Bacterial resistance to antimicrobial photodynamic therapy: A critical update.

Bacterial antibiotic resistance is one of the most significant challenges for public health. The increase in bacterial resistance, mainly due to microorganisms harmful to health, and the need to search for alternative treatments to contain infections that cannot be treated by conventional antibiotic therapy has been aroused. An alternative widely studied in recent decades is antimicrobial photodynamic therapy (aPDT), a treatment that can eliminate microorganisms through oxidative stress. Although this therapy has shown satisfactory results in infection control, it is still controversial in the scientific community whether bacteria manage to develop resistance after successive applications of aPDT. Thus, this work provides an overview of the articles that performed successive aPDT applications in models using bacteria published since 2010, focusing on sublethal dose cycles, highlighting the main PSs tested, and addressing the possible mechanisms for developing tolerance or resistance to aPDT, such as efflux pumps, biofilm formation, OxyR and SoxRS systems, catalase and superoxide dismutase enzymes and quorum sensing.

Simultaneous elimination of antibiotic-resistant bacteria and antibiotic resistance genes by different Fe-N co-doped biochars activating peroxymonosulfate: The key role of pyridine-N and Fe-N sites.

The coexistence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in the environment poses a potential threat to public health. In our study, we have developed a novel advanced oxidation process for simultaneously removing ARGs and ARB by two types of iron and nitrogen-doped biochar derived from rice straw (FeN-RBC) and sludge (FeN-SBC). All viable ARB (approximately 108 CFU mL-1) was inactivated in the FeN-RBC/ peroxymonosulfate (PMS) system within 40 min and did not regrow after 48 h even in real water samples. Flow cytometry identified 96.7 % of dead cells in the FeN-RBC/PMS system, which verified the complete inactivation of ARB. Thorough disinfection of ARB was associated with the disruption of cell membranes and intracellular enzymes related to the antioxidant system. Whereas live bacteria (approximately 200 CFU mL-1) remained after FeN-SBC/PMS treatment. Intracellular and extracellular ARGs (tetA and tetB) were efficiently degraded in the FeN-RBC/PMS system. The production of active species, primarily •OH, SO4•- and Fe (IV), as well as electron transfer, were essential to the effective disinfection of FeN-RBC/PMS. In comparison with FeN-SBC, the better catalytic performance of FeN-RBC was mainly ascribed to its higher amount of pyridine-N and Fe0, and more reactive active sites (such as CO group and Fe-N sites). Density functional theory calculations indicated the greater adsorption energy and Bader charge, more stable Fe-O bond, more easily broken OO bond in FeN-RBC/PMS, which demonstrated the stronger electron transfer capacity between FeN-RBC and PMS. To encapsulate, our study provided an efficient and dependable method for the simultaneous elimination of ARGs and ARB in water.

Discovery of Salifungin as a Repurposed Antibiotic against Methicillin-Resistant Staphylococcus aureus with Limited Resistance Development.

Exploring novel antimicrobial drugs and strategies has become essential to the fight MRSA-associated infections. Herein, we found that membrane-disrupted repurposed antibiotic salifungin had excellent bactericidal activity against MRSA, with limited development of drug resistance. Furthermore, adding salifungin effectively decreased the minimum inhibitory concentrations of clinical antibiotics against Staphylococcus aureus. Evaluations of the mechanism demonstrated that salifungin disrupted the level of H+ and K+ ions using hydrophilic and lipophilic groups to interact with bacterial membranes, causing the disruption of bacterial proton motive force followed by impacting on bacterial the function of the respiratory chain and adenosine 5'-triphosphate, thereby inhibiting phosphatidic acid biosynthesis. Moreover, salifungin also significantly inhibited the formation of bacterial biofilms and eliminated established bacterial biofilms by interfering with bacterial membrane potential and inhibiting biofilm-associated gene expression, which was even better than clinical antibiotics. Finally, salifungin exhibited efficacy comparable to or even better than that of vancomycin in the MRSA-infected animal models. In conclusion, these results indicate that salifungin can be a potential drug for treating MRSA-associated infections.

Combating infections from drug-resistant bacteria: Unleashing synergistic broad-spectrum antibacterial power with high-entropy MXene/CDs.

The growing resistance of bacteria to antibiotics has posed challenges in treating associated bacterial infections, while the development of multi-model antibacterial strategies could efficient sterilization to prevent drug resistance. High-entropy MXene has emerged as a promising candidate for antibacterial synergy with inherent photothermal and photodynamic properties. Herein, a high-entropy nanomaterial of MXene/CDs was synthesized to amplify oxidative stress under near-infrared laser irradiation. Well-exfoliated MXene nanosheets have proven to show an excellent photothermal effect for sterilization. The incorporation of CDs could provide photo-generated electrons for MXene nanosheets to generate ROS, meanwhile reducing the recombination of electron-hole pairs to further accelerate the generation of photo-generated electrons. The MXene/CDs material demonstrates outstanding synergistic photothermal and photodynamic effects, possesses excellent biocompatibility and successfully eliminates drug-resistant bacteria as well as inhibits biofilm formation. While attaining a remarkable killing efficiency of up to 99.99% against drug-resistant Escherichia coli and Staphylococcus aureus, it also demonstrates outstanding antibacterial effects against four additional bacterial strains. This work not only establishes a synthesis precedent for preparing high-entropy MXene materials with CDs but also provides a potential approach for addressing the issue of drug-resistant bacterial infections.

In vitro Antibacterial Activity of Ethanolic Tanao Si Kan Dang RD1 (Cannabis sativa L.) Extracts Against Human Antibiotic-Resistant Bacteria.

<b>Background and Objective:</b> A new strain of cannabis, <i>Cannabis sativa</i> L. Tanao Si Kan Dang RD1, has been approved and registered by the Rajamangala University of Technology Isan, Thailand. The <i>C. sativa</i> is acknowledged for its medicinal properties which demonstrated various therapeutic properties, such as anti-cancer and antibacterial activities. This study aimed to investigate the antibacterial activity of ethanolic extracts from the stems and leaves of the Tanao Si Kan Dang RD1 strain against seven antibiotic-resistant bacteria. <b>Materials and Methods:</b> The primary antibacterial activity of ethanolic Tanao Si Kan Dang RD1 extracts were determined using the disc diffusion method, while the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined using the broth microdilution method. <b>Results:</b> The largest inhibition zone, measuring 12 mm, was observed in leaf extracts against <i>Pseudomonas aeruginosa</i> 101. The lowest MIC, at 0.78 mg/mL, was obtained from stem extracts against <i>Stenotrophomonas maltophilia</i>. The lowest MBCs, at 12.5 mg/mL, were observed in leaf extracts against <i>Enterococcus faecalis</i>, <i>Acinetobacter baumannii</i>, multidrug-resistant <i>Klebsiella</i> <i>pneumoniae</i>, <i>Stenotrophomonas maltophilia</i> and <i>Pseudomonas aeruginosa</i> 101 and stem extracts against <i>Acinetobacter baumannii</i>, multidrug-resistant <i>Klebsiella pneumoniae</i>, <i>Stenotrophomonas maltophilia</i> and <i>Pseudomonas aeruginosa</i> 101. <b>Conclusion:</b> This study presents a novel finding regarding the antibacterial activity of ethanolic extracts from the leaves and stems of Tanao Si Kan Dang RD1 against antibiotic-resistant bacteria. The potential application of these cannabis plant extracts in the development of antibiotics capable of combating antibiotic-resistant pathogenic bacteria represents a promising strategy to address a significant global health concern.

Identification of an Optimized Clinical Development Candidate from Cilagicin, an Antibiotic That Evades Resistance by Dual Polyprenyl Phosphate Binding.

Cilagicin is a dual polyprenyl phosphate binding lipodepsipeptide antibiotic with strong activity against clinically relevant Gram-positive pathogens while evading antibiotic resistance. Cilagicin showed high serum binding that reduced its in vivo efficacy. Cilagicin-BP, which contains a biphenyl moiety in place of the N-terminal myristic acid found on cilagicin, showed reduced serum binding and increased in vivo efficacy but decreased potency against some pathogens. Here, we manipulated the acyl tail and the peptide core of cilagicin to identify an optimized collection of structural features that maintain potent antibiotic activity against a wide range of pathogens in the presence of serum. This led to the identification of the optimized antibiotic dodecacilagicin, which contains an N-terminal dodecanoic acid. Dodecacilagicin exhibits low MICs against clinically relevant pathogens in the presence of serum, retains polyprenyl phosphate binding, and evades resistance development even after long-term antibiotic exposure, making dodecacilagicin an appealing candidate for further therapeutic development.

Identification of CH2-linked quinolone-aminopyrimidine hybrids as potent anti-MRSA agents: Low resistance potential and lack of cross-resistance with fluoroquinolone antibiotics.

The structural optimization of B14, an antibacterial agent we previously obtained, has led to the discovery of a new class of CH2-linked quinolone-aminopyrimidine hybrids with potent anti-MRSA activities. Surprisingly, the hybrids lacking a C-6 fluoro atom at the quinolone nucleus showed equal or even stronger anti-MRSA activities than their corresponding 6-fluoro counterparts, despite the well-established structure-activity relationships (SARs) indicating that the 6-fluoro substituent enhances the antibacterial activity in conventional fluoroquinolone antibiotics. Moreover, these new hybrids, albeit structurally related to conventional fluoroquinolones, showed no cross-resistance with fluoroquinolone drugs. The most active compound, 15m, exhibited excellent activities with a MIC value of 0.39 µg/mL against both fluoroquinolone-sensitive strain USA500 and -resistant MRSA isolate Mu50. Further resistance development studies indicated MRSA is unlikely to acquire resistance against 15m. Moreover, 15m displayed favorable in vivo half-life and safety profiles. These findings suggest a rationale for further evolution of quinolone antibiotics with a high barrier to resistance.

Copper selenide nanosheets with photothermal therapy-related properties and multienzyme activity for highly effective eradication of drug resistance.

Bacterial infections are among the most significant causes of death in humans. Chronic misuse or uncontrolled use of antibiotics promotes the emergence of multidrug-resistant superbugs that threaten public health through the food chain and cause environmental pollution. Based on the above considerations, copper selenide nanosheets (CuSe NSs) with photothermal therapy (PTT)- and photodynamic therapy (PDT)-related properties have been fabricated. These CuSe NSs possess enhanced PDT-related properties and can convert O2 into highly toxic reactive oxygen species (ROS), which can cause significant oxidative stress and damage to bacteria. In addition, CuSe NSs can efficiently consume glutathione (GSH) at bacterial infection sites, thus further enhancing their sterilization efficacy. In vitro antibacterial experiments with near-infrared (NIR) irradiation have shown that CuSe NSs have excellent photothermal bactericidal properties. These experiments also showed that CuSe NSs exerted excellent bactericidal effects on wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) and significantly promoted the healing of infected wounds. Because of their superior biological safety, CuSe NSs are novel copper-based antimicrobial agents that are expected to enter clinical trials, serving as a modern approach to the major problem of treating bacterially infected wounds.

The evaluation of Staphylococcus aureus and Staphylococcus epidermidis in hospital air, their antibiotic resistance and sensitivity of S. aureus to cefoxitin.

Staphylococci as a nosocomial infection agent, increases the possibility of contracting diseases such as wound infection, sepsis and skin infections in humans. It was shown that Staphylococcus aureus considered as a commensal organism causing various both endemic and epidemic hospital-acquired infections. Air samples were collected from Sina Hospital, Hamadan city, which dedicated to various respiratory diseases and analysed by biochemical tests. The resistance and sensitivity of bacterial strains to the cefoxitin antibiotic were also determined. Staphylococcus aureus density (CFU/m3) were measured in the air of various wards as follows: infectious 13.35 ± 7.57, poisoning 29.84 ± 33.43, emergency 8.64 ± 2.72, eye operation room 0, recovery room 6.28 ± 4.90, skin outpatient operation room 4.71 ± 2.36, respiratory isolation 0, ICU 0.79 ± 1.36, and the administrative room 6.28 ± 5.93; while the Staphylococcus epidermidis were as follows: infectious 1.57 ± 2.35, poisoning 2.35 ± 4.08, emergency 2.35 ± 2.35, eye operation room 0, recovery room 0.78 ± 1.36, skin outpatient operation room 2.35 ± 2.35, respiratory isolation 0, ICU 2.35 ± 4.08, and the administrative room 1.57 ± 1.36. The positive and negative control samples showed a concentration of 0. Moreover, among the S. aureus isolates, 33.3% were found to be resistant to cefoxitin, while 40.6% showed to be sensitive. Based on the results, the number of active people and the type and quality of ventilation are very effective in the air quality of various wards of hospital. The poisoning section showed the most contaminated air and the highest resistance and sensitivity to the cefoxitin antibiotic.

Blue-Light-Activated Water-Soluble Sn(IV)-Porphyrins for Antibacterial Photodynamic Therapy (aPDT) against Drug-Resistant Bacterial Pathogens.

Antimicrobial resistance has emerged as a global threat to the treatment of infectious diseases. Antibacterial photodynamic therapy (aPDT) is a promising alternative approach and is highly suitable for the treatment of cutaneous bacterial infections through topical applications. aPDT relies on light-responsive compounds called photosensitizer (PS) dyes, which generate reactive oxygen species (ROS) when induced by light, thereby killing bacterial cells. Despite several previous studies in this area, the molecular details of targeting and cell death mediated by PS dyes are poorly understood. In this study, we further investigate the antibacterial properties of two water-soluble Sn(IV) tetrapyridylporphyrins that were quaternized with methyl and hexyl groups (1 and 2). In this follow-up study, we demonstrate that Sn(IV)-porphyrins can be photoexcited by blue light (a 427 nm LED) and exhibit various levels of bactericidal activity against both Gram-(+) and Gram-(-) strains of bacteria. Using localization studies through fluorescence microscopy, we show that 2 targets the bacterial membrane more effectively than 1 and exhibits comparatively higher aPDT activity. Using multiple fluorescence reporters, we demonstrate that photoactivation of 1 and 2 results in extensive collateral damage to the bacterial cells including DNA cleavage, membrane damage, and delocalization of central systems necessary for bacterial growth and division. In summary, this investigation provides deep insights into the mechanism of bacterial killing mediated by the Sn(IV)-porphyrins. Moreover, our approach offers a new method for evaluating the activity of PS, which may inspire the discovery of new PS with enhanced aPDT activity.

Chlorite and bromate alter the conjugative transfer of antibiotic resistance genes: Co-regulation of oxidative stress and energy supply.

The widespread use of disinfectants during the global response to the 2019 coronavirus pandemic has increased the co-occurrence of disinfection byproducts (DBPs) and antibiotic resistance genes (ARGs). Although DBPs pose major threats to public health globally, there is limited knowledge regarding their biological effects on ARGs. This study aimed to investigate the effects of two inorganic DBPs (chlorite and bromate) on the conjugative transfer of RP4 plasmid among Escherichia coli strains at environmentally relevant concentrations. Interestingly, the frequency of conjugative transfer was initially inhibited when the exposure time to chlorite or bromate was less than 24 h. However, this inhibition transformed into promotion when the exposure time was extended to 36 h. Short exposures to chlorite or bromate were shown to impede the electron transport chain, resulting in an ATP shortage and subsequently inhibiting conjugative transfer. Consequently, this stimulates the overproduction of reactive oxygen species (ROS) and activation of the SOS response. Upon prolonged exposure, the resurgent energy supply promoted conjugative transfer. These findings offer novel and valuable insights into the effects of environmentally relevant concentrations of inorganic DBPs on the conjugative transfer of ARGs, thereby providing a theoretical basis for the management of DBPs.

Compensatory evolution in NusG improves fitness of drug-resistant M. tuberculosis.

Drug-resistant bacteria are emerging as a global threat, despite frequently being less fit than their drug-susceptible ancestors1-8. Here we sought to define the mechanisms that drive or buffer the fitness cost of rifampicin resistance (RifR) in the bacterial pathogen Mycobacterium tuberculosis (Mtb). Rifampicin inhibits RNA polymerase (RNAP) and is a cornerstone of modern short-course tuberculosis therapy9,10. However, RifR Mtb accounts for one-quarter of all deaths due to drug-resistant bacteria11,12. We took a comparative functional genomics approach to define processes that are differentially vulnerable to CRISPR interference (CRISPRi) inhibition in RifR Mtb. Among other hits, we found that the universally conserved transcription factor NusG is crucial for the fitness of RifR Mtb. In contrast to its role in Escherichia coli, Mtb NusG has an essential RNAP pro-pausing function mediated by distinct contacts with RNAP and the DNA13. We find this pro-pausing NusG-RNAP interface to be under positive selection in clinical RifR Mtb isolates. Mutations in the NusG-RNAP interface reduce pro-pausing activity and increase fitness of RifR Mtb. Collectively, these results define excessive RNAP pausing as a molecular mechanism that drives the fitness cost of RifR in Mtb, identify a new mechanism of compensation to overcome this cost, suggest rational approaches to exacerbate the fitness cost, and, more broadly, could inform new therapeutic approaches to develop drug combinations to slow the evolution of RifR in Mtb.

Clinical crusade: zosurabalpin's charge against antibiotic resistance.

In a recent report, Zampaloni et al. describe a novel tethered macrocyclic peptide (MCP) antibiotic, zosurabalpin, that disrupts the essential function of the LptB2FGC complex in Gram-negative bacteria and demonstrates efficacy against carbapenem-resistant Acinetobacter baumannii (CRAB). Its preclinical success suggests a substantial shift in treating antibiotic resistance, pending clinical trials to validate its effectiveness, pharmacokinetics, and resistance management.

System-wide approaches to antimicrobial therapy and antimicrobial resistance in the UK: the AMR-X framework.

Antimicrobial resistance (AMR) threatens human, animal, and environmental health. Acknowledging the urgency of addressing AMR, an opportunity exists to extend AMR action-focused research beyond the confines of an isolated biomedical paradigm. An AMR learning system, AMR-X, envisions a national network of health systems creating and applying optimal use of antimicrobials on the basis of their data collected from the delivery of routine clinical care. AMR-X integrates traditional AMR discovery, experimental research, and applied research with continuous analysis of pathogens, antimicrobial uses, and clinical outcomes that are routinely disseminated to practitioners, policy makers, patients, and the public to drive changes in practice and outcomes. AMR-X uses connected data-to-action systems to underpin an evaluation framework embedded in routine care, continuously driving implementation of improvements in patient and population health, targeting investment, and incentivising innovation. All stakeholders co-create AMR-X, protecting the public from AMR by adapting to continuously evolving AMR threats and generating the information needed for precision patient and population care.

Common and varied molecular responses of Escherichia coli to five different inhibitors of the lipopolysaccharide biosynthetic enzyme LpxC.

A promising yet clinically unexploited antibiotic target in difficult-to-treat Gram-negative bacteria is LpxC, the key enzyme in the biosynthesis of lipopolysaccharides, which are the major constituents of the outer membrane. Despite the development of dozens of chemically diverse LpxC inhibitor molecules, it is essentially unknown how bacteria counteract LpxC inhibition. Our study provides comprehensive insights into the response against five different LpxC inhibitors. All compounds bound to purified LpxC from Escherichia coli. Treatment of E. coli with these compounds changed the cell shape and stabilized LpxC suggesting that FtsH-mediated proteolysis of the inactivated enzyme is impaired. LpxC inhibition sensitized E. coli to vancomycin and rifampin, which poorly cross the outer membrane of intact cells. Four of the five compounds led to an accumulation of lyso-phosphatidylethanolamine, a cleavage product of phosphatidylethanolamine, generated by the phospholipase PldA. The combined results suggested an imbalance in lipopolysaccharides and phospholipid biosynthesis, which was corroborated by the global proteome response to treatment with the LpxC inhibitors. Apart from LpxC itself, FabA and FabB responsible for the biosynthesis of unsaturated fatty acids were consistently induced. Upregulated compound-specific proteins are involved in various functional categories, such as stress reactions, nucleotide, or amino acid metabolism and quorum sensing. Our work shows that antibiotics targeting the same enzyme do not necessarily elicit identical cellular responses. Moreover, we find that the response of E. coli to LpxC inhibition is distinct from the previously reported response in Pseudomonas aeruginosa.

Overcoming antibiotic resistance caused by genetic mutations of Helicobacter pylori with mucin adhesive polymer-based therapeutics.

Herein, we describe the 3'-sialyllactose-polyethyleneimine-chlorine e6 conjugate (3PC), meticulously engineered to effectively target Helicobacter bacteria (H. pylori) within the gastric environment. The composition of 3PC comprises polyethyleneimine, a cationic polymer, 3'-sialyllactose, which exhibits a specific binding affinity for H. pylori surface proteins, and a photosensitizer capable of generating oxygen radicals in response to specific wavelengths. The distinctive feature of 3PC lies in its capacity to enhance interaction with the anionic mucus layer facilitated by electrostatic forces. This interaction results in prolonged residence within the intestinal environment. The extended vacation in the intestinal milieu overcomes inherent limitations that have historically impeded conventional antibiotics from efficiently reaching and targeting H. pylori. 3PC can be harnessed as a potent tool for antibacterial photodynamic therapy, and its versatility extends to addressing the challenges posed by various antibiotic-resistant strains. The exceptional efficacy of 3PC in enhancing intestinal residence time and eradicating H. pylori has been robustly substantiated in animal models, particularly in mice. In summary, 3PC is a formidable agent capable of eradicating H. pylori, irrespective of its antibiotic resistance status, by efficiently penetrating and selectively targeting the mucus layer within the gastric environment.

Activity of zinc oxide and zinc borate nanoparticles against resistant bacteria in an experimental lung cancer model.

BACKGROUND: Recent research indicates a prevalence of typical lung infections, such as pneumonia, in lung cancer patients. Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii stand out as antibiotic-resistant pathogens. Given this, there is a growing interest in alternative therapeutic avenues. Boron and zinc derivatives exhibit antimicrobial, antiviral, and antifungal properties. OBJECTIVES: This research aimed to establish the effectiveness of ZnO and ZB NPs in combating bacterial infections in lung cancer cell lines. METHODS: Initially, this study determined the minimal inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of zinc oxide nanoparticles (ZnO NPs) and zinc borate (ZB) on chosen benchmark strains. Subsequent steps involved gauging treatment success through a lung cancer-bacteria combined culture and immunohistochemical analysis. RESULTS: The inhibitory impact of ZnO NPs on bacteria was charted as follows: 0.97 µg/mL for K. pneumoniae 700603, 1.95 µg/mL for P. aeruginosa 27853, and 7.81 µg/mL for Acinetobacter baumannii 19,606. In comparison, the antibacterial influence of zinc borate was measured as 7.81 µg/mL for Klebsiella pneumoniae 700603 and 500 µg/mL for both P. aeruginosa 27853 and A.baumannii 19606. After 24 h, the cytotoxicity of ZnO NPs and ZB was analyzed using the MTT technique. The lowest cell viability was marked in the 500 µg/mL ZB NPs group, with a viability rate of 48.83% (P < 0.001). However, marked deviations appeared at ZB concentrations of 61.5 µg/mL (P < 0.05) and ZnO NPs at 125 µg/mL. CONCLUSION: A synergistic microbial inhibitory effect was observed when ZnO NP and ZB were combined against the bacteria under investigation.

The Percentage of Antibiotic Resistance in Uncomplicated Community-Acquired Urinary Tract Infections.

BACKGROUND: Uncomplicated bacterial urinary tract infections(uUTIs) are commonly seen in outpatient practice. They are usuallytreated empirically with antibiotics. The pertinent German ClinicalPractice Guideline contains recommendations on antibiotic selection,with the additional advice that the local resistance situationshould be considered as well. However, up-to-date information onlocal resistance is often unavailable, because microbiological testingis mainly recommended for complicated UTIs. Resistance ratesare often higher in recurrent uUTIs than in single episodes. In thisstudy, we aimed to determine the resistance rates of Escherichiacoli (E. coli) in patients with community-acquired uUTIs and tomake these data available to the treating physicians. METHODS: In a nationwide cross-sectional study in Germany (DRKS00019059), we determined the percentages of resistance to antibioticsrecommended for uUTIs (first choice: fosfomycin, nitro -xoline, mecillinam, nitrofurantoin, trimethoprim; second choice:cefpodoxime, ciprofloxacin, cotrimoxazole, levofloxacin, norfloxacin,ofloxacin) over the period 2019-2021. The data were stratified bysingle episodes vs. recurrent UTIs (rUTIs). RESULTS: Data from 2390 subjects were analyzed. E. coli was foundin 75.4% of the samples with positive urine cultures (1082 out of1435). The resistance rate of E. coli in single episodes (n = 725)was less than 15% for all antibiotics tested. In rUTIs(n = 357), resistance rates were also less than 15%for the most part; the only exceptions were trimethoprim(21.4%) and cotrimoxazole (19.3%). CONCLUSION: For single episodes of uUTI, all of theantibiotics studied can be recommended, at least asfar as their resistance profiles are concerned. Forrecurrent UTI, all but trimethoprim and cotrimoxazolecan be recommended. The second-choice antibioticsexamined do not have a more favorable resistanceprofile than the first-choice antibiotics.

Mycobacterium abscessus extracellular vesicles increase mycobacterial resistance to clarithromycin in vitro.

Nontuberculous Mycobacteria (NTM) are a group of emerging bacterial pathogens that have been identified in cystic fibrosis (CF) patients with microbial lung infections. The treatment of NTM infection in CF patients is challenging due to the natural resistance of NTM species to many antibiotics. Mycobacterium abscessus is one of the most common NTM species found in the airways of CF patients. In this study, we characterized the extracellular vesicles (EVs) released by drug-sensitive M. abscessus untreated or treated with clarithromycin (CLR), one of the frontline anti-NTM drugs. Our data show that exposure to CLR increases mycobacterial protein trafficking into EVs as well as the secretion of EVs in culture. Additionally, EVs released by CLR-treated M. abscessus increase M. abscessus resistance to CLR when compared to EVs from untreated M. abscessus. Proteomic analysis further indicates that EVs released by CLR-treated M. abscessus carry an increased level of 50S ribosomal subunits, the target of CLR. Taken together, our results suggest that EVs play an important role in M. abscessus resistance to CLR treatment.

Investigating the effects of zinc oxide and titanium dioxide nanoparticles on the formation of biofilm and persister cells in Klebsiella pneumoniae.

The biofilm formation in klebsiella pneumoniae isolates poses a significant problem as it can result in treatment failure and the development of chronic infections. These biofilms act as protective barriers, rendering the bacteria resistant to antibiotics. Additionally, persister cells, which make up a small fraction of the bacterial population, have the ability to enter a dormant state after treatment with high doses of antibiotics. These persister cells play a crucial role in the high level of biofilm-mediated tolerance to antibiotics. The present study aimed to investigate the impact of Zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles on the formation of biofilm and persister cells in K. pneumoniae. The minimum inhibitory concentration (MIC) of colistin in K. pneumoniae ATCC 13883 was determined using the microdilution method. The formation of persister cells was evaluated by introducing sub-MIC of colistin. Subsequently, the MIC of ZnO NPs and TiO2 NPs in these persister cells was assessed using the microdilution method. Furthermore, the effects of nanoparticles on the expression levels of biofilm-associated genes were analyzed using real-time polymer chain reaction (PCR). The MIC values for colistin, ZnO, and TiO2 were determined at 2, 12.5, and 6.25 µg/mL, respectively. In the presence of nanoparticles, biofilm formation decreased. Real-time PCR results showed the messenger RNA (mRNA) level of mrkH and fimH were decreased and the expression of luxS and mazF were increased. Biofilm formation of K. pneumoniae ATCC 1383 was inhibited in response to nanoparticles. According to the results of the present study use of nanoparticles may help control multidrug-resistant (MDR) infections in hospitalized patients.