Concentrations Of Rifampicin Research Articles

Dissemination of arr-2 and arr-3 is associated with class 1 integrons in Klebsiella pneumoniae clinical isolates from Portugal.

\nKlebsiella pneumoniae is a common pathogen of healthcare-associated infections expressing a plethora of antimicrobial resistance loci, including ADP-ribosyltransferase coding genes (arr), able to mediate rifampicin resistance. The latter has activity against a broad range of microorganisms by inhibiting DNA-dependent RNA polymerases. This study aims to characterise the arr distribution and genetic context in 138 clinical isolates of K. pneumoniae and correlate these with rifampicin resistance. All isolates were subjected to whole-genome sequencing for species identification, typing and AMR genes identification, along with the determination of the minimum inhibitory concentration (MIC) of rifampicin. Molecular detection of arr genes and class 1 integrons was performed for rifampicin-resistant isolates. Efflux activity was investigated as a possible determinant of rifampicin resistance in isolates devoid of known genetic determinants. Twelve isolates exhibited high rifampicin MICs (≥ 64mg/L), 124 showed intermediate MICs (16-32mg/L) and two displayed low (8mg/L) MICs. Two arr allelic variants, arr-2 and arr-3, were found across one and nine K. pneumoniae isolates, respectively, all within class 1 integrons, including a newly described integron, and all associated with high rifampicin MICs (≥ 64mg/L). Elevated resistance levels were additionally linked to increased arr-2/3 expression and closer proximity to the promoter. No arr gene or rpoB mutations were found across the remaining two isolates and no correlation between efflux activity and high-level rifampicin resistance was found for both isolates. In conclusion, this study demonstrates that arr genes confer high levels of rifampicin resistance in K. pneumoniae highlighting its widespread dissemination within class 1 integrons.

Sirtuin inhibitors reduce intracellular growth of M. tuberculosis in human macrophages via modulation of host cell immunity

Host-directed therapies aiming to strengthen the body’s immune system, represent an underexplored opportunity to improve treatment of tuberculosis (TB). We have previously shown in Mycobacterium tuberculosis (Mtb)-infection models and clinical trials that treatment with the histone deacetylase (HDAC) inhibitor, phenylbutyrate (PBA), can restore Mtb-induced impairment of antimicrobial responses and improve clinical outcomes in pulmonary TB. In this study, we evaluated the efficacy of different groups of HDAC inhibitors to reduce Mtb growth in human immune cells. A panel of 21 selected HDAC inhibitors with different specificities that are known to modulate infection or inflammation was tested using high-content live-cell imaging and analysis. Monocyte-derived macrophages or bulk peripheral blood cells (PBMCs) were infected with the green fluorescent protein (GFP)-expressing Mtb strains H37Ra or H37Rv and treated with HDAC inhibitors in the micromolar range in parallel with a combination of the first-line antibiotics, rifampicin, and isoniazid. Host cell viability in HDAC inhibitor treated cell cultures was monitored with Cytotox-red. Seven HDAC inhibitors were identified that reduced Mtb growth in macrophages > 45–75% compared to average 40% for PBA. The most effective compounds were inhibitors of the class III HDAC proteins, the sirtuins. While these compounds may exhibit their effects by improving macrophage function, one of the sirtuin inhibitors, tenovin, was also highly effective in extracellular killing of Mtb bacilli. Antimicrobial synergy testing using checkerboard assays revealed additive effects between selected sirtuin inhibitors and subinhibitory concentrations of rifampicin or isoniazid. A customized macrophage RNA array including 23 genes associated with cytokines, chemokines and inflammation, suggested that Mtb-infected macrophages are differentially modulated by the sirtuin inhibitors as compared to PBA. Altogether, these results demonstrated that sirtuin inhibitors may be further explored as promising host-directed compounds to support immune functions and reduce intracellular growth of Mtb in human cells.

Phenotypic Resistance to Rifampicin of Mycobacterium tuberculosis with the rpoB Leu430Pro Mutation

The objective: to determine the role of the rpoB Leu430Pro mutation in the degree of phenotypic resistance of Mycobacterium tuberculosis to rifampicin.Subjects and Methods. The WHO classifies the rpoB Leu430Pro mutation of Mycobacterium tuberculosis as a borderline resistance mutation but of clinical significance. From an array of cultures, we selected and analyzed 14 isolates of M. tuberculosis with discrepancies in the results of molecular genetic and phenotypic testing, carrying only this mutation in rpoB. For all samples, the phenotypic resistance level (MIC) of these isolates to rifampicin was determined using BACTEC MGIT 960 and Middlebrook 7H11 medium.Results. It was found out that 12 of 14 isolates had the rifampicin MIC below the current critical concentration when tested by both methods, thus they were phenotypically sensitive. One isolate was resistant when tested with Middlebrook 7H11 but susceptible when tested with BACTEC MGIT 960. Only one isolate which had the additional rpoB F425L mutation demonstrated high-level phenotypic resistance when tested by the same tests. Our data indicate that the clinical significance of this mutation requires clarification since even a decrease in the critical concentration of rifampicin does not lead to unambiguous results of molecular genetic and phenotypic tests. It is necessary to standardize the use of various molecular genetic tests and principles of their clinical interpretation to optimize strategies for managing patients with tuberculosis caused by M. tuberculosis with the rpoB Leu430Pro mutation.

Molecularly imprinted electrochemiluminescence sensor based on luminol functionalized Co-MOF for rifampicin detection.

A highly sensitive molecularly imprinted electrochemiluminescence (MIECL) sensor was developed for detecting rifampicin (RIF) based on luminol@Co-MOF. Co-MOF had a significant enhancement of ECL signaling in the luminol-O2 system. Molecular imprinted polymers (MIPs) with the introduction of RIF provide new properties for the specific recognition of RIF. A noteworthy decrease in ECL intensity was observed with higher concentrations of RIF. Consequently, the ECL signal was controlled by RIF elution from and adsorption by the MIP, thus establishing a new method for RIF detection. Under optimal conditions, this sensor exhibited linear detection ranges of RIF between 1.0 × 10-11mol L-1 and 1.0 × 10-6mol L-1, with a detection limit of 3.3 × 10-12mol L-1 (S/N = 3). The recoveries ranged between 98.1 and 106.0% in fish samples. This method can be used as a sensitive and rapid method to detect RIF in real samples.

Identification of human pregnane X receptor antagonists utilizing a high-throughput screening platform.

Pregnane X receptor (PXR) is a xenobiotic-sensing nuclear receptor with a well-established role in regulating drug metabolism and clearance. Recent studies have shown that PXR is involved in cell proliferation, apoptosis, immune response, and energy homeostasis. It is important to identify compounds that may modulate PXR activity to prevent drug-drug interactions, distinguish chemicals which could potentially generate toxicity, and identify compounds for further development towards therapeutic usage. In this study, we have screened the National Center for Advancing Translational Sciences (NCATS) Pharmacologically Active Chemical Toolbox (NPACT) library, which consists of 5,099 unique pharmacologically active synthetic and naturally derived small molecules to identify PXR antagonists. Ninety-four compounds were identified as potential PXR antagonists through a primary screen and 66 were confirmed in a confirmation study. Of these compounds, twenty potential PXR antagonists, including gamma-secretase modulator 2 (GSM2) and fusidic acid, were selected for further study based on their efficacy, potency, and novelty. Their PXR inhibition abilities were assessed by examining their effects on cytrochrome P450 (CYP) 3A4 mRNA expression using metabolically competent HepaRG cells. Additionally, a pharmacological inhibition assay using various concentrations of rifampicin as a stimulator was performed in HepG2-CYP3A4-hPXR cells to confirm the activity of the 20 selected compounds against PXR. Finally, HepaRG cells were used to confirm PXR antagonism by verification of a concentration-dependent decrease of CYP3A4 when co-treated with the known PXR agonist, rifampicin. Additionally, the potent actives were further investigated using molecular docking to find the potential interactions of the novel ligands with the active sites of hPXR. To our knowledge from the current study, GSM2 and fusidic acid have been identified as novel PXR antagonists, which provides useful information for further investigation regarding possible drug-drug interactions, as well as the detection of potential therapeutic effects or other toxic consequences.

A novel C-4-modified isotetrone acts as a potent bio-enhancer to augment the activities of anti-tuberculosis drugs against Mycobacterium tuberculosis

Mycobacterium tuberculosis is a deadly pathogen that claims millions of lives every year. Current research focuses on finding new anti-tuberculosis drugs that are safe and effective, with lesser side effects and toxicity. One important approach is to identify bio-enhancers that can improve the effectiveness of anti-tuberculosis drugs, resulting in reduced doses and shortened treatment times. The present study investigates the use of C-4 modified isotetrones as bio-enhancers. A series of studies suggest an isotetrone, labeled as C11, inhibits growth, improves MIC, MBC and enhances the killing of M. tuberculosis H37Rv strain when used in combination with the first line and injectable anti-TB drugs in a dose-dependent manner. The combination of C11 and rifampicin also reduces the generation of spontaneous mutants against rifampicin and reaches a mutation prevention concentration (MPC) with moderate rifampicin concentrations. The identified compounds are effective against the MDR strain of M. tuberculosis and non-cytotoxic in HepG2 cells. We find that C11 induces the generation of reactive oxygen species (ROS) inside macrophages and within bacteria, resulting in better efficacy.

Effects of Secondary Amine and Molecular Weight on the Biological Activities of Cationic Amphipathic Antimicrobial Macromolecules.

Cationic amphipathic antimicrobial agents inspired by antimicrobial peptides (AMPs) have shown potential in combating multidrug-resistant bacteria because of minimal resistance development. Here, this study focuses on the development of novel cationic amphipathic macromolecules in the form of dendrons and polymers with different molecular weights that employ secondary amine piperidine derivative as the cationic moiety. Generally, secondary amine compounds, especially at low molecular weights, have stronger bacteriostatic, bactericidal, and inner membrane disruption abilities than those of their primary amine counterparts. Low molecular weight D2 dendrons with two cationic centers and one hydrophobic dodecyl chain produce outstanding synergistic activity with the antibiotic rifampicin against Escherichia coli, where one-eighth of the standalone dose of D2 dendrons could reduce the concentration of rifampicin required by up to 4000-fold. The low molecular weight compounds are also less toxic and therefore have higher therapeutic index values compared to compounds with larger molecular weights. This study thus reveals key information that may inform the design of future synthetic AMPs and mimics, specifically, the design of low-molecular-weight compounds with secondary amine as the cationic center to achieve high antimicrobial potency and biocompatibility.

Plasma and urinary CP I and CP III concentrations in chimeric mice with human hepatocytes after rifampicin administration.

The interest in transporter-mediated drug interactions has been increasing in the field of drug development. In this study, we measured the plasma and urinary concentrations of coproporphyrin (CP) I and CP III as endogenous substrates for organic anion-transporting polypeptide (OATP) using chimeric mice with human hepatocytes (PXB mice) and examined the influence of an OATP inhibitor, rifampicin (RIF). CP I and CP III were actively taken up intracellularly, and RIF inhibited the uptake in a concentration-dependent manner for both CP I and CP III in human hepatocytes (PXB-cells). Single doses of RIF at 10 and 30 mg/kg were orally or intravenously administered to PXB mice and wild-type ICR mice. Plasma concentrations (AUC0-8h) of CP I increased in both mice. However, a marked increase in CP III was only observed in ICR mice, after intravenous administration of RIF at 30 mg/kg. The IC50 values of RIF for intracellular CP I/III uptake and the unbound plasma concentrations of RIF suggested that the increase in plasma CP I is associated with the exposure of RIF to OATPs. The 24-h cumulative urinary excretions of CP I and CP III increased in both mice, but more markedly in PXB mice. Thus, RIF increased the plasma and urinary concentrations of CP I and CP III in the mice, as reported in humans, and CP I may be a more sensitive biomarker of OATP-mediated drug interactions in PXB mice.

Optimizing β-lactam-containing antibiotic combination therapy for the treatment of Buruli ulcer.

The current treatment for Buruli ulcer is based on empirical evidence of efficacy. However, there is an opportunity for shortening its duration and improving response rates. Evolving understanding of the pharmacokinetic-pharmacodynamic relationships provides the basis for a stronger dose rationale for antibiotics. In conjunction with modelling and simulation, it is possible to identify dosing regimens with the highest probability of target attainment (PTA). This investigation aims to: (i) assess the dose rationale for a new combination therapy including amoxicillin/clavulanic acid (AMX/CLV) currently in clinical trials; and (ii) compare its performance with alternative dosing regimens including rifampicin, clarithromycin and AMX/CLV. In vitro estimates of the minimum inhibitory (MIC) concentration were selected as a measure of the antibacterial activity of different drug combinations. Clinical trial simulations were used to characterize the concentration vs. time profiles of rifampicin, clarithromycin and amoxicillin in a virtual cohort of adult and paediatric patients, considering the effect of baseline covariates on disposition parameters and interindividual variability in exposure. The PTA of each regimen was then assessed using different thresholds of the time above MIC. A weight-banded dosing regimen including 150-600 mg rifampicin once daily, 250-1000 mg clarithromycin and AMX/CLV 22.5mg/kg /1000 mg twice daily ensures higher PTA than the standard of care with AMX/CLV 45 mg/kg/2000 mg once daily. The higher PTA values support the proposed 4-drug combination (rifampicin, clarithromycin, AMX/CLV) currently under clinical investigation. Our findings also suggest that higher rifampicin doses might contribute to enhanced treatment efficacy.

Elucidating the effect of drug-induced mitochondrial dysfunction on insulin signaling and glucose handling in skeletal muscle cell line (C2C12) in vitro.

Efavirenz, tenofovir, rifampicin, simvastatin, lamotrigine and clarithromycin are known potential mitochondrial toxicants. Mitochondrial toxicity has been reported to disrupt the chain of events in the insulin signalling pathway. Considering the upward trajectory of diabetes mellitus prevalence, studies which seek to uncover probable risk factors for developing diabetes should be encouraged. This study aimed to evaluate the intracellular mechanisms leading to the development of insulin resistance in the presence of various conventional pharmacological agents reported as potential mitochondrial toxicants in skeletal muscle cell line. Differentiated C2C12 preparations were exposed to multiple concentrations of efavirenz, tenofovir, rifampicin, simvastatin, lamotrigine, and clarithromycin, separately. Glucose handling was evaluated by observing the changes in insulin-stimulated glucose uptake and assessing the changes in GLUT4 translocation, GLUT4 expression and Akt expression. The changes in mitochondrial function were evaluated by assessing mitochondrial membrane integrity, cellular ATP production, generation of intracellular reactive oxygen species, expression of tafazzin and quantification of medium malonaldehyde. Insulin stimulated glucose uptake was perturbed in C2C12 pre-treated with potential mitotoxicants. Additionally, ATP synthesis, alterations in mitochondrial membrane potential, excessive accumulation of ROS and malonaldehyde were observed in the presence of potential mitotoxicants. Particularly, we observed suppression of proteins involved in the insulin signalling pathway and maintenance of mitochondrial function namely GLUT4, Akt and tafazzin. Mitochondrial toxicants can potentially induce insulin resistance emanating from mitochondrial dysfunction. These new findings will contribute to the understanding of underlying mechanisms involved in the development of insulin resistance linked to mitochondrial dysfunction.

Pharmacokinetics of extended-release clarithromycin in patients with Mycobacterium ulcerans infection

Clarithromycin extended-release (CLA-ER) was used as companion drug to rifampicin (RIF) for Mycobacterium ulcerans infection in the intervention arm of a WHO drug trial. RIF enhances CYP3A4 metabolism, thereby reducing CLA serum concentrations, and RIF concentrations might be increased by CLA co-administration. We studied the pharmacokinetics of CLA-ER at a daily dose of 15 mg/kg combined with RIF at a dose of 10 mg/kg in a subset of trial participants, and compared these to previously obtained pharmacokinetic data. Serial dried blood spot samples were obtained over a period of ten hours, and analyzed by LC–MS/MS in 30 study participants—20 in the RIF-CLA study arm, and 10 in the RIF-streptomycin study arm. Median CLA Cmax was 0.4 mg/L—and median AUC 3.9 mg*h/L, following 15 mg/kg CLA-ER. Compared to standard CLA dosed at 7.5 mg/kg previously, CLA-ER resulted in a non-significant 58% decrease in Cmax and a non-significant 30% increase in AUC. CLA co-administration did not alter RIF Cmax or AUC. Treatment was successful in all study participants. No effect of CLA co-administration on RIF pharmacokinetics was observed. Based on our serum concentration studies, the benefits CLA-ER over CLA immediate release are unclear.

Synergistic combination of baicalein and rifampicin against Staphylococcus aureus biofilms.

Staphylococcus aureus, a Gram-positive bacterium, is a predominant pathogen associated with various infections. The rapid emergence of antibiotic resistance has intensified the challenge of managing fracture-related infections in severe osteoporotic patients. Rifampicin, a potent antimicrobial agent employed against fracture and implant-related infections, necessitates combination therapies due to its susceptibility to antibiotic resistance. In this study, we explored the potential of baicalein, a bioactive flavonoid from Oroxylum indicum and Scutellaria baicalensis, in combination with rifampicin against S. aureus biofilms invitro. The minimum inhibitory concentration of baicalein and rifampicin were determined as 500 μg/mL and 12.5 ng/mL respectively. The synergistic activity of baicalein and rifampicin was determined by the fractional inhibitory concentration index (FICI) using checkerboard assay. The results showed the FICI of baicalein and rifampicin was lesser than 0.5, demonstrating synergistic effect. Furthermore, the efficacy of baicalein and rifampicin, both individually and in combination, was evaluated for biofilm inhibition and eradication. Scanning electron microscopy and confocal laser microscopy also confirmed that the synergistic combinations effectively removed most of the biofilms and partially killed pre-formed biofilms. In conclusion, the findings demonstrate that baicalein is as effective as rifampicin in inhibiting and eradicating S. aureus biofilms. Their combination exhibits synergistic effect, enhancing their bactericidal effect in completely eradicating S. aureus biofilms. The findings of this research underscore the research potential of combining baicalein and rifampicin as a novel therapeutic strategy against S. aureus biofilms, offering a promising direction for future research in the treatment of fracture-related S. aureus infections.

Identification of gene targets that potentiate the action of rifampicin on Mycobacterium bovis BCG.

Tuberculosis (TB) caused by bacteria of the Mycobacterium tuberculosis complex remains one of the most important infectious diseases of mankind. Rifampicin is a first line drug used in multi-drug treatment of TB, however, the necessary duration of treatment with these drugs is long and development of resistance is an increasing impediment to treatment programmes. As a result, there is a requirement for research and development of new TB drugs, which can form the basis of new drug combinations, either due to their own anti-mycobacterial activity or by augmenting the activity of existing drugs such as rifampicin. This study describes a TnSeq analysis to identify mutants with enhanced sensitivity to sub-minimum inhibitory concentrations (MIC) of rifampicin. The rifampicin-sensitive mutants were disrupted in genes of a variety of functions and the majority fitted into three thematic groups: firstly, genes that were involved in DNA/RNA metabolism, secondly, genes involved in sensing and regulating mycobacterial cellular systems, and thirdly, genes involved in the synthesis and maintenance of the cell wall. Selection at two concentrations of rifampicin (1/250 and 1/62 MIC) demonstrated a dose response for mutants with statistically significant sensitivity to rifampicin. The dataset reveals mechanisms of how mycobacteria are innately tolerant to and initiate an adaptive response to rifampicin; providing putative targets for the development of adjunctive therapies that potentiate the action of rifampicin.

Enhance the Antimycobacterial Activity of Streptomycin with Ebselen as an Antibiotic Adjuvant Through Disrupting Redox Homeostasis.

Tuberculosis (TB) remains a major health threat worldwide, and the spread of drug-resistant (DR) TB impedes the reduction of the global disease burden. Ebselen (EbSe) targets bacterial thioredoxin reductase (bTrxR) and causes an imbalance in the redox status of bacteria. Previous work has shown that the synergistic action of bTrxR and sensitization to common antibiotics by EbSe is a promising strategy for the treatment of DR pathogens. Thus, we aimed to evaluate whether EbSe could enhance anti-TB drugs against Mycobacterium marinum (M. marinum) which is genetically related to Mycobacterium tuberculosis (Mtb) and resistant to many antituberculosis drugs. Minimum inhibitory concentrations (MIC) of isoniazid (INH), rifampicin (RFP), and streptomycin (SM) against M. marinum were determined by microdilution. The Bliss Independence Model was used to determine the adjuvant effects of EbSe over the anti-TB drugs. Thioredoxin reductase activity was measured using the DTNB assay, and its effects on bacterial redox homeostasis were verified by the elevation of intracellular ROS levels and intracellular GSH levels. The adjuvant efficacy of EbSe as an anti-TB drug was further evaluated in a mouse model of M. marinum infection. Cytotoxicity was observed in the macrophage cells Raw264.7 and mice model. The results reveal that EbSe acts as an antibiotic adjuvant over SM on M. marinum. EbSe + SM disrupted the intracellular redox microenvironment of M. marinum by inhibiting bTrxR activity, which could rescue mice from the high bacterial load, and accelerated recovery from tail injury with low mammalian toxicity. The above studies suggest that EbSe significantly enhanced the anti-Mtb effect of SM, and its synergistic combination showed low mammalian toxicity in vitro and in vivo. Further efforts are required to study the underlying mechanisms of EbSe as an antibiotic adjuvant in combination with anti-TB drug MS.

Antimicrobial susceptibility in Clostridioides difficile varies according to European region and isolate source.

Clostridioides difficile epidemiology is evolving with country-associated emerging and resistant ribotypes (RT). Antimicrobial susceptibility testing of C. difficile isolated from clinical and animal samples collected across Europe in 2018 was performed to provide antimicrobial resistance data and according to C. difficile RTs and source. Samples were cultured for C. difficile and isolates PCR ribotyped. Metronidazole, vancomycin, fidaxomicin, moxifloxacin, clindamycin, imipenem, tigecycline, linezolid, rifampicin and meropenem minimum inhibitory concentrations (MICs) for 280 clinical and 126 animal isolates were determined by Wilkins-Chalgren agar dilution. Fidaxomicin was the most active antimicrobial (all isolates geometric mean MIC = 0.03 mg/L) with no evidence of reduced susceptibility. Metronidazole MICs were elevated among RT027 (1.87 mg/L) and RT181 clinical isolates (1.03 mg/L). RT027 and RT181 had elevated geometric mean moxifloxacin MICs (14.49 mg/L, 16.88 mg/L); clindamycin (7.5 mg/L, 9.1 mg/L) and rifampicin (0.6 mg/L, 21.5 mg/L). Five isolates (RT002, RT010 and RT016) were metronidazole resistant (MIC = 8 mg/L) and 10 (RT027; RT198) had intermediate resistance (4 mg/L). Metronidazole MICs were not elevated in animal isolates. Increased geometric mean vancomycin MICs were observed among RT078, mostly isolated from animals, but there was no resistance (MIC ≥ 4 mg/L). Clinical and animal isolates of multiple RTs showed resistance to moxifloxacin and clindamycin. No resistance to imipenem or meropenem was observed. Increased antimicrobial resistance was detected in eastern Europe and mostly associated with RT027 and related emerging RT181, while clinical isolates from northern and western Europe had the lowest general levels of resistance.

Optimization of experimental conditions using central composite design for rifampicin removal

This research aims to optimize the impact of parametric conditions on the adsorption process of rifampicin, a drug used in tuberculosis treatment. The study specifically focuses on activated carbon derived from waste generated by a food processing facility, namely cacao shells (CS). Referred to as ACAFW (Activated Carbon Alimentary Factory Waste), the study utilizes a three-factor central composite design (CCD) experimental approach. The investigation is further connected to a parametric study aimed at verifying the effectiveness of the CCD model. Optimal treatment conditions were identified, including a pH of 6, an adsorbent dose of 0.3 g, and an antituberculosis concentration of 10 mg/L. These conditions demonstrated a close alignment between the obtained results (pH of 5.96, ACAFW dose of 0.328 g, and rifampicin concentration of 11.64 mg/L). The study employs a combination of the density functional theory (DFT) approach and infrared (IR) analysis to unravel the structure of rifampicin. Additionally, differential thermal analysis/thermogravimetry (DTA/TG) and Brunauer–Emmett–Teller (BET) analyses were conducted on the material. ACAFW showcased surface areas exceeding 1394 m2/g, and a microporous volume of 0.400 cm³/g. The results from the kinetic study imply that the adsorption process is influenced by competition between internal and external diffusion.

In vitro interactions of combinations of colistin with meropenem, rifampicin and tigecycline in colistin-resistant, biofilm-forming Klebsiella pneumoniae

In this study, it was aimed to reveal the in vitro interactions of combinations of colistin with meropenem, rifampicin and tigecycline in colistin-resistant, biofilm-forming Klebsiella pneumonia. A total of 30 isolates, 15 of which formed biofilms and 15 did not form biofilms, were randomly selected from K. pneumoniae isolates growing in blood samples. The synergy rates of colistin-meropenem, colistin-tigecycline, colistin-rifampicin combinations in planktonic/sessile bacteria are; It was determined as 83,3%/73,3%, 66,6%/33,3%, 100%/60% respectively. Biofilm inhibitory concentration (BIC) of colistin, meropenem, tigecycline, and rifampicin significantly increased after biofilm formation. The synergistic activity seen in the sessile form was independent of the planktonic form. Although a high synergistic effect was observed in the meropenem-colistin combination on sessile bacteria, colistin had very high BIC ​​in all combinations. Large-scale studies are needed in which the number of isolates studied is large, bacterial resistance profiles are evaluated genomically, and various antimicrobial groups are included.

CRISPR Interference-Mediated Silencing of the mmpL3 Gene in Mycobacterium smegmatis and Its Impact on Antimicrobial Susceptibility.

The discovery of novel therapeutic agents, especially those targeting mycobacterial membrane protein large 3 (mmpL3), has shown promise. In this study, the CRISPR interference-Streptococcus thermophilus nuclease-deactivated Cas9 (CRISPRi-dCas9Sth1) system was utilized to suppress mmpL3 expression in Mycobacterium smegmatis, and its impacts on susceptibility to antimicrobial agents were evaluated. The repression of the mmpL3 gene was confirmed by RT-qPCR. The essentiality, growth curve, viability, and antimicrobial susceptibility of the mmpL3 knockdown strain were investigated. mmpL3 silencing was achieved by utilizing 0.5 and 1 ng/mL anhydrotetracycline (ATc), resulting in reductions in the expression of 60.4% and 74.4%, respectively. mmpL3 silencing led to a significant decrease in bacterial viability when combined with one-half of the minimal inhibitory concentrations (MICs) of rifampicin, rifabutin, ceftriaxone, or isoniazid, along with 0.1 or 0.5 ng/mL ATc (p < 0.05). However, no significant difference was observed for clarithromycin or amikacin. The downregulation of the mmpL3 gene in mycobacteria was achieved through the use of CRISPRi-dCas9Sth1, resulting in growth deficiencies and resensitization to certain antimicrobial agents. The impact was dependent upon the level of gene expression.

Substrate geometry affects population dynamics in a bacterial biofilm

Biofilms inhabit a range of environments, such as dental plaques or soil micropores, often characterized by noneven surfaces. However, the impact of surface irregularities on the population dynamics of biofilms remains elusive, as most experiments are conducted on flat surfaces. Here, we show that the shape of the surface on which a biofilm grows influences genetic drift and selection within the biofilm. We culture Escherichia coli biofilms in microwells with a corrugated bottom surface and observe the emergence of clonal sectors whose size corresponds to that of the corrugations, despite no physical barrier separating different areas of the biofilm. The sectors are remarkably stable and do not invade each other; we attribute this stability to the characteristics of the velocity field within the biofilm, which hinders mixing and clonal expansion. A microscopically detailed computer model fully reproduces these findings and highlights the role of mechanical interactions such as adhesion and friction in microbial evolution. The model also predicts clonal expansion to be limited even for clones with a significant growth advantage-a finding which we confirm experimentally using a mixture of antibiotic-sensitive and antibiotic-resistant mutants in the presence of sublethal concentrations of the antibiotic rifampicin. The strong suppression of selection contrasts sharply with the behavior seen in range expansion experiments in bacterial colonies grown on agar. Our results show that biofilm population dynamics can be affected by patterning the surface and demonstrate how a better understanding of the physics of bacterial growth can be used to control microbial evolution.

Integration of Ag2S QDs in 3D Zn3V2O8 nanoflower for visible light driven effective photocatalytic degradation of rifampicin: Insights into preparation, mechanism and by-product toxicity evaluation

Water contamination is regarded as one of the most important concerns in the last decade and its crucial to develop an efficient and productive technique to remediate organic pollutants from waters. Photocatalytic degradation processesare advanced oxidation procedure and a promising technique for the degradation of organic pollutants. In this study, we fabricated Ag2S/Zn3V2O8 nanocomposite (AS/ZVO NCs) for the degradation of rifampicin (RIF) by ultrasonicated co-precipitation strategy. The NCs was optimally synthesized with varying deposition concentrations, among which 5%-Ag2S/Zn3V2O8 (5%-AS/ZVO) exhibited superior photocatalytic activity (95.5%) under visible light irradiation. Moreover, the experiments were conducted at diverse operational parameters such as different NCs dosage, different concentration of RIF, pH, and ions, to investigate the impact on the photocatalytic degradation of RIF. Notably, XRD and XPS results of used 5%-AS/ZVO NCs demonstrated commendable stability and possess sustained integrity in structure after six consecutive cycle tests. The scavenging study and radical trapping experiments confirmed the formation of •OH and O2•- during photocatalytic reaction. The mechanism of photocatalytic degradation of RIF by 5%-AS/ZVO NCs was proposed and the pathway was predicted based on the GC-MS results. The current study provides a comprehensive understanding for designing efficient photocatalysts for the environmental remediation applications.