Solid Agar Research Articles

Isolation and identification of bacteria with capability of starch, cellulose and protein decomposition from Frass of Black Soldier Fly (Hermetia Illucens) Larvae

This research isolated and identified bacteria with capability of starch, cellulose and protein decomposition from frass of black soldier fly (Hermetia Illucens) larvae (BFL). Dilute suspension of BFL frass was spread on petri dishes with solid Nutrient Agar for bacteria isolation. Selection and evaluation of bacteria with capability of starch, cellulose and protein decomposition was based on their ability of creating halo zone on starch agar, CMC and skim milk media. Identification of selected bacterial isolates was based on 16S rDNA sequences. There were 44 bacterial strains isolated from BSFL frass. Bacterial strains with the best capability of starch, cellulose and protein decomposition were CCRL21 and CCRL16 with halo zone radii of 1.5 cm and 0.8 cm; CCRL16, CCRL20 with halo zone radii with the similar size of 0.83 cm; and CCRL44 has the best ability of protein decomposition with an average halo zone radius about 2.47 cm, respectively. Six bacterial strains with good ability of degrading cellulose, starch and protein were identified as Bacillus paramycoides CCRL1; Bacillus altitudinis CCRL16, Bacillus spizizenii CCRL20, Bacillus altitudinis CCRL21, Lysinibacillus pakistanensis CCRL32 and Paenibacillus silvae CCRL43.

P076 Abdominal pain severity for IBD in remission correlates with genetic clustering and enzymatic activity of faeces-derived Candida albicans strains

Abstract Background Abdominal pain is a common occurrence for approximately 39% of patients with inflammatory bowel diseases in remission (quiescent IBD; qIBD). There is increasing evidence for a contributing role of the gastrointestinal fungal community (i.e., mycobiome) in relation to intestinal inflammation and irritable bowel syndrome (IBS). As such, abundance of Candida spp. and sub-species variation of Candida albicans were previously associated with IBD severity. In the current study, we aim to investigate mycobiome of patients with qIBD and qIBD with abdominal pain (qIBD–AP). Methods Patients with qIBD (defined as faecal calprotectin (FCP) ≤250 μg/g) with (n=91) or without (n=58) abdominal pain provided faecal samples. Abdominal pain was scored based on either the Irritable Bowel Syndrome Symptom Severity Scale (IBS–SSS) or Gastrointestinal Symptom Rating Score (GSRS) questionnaire. Faecal fungal communities were determined based on Internal Transcribed Spacer 1 (ITS1) sequencing. Cultivable yeasts from faecal samples were identified using Matrix Assisted Laser Deionization Time–of–Flight Mass Spectrometry. C. albicans strains (n=137 from 29 patients) were genotyped by ITS Sanger sequencing analysis and typing of seven microsatellite loci. Release of virulence-related enzymes (proteinase, phospholipase, lipase, esterase) by C. albicans was assessed through determination of precipitation zones on solid agar mediums containing enzyme-specific substrates. Results Descriptive mycobiota analysis revealed limited differences between compositions of qIBD and qIBD–AP patients, but a discriminative signature for abdominal pain was extracted using machine-based learning models. While ITS Sanger sequencing of faeces-derived C. albicans was insufficient to elucidate genetic variability, analysis of microsatellite loci revealed extensive variability and clustering into six clone clusters and a likely distinction between qIBD and qIBD-AP patients (Fig. 1). Phospholipase enzymatic activity of C. albicans strains correlated with GSRS–Abdominal Pain sub-score, as did proteinase activity with severity of abdominal pain according to the IBS–SSS (Fig. 2). Additionally, lipase activity inversely correlated with faecal calprotectin (Fig. 2). Conclusion The faecal gut mycobiome is associated with self–reported abdominal pain in patients with IBD in remission. This notion is based on both compositional and culture-dependent methods and specified clones of C. albicans may selectively contribute to abdominal pain for qIBD patients. This study opens further possibilities to investigate the role of faecal gut fungi in light of abdominal pain for qIBD-AP patients.

Effect of culture method on storage, plasma, and dry heat treatment resistance of Salmonella enterica serovar Typhimurium on black pepper.

The purpose of this study was to determine the effect of the culture method on the resistance of Salmonella Typhimurium in low water activity foods to storage, plasma, and dry heat. Whole black peppers were used as the model food. S. Typhimurium cultured in liquid broth (tryptic soy broth) or solid agar (tryptic soy agar) and inoculated on whole black pepper was stored or treated with cold plasma or dry heat. Inactivation of S. Typhimurium cultured in liquid medium was higher in all the treatments. Liquid-cultured S. Typhimurium showed higher DPPP=O (diphenyl-1-pyrenylphosphine oxide) values compared to the solid-cultured S. Typhimurium after plasma or dry heat treatment. Furthermore, the unsaturated fatty acid and saturated fatty acid ratio (USFA/SFA) was significantly (P<0.05) reduced from 0.41 to 0.29 when S. Typhimurium was cultured on solid agar. These results suggested that the use of food-borne pathogens cultured on solid agar is more suitable for low water activity food pasteurization studies.

Evaluation of possibility of cultivation of acid resistant bacteria on solid egg-based and agar cultural media.

The increase in the number of patients at risk for opportunistic infections caused by rare bacteria, which include individual representatives of acid-resistant bacteria (ARB), is a serious problem in modern health care. Significant difficulties in the etiological diagnosis of mycobacteriosis, nocardiosis, and actinomycosis are associated not only with the problem of identifying the main pathogens but also with certain difficulties in isolating pathogens from biological material. The research provides data on 402 strains of ARB, which were isolated from various biological materials obtained from patients during examination for tuberculosis. All samples of biological material were negative on the Mycobacterium tuberculosis complex. The isolates were identified on the MALDI-ToF mass spectrometer. The cultural characteristics of ARB were evaluated on the solid Löwenstein-Jensen egg-based culture media, universal chromogenic media, and 5% blood agar with lamb blood. The studies carried out indicate the possibility of culturing ARB representatives on agar media. At the same time, based on the comparison of the growth properties of ARB, it was found that the universal chromogenic media provides more acceptable conditions for the isolation of nontuberculous mycobacteria (NTM) compared to blood agar. The comparison of the growth rate of bacteria did not reveal significant differences for fastly growing NTM. For slowly growing species, the growth rate on blood agar was lower than on chromogenic media and on the Löwenstein-Jensen media. Thus, the use of a universal chromogenic media during incubation makes it possible to isolate and preidentify representatives of the ARB under the conditions of standard operating procedures of the microbiological laboratory.

Studies on antibacterial efficacy of ZnO nanoparticles using Tanner's Cassia flower extract from green synthesis

Sodium Hydroxide is used in the green synthesis approach (chemical precipitation method) to produce zinc oxide nanoparticles from zinc nitrate and extracts of Tanner's Cassia.The produced nanoparticles are tested using techniques like powder X-ray diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX) and antimicrobial activity. The X-ray diffraction Scherer's formula is used to determine the size of the ZnO particles.The measured size of the particle is 20.82 nm. In the XRD graph, ZnO nanoparticles are visible as crystalline peaks, whereas the rest is amorphous. The functional groups like ZnO, CC and CN bonds are confirmed by the FTIR data. SEM is used to examine the microstructure and identify aggregation. From EDAX, elemental composition of the sample is found to be having Zinc 70.36% and Oxygen 29.64%. The disk diffusion test is performed on solid agar plates and is found that it is effective against E. coli bacteria as an antibacterial substance.

Theory and application of growth delay analysis of colony formation for evaluation of injured population of the stressed fungal conidia.

A new concept of injured population assessment is proposed, in which the size of the injured population in stressed mold spores is evaluated by analyzing the colony formation process on a solid agar medium. In this method, a small paper disc containing mold spores is placed on a subculture agar plate, and the linear increase in the radius of the colony formed by development from the spore is measured over time. Then, the principle of the previously reported growth delay analysis (GDA) method originally using a liquid medium is applied to obtain the integrated viable ratio (IV) of the stressed population from the delay time relative to the growth of the unstressed population. On the other hand, the viable ratio (V) to the initial value as the colony count obtained with the stressed culture is obtained; the difference between the logarithms of V and IV is determined as the log number of the injured population. Applying this analysis method to heated spores of Cladosporium sphaerospermum, we determined the size of the injured population that occurred. This method was considered to be effective as a new method for quantifying injured populations using a solid medium.

Diagnosing Different Types of Bacteria on Culex Mosquito Spp. (Diptera: Culicidae) in Baghdad.

Introduction The genus of mosquitoes is also one of the important factors affecting the diversity of bacteria; the aim of the current research is to isolate the types of bacteria from adult mosquitoes that grow near stagnant water ponds in Baghdad Governorate, in order to collect information about bacterial species common in mosquitoes present in the area. Methods A number of Culicidae mosquito specimens were collected from Abu Ghraib, Baghdad, and the isolation of microorganisms from mosquitoes after prepared culture media and then a biochemical study of the identification characteristics of bacterial isolates was done. Result Some morphological traits were studied, and their production of catalase and oxidase enzymes was determined; 2×103 bacterial cells/ml of different genera and species were isolated on a solid agar nutrient medium for insect models. Bacterial colonies appeared with shapes ranging from pinworms to colonies with flat edges, white color, and smooth surfaces, and some types of fungi were isolated with a number of 1×102 cells/ml. Bacterial cells were isolated on the optional MacConkey medium, only less than 100 cells/ml when using the direct method, and the number reached 1×102 bacterial cells/ml for some models. Many Bacillus isolates were isolated, and the cells that formed the spores appeared in rods of different sizes, and the shape and location of the spores differed from the mother cells, where the isolate Bacillus speciesappeared in small-sized cells with a medial cylindrical sporeand in the form of thin rod-shaped cells with a cylindrical spore. The spores are large, medium in size, and from the mother cell, while the sporophyte took a sub-terminal position in isolate Bacillus spp.The sporophyte appeared in a barrel shape, the average of the parent cell in the isolate, and the spheroid was mediated by the parent cell, and the cells of the isolate were characterized by their small sizeand the location of the sporophyte under the two ends where the most isolated were Bacillus, Enterobacteriaceae species. Conclusion Several types of bacteria accompanying mosquitoes were isolated, Bacillus spp., Staphylococcus, and Streptococcus faecalis, which causemany diseases in humans and needmolecular diagnosis to confirm the isolated species more accurately.

Critical Effect of H2O2 in the Agar Plate on the Growth of Laboratory and Environmental Strains.

We previously showed that autoclaving in preparing agar media is one of the sources of hydrogen peroxide (H2O2) in the medium. This medium-embedded H2O2 was shown to lower the total colony count of environmental microorganisms. However, the critical concentrations of H2O2 detrimental to colony formation on the agar plate remain largely undetermined. Herein, we elucidated the specific effect of H2O2 on microbial colony formation on solid agar medium by external supplementation of varying amounts of H2O2. While common laboratory strains (often called domesticated microbes) formed colonies in the presence of high H2O2 concentrations (48.8 μM or higher), microbes from a freshwater sample demonstrated greatly decreased colony counts in the presence of 8.3 μM H2O2. This implies that environmental microbes are susceptible to much lower concentrations of H2O2 than laboratory strains. Among the emergent colonies on agar plates supplemented with different H2O2 concentrations, the relative abundance of betaproteobacterial colonies was found to be lower on plates containing higher amounts of H2O2. Further, the growth of the representative betaproteobacterial isolates was completely inhibited in the presence of 7.2 μM H2O2. Therefore, our study clearly demonstrates that low micromolar levels of H2O2 in agar plates critically affect growth of environmental microbes, and large portions of those are far more susceptible to the same than laboratory strains. IMPORTANCE It is well-known that most of environmental microorganisms do not form colonies on agar medium despite that agar medium is the commonly used solidified medium. We previously demonstrated the negative effects of H2O2 generation during agar medium preparation on colony formation. In the present study, we investigated the independent effect of H2O2 on microbial growth by adding different concentrations of H2O2 to agar medium. Our results demonstrate for the first time that even low micromolar levels of H2O2 in agar plates, that are far lower than previously recognized as significant, adversely affect colony number obtained from freshwater inoculum.

Variability in metabolites produced by Talaromyces pinophilus SPJ22 cultured on different substrates

BackgroundSeveral metabolites released by fungal species are an essential source of biologically active natural substances. Gas chromatography high resolution time-of-flight mass spectrometry (GC-HRTOF-MS) is one of the techniques used in profiling the metabolites produced by microorganisms, including Talaromyces pinophilus. However, there is limited information regarding differential substrates’ impacts on this fungal strain’s metabolite profiling. This study examined the metabolite profile of T. pinophilus strain SPJ22 cultured on three different media, including solid czapek yeast extract agar (CYA), malt extract agar (MEA) and potato dextrose agar (PDA) using GC-HRTOF-MS. The mycelia including the media were plugged and dissolved in 5 different organic solvents with varying polarities viz.: acetonitrile, dichloromethane, hexane, 80% methanol and water, and extracts analysed on GC-HRTOF-MS.ResultsThe study revealed the presence of different classes of metabolites, such as fatty acids (2.13%), amides (4.26%), alkanes (34.04%), furan (2.13%), ketones (4.26%), alcohols (14.89%), aromatic compounds (6.38%), and other miscellaneous compounds (17.02%). Significant metabolites such as acetic acid, 9-octadecenamide, undecanoic acid methyl ester, hydrazine, hexadecane, nonadecane, eicosane, and other compounds reported in this study have been widely documented to have plant growth promoting, antimicrobial, anti-inflammatory, antioxidant, and biofuel properties. Furthermore, T. pinophilus grown on PDA and MEA produced more than twice as many compounds as that grown on CYA.ConclusionThus, our result showed that the production of essential metabolites from T. pinophilus is substrate dependent, with many of these metabolites known to have beneficial characteristics, and as such, this organism can be utilised as a sustainable and natural source for these useful organic molecules.

Using colony size to measure fitness in Saccharomyces cerevisiae.

Competitive fitness assays in liquid culture have been a mainstay for characterizing experimental evolution of microbial populations. Growth of microbial strains has also been extensively characterized by colony size and could serve as a useful alternative if translated to per generation measurements of relative fitness. To examine fitness based on colony size, we established a relationship between cell number and colony size for strains of Saccharomyces cerevisiae robotically pinned onto solid agar plates in a high-density format. This was used to measure growth rates and estimate relative fitness differences between evolved strains and their ancestors. After controlling for edge effects through both normalization and agar-trimming, we found that colony size is a sensitive measure of fitness, capable of detecting 1% differences. While fitnesses determined from liquid and solid mediums were not equivalent, our results demonstrate that colony size provides a sensitive means of measuring fitness that is particularly well suited to measurements across many environments.

Targeted dose delivery of Mycobacterium tuberculosis in mice using silicon antifoaming agent via aerosol exposure system.

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that forms aggregates (clumps) on solid agar plates and in liquid media. Detergents such as Tween 80/Tyloxapol are considered the gold standard to disrupt clump formation in Mtb cultures. The presence of detergent, however, may generate foam and hinder Mtb aerosolization thus requiring addition of an antifoam agent for optimal Mtb aerosol-based procedures. Aerosol inhalation can be technically challenging, in particular to achieve a reproducible inhaled target dose. In this study, the impact of an antifoam, the silicon antifoaming agent (SAF), on Mtb aerosolization and whole-body mouse aerosol infection was investigated. A comparative study using SAF in a liquid suspension containing Mycobacterium bovis BCG (M. bovis BCG) or Mtb H37Rv did not cause any adverse effect on bacterial viability. Incorporation of SAF during mycobacteria inhalation procedures revealed that aerosolized mycobacterial strains were maintained under controlled environmental conditions such as humidity, temperature, pressure, and airflow inside the aerosol chamber. In addition, environmental factors and spray factors were not affected by the presence of SAF in mycobacterial cultures during aerosolization. Spray factor was significantly less during aerosol procedures with a low-input dose of mycobacteria in comparison to high-dose, as predicted. The mycobacterial load recovered in the biosampler (AGI) was ~2–3 logs lower than nebulizer or input bacterial load. A consistent Mtb bacillary load determined in mouse lungs indicates that SAF does not affect mycobacteria aerosolization during the aerosol generation process. These data confirmed that 1) SAF prevents formation of excessive foam during aerosolization, 2) SAF had no negative impact on mycobacterial viability within aerosol droplets, 3) Mtb droplets within aerosol-generated particles are well within the range required for reaching and depositing deep into lung tissue, and 4) SAF had no negative impact on achieving a target dose in mice exposed to Mtb aerosol.

Spatio-temporal based deep learning for rapid detection and identification of bacterial colonies through lens-free microscopy time-lapses.

Detection and identification of pathogenic bacteria isolated from biological samples (blood, urine, sputum, etc.) are crucial steps in accelerated clinical diagnosis. However, accurate and rapid identification remain difficult to achieve due to the challenge of having to analyse complex and large samples. Current solutions (mass spectrometry, automated biochemical testing, etc.) propose a trade-off between time and accuracy, achieving satisfactory results at the expense of time-consuming processes, which can also be intrusive, destructive and costly. Moreover, those techniques tend to require an overnight subculture on solid agar medium delaying bacteria identification by 12-48 hours, thus preventing rapid prescription of appropriate treatment as it hinders antibiotic susceptibility testing. In this study, lens-free imaging is presented as a possible solution to achieve a quick and accurate wide range, non-destructive, label-free pathogenic bacteria detection and identification in real-time using micro colonies (10-500 μm) kinetic growth pattern combined with a two-stage deep learning architecture. Bacterial colonies growth time-lapses were acquired thanks to a live-cell lens-free imaging system and a thin-layer agar media made of 20 μl BHI (Brain Heart Infusion) to train our deep learning networks. Our architecture proposal achieved interesting results on a dataset constituted of seven different pathogenic bacteria-Staphylococcus aureus (S. aureus), Enterococcus faecium (E. faecium), Enterococcus faecalis (E. faecalis), Staphylococcus epidermidis (S. epidermidis), Streptococcus pneumoniae R6 (S. pneumoniae), Streptococcus pyogenes (S. pyogenes), Lactococcus Lactis (L. Lactis). At T = 8h, our detection network reached an average 96.0% detection rate while our classification network precision and sensitivity averaged around 93.1% and 94.0% respectively, both were tested on 1908 colonies. Our classification network even obtained a perfect score for E. faecalis (60 colonies) and very high score for S. epidermidis at 99.7% (647 colonies). Our method achieved those results thanks to a novel technique coupling convolutional and recurrent neural networks together to extract spatio-temporal patterns from unreconstructed lens-free microscopy time-lapses.

Induction of amphotericin B resistance in susceptible Candida auris by extracellular vesicles

ABSTRACT Drug resistance derived from extracellular vesicles (EVs) is an increasingly important research area but has seldom been described regarding fungal pathogens. Here, we characterized EVs derived from a triazole-resistant but amphotericin B-susceptible strain of Candida auris. Nano- to microgram concentrations of C. auris EVs prepared from both broth and solid agar cultures could robustly increase the yeast’s survival against both pure and clinical amphotericin B formulations in a dose-dependent manner, resulting in up to 16-fold changes of minimum inhibitory concentration. Meanwhile, this effect was not observed upon addition of these EVs to C. albicans, nor upon addition of C. albicans EVs to C. auris. No change in susceptibilities was observed upon EV treatment for fluconazole, voriconazole, micafungin, and flucytosine. Mass spectrometry indicated the presence of immunogenic-/drug resistance-implicated proteins in C. auris EVs, including alcohol dehydrogenase 1 as well as C. albicans Mp65-like and Xog1-like proteins in high quantities. Based on these observations, we propose a potential species-specific role for EVs in amphotericin B resistance in C. auris. These observations may provide critical insights into treatment of multidrug-resistant C. auris.

Biotropic liquid crystal phase transformations in cellulose-producing bacterial communities

Biological functionality is often enabled by a fascinating variety of physical phenomena that emerge from orientational order of building blocks, a defining property of nematic liquid crystals that is also pervasive in nature. Out-of-equilibrium, "living" analogs of these technological materials are found in biological embodiments ranging from myelin sheath of neurons to extracellular matrices of bacterial biofilms and cuticles of beetles. However, physical underpinnings behind manifestations of orientational order in biological systems often remain unexplored. For example, while nematiclike birefringent domains of biofilms are found in many bacterial systems, the physics behind their formation is rarely known. Here, using cellulose-synthesizing Acetobacter xylinum bacteria, we reveal how biological activity leads to orientational ordering in fluid and gel analogs of these soft matter systems, both in water and on solid agar, with a topological defect found between the domains. Furthermore, the nutrient feeding direction plays a role like that of rubbing of confining surfaces in conventional liquid crystals, turning polydomain organization within the biofilms into a birefringent monocrystal-like order of both the extracellular matrix and the rod-like bacteria within it. We probe evolution of scalar orientational order parameters of cellulose nanofibers and bacteria associated with fluid-gel and isotropic-nematic transformations, showing how highly ordered active nematic fluids and gels evolve with time during biological-activity-driven, disorder-order transformation. With fluid and soft-gel nematics observed in a certain range of biological activity, this mesophase-exhibiting system is dubbed "biotropic," analogously to thermotropic nematics that exhibit solely orientational order within a temperature range, promising technological and fundamental-science applications.

Bacteriological Profile of Palm Oil Sale Sites in Selected Markets in Kaduna State, Nigeria

The bacteriological profile of palm oil sale sites in selected markets in Kaduna state, Nigeria were evaluated using standard techniques by collecting a (60) soil samples. Aside from bacteriological profile, pH, moisture content, temperature and lipase activity analyzed. The soil samples had pH that ranged from acidic to neutral (3.0-8.00) which indicates the presence of hydrolytic enzymes. Microorganisms isolated from soil samples palm oil sale sites were screened from their lipase producing ability. A total of (10) ten bacteria belonging to the genera Bacillus, Streptococcus, Lactobacillus, Streptobacillus, Micrococcus, Staphylococcus and Pseudomonas. The lipolytic activity of the bacteria when screened on solid agar ranged for 1.1 to 3.2cm, 2.3-3.7cm, 2.3-6.7cm at 24, 48 and 72hours respectively while that of fungal species ranged from 0.6 to12cm, 0.3-1.5cm and 1.1-1. 7cm at 3,7,14 days of incubation respectively. Exo-enzyme was produced from the various species screened for lipolytic activities. The study shows that Bacillus subtilis and Trichoderma spp. had high potential.

Identification of Mutations Associated With Macozinone-Resistant in Mycobacterium Tuberculosis.

Novel anti-tuberculosis drug macozinone (MCZ) is identified as a drug candidate and is currently under clinical development for the treatment of tuberculosis. However, the mutations conferring resistance to MCZ remain inadequately characterized. In this study we investigated resistant mutations to the MCZ through de novo resistance selection in vitro. This was accomplished by passing the Mycobacterium tuberculosis H37Rv on solid agar plates, which were infused with the antibiotic. Through whole genome sequencing and targeted PCR genomic resistance conferring SNPs were catalogued, and the resistant phenotype was analyzed by MABA test. Of MCZ-resistant clones obtained in vitro the mutation of C387S in dprE1 is only observed in high-level resistant clones (MIC90 > 500ng/mL) indicating that C387S mutation is directly related to high-level MCZ-resistance. In addition, high-level resistance to MCZ can occur in clone grew on agar plates infused with low concentration MCZ, which means low concentration MCZ induction can produce high-level drug-resistance and it is easy to produce high-level MCZ-resistance. We also found two new mutations (G61A and G248A) in dprE1 for the first time. The MIC90 of other clones except the clones carrying the C387S mutation was at the same level (20ng/mL > MIC90 > 2ng/mL). Of low-level resistant clones other gene mutations involved in drug efflux or membrane permeability were found (pepQ, Rv0678, arsC, etc.), with highest mutation frequency in Rv0678 (50/64, 78.12%). It suggests that there may be new mechanisms independent of dprE1 mutations.

Bioethanol production from seaweed solid waste biomass of agar processing

This paper describes about the potential application of renewable energy sources from biomass (seaweed waste) to replace fossil fuels combustion which produced CO2 emission and heavy metal pollution. The objective of the research is to utilize the seaweed solid waste from agar production industry for bioethanol feedstock. The enzymatic method was carried out for glucose production with the addition 1% of surfactant Tween 20 during the saccharification process of three kinds of substrate concentration (20, 25, 30% dw) and 10 FPU/g substrate for the cellulose concentration and used S. cerevisae as yeast in the fermentation process for bioethanol production. The result showed that the highest reducing sugar value (122.4 mg/mL) and 2.86% for the bioethanol content were from 30% dw treatment of substrate concentration of solid agar waste. Therefore, the waste from agar industry is a potential raw material to be used as biofuel and could reduce the heavy metal problems.

Effective pulsed light treatments for inactivating Salmonella enterica serotypes

Pulsed light (PL) is a nonthermal treatment that kills microorganisms by exposing them to short-duration pulses of high-intensity broad-spectrum light. This study evaluated the PL inactivation of different serotypes of Salmonella enterica subsp. enterica (Typhimurium, Enteritidis, Heidelberg, and Minnesota) to specifically assess how pulse width and voltage can affect treatment effectiveness. Bacterial suspensions were spread onto solid agar plates, used as a model food surface, and then treated with PL at different treatment parameters (voltage, pulse width, and fluence). Surviving cells were recovered, enumerated, and the proportion of surviving cells were determined. The log-linear model was used to characterize inactivation kinetics. Three independent replicates were performed for all treatments, and data were analyzed statistically. The results obtained with S. Typhimurium highlighted that the inactivation effectiveness of PL treatment could be enhanced by selecting the right combination of parameters within the practical limitations of the equipment. Higher voltages delivered more energy with pulse width, (i.e., a higher irradiance) resulting in a more lethal process. PL was very effective for the inactivation of Salmonella, and a 6 to 7 log reduction was achieved for all four serotypes and their cocktail, after a single light pulse with a fluence of 338 mJ/cm2 and 280 mJ/cm2, at 2500 V (200 μs) and 3000 V (100 μs), respectively. The results demonstrated similar log reductions for individual serotypes and the cocktail.

Microbiological Diagnosis of Osteoarticular Infections: Comparison between BacT/Alert Bottles and Schaedler Broth.

ABSTRACTMicrobiological diagnosis of osteoarticular infections (OAIs) is based on culture on several media. Experts recommend the use of liquid media, such as Schaedler broth, but many laboratories use blood culture media with automated detection instead for convenience. We aimed to evaluate the performance of culturing in BacT/Alert (bioMérieux) bottles for the microbiological diagnosis of OAI versus culturing in Schaedler broth. This prospective study was conducted on all osteoarticular specimens sent to the microbiology laboratories of the Versailles and Diaconesses Croix Saint-Simon hospitals between October 2016 and February 2017. Each sample was inoculated onto solid agar, into BacT/Alert bottles incubated for 14 days, and into a Schaedler broth incubated for 14 days with daily reading. The gold standard was defined as follow: OAI was diagnosed for a patient if at least two samples were positive for a nonskin microorganism and at least three for a cutaneous species. The times to detection were compared. A total of 1,616 specimens from 349 patients were collected. BacT/Alert bottles were significantly more sensitive than the Schaedler process for OAI diagnosis (114/135 OAI detected by BacT/Alert bottles; 91/135 OAI detected by Schaedler broth; +17.0% [95% confidence interval {CI}, 6.8%, 27.3%]; P = 0.0004). The time to detection was significantly shorter using BacT/Alert bottles (2.0 ± 2.2 days) than using Schaedler broth (4.6 ± 3.6 days, P < 0.0001). The culture of osteoarticular specimens in BacT/Alert bottles allows bacterial enrichment with an automated detection of positivity. Their use decreased detection time and increased sensitivity, making it a useful tool for the diagnosis of OAI that should be included among the recommended media.IMPORTANCE Microbiological diagnosis of OAI is based on culture on several media. French experts recommend the use of liquid media such as Schaedler broth, but many laboratories use blood culture media with automated detection in substitution because it is more convenient. We report here a prospective multicentric study evaluating the performance of culture in BacT/Alert (bioMérieux) bottles for microbiological diagnosis of OAI in comparison with culture in Schaedler broth. A total of 1,616 osteoarticular specimens from 349 patients were collected and inoculated onto agar, into BacT/Alert aerobic and anaerobic bottles, and into a Schaedler broth. BacT/Alert bottles were significantly more sensitive than the Schaedler process for OAI diagnosis (+17.0% [95% CI, 6.8%, 27.3%], P = 0.0004). The time to detection was significantly shorter for the BacT/Alert bottles (2.0 ± 2.2 days) than for Schaedler broth (4.6 ± 3.6 days, P < 0.0001). This study suggests that the use of BacT/Alert bottles should be recommended in microbiological diagnosis of OAI.

Antimicrobial effects of microwave plasma-activated water with skin protective effect for novel disinfectants in pandemic era

Skin antiseptics have important implications for public health and medicine. Although conventional antiseptics have considerable antimicrobial activity, skin toxicity and the development of resistance are common problems. Plasma-treated water has sterilization and tissue-regenerative effects. Therefore, the aim of this study was to identify whether plasma-activated water (PAW) manufactured by our microwave plasma system can be used as a novel antiseptic solution for skin protection. PAW was produced by dissolving reactive nitrogen oxide gas using microwave plasma in deionized water. The antibacterial effects of PAW against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Salmonella typhimurium and effective concentrations were investigated by a solid agar plate assay. The factors mediating the effects of PAW were evaluated by the addition of reactive species scavengers. Cytotoxicity and cell viability assays were performed to examine the protective effect of PAW on normal skin cells. PAW exhibited excellent sterilization and no toxicity in normal skin cells. Experiments also confirmed the potential of PAW as a sanitizer for SARS-CoV-2. Our findings support the use of PAW as an effective skin disinfectant with good safety in the current situation of a global pandemic.