The inhibitory effect of a Lactobacillus acidophilus derived biosurfactant on Serratia marcescens biofilm formation

Objective(s): Serratia marcescens is one of the nosocomial pathogen. The ability to form biofilm is an important feature in the pathogenesis of S. marcescens. The aim of this study was to determine the anti�adhesive properties of a biosurfactant isolated from Lactobacillus acidophilus ATCC 4356, on S. marcescens strains. Materials and Methods: Lactobacillus acidophilus ATCC 4356, was selected as a probiotic strain to produce biosurfactant. Anti�adhesive activities was determined by pre�coating and co� incubating methods in 96�well culture plates. Results: The FTIR analysis of derived biosurfactant revealed the composition as protein component. Because of the release of such biosurfactants, L. acidophilus was able to interfere with the adhesion and biofilm formation of the S. marcescens strains. In co� incubation method this biosurfactant in 2.5 mg/ml concentration showed anti�adhesive activity against all tested strains of S. marcescens (P<0.05). Conclusion: Our results show anti�adhesive properties of L. acidophilus biosurfactant will be useful against microorganisms responsible for infections in the urinary, vaginal and gastrointestinal tracts, as well as skin, making it a suitable alternative to conventional antibiotics. © 2015, Mashhad University of Medical Sciences. All rights reserved

A Survey on Exotic Signatures for Post-quantum Blockchain: Challenges and Research Directions

Blockchain technology provides efficient and secure solutions to various online activities by utilizing a wide range of cryptographic tools. In this article, we survey the existing literature on post-quantum secure digital signatures that possess exotic advanced features and that are crucial cryptographic tools used in the blockchain ecosystem for (1) account management, (2) consensus efficiency, (3) empowering scriptless blockchain, and (4) privacy. The exotic signatures that we particularly focus on in this work are the following: multi-/aggregate, threshold, adaptor, blind, and ring signatures. Herein the term "exotic"refers to signatures with properties that are not just beyond the norm for signatures, e.g., unforgeability, but also imbue new forms of functionalities. Our treatment of such exotic signatures includes discussions on existing challenges and future research directions in the post-quantum space. We hope that this article will help to foster further research to make post-quantum cryptography more accessible so that blockchain systems can be made ready in advance of the approaching quantum threats

PrivGenDB: Efficient and privacy-preserving query executions over encrypted SNP-Phenotype database

Privacy and security issues limit the query executions over genomics datasets, notably single nucleotide polymorphisms (SNPs), raised by the sensitivity of this type of data. Therefore, it is important to ensure that executing queries on these datasets do not reveal sensitive information, such as the identity of the individuals and their genetic traits, to a data server. In this paper, we propose and present a novel model, we call PrivGenDB, to ensure the confidentiality of SNP-phenotype data while executing queries. The confidentiality in PrivGenDB is enabled by its system architecture and the search functionality provided by searchable symmetric encryption (SSE). To the best of our knowledge, PrivGenDB construction is the first SSE-based approach ensuring the confidentiality of SNP-phenotype data as the current SSE-based approaches for genomic data are limited only to substring search and range queries on a sequence of genomic data. Besides, a new data encoding mechanism is proposed and incorporated in the PrivGenDB model. This enables PrivGenDB to handle the dataset containing both genotype and phenotype and also support storing and managing other metadata, like gender and ethnicity, privately. Furthermore, different queries, namely Count, Boolean, Negation and k′-out-of-k match queries used for genomic data analysis, are supported and executed by PrivGenDB. The execution of these queries on genomic data in PrivGenDB is efficient and scalable for biomedical research and services. These are demonstrated by our analytical and empirical analysis presented in this paper. Specifically, our empirical studies on a dataset with 5000 entries (records) containing 1000 SNPs demonstrate that a count/Boolean query and a k′-out-of-k match query over 40 SNPs take approximately 4.3s and 86.4μs, respectively, outperforming the existing schemes

Antagonistic activities of some probiotic lactobacilli culture supernatant on serratia marcescens swarming motility and antibiotic resistance

Background and Objectives: Serratia marcescens, a potentially pathogenic bacterium, benefits from its swarming motility and resistance to antibiotic as two important virulence factors. Inappropriate use of antibiotics often results in drug resistance phenomenon in bacterial population. Use of probiotic bacteria has been recommended as partial replacement. In this study, we investigated the effects of some lactobacilli culture supernatant on swarming, motility and antibiotic resistance of S. marcescens. Materials and Methods: Antimicrobial activity of lactobacilli supernatant and susceptibility testing carried out on S. marcescens isolates. Pretreatment effect of lactobacilli culture supernatant on antibiotic - resistance pattern in S. marcescens was determined by comparison of the MIC of bacteria before and after the treatment. Results: Our results showed that pretreatment with L. acidophilus ATCC 4356 supernatant can affect the resistance of Serratia strains against ceftriaxone, but it had no effect on the resistance to other antibiotics. Furthermore, culture supernatant of lactobacilli with concentrations greater than 2, had an effect on the swarming ability of S. marcescens ATCC 13880 and inhibited it. Conclusion: Probiotic bacteria and their metabolites have the ability to inhibit virulence factors such as antibiotic resistance and swarming motility and can be used as alternatives to antibiotics. © 2018, Tehran University of Medical Science. All rights reserved

Antibiofilm activity of cell-free supernatant from Lactobacillus casei in Pseudomonas aeruginosa

Background: Pseudomonas aeruginosa, as an important opportunistic pathogen, can produce P. aeruginosa. biofilm. Intrinsically resistant to antimicrobial agent, the biofilm causes difficulties in various healthcare settings. Lactobacilli are known to secrete inhibitory substances in cell-free supernatant (CFS) to prevent infection by pathogenic organisms. The purpose of this study was to evaluate the inhibitory effects of CFS from Lactobacillus casei PTCC: 1608 on biofilm formation of P. aeruginosa PTCC: 1430. Materials and Methods: In this experimental study, CFS from Lactobacillus was separated by centrifugation. The antimicrobial effect of CFS from L. casei was evaluated by agar well diffusion assay. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by microdilution method according to CLSL standard. Finally, biofilm-production ability of P. aeruginosa as a percentage was determined in the presence of CFS from L. casei using the modified microtiter plate method. Results: Results showed that CFS from L. casei has a significant effect on the tested strain and the MIC and MBC values for the strain were the same (62.5 µl ⁄ ml). Furthermore, in the presence of CFS from L. casei, biofilm production in MIC (87±2.6) and Sub-MIC concentration was considerably inhibited. Conclusion: CFS from L. casei is effective in killing P. aeruginosa. biofilm. Therefore, this material appears to be a promising agent for prophylaxis against various pseudomonal infections

Antimicrobial effect of probiotics in combination with prebiotics against Staphylococcus aureus and Listeria monocytogenes

Background and Objective: Probiotc bacteria have benefical effect on consumer health. This study was done to investigate the antimicrobial effect of several probiotic in combinations with different prebiotics against food patoghenic bacteria including Staphylococcus aureus and Listeria monocytogenes. Methods: In this descriptive - analytical study, probiotics including Lactobacillus plantarum, L. acidophilus, L. fermntum, L. casei and L. rhamnosus with prebiotics (1%) including raffinose, lactulose, inulin and trehalose were cultured in MRS broth for 24 hours at 30ºC in anaerobic conditions. Antimicrobial property of them was determined with well diffusion plate's method. Results: Probiotics in the presence of prebiotics indicated the higher antimicrobial effect compared to probiotics alone (P<0.05). The application of prebiotics such as L. casei with raffinose showed higher antimicrobial property against Listeria monocytogenes than the free prebiotics consumption. The diameter of inhibitory growth zone in the presence of raffinose as a prebiotics was 14.66 mm and its absence reduced to 11.75 mm. Conclusion: Antimicrobial effect of probiotics in combination with prebiotics against Staphylococcus aureus and Listeria monocytogenes was higher than probiotics consumption alone

Biofilm Formation of Listeria monocytogenes on Various Surfaces

Introduction & Objective: Listeria monocytogenes is considered as a ubiquitous foodborne pathogen which can lead to serious infections, especially in newborns, elderly, pregnant, and immunocompromised people. The organism has been isolated from many foods and may cause meningitis, septicemia and abortion in pregnant women. Also L. monocytogenes forms biofilms on many food contact surface materials and medical devices. Development of biofilms on many surfaces is a potential source of contamination of foods that may lead to spoilage or transmission of foodborne pathogens. Materials & Methods: Biofilm formation of L. monocytogenes (RITCC 1293 serotype 4a) was investigated. Hydrophobicity of L. monocytogenes was measured by MATH method. Then biofilm formation of the organism was assessed at 2, 4, 8, 16 and 20 hours on stainless steel (type 304 no 2B), polyethylene and glass by drop plate method. Results: Results indicated that L. monocytogenes with 85% of hydrophobicity formed biofilm on each of three surfaces. Biofilm formation on stainless steel surfaces was significantly more than other surfaces (p<0.05). Conclusion: The ability of biofilm formation of L. monocytogenes on medical devices and food containers is very important as far as hygiene and disease outbreaks are concerned