Relevant Bacterial Strains Research Articles

Naturally derived 3-aminoquinuclidine salts as new promising therapeutic agents

Quaternary ammonium compounds (QACs) are a biologically active group of chemicals with a wide range of different applications. Due to their strong antibacterial properties and broad spectrum of activity, they are commonly used as ingredients in antiseptics and disinfectants. In recent years, the spread of bacterial resistance to QACs, exacerbated by the spread of infectious diseases, has seriously threatened public health and endangered human lives. Recent trends in this field have suggested the development of a new generation of QACs, in parallel with the study of bacterial resistance mechanisms. In this work, we present a new series of quaternary 3-substituted quinuclidine compounds that exhibit potent activity across clinically relevant bacterial strains. Most of the derivatives had minimal inhibitory concentrations (MICs) in the low single-digit micromolar range. Notably, QApCl and QApBr were selected for further investigation due to their strong antibacterial activity and low toxicity to human cells along with their minimal potential to induce bacterial resistance. These compounds were also able to inhibit the formation of bacterial biofilms more effectively than commercial standard, eradicating the bacterial population within just 15 min of treatment. The candidates employ a membranolytic mode of action, which, in combination with the generation of reactive oxygen species (ROS), destabilizes the bacterial membrane. This treatment results in a loss of cell volume and alterations in surface morphology, ultimately leading to bacterial cell death. The prominent antibacterial potential of quaternary 3-aminoquinuclidines, as exemplified by QApCl and QApBr, paves the way for new trends in the development of novel generation of QACs.

Electrochemical Quantification of Tobramycin Retention in Pseudomonas Aeruginosa as Antimicrobial Susceptibility Indicator

The emergence and spread of bacterial resistance to antibiotics has developed into one of the most challenging threats to public health. Antibiotic susceptibility tests (ASTs) for bacterial infections are now essential, because they provide guidance for physicians in the selection of antibiotics, to which bacteria will respond. Most current AST methods require long periods of time, because of bacterial growth and incubation, leading to a prolonged and overuse of broad-spectrum antibiotics. Thus, there is a growing demand for methods and technologies that enable rapid antibiotic susceptibility assessment. Due to advantages related to cost-effectiveness, rapid response time and high sensitivity,electrochemical detection methods are promising analytical tools that can successfully quantify antibiotic uptake and retention in clinically relevant bacterial strains. This study presents the electroanalytical quantification of tobramycin (TOB) retention in susceptible and resistant bacterial strains of Pseudomonas aeruginosa. The electrochemical behavior of TOB was characterized by voltammetry, identifying redox potentials, the current dependence on pH conditions, and the detection limit at unmodified glassy carbon electrodes. The presented methodology was able to distinguish between susceptible and resistant bacterial strains, and is also capable of identifying varying degrees of resistance against TOB. The presented approach detects the immediate interaction of bacteria with an antibiotic, without the need of complex and cost-intense equipment related to genomic testing methods

Advances in silver nanoparticles: a comprehensive review on their potential as antimicrobial agents and their mechanisms of action elucidated by proteomics.

Nanoparticles play a crucial role in the field of nanotechnology, offering different properties due to their surface area attributed to their small size. Among them, silver nanoparticles (AgNPs) have attracted significant attention due to their antimicrobial properties, with applications that date back from ancient medicinal practices to contemporary commercial products containing ions or silver nanoparticles. AgNPs possess broad-spectrum biocidal potential against bacteria, fungi, viruses, and Mycobacterium, in addition to exhibiting synergistic effects when combined with certain antibiotics. The mechanisms underlying its antimicrobial action include the generation of oxygen-reactive species, damage to DNA, rupture of bacterial cell membranes and inhibition of protein synthesis. Recent studies have highlighted the effectiveness of AgNPs against various clinically relevant bacterial strains through their potential to combat antibiotic-resistant pathogens. This review investigates the proteomic mechanisms by which AgNPs exert their antimicrobial effects, with a special focus on their activity against planktonic bacteria and in biofilms. Furthermore, it discusses the biomedical applications of AgNPs and their potential non-preparation of antibiotic formulations, also addressing the issue of resistance to antibiotics.

Harnessing Plant-Based Nanoparticles for Combatting Multidrug-Resistant Bacteria

The emergence of multidrug-resistant organisms poses a significant challenge to public health worldwide. In response, plant-based nanoparticles have garnered attention for their potential as novel antimicrobial agents. These nanoparticles are derived from various plant sources and exhibit inherent antimicrobial properties due to their phytochemical composition. Nanoparticles synthesized from spinach (Spinacia oleracea) and orange (Citrus sinensis) extracts, loaded with salts of Cu and Zn, were evaluated for their antimicrobial activity against multidrug-resistant bacteria. Antimicrobial efficacy was assessed through agar well diffusion assays against clinically relevant multidrug-resistant bacterial strains of Pseudomonas aeruginosa MTCC 74, Staphylococcus aureus MTCC 902, Klebsiella pneumoniae MTCC 661. The nanoparticles exhibited potent antimicrobial effects, significantly inhibiting the growth of tested bacteria even when compared to commercially available antibiotics. These findings highlight the potential of plant-based nanoparticles loaded with Cu and Zn salts as effective agents against multidrug-resistant bacteria, offering a promising avenue for future antimicrobial therapies.

L-carnitine co-administration prevents colistin-induced mitochondrial permeability transition and reduces the risk of acute kidney injury in mice

Colistin is a polymyxin antibiotic currently experiencing renewed clinical interest due to its efficacy in the treatment of multidrug resistant (MDR) bacterial infections. The frequent onset of acute dose-dependent kidney injury, with the potential of leading to long-term renal damage, has limited its use and hampered adequate dosing regimens, increasing the risk of suboptimal plasma concentrations during treatment. The mechanism of colistin-induced renal toxicity has been postulated to stem from mitochondrial damage, yet there is no direct evidence of colistin acting as a mitochondrial toxin. The aim of this study was to evaluate whether colistin can directly induce mitochondrial toxicity and, if so, uncover the underlying molecular mechanism. We found that colistin leads to a rapid permeability transition of mitochondria isolated from mouse kidney that was fully prevented by co-incubation of the mitochondria with desensitizers of the mitochondrial transition pore cyclosporin A or L-carnitine. The protective effect of L-carnitine was confirmed in experiments in primary cultured mouse tubular cells. Consistently, the relative risk of colistin-induced kidney damage, calculated based on histological analysis as well as by the early marker of tubular kidney injury, Kim-1, was halved under co-administration with L-carnitine in vivo. Notably, L-carnitine neither affected the pharmacokinetics of colistin nor its antimicrobial activity against relevant bacterial strains. In conclusion, colistin targets the mitochondria and induces permeability transition thereof. L-carnitine prevents colistin-induced permeability transition in vitro. Moreover, L-carnitine co-administration confers partial nephroprotection in mice treated with colistin, without interfering with its pharmacokinetics and antibacterial activity.

The giant panda gut harbors a high diversity of lactic acid bacteria revealed by a novel culturomics pipeline.

Some lactic acid bacteria (LAB) can provide significant health benefits, which are critically important for the conservation of endangered animals, such as giant pandas. However, little is known about the diversity and culturability of LAB in the giant panda gut microbiota. To understand the roles of LAB in giant panda conservation, it is critical to culture bacterial strains of interest. In this study, we established a pipeline to culture bacterial strains using enrichment of target bacteria with different liquid media and growth conditions. Then, the strains were isolated in solid media to study their functions. Using 210 samples from the culture enrichment method and 138 culture-independent samples, we obtained 1120 amplicon sequencing variants (ASVs) belonging to Lactobacillales. Out of the 1120 ASVs, 812 ASVs from the culture enrichment approach were twofold more diverse than 336 ASVs from the culture-independent approach. Many ASVs of interest were not detected in the culture-independent approach. Using this pipeline, we isolated many relevant bacterial strains and established a giant panda gut bacteria strain collection that included strains with low-abundance in culture-independent samples and included most of the giant panda LAB described by other researchers. The strain collection consisted of 60 strains representing 35 species of 12 genera. Thus, our pipeline is powerful and provides guidance in culturing gut microbiota of interest in hosts such as the giant panda.IMPORTANCECultivation is necessary to screen strains to experimentally investigate microbial traits, and to confirm the activities of novel genes through functional characterization studies. In the long-term, such work can aid in the identification of potential health benefits conferred by bacteria and this could aid in the identification of bacterial candidate strains that can be applied as probiotics. In this study, we developed a pipeline with low-cost and user-friendly culture enrichment to reveal the diversity of LAB in giant pandas. We compared the difference between culture-independent and culture enrichment methods, screened strains of interest that produced high concentrations of short-chain fatty acids (SCFAs), and we investigated the catalog of virulence factors, antibiotic resistance, butyrate and lactate synthesis genes of the strains at a genomic level. This study will provide guidance for microbiota cultivation and a foundation for future research aiming to understand the functions of specific strains.

Exploring the therapeutic potential of silver nanocomposition of Catharanthus roseus leaves extract for antimicrobial and antiviral activities: A pilot study

Silver nanoparticles (AgNPs) synthesized from natural sources offer promising solutions for combating microbial and viral infections. Catharanthus roseus (Periwinkle), renowned for its diverse pharmacological properties, provides a sustainable and eco-friendly method for producing AgNPs with significant antimicrobial and antiviral effects. This study explores the cytotoxic potential of AgNPs derived from C. roseus and their antibacterial, antifungal, and anti-HIV activities, highlighting the novelty of employing a green synthesis approach. AgNPs from C. roseus leaf extract (AgNP-CR) were synthesized and characterized using spectroscopic and microscopic techniques to determine their physicochemical properties. The antibacterial activity of AgNP-CR was assessed against clinically relevant bacterial strains, and antifungal activity was evaluated against common fungal pathogens. Additionally, anti-HIV activity was investigated through in vitro assays using HIV-infected cells. Results demonstrated significant antibacterial activity of AgNP-CR against both gram-positive and gram-negative bacteria. Furthermore, AgNP-CR exhibited antifungal activity against pathogenic Aspergillus species. Importantly, AgNP-CR showed promising anti-HIV activity by inhibiting viral replication and cytopathic effects in infected cells. Cytotoxicity assays were also conducted to ensure the safety profile of the nanoparticles. Overall, this pilot study underscores the therapeutic potential of AgNPs synthesized from C. roseus in addressing bacterial, fungal, and viral infections. Further research is warranted to elucidate their mechanisms of action and optimize formulations for clinical applications.

Bactericidal effect of tetracycline in E. coli strain ED1a may be associated with ribosome dysfunction

Ribosomes translate the genetic code into proteins. Recent technical advances have facilitated in situ structural analyses of ribosome functional states inside eukaryotic cells and the minimal bacterium Mycoplasma. However, such analyses of Gram-negative bacteria are lacking, despite their ribosomes being major antimicrobial drug targets. Here we compare two E. coli strains, a lab E. coli K-12 and human gut isolate E. coli ED1a, for which tetracycline exhibits bacteriostatic and bactericidal action, respectively. Using our approach for close-to-native E. coli sample preparation, we assess the two strains by cryo-ET and visualize their ribosomes at high resolution in situ. Upon tetracycline treatment, these exhibit virtually identical drug binding sites, yet the conformation distribution of ribosomal complexes differs. While K-12 retains ribosomes in a translation-competent state, tRNAs are lost in the vast majority of ED1a ribosomes. These structural findings together with the proteome-wide abundance and thermal stability assessments indicate that antibiotic responses are complex in cells and can differ between different strains of a single species, thus arguing that all relevant bacterial strains should be analyzed in situ when addressing antibiotic mode of action.

Discovery of Biofilm Inhibitors from the Microbiota of Marine Egg Masses.

Biofilms commonly develop in immunocompromised patients, which leads to persistent infections that are difficult to treat. In the biofilm state, bacteria are protected against both antibiotics and the host's immune system; currently, there are no therapeutics that target biofilms. In this study, we screened a chemical fraction library representing the natural product capacity of the microbiota of marine egg masses, namely, the moon snail egg collars. This led to the identification of active fractions targeting both Pseudomonas aeruginosa and Staphylococcus aureus biofilms. Subsequent analysis revealed that a subset of these fractions were capable of eradicating preformed biofilms, all against S.aureus. Bioassay-guided isolation led us to identify pseudochelin A, a known siderophore, as a S.aureus biofilm inhibitor with an IC50 of 88.5 μM. Mass spectrometry-based metabolomic analyses revealed widespread production of pseudochelin A among fractions possessing S.aureus antibiofilm properties. In addition, a key biosynthetic gene involved in producing pseudochelin A was detected on 30% of the moon snail egg collars and pseudochelin A is capable of inhibiting the formation of biofilms (IC50 50.6 μM) produced by ecologically relevant bacterial strains. We propose that pseudochelin A may have a role in shaping the microbiome or protecting the egg collars from microbiofouling.

Efficacy of 233 nm LED far UV-C-radiation against clinically relevant bacterial strains in the phase 2/ step 2 in vitro test on basis of EN 14561 and on an epidermis cell model

IntroductionHealthcare-acquired infections and overuse of antibiotics are a common problem. Rising emergence of antibiotic and antiseptic resistances requires new methods of microbial decontamination or decolonization as the use of far-UV-C radiation. MethodsThe microbicidal efficacy of UV-C radiation (222 nm, 233 nm, 254 nm) was determined in a quantitative carrier test and on 3D-epidermis models against Staphylococcus (S.) aureus, S.epidermidis, S.haemolyticus, S.lugdunensis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. To mimic realistic conditions, sodium chloride solution, mucin, albumin, artificial saliva, artificial wound exudate and artificial sweat were used. ResultsIn sodium chloride solution, irradiation with a dose of 40 mJ/cm2 (233 nm) was sufficient to achieve 5 lg reduction independent of bacteria genus or species. In artificial sweat, albumin and artificial wound exudate, a reduction >3 lg was reached for most of the bacteria. Mucin and artificial saliva decreased the reduction to <2 lg. On 3D epidermis models, reduction was lower than in the carrier test. ConclusionUV-C radiation at 233 nm was proven to be efficient in bacteria inactivation independent of genus or species thus being a promising candidate for clinical use in the presence of humans and on skin/mucosa.

Biogenic Ag2O nanoparticles with "Hoja Santa" (Piper auritum) extract: characterization and biological capabilities.

The 'sacred leaf' or "Hoja Santa" (Piper auritum Kunth) has a great value for Mexican culture and has gained popularity worldwide for its excellent properties from culinary to remedies. To contribute to its heritage, in this project we proposed the green synthesis of silver oxide nanoparticles (Ag2O NPs) using an extract of "Hoja Santa" (Piper auritum) as a reducing and stabilizing agent. The synthesized Ag2O NPs were characterized by UV-Visible spectroscopy (plasmon located at 405nm), X-ray diffraction (XRD) (particle size diameter of 10nm), scanning electron microscopy (SEM) (particle size diameter of 13.62 ± 4.61nm), and Fourier-transform infrared spectroscopy (FTIR) (functional groups from "Hoja Santa" attached to nanoparticles). Antioxidant capacity was evaluated using DPPH, ABTS and FRAP methods. Furthermore, the antimicrobial activity of NPs against a panel of clinically relevant bacterial strains, including both Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Salmonella Enteritidis and Escherichia coli O157:H7), was over 90% at concentrations of 200µg/mL. Additionally, we assessed the antibiofilm activity of the NPs against Pseudomonas aeruginosa (reaching 98% of biofilm destruction at 800µg/mL), as biofilm formation plays a crucial role in bacterial resistance and chronic infections. Moreover, we investigated the impact of Ag2O NPs on immune cell viability, respiratory burst, and phagocytic activity to understand their effects on the immune system.

In vitro antibacterial activity of antiretroviral drugs on key commensal bacteria from the human microbiota.

Antiretroviral therapy has improved life expectancy in HIV-infected patients. However, people living with HIV under antiretroviral therapy are at higher risks of developing chronic complications and acquiring multidrug resistant bacteria than healthy population. These factors have been associated with shifts in gut microbiome composition and immune activation. It is unclear how antiretroviral drugs affect gut microbiota composition, but it has been observed that antiretroviral treatment is not able to fully restore gut health after HIV infection. Additionally, some antiretroviral drugs have shown antibacterial activity suggesting that these drugs could have a direct impact on the human microbiome composition. We determined the in vitro antibacterial activity of 16 antiretroviral drugs against a set of key clinically relevant and human commensal bacterial strains. Our results demonstrate that 5 antiretroviral drugs have in vitro antibacterial activity against gut and vaginal human commensal bacteria. Zidovudine has antibacterial activity against Escherichia coli, Klebsiella pneumoniae and Prevotella bivia, abacavir against Gardnerella vaginalis, efavirenz against G. vaginalis and P. bivia and bictegravir against Enterococcus spp. and G. vaginalis. Moreover, we describe for the first time that elvitegravir has antibacterial activity against G. vaginalis and P. bivia and, most importantly, against vancomycin-resistant Enterococcus spp. and methicillin-resistant Staphylococcus aureus strains with MIC values of 4-16 and 4 µg/mL, respectively showing high level of effectiveness against the tested multidrug-resistant bacteria. Our results underscore that some antiretroviral drugs may influence the human microbiota composition. In addition, we report the potential use of elvitegravir to treat multidrug-resistant Gram-positive bacteria warranting the need of clinical studies to repurpose this antiretroviral drug.

Municipal wastewater treatment plant showing a potential reservoir for clinically relevant MDR bacterial strains co-occurrence of ESBL genes and integron-integrase genes

Municipal wastewater treatment plants (MWWTPs) are a milieu for co-occurrence of multiple antibiotic resistance genes (ARGs). This facilitates mixing and genetic exchange; and promotes dissemination of multidrug resistance (MDR) to wastewater bacterial communities which is hazardous for the effluent receiving environment. This study investigated the co-occurrence of extended-spectrum beta-lactamase (ESBL) genes (blaTEM, blaCTX-M, blaSHV, blaOXA), and integron-integrase genes (intI1, intI2, intI3) in MDR bacteria isolated from the Bharwara MWWTP in Lucknow, India. Thirty-one MDR bacterial colonies resistant to three or more antibiotics were isolated from three treatment stages of this MWWTP. Six of these: Staphylococcus aureus, Serratia marcescens, Salmonella enterica, Shigella sonnei, Escherichia coli, and Bacillus sp. Had co-occurrence of ESBL and integron-integrase genes. These six isolates were examined for the occurrence of MDR efflux genes (qacA, acrB) and ARGs (aac(3)-1, qnrA1, tetA, vanA) and tested for resistance against 12 different antibiotics. The highest resistance was against penicillin-G (100%) and lowest for chloramphenicol (16.66%). Bacillus sp. Isolate BWKRC6 had the highest co-occurrence of antibiotic resistance-determining genes and was resistant to all the 12 antibiotics tested. The co-occurrence of ESBL, integron-integrase, antibiotic resistance-determining and MDR efflux genes in bacteria isolated from the Bharwara MWWTP indicates that the wastewaters of this treatment plant may have become a hotspot for MDR bacteria and may present human and environmental health hazards. Therefore, there is need for a rapid action to limit the spread of this threat. Public regulatory authorities must urgently implement measures to prevent MWWTPs becoming reservoirs for evolution of antibiotic resistance genes and development of antibiotic resistance.

Antibacterial efficacy of low-dosage silver nanoparticle-sodium alginate-chitosan nanocomposite films against pure and clinical acne strains.

The silver nanoparticles-sodium alginate-chitosan (AgNPs-Alg-Chi) nanocomposite film is a compelling material with demonstrated antibacterial efficacy against various pure bacterial strains. However, its potential cytotoxicity at elevated Ag doses warrants investigation. There is a notable dearth of studies assessing its antibacterial effectiveness against clinically relevant bacterial strains, notably Cutibacterium acnes. This study aims to assess the antibacterial efficacy of the low-dose AgNPs-Alg-Chi nanocomposite films on both pure bacterial strains and strains isolated from clinical samples obtained from 65 acne patients. The films were synthesized using green methods, incorporating kumquat (Citrus japonica) extract as a silver ion-reducing agent. The material characterization methods include UV-Vis and FTIR spectroscopies, SEM-EDS, XPS, cell culture, and MTT assay. We successfully fabricated the AgNPs-Alg-Chi nanocomposite films with a low-loading dose of Ag NPs (≤11 μg mL-1, and 37.8 ± 11.5 nm in size). The AgNPs-Alg-Chi nanocomposite film demonstrated comparable antibacterial efficacy to the AgNPs-Chi solution, with MIC values ranging from 3.67 to 5.50 μg mL-1 (p > 0.05) across all strains. Importantly, the AgNPs-Alg-Chi films demonstrated excellent biocompatibility with human keratinocytes (HaCaT cells), maintaining cell viability above 70%. The present AgNPs-Alg-Chi nanocomposite films synthesized by a green approach demonstrated potent antibacterial activity, making them promising for further development into suitable products for human use.

Antibacterial Efficiency of Tanacetum vulgare Essential Oil against ESKAPE Pathogens and Synergisms with Antibiotics.

Medicinal plants with multiple targets of action have become one of the most promising solutions in the fight against multidrug-resistant (MDR) bacterial infections. Tanacetum vulgare (Tansy) is one of the medicinal plants with antibacterial qualities that deserve to be studied. Thus, this research takes a closer look at tansy extract's composition and antibacterial properties, aiming to highlight its potential against clinically relevant bacterial strains. In this respect, the antibacterial test was performed against several drug-resistant pathogenic strains, and we correlated them with the main isolated compounds, demonstrating the therapeutic properties of the extract. The essential oil was extracted via hydrodistillation, and its composition was characterized via gas chromatography. The main isolated compounds known for their antibacterial effects were α-Thujone, β-Thujone, Eucalyptol, Sabinene, Chrysanthenon, Camphor, Linalool oxide acetate, cis-Carveol, trans-Carveyl acetate, and Germacrene. The evaluation of the antibacterial activity was carried out using the Kirby-Bauer and binary microdilution methods on Gram-positive and Gram-negative MDR strains belonging to the ESKAPE group (i.e., Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.). Tansy essential oil showed MIC values ranging from 62.5 to 500 μg/mL against the tested strains. Synergistic activity with different classes of antibiotics (penicillins, cephalosporins, carbapenems, monobactams, aminoglycosides, and quinolones) has also been noted. The obtained results demonstrate that tansy essential oil represents a promising lead for developing new antimicrobials active against MDR alone or in combination with antibiotics.

A Simple Biosensor Based on Streptavidin-HRP for the Detection of Bacteria Exploiting HRPs Molecular Surface Properties

Bacterial contamination of water and food sources is still a major source of diseases. Early detection of potential pathogens is key to prevent their spreading and severe health risks. Here, we describe a fast, low-cost detection assay based on horseradish peroxidase (HRP) conjugated to streptavidin for the direct identification of bacteria. Streptavidin can bind to bacterial cells due to its high affinity for biotin, a natural component of microbial cell surfaces. Upon binding to bacteria, the HRP converts a chromogenic substrate, resulting in a visible color change. In the present study, we evaluated different detection platforms regarding their compatibility with the detection principle. To reduce background signals and increase the sensitivity of HRP-based assays, the binding of HRP to surfaces and biomolecules was intensively investigated. The final assay successfully detected the most relevant bacterial strains in drinking water, such as Escherichia coli, Klebsiella pneumonia, and Enterobacter cloacae.

Algorithmic Programming of Sequential Logic and Genetic Circuits for Recording Biochemical Concentration in a Probiotic Bacterium.

Through the implementation of designable genetic circuits, engineered probiotic microorganisms could be used as noninvasive diagnostic tools for the gastrointestinal tract. For these living cells to report detected biomarkers or signals after exiting the gut, the genetic circuits must be able to record these signals by using genetically encoded memory. Complex memory register circuits could enable multiplex interrogation of biomarkers and signals. A theory-based approach to create genetic circuits containing memory, known as sequential logic circuits, was previously established for a model laboratory strain of Escherichia coli, yet how circuit component performance varies for nonmodel and clinically relevant bacterial strains is poorly understood. Here, we develop a scalable computational approach to design robust sequential logic circuits in probiotic strain Escherichia coli Nissle 1917 (EcN). In this work, we used TetR-family transcriptional repressors to build genetic logic gates that can be composed into sequential logic circuits, along with a set of engineered sensors relevant for use in the gut environment. Using standard methods, 16 genetic NOT gates and nine sensors were experimentally characterized in EcN. These data were used to design and predict the performance of circuit designs. We present a set of genetic circuits encoding both combinational logic and sequential logic and show that the circuit outputs are in close agreement with our quantitative predictions from the design algorithm. Furthermore, we demonstrate an analog-like concentration recording circuit that detects and reports three input concentration ranges of a biochemical signal using sequential logic.

Antibacterial Effect of Topically Administered Tranexamic Acid in Large Joint Arthroplasty

Tranexamic acid (TXA) is a synthetic derivative of the amino acid lysine and is commonly used as an antifibrinolytic agent in large joint surgery, such as knee arthroplasty, to minimize blood loss and its associated complications. Some studies have suggested that perioperative intravenous TXA application lowers the incidence of postoperative infections after hip and knee arthroplasty. While its effects on bacteria are not its primary purpose, more research is needed further to elucidate the extent of TXA’s impact on bacterial inhibition and its clinical relevance. In order to determine possible inhibitory effects, 22 clinically relevant bacterial strains were exposed to different TXA concentrations. Two different assays were performed: a microdilution assay with traditional endpoint measurements and a kinetic growth assay for a time-dependent susceptibility assessment. With the microdilution technique, a growth inhibitory effect became evident at higher TXA concentrations (50 and 100 mg/mL) on eight tested bacterial strains, of which four demonstrated absence of growth at 100 mg/mL, suggesting minimal inhibitory concentration. However, the kinetic growth assay revealed more specific TXA-induced dynamic changes in the bacterial growth of all tested bacterial strains. This study showed that TXA affects the growth dynamics of bacteria by altering their lag phase duration, exponential growth rate, and population density and may contribute to the prevention of implant-associated infections.

Antimicrobial Resistance Studies Using Raman Spectroscopy on Clinically Relevant Bacterial Strains.

There has been a steep rise in the emergence of antibiotic-resistant bacteria in the past few years. A timely diagnosis can help in initiating appropriate antibiotic therapy. However, conventional techniques for diagnosing antibiotic resistance are time-consuming and labor-intensive. Therefore, we investigated the potential of Raman spectroscopy as a rapid surveillance technology for tracking the emergence of antibiotic resistance. In this study, we used Raman spectroscopy to differentiate clinical isolates of antibiotic-resistant and -sensitive bacteria of Escherichia coli, Acinetobacter baumannii, and Enterobacter species. The spectra were collected with or without exposure to various antibiotics (ciprofloxacin, gentamicin, meropenem, and nitrofurantoin), each having a distinct mechanism of action. Ciprofloxacin- and meropenem-treated sensitive strains showed a decrease in the intensity of Raman bands associated with DNA (667, 724, 785, 1378, 1480, and 1575 cm-1) and proteins (640 and 1662 cm-1), coupled with an increase in the intensity of lipid bands (891, 960, and 1445 cm-1). Gentamicin- and nitrofurantoin-treated sensitive strains showed an increase in the intensity of nucleic acid bands (668, 724, 780, 810, 1378, 1480, and 1575 cm-1) while a decrease in the intensity of protein bands (640, 1003, 1606, and 1662 cm-1) and the lipid band (1445 cm-1). The Raman spectral changes observed in the antibiotic-resistant strains were opposite to that of antibiotic-sensitive strains. The Raman spectral data correlated well with the antimicrobial susceptibility test results. The Raman spectral dataset was used for partial least-squares (PLS) analysis to validate the biomarkers obtained from the univariate analysis. Overall, this study showcases the potential of Raman spectroscopy for detecting antibiotic-resistant and -sensitive bacteria.

A novel immuno-molecular strategy for the detection of Streptococcus pneumoniae serotypes in human cerebrospinal and middle ear fluids

Streptococcus pneumoniae is one of the most common microorganisms causing acute otitis media (AOM) in children. While bacterial culture of middle ear fluid (MEF) is the gold standard to detect the etiological organisms, several host and pathogen factors impact the survival of the organisms resulting in false negatives. To overcome this limitation, we have developed and validated an innovative multiplex immuno-molecular assay to screen and detect the S. pneumoniae 15-valent pneumococcal conjugate vaccine (PCV15; STs 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F, and 33F) vaccine serotypes in MEF. This novel in vitro approach involves two-step testing. First, the MEF specimens were tested for highly conserved pneumococcal genes, autolysin, lytA, and pneumolysin, ply using direct PCR to identify pneumococcus positive specimens. The pneumococcus positive specimens were screened for the presence of vaccine serotype specific pneumococcal polysaccharides using a 15-plex Pneumococcal Antigen Detection (PAD) assay, with specific capture and detection monoclonal antibodies. Due to the lack of availability of MEF samples, cerebrospinal fluid (CSF) was used as the surrogate matrix for the development and validation of the PCR-PAD assays. The PCR and PAD assays were separately evaluated for sensitivity and specificity. Subsequently, the PCR-PAD assays were cross-validated with human MEF samples (n = 39) which were culture confirmed to contain relevant bacterial strains. The combined PCR-PAD assays demonstrated high rate of agreement 94.9% (95% CI; 82.7, 99.4%) with historical Quellung serotype data of these MEF samples. This novel PCR-PAD assay demonstrates the feasibility of combining molecular and immunological assays to screen and identify PCV15 pneumococcal vaccine serotypes in AOM clinical samples.