Molecular characterization and differential effects of levofloxacin and ciprofloxacin on the potential for developing quinolone resistance among clinical Pseudomonas aeruginosa isolates

Diversification of Pseudomonas aeruginosa After Inhaled Tobramycin Therapy of Cystic Fibrosis Patients: Genotypic and Phenotypic Characteristics of Paired Pre- and Post-Treatment Isolates

This study examines the impact of inhaled tobramycin therapy on the within-host changes in P. aeruginosa strains isolated from Bulgarian patients with CF prior to and post treatment. Genotypic comparison by RAPD-PCR indicated that most of the pre-treatment isolates had a high similarity and were genetically comparatively close to strains from other countries with known increased morbidity or treatment requirements. Most of the post-treatment isolates were, however, genetically distant from their pre-treatment counterparts, showing genotypic diversification after the treatment. Phenotypic comparisons showed a lower ODmax reached during groswth and an increased lag-time in the post-treatment isolates. All strains were capable of invasion and intracellular reproduction within A549 cultured cells. The addition of sub-inhibitory amounts (1/4 or 1/2 MIC) of tobramycin during growth showed the higher relative fitness (as a percentage of the untreated control) of the post-treatment strains. The effects of sub-MICs on biofilm growth did not show such a pronounced trend. However, when a resazurin-based viability test was applied, the advantage of the post-treatment strains was confirmed for both broth and biofilm cultures. In spite of that, according to the determined MIC values, all isolates were tobramycin-sensitive, and the data from this study imply the development of tolerance to the antibiotic in the strains that survived the treatment.

Impact of meropenem exposure on fluoroquinolone and carbapenem resistance in Pseudomonas aeruginosa infection in inpatients in a Japanese university hospital: Insights into oprD mutations and efflux pump overexpression

OBJECTIVES

In Pseudomonas aeruginosa isolates, emerging meropenem resistance beyond imipenem resistance has become a problem. In this study, we aimed to investigate the relationship between the in vivo acquisition of antimicrobial resistance in fluoroquinolone- and carbapenem-resistant P. aeruginosa clinical isolates, the underlying molecular mechanisms, and exposure to antimicrobial agents.

METHODS

Pulsed-field gel electrophoreses were performed to study the molecular relatedness of nine clinical isolates from a Japanese hospital. The minimal inhibitory concentrations of clinically relevant antibiotics were determined. Quantitative PCR was performed to analyze oprD, mexB, mexC, mexE, and mexY expression. DNA sequencing was performed to identify mutations.

RESULTS

Eight of nine strains were metallo-β-lactamase (MBL) negative, and one strain was MBL positive. All eight non-MBL-resistant strains harbored mutations in the quinoline-resistance-determining regions (QRDR) of gyrA, gyrB, or parC. Five of the eight non-MBL strains had T83I, two had D87N, and one had both T83I and D87N mutations in gyrA. Of these eight strains, three carrying gyrA mutations had another QRDR mutation in subunits, gyrB or parC, associated with mexY overexpression. Additionally, seven of eight dual fluoroquinolone and carbapenem-resistant isolates carried a premature termination codon within oprD, containing either F170L or L7 shortening.

CONCLUSIONS

In dual fluoroquinolone- and carbapenem-resistant P. aeruginosa, alterations in the OprD porin and the presence of an active EP are primary resistance mechanisms. Meropenem exposure within the past 59 days may have contributed to the selection of the oprD mutant overexpressing mexB, and meropenem exposure within the past 6 months may have contributed to meropenem resistance.

NIR-Activated Hydrogel with Dual-Enhanced Antibiotic Effectiveness for Thorough Elimination of Antibiotic-Resistant Bacteria

Antibiotic resistance has become a critical health crisis globally. Traditional strategies using antibiotics can lead to drug-resistance, while inorganic antimicrobial agents can cause severe systemic toxicity. Here, we have developed a dual-antibiotic hydrogel delivery system (PDA-Ag@Levo/CMCS), which can achieve controlled release of clinical antibiotics levofloxacin (Levo) and classic nanoscale antibiotic silver nanoparticles (AgNPs), effectively eliminating drug-resistant P. aeruginosa. Benefiting from the photothermal (PTT) effect of polydopamine (PDA), the local high temperature generated by PDA-Ag@Levo/CMCS can quickly kill bacteria through continuous and responsive release of dual-antibiotics to restore sensitivity to ineffective antibiotics. Moreover, AgNPs could significantly improve the efficiency of traditional antibiotics by disrupting bacterial membranes and reducing their toxicity to healthy tissues. A clever combination of PTT and drug-combination therapy can effectively eliminate biofilms and drug-resistant bacteria. Mechanism studies have shown that PDA-Ag@Levo might eliminate drug-resistant P. aeruginosa by disrupting biofilm formation and protein synthesis, and inhibit the resistance mutation of P. aeruginosa by promoting the expression of related genes, such as rpoS, dinB, and mutS. Collectively, the synergistic effect of this dual-antibiotic hydrogel combined with PTT provides a creative strategy for eliminating drug-resistant bacteria in chronic infection wounds.

Selective Serotonin Reuptake Inhibitors: Antimicrobial Activity Against ESKAPEE Bacteria and Mechanisms of Action

Background: Multidrug-resistant bacteria cause over 700,000 deaths annually, a figure projected to reach 10 million by 2050. Among these bacteria, the ESKAPEE group is notable for its multiple resistance mechanisms. Given the high costs of developing new antimicrobials and the rapid emergence of resistance, drug repositioning offers a promising alternative. Results: This study evaluates the antibacterial activity of sertraline and paroxetine. When tested against clinical and reference strains from the ESKAPEE group, sertraline exhibited minimum inhibitory concentration (MIC) values between 15 and 126 μg/mL, while the MIC values for paroxetine ranged from 60 to 250 μg/mL. Both drugs effectively eradicated bacterial populations within 2 to 24 h and caused morphological changes, such as protrusions and cellular fragmentation, as shown by electron scanning microscopy. Regarding their mechanisms of action as antibacterials, for the first time, increased membrane permeability was detected, as evidenced by heightened dye absorption, along with the increased presence of total proteins and dsDNA in the extracellular medium of Escherichia coli ATCC2 25922 and Staphylococcus aureus ATCC 25923, and oxidative stress was also detected in bacteria treated with sertraline and paroxetine, with reduced efficiency observed in the presence of antioxidants and higher levels of oxygen-reactive species evidenced by their reaction with 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate. The drugs also inhibited bacterial efflux pumps, increasing ethidium bromide accumulation and enhancing tetracycline activity in resistant strains. Conclusions: These findings indicate that sertraline and paroxetine could serve as alternative treatments against multidrug-resistant bacteria, as well as efflux pump inhibitors (EPIs), and they support further development of antimicrobial agents based on these compounds.

Comparing antibiotic resistance and virulence profiles of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa from environmental and clinical settings

Antibiotic resistance and virulence profiles of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa, isolated from water sources collected in informal settlements, were compared to clinical counterparts. Cluster analysis using repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) indicated that, for each respective species, low genetic relatedness was observed between most of the clinical and environmental isolates, with only one clinical P. aeruginosa (PAO1) and one clinical K. pneumoniae (P2) exhibiting high genetic similarity to the environmental strains. Based on the antibiograms, the clinical E. faecium Ef CD1 was extensively drug resistant (XDR); all K. pneumoniae isolates (n = 12) (except K. pneumoniae ATCC 13883) were multidrug resistant (MDR), while the P. aeruginosa (n = 16) isolates exhibited higher susceptibility profiles. The tetM gene (tetracycline resistance) was identified in 47.4 % (n = 6 environmental; n = 3 clinical) of the E. faecium isolates, while the blaKPC gene (carbapenem resistance) was detected in 52.6 % (n = 7 environmental; n = 3 clinical) and 15.4 % (n = 2 environmental) of the E. faecium and K. pneumoniae isolates, respectively. The E. faecium isolates were predominantly poor biofilm formers, the K. pneumoniae isolates were moderate biofilm formers, while the P. aeruginosa isolates were strong biofilm formers. All E. faecium and K. pneumoniae isolates were gamma (γ)-haemolytic, non-gelatinase producing (E. faecium only), and non-hypermucoviscous (K. pneumoniae only), while the P. aeruginosa isolates exhibited beta (β)-haemolysis and produced gelatinase. The fimH (type 1 fimbriae adhesion) and ugE (uridine diphosphate galacturonate 4-epimerase synthesis) virulence genes were detected in the K. pneumoniae isolates, while the P. aeruginosa isolates possessed the phzM (phenazine production) and algD (alginate biosynthesis) genes. Similarities in antibiotic resistance and virulence profiles of environmental and clinical E. faecium, K. pneumoniae, and P. aeruginosa, thus highlights the potential health risks posed by using environmental water sources for daily water needs in low-and-middle-income countries.

Uncovering Microbial Composition of the Tissue Microenvironment in Bladder Cancer using RNA Sequencing Data

Purpose: Bladder cancer (BC) is one of the top 10 common tumors in the world. It has been reported that microbiota can colonize tissues and play important roles in tumorigenesis and progression. However, the current understanding of microorganisms in the BC tissue microenvironment remains unclear. Methods: In this study, we integrated the RNA-seq data of 479 BC tissue samples from seven datasets combined with a range of bioinformatics tools to explore the landscape of microbiome in the BC tissue microenvironment. Results: The pan-microbiome was estimated to surpass 1,400 genera. A total of seven core microbiota (Bacillus, Corynebacterium, Cutibacterium, Escherichia, Halomonas, Pasteurella, and Streptomyces) were identified. Among them, Bacillus was widely distributed in all datasets with a high relative abundance (10.11% of all samples on average). Moreover, some biological factors, including tissue source and tumor grade, were found significant effects on the microbial composition of the bladder tissue. Pseudomonas, Porphyrobacter, and Acinetobacter were enriched in tumor tissues, while Mycolicibacterium and Streptomyces were enriched in patients who showed durable response to BCG therapy. In addition, we established microbial co-occurrence networks and found that the BCG therapy may attenuate the microbiological interactions. Conclusions: This study clearly provided a microbial landscape of the BC tissue microenvironment, which was important for exploring the interactions between microorganisms and BC tissues. The identified specific taxa might be potential biomarkers for BC.

Molecular Characteristics of Colistin Resistance in Acinetobacter baumannii and the Activity of Antimicrobial Combination Therapy in a Tertiary Care Medical Center in Lebanon

(1) Background: Infections with pan-drug-resistant (PDR) bacteria, such as A. baumannii, are becoming increasingly common, especially in healthcare facilities. In this study, we selected 15 colistin-resistant clinical A. baumannii isolates from a hospital in Beirut, Lebanon, to test combination therapies and determine their sequence types (STs) and the mechanism of colistin resistance using whole-genome sequencing (WGS). (2) Methods: Antimicrobial susceptibility testing via broth microdilution against 12 antimicrobials from different classes and growth rate assays were performed. A checkerboard assay was conducted on PDR isolates using six different antimicrobials, each in combination with colistin. Genomic DNA was extracted from all isolates and subjected to WGS. (3) Results: All isolates were resistant to all tested antimicrobials with the one exception that was susceptible to gentamicin. Combining colistin with either meropenem, ceftolozane-tazobactam, or teicoplanin showed synergistic activity. Sequencing data revealed that 67% of the isolates belonged to Pasteur ST2 and 33% to ST187. Furthermore, these isolates harbored a number of resistance genes, including blaOXA-23. Mutations in the pmrC gene were behind colistin resistance. (4) Conclusions: With the rise in antimicrobial resistance and the absence of novel antimicrobial production, alternative treatments must be found. The combination therapy results from this study suggest treatment options for PDR ST2 A. baumannii-infected patients.

Multidrug-Resistant Commensal and Infection-Causing Staphylococcus spp. Isolated from Companion Animals in the Valencia Region

The emergence of antimicrobial resistance (AMR) and multidrug resistance (MDR) among microorganisms to commonly used antibiotics is a growing concern in both human and veterinary medicine. Companion animals play a significant role in the epidemiology of AMR, as their population is continuously increasing, posing a risk of disseminating AMR, particularly to strains of public health importance, such as methicillin-resistant Staphylococcus strains. Thus, this study aimed to investigate the prevalence of AMR and MDR in commensal and infection-causing Staphylococcus spp. in dogs and cats in Valencia region. For this purpose, 271 samples were taken from veterinary centers to assess antimicrobial susceptibility against 20 antibiotics, including some of the most important antibiotics for the treatment of Staphylococcus infections, including the five last resort antibiotics in this list. Of all the samples, 187 Staphylococcus spp. strains were recovered from asymptomatic and skin-diseased dogs and cats, of which S. pseudintermedius (≈60%) was more prevalent in dogs, while S. felis (≈50%) was more prevalent in cats. In the overall analysis of the isolates, AMR was observed for all antibiotics tested, including those crucial in human medicine. Furthermore, over 70% and 30% of the strains in dogs and cats, respectively, exhibited MDR. This study highlights the significance of monitoring the trends in AMR and MDR among companion animals. The potential contribution of these animals to the dissemination of AMR and its resistance genes to humans, other animals, and their shared environment underscores the necessity for adopting a One Health approach.