding information for the first 146 amino acids of β-galactosidase. Vectors of this type are used in host cells that express the carboxy-terminal portion of β-galactosidase. Although neither the host-encoded fragments nor the plasmid-encoded fragments of β-galactosidase are themselves active, they can associate to form an enzymatically active protein. This type of complementation, in which deletion mutants of the operator-proximal segment of the lacZ gene are complemented by β-galactosidase-negative mutants that have the operator-proximal region intact, is called α-complementation. The lac+ bacteria that result from α-complementation are easily recognized because they form blue colonies in the presence of the chromogenic substrate X-Gal. However, insertion of a fragment of foreign DNA into the polycloning site of the plasmid almost invariably results in production of an amino-terminal fragment that is no longer capable of α-complementation. Bacteria carrying recombinant plasmids therefore form white colonies. To screen bacterial colonies, the chromogenic substrate X-Gal and the gratuitous inducer IPTG are mixed with suitable dilution of a culture, combined with molten top agar, and then spread on agar plates containing the appropriate antibiotic. The efficiency of transformation is slightly higher when the bacteria are plated in top agar rather than on the surface of agar plates. Perhaps the transformed bacteria prefer the slightly anaerobic state within the soft agar or the isosmolarity provided by the agar medium.

Bismuth Phosphinates in Bi-Nanocellulose Composites and their Efficacy towards Multi-Drug Resistant Bacteria.

A series of poorly soluble phenyl bis-phosphinato bismuth(III) complexes [BiPh(OP(=O)R1 R2 )2 ] (R1 =R2 =Ph; R1 =R2 =p-OMePh; R1 =R2 =m-NO2 Ph; R1 =Ph, R2 =H; R1 =R2 =Me) have been synthesised and characterised, and shown to have effective antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The bismuth complexes were incorporated into microfibrillated (nano-) cellulose generating a bismuth-cellulose composite as paper sheets. Antibacterial evaluation indicates that the Bi-cellulose materials have analogous or greater activity against Gram positive bacteria when compared with commercial silver based additives: silver sulfadiazine loaded at 0.43 wt % into nanocellulose produces a 10 mm zone of inhibition on the surface of agar plates containing S. aureus whereas [BiPh(OP(=O)Ph2 )2 ] loaded at 0.34 wt % produces an 18 mm zone of inhibition. These phenyl bis-phosphinato bismuth(III) complexes show potential to be applied in materials in healthcare facilities, to inhibit the growth of bacteria capable of causing serious disease.

Curcuma longa L.- and Piper nigrum-based hydrolysate, with high dextrose content, shows antioxidant and antimicrobial properties

A turmeric-and-black-pepper-based hydrolysate (HTBP) was developed. The polyphenolic compounds content, antioxidant activity [1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP)] and antimicrobial activity [minimal inhibitory concentration (macro-dilution method) and minimum bactericidal concentration (inoculating the surfaces of agar plates)] were evaluated. Furthermore, the best solvent for extraction of the polyphenolic compounds and curcumin, the main bioactive in turmeric flour (TF), was established. In addition, the tautomeric conformation of curcumin (present in TF and HTBP) was determined by using Fourier-transform infrared spectroscopy (FT-IR). The HTBP was obtained by complete hydrolysis of the starch to dextrose and showed the same curcumin content as TF, suggesting that the starch hydrolysis allowed the release of curcumin from the starch matrix. The antioxidant results indicated that curcumin was responsible for reducing the ferric ion, in the FRAP assay. The presence of piperine in HTBP was confirmed by FT-IR. The ethanol extracts of TF and HTBP showed antibacterial activity against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Salmonella Enteritidis, Salmonella Typhi and Pseudomonas aeruginosa.

The Composition and Structure of Biofilms Developed by Propionibacterium acnes Isolated from Cardiac Pacemaker Devices.

The present study aimed to understand the biofilm formation mechanism of Propionibacterium acnes by analyzing the components and structure of the biofilms. P. acnes strains were isolated from the surface of explanted cardiac pacemaker devices that exhibited no clinical signs of infection. Culture tests using a simple stamp culture method (pressing pacemakers against the surface of agar plates) revealed frequent P. acnes colonization on the surface of cardiac pacemaker devices. P. acnes was isolated from 7/31 devices, and the isolates were categorized by multilocus sequence typing into five different sequence types (STs): ST4 (JK18.2), ST53 (JK17.1), ST69 (JK12.2 and JK13.1), ST124 (JK5.3), ST125 (JK6.2), and unknown ST (JK19.3). An in vitro biofilm formation assay using microtiter plates demonstrated that 5/7 isolates formed biofilms. Inhibitory effects of DNase I and proteinase K on biofilm formation varied among isolates. In contrast, dispersin B showed no inhibitory activity against all isolates. Three-dimensional live/dead imaging of P. acnes biofilms with different biochemical properties using confocal laser microscopy demonstrated different distributions and proportions of living and dead cells. Additionally, it was suggested that extracellular DNA (eDNA) plays a role in the formation of biofilms containing living cells. Ultrastructural analysis of P. acnes biofilms using a transmission electron microscope and atmospheric scanning electron microscope revealed leakage of cytoplasmic components along with cell lysis and fibrous structures of eDNA connecting cells. In conclusion, the biochemical properties and structures of the biofilms differed among P. acnes isolates. These findings may provide clues for establishing countermeasures against biofilm-associated infection by P. acnes.

Bacteria inactivation by atmospheric pressure plasma jet treatment

Atmospheric pressure plasmas have achieved great scientific and technological advances for a wide range of applications including the field of antimicrobial treatment. In this paper, a home-made atmospheric pressure plasma jet device was built and the effects of air plasma treatments on the inactivation of pure bacterial culture (Escherichia coli ATCC 8739) deposited onto the surface of agar plates were investigated. Plasmas were generated using high voltage discharge for 30, 60 and 90 s. The number of viable microorganisms was determined using a plate count method. Microbial Log10 reduction depended on the time of exposure and feed gas flow. A significant reduction of about 2.5 Log10 for E. coli was achieved within 60 s of plasma treatment. This result can be related to the presence of reactive species in the plasma volume, in particular, O radicals.

A novel photosensitization treatment for the inactivation of fungal spores and cells mediated by curcumin

The global concerns regarding the emergence of fungicide-resistant strains and the impact of the excessive use of fungicidal practises on our health, food, and environment have increased, leading to a demand for alternative clean green technologies as treatments. Photosensitization is a treatment that utilises a photosensitiser, light and oxygen to cause cell damage to microorganisms. The effect of photosensitization mediated by curcumin on Aspergillus niger, Aspergillus flavus, Penicillium griseofulvum, Penicillium chrysogenum, Fusarium oxysporum, Candida albicans and Zygosaccharomyces bailii was investigated using three methods. The viability of spores/cells suspended in aqueous buffer using different concentrations of curcumin solution (100–1000μM) and light dose (0, 24, 48, 72 and 96J/cm2) were determined. Spraying curcumin solution on inoculated surfaces of agar plates followed by irradiation and soaking spores/cells in curcumin solution prior to irradiation was also investigated. In aqueous mixtures, photosensitised spores/cells of F. oxysporum and C. albicans were inhibited at all light doses and curcumin concentrations, while inactivation of A. niger, A. flavus P. griseofulvum, P. chrysogenum and Z. bailii were highly significant (P<0.001) reduced by 99%, 88.9%, 78%, 99.7% and 99.2% respectively. On the surface of agar plates, spores/cells exposed to a light dose of 360J/cm2 sprayed with curcumin at 800μM showed complete inhibition for A. niger, F. oxysporum, C. albicans and Z. bailii, while A. flavus P. griseofulvum, and P. chrysogenum reduced by 75%, 80.4% and 88.5% respectively. Soaking spores/cells with curcumin solution prior to irradiation did not have a significant effect on the percentage reduction. These observations suggest that a novel photosensitization mediated curcumin treatment is effective against fungal spores/cells and the variation of percentage reduction was dependent on curcumin concentration, light dosage and fungal species.

Inactivation of human pathogenic dermatophytes by non-thermal plasma

Non-thermal plasma (NTP) was tested as an in vitro deactivation method on four human pathogenic dermatophytes belonging to all ecological groups including anthropophilic Trichophyton rubrum and Trichophyton interdigitale, zoophilic Arthroderma benhamiae, and geophilic Microsporum gypseum. The identification of all strains was confirmed by sequencing of ITS rDNA region (internal transcribed spacer region of ribosomal DNA). Dermatophyte spores were suspended in water or inoculated on agar plates and exposed to NTP generated by a positive or negative corona discharge, or cometary discharge. After 15min of exposure to NTP a significant decrease in the number of surviving spores in water suspensions was observed in all species. Complete spore inactivation and thus decontamination was observed in anthropophilic species after 25min of exposure. Similarly, a significant decrease in the number of surviving spores was observed after 10–15min of exposure to NTP on the surface of agar plates with full inhibition after 25min in all tested species except of M. gypseum. Although the sensitivity of dermatophytes to the action of NTP appears to be lower than that of bacteria and yeast, our results suggest that NTP has the potential to be used as an alternative treatment strategy for dermatophytosis and could be useful for surface decontamination in clinical practice.

Lethal effect of blue light-activated hydrogen peroxide, curcumin and erythrosine as potential oral photosensitizers on the viability of Porphyromonas gingivalis and Fusobacterium nucleatum.

Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of hydrogen peroxide, curcumin and erythrosine as potential oral photosensitizers on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation. Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) in combination with erythrosine (22 µm), curcumin (60 µM) and hydrogen peroxide (0.3 mM) for 5 min. Bacterial samples from each treatment groups (radiation-only group, photosensitizer-only group and blue light-activated photosensitizer group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation. RESULTS for antibacterial assays on P. gingivalis confirmed that curcumin, Hydrogen peroxide and erythrosine alone exerted a moderate bactericidal effect which enhanced noticeably in conjugation with visible light. The survival rate of P. gingivalis reached zero present when the suspension exposed to blue light-activated curcumin and hydrogen peroxide for 2 min. Besides, curcumin exerted a remarkable antibacterial activity against F. nucleatum in comparison with erythrosine and hydrogen peroxide (P=0.00). Furthermore, the bactericidal effect of visible light alone on P. gingivalis as black-pigmented bacteria was significant. Our result suggested that visible blue light in the presence of erythrosine, curcumin and hydrogen peroxide would be consider as a potential approach of PDT to kill the main gramnegative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally invasive antibacterial treatment of plaque induced periodontal pathologies.

Seasonal Variability of the Price and Quality of Fresh Red Porgy Fish Sold in the Local Market of Igoumenitsa, NW Greece

Farmed Red porgy (Pagrus pagrus) is one of the “new candidate fish species” for the diversification of Mediterranean aquaculture which is predomintly based on the cultivation of the European sea bass, (Dicenfrarchus labrax), and the gilthead sea bream, (Sparus aurata). The quality of farmed red porgy (Pagrus pagrus) was investigated with samples obtained from the local fish market in the region of Igoumenitsa, NW Greece. Sample of the fish (ungutted and with scales) were purchased from three local fish mongers (the purchased fish were coded as Fish monger 1, 2 and 3) and transported to the laboratory within few minutes, using foamed polystyrene boxes covered with. The average weight of whole fish ranged between 271 and 289g. A sample of the fish flesh taken from the upper epaxial region was transferred aseptically to a stomacher bag containing sterile buffered peptone water solution (0.1%) and homogenized. After serial dilutions in 0.1% peptone water, the homogenates were spread on the surface of agar plates. Total viable counts (TVC) were determined using plate count agar after incubation at 30oC for 3 days. The quality attributes monitored during the present work included bacterial load (total mesophilic) and the pH of the flesh. The pH values varied between 6.54 and 6.69. The results indicate a possible influence of season on the bacterial load of fish sold in the market. Nevertheless, the parameters investigated in the present work indicate that the bacteria load was well below the legal limit and that fish were sold within few days after harvesting. The peak of bacterial load in the summer samples may be a result of a seasonal variability in ambient water temperature as well post harvesting contamination of the farmed fish and temperature fluctuations during handling and transportation.

Inactivation of avirulent pgm+ and Δpgm Yersinia pestis by ultraviolet light (UV-C)

Yersinia pestis is the causative agent of bubonic plague. Though not considered a foodborne pathogen, Y. pestis can survive, and even grow, in some foods, and the foodborne route of transmission is not without precedent. As such, concerns exist over the possible intentional contamination of foods with this deadly pathogen. Here we report the inactivation of avirulent (pYV-minus) strains of Y. pestis by ultraviolet light (UV-C, 254 nm). Two strains of Y. pestis containing an intact pgm virulence locus (pgm+) and strains from which the pgm locus was spontaneously deleted (Δpgm) were tested using cells grown in both logarithmic and stationary phase. The D10 values for inactivation (the UV-C dose required to inactivate one log of bacterial cells) of Y. pestis on the surface of agar plates ranged from 0.69 to 1.09 mJ/cm2. A significant difference was observed between the inactivation of cells of Y. pestis strain Yokohama grown in logarithmic and stationary phases, but no significant difference between growth phase sensitivity to UV-C was observed in Y. pestis strain Kuma. No difference in D10 values was observed between pgm+ and Δpgm strains of Yokohama grown to either logarithmic or stationary phase. A measurable difference was observed between the D10 of Kuma pgm+ and Kuma Δpgm grown in logarithmic phase, but this difference was diminished in the Kuma strains grown to stationary phase. Though strain variations exist, the results showing that UV-C can inactivate Y. pestis cells on agar surfaces suggest that UV-C would be effect in inactivating Y. pestis on food surfaces, particularly foods with a smooth surface.

Bactericidal effect of visible light in the presence of erythrosine on Porphyromonas gingivalis and Fusobacterium nucleatum compared with diode laser, an in vitro study.

Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Besides, the ability of laser irradiation in the presence of photosensitizing agent to lethal effect on oral bacteria is well documented. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of plaque disclosing agent erythrosine as photosensitizer on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation, comparing with the near-infrared diode laser. Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) used to photopolymerize composite resine dental restoration in combination with erythrosine (22 µm) up to 5 minutes. Bacterial sample were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. Bacterial samples from each treatment groups (radiation-only group, erythrosine-only group and light or laser with erythrosine group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation. Exposure to visible blue light and diode laser in conjugation with erythrosine significantly reduced both species examined viability, whereas erythrosine-treated samples exposed to visible light suggested a statically meaningful differences comparing to diode laser. In addition, bactericidal effect of visible light or diode laser alone on P. gingivalis as black-pigmented bacteria possess endogenous porphyrins was noticeably. Our result suggested that visible blue light source in the presence of plaque disclosing agent erythrosine could can be consider as potential approach of PDT to kill the main gram-negative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally invasive antibacterial treatment of plaque induced periodontal pathologies.

Inactivation of possible micromycete food contaminants using the low-temperature plasma and hydrogen peroxide

The inhibition effect of hydrogen peroxide aerosol, low-temperature plasma and their combinations has been studied on several micromycetes spores. The low-temperature plasma was generated in corona discharges in the open air apparatus with hydrogen peroxide aerosol. Micromycete spores were inoculated on the surface of agar plates, exposed solely to the hydrogen peroxide aerosol, corona discharge or their combination. After incubation the diameter of inhibition zone was measured. The solely positive corona discharge exhibits no inactivation effect, the solely negative corona discharge and solely hydrogen peroxide aerosol exhibit the inactivation effect, however their combinations exhibit to be much more effective. Low-temperature plasma and hydrogen peroxide aerosol present a possible alternative method of microbial decontamination of food, food packages or other thermolabile materials.

Inactivation of Listeria monocytogenes on agar and processed meat surfaces by atmospheric pressure plasma jets

An apparatus for generating atmospheric pressure plasma (APP) jet was used to investigate the inactivation of Listeria monocytogenes on the surface of agar plates and slices of cooked chicken breast and ham. He, N2 (both 7 L/min), and mixtures of each with O2 (0.07 L/min) were used to produce the plasma jets. After treatment for 2 min with APP jets of He, He + O2, N2, or N2 + O2, the numbers of L. monocytogenes on agar plates were reduced by 0.87, 4.19, 4.26, and 7.59 log units, respectively. Similar treatments reduced the L. monocytogenes inoculated onto sliced chicken breast and ham by 1.37 to 4.73 and 1.94 to 6.52 log units, respectively, according to the input gas used with the N2 + O2 mixture being the most effective. Most APP jets reduced the numbers of aerobic bacteria on the meat surfaces to <102 CFU/g, and the numbers remained below that level of detection after storage at 10 °C for 7 days. The results indicate that APP jets are effective for the inactivation of L. monocytogenes on sliced meats and for prolonging the shelf-life of such foods.