Multidrug-resistant Bacterial Pathogens Research Articles

Metabolomics-guided identification of compounds with antibacterial and antioxidant activities from Polygonatum sibiricum-derived endophytic fungi

BackgroundInfections caused by multidrug resistant bacterial pathogens have been recognized as major global healthcare threat to medicinal, agricultural and pharmaceutical industries by World Health Organization. In this regard, the present study was aimed to isolate endophytes from medicinal plant Polygonatum sibiricum (P. sibiricum) and to investigate their antibacterial efficacy, radical scavenging ability and chemical fingerprinting using Gas Chromatography–Mass Spectrum (GC–MS) analysis.ResultsTwo endophytic fungi Talaromyces assiutensis HJ.14 (T. assiutensis) and Fusarium oxysporum HJ.15 (F. oxysporum) were isolated and identified from the rhizomes of P. sibiricum. Among the extracts screened, ethyl acetate extract of F. oxysporum HJ.15 showed maximum antibacterial activity with the zones of inhibition ranging from 10.98 ± 0.19 to 15.66 ± 1.49 mm and the MIC values ranging from 0.24 to 1.88 µg/mL against the tested bacterial pathogens. In addition, it showed significant antioxidant activity with EC50 values of 6.21–17.97 µg/mL. Further, GC–MS analysis revealed the presence of propanoic acid ethyl ester, hexadecanoic acid methyl ester, hexadecanoic acid ethyl ester, 9-Octadecenoic acid (Z)-methyl ester, 1-Octanol, 2-Undecenal, butanoic acid, 3-hydroxy- and hexanoic acid were the most abundant compounds in the active crude extract which was responsible for the significant antibacterial and antioxidant properties.ConclusionsIn summary, our results clearly suggest that the F. oxysporum HJ.15 will be a promising starting point for the isolation of active antibacterial compounds with antioxidant properties.

Mechanistic insights of Euphorbia milii des moul mediated biocompatible and non-cytotoxic, antimicrobial nanoparticles: an answer to multidrug resistant bacteria.

The emergence of drug-resistant microbial pathogens is a matter of global concern and become more serious if they linked with healthcare-associated infections (HAIs). As per World Health Organization statistics, multidrug-resistant (MDR) bacterial pathogens account for between 7 and 12%of the worldwide burden of HAIs. The need for an effective and environmentally sustainable response to this situation is urgent. The primary goal of this study was to create copper nanoparticles that are biocompatible and non-toxic by using an extract of Euphorbia des moul, and then to test these nanoparticles' bactericidal efficacy against MDR strains of Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, and Acinetobacter baumannii. UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy techniqueswere used to characterize the biogenic G-CuNPs. It was found thatG-CuNPs were spherical inshape,with an average diameter of ~ 40nm and a charge density of - 21.52mV. The G-CuNPsfully eradicated the MDR strains at a dosage of 2mg/ml with 3h of incubation time. Mechanistic analysisshowed that theG-CuNPs efficiently disrupted the cell membrane and damaged the DNA and by generating more reactive oxygen species. Moreover, cytotoxic examination revealedthat G-CuNPs displayed < 5% toxicity at 2mg/ml concentration on human RBCs, PBMCs, and A549 cell lines, suggesting that they are biocompatible. This nano-bioagent is an eco-friendly, non-cytotoxic, non-hemolytic organometallic copper nanoparticles (G-CuNPs) with a high therapeutic index for possible use in the prevention of biomedical device-borne infections by preparing an antibacterial layer on indwellingmedical devices. However, its potential clinical use has to be further studied through in vivo testing with an animal model.

The LiaFSR-LiaX System Mediates Resistance of Enterococcus faecium to Peptide Antibiotics and to Aureocin A53- and Enterocin L50-Like Bacteriocins.

Multidrug-resistant Enterococcus faecium strains are currently a leading cause of difficult-to-treat nosocomial infections. The emerging resistance of enterococci to last-resort antibiotics, such as daptomycin, prompts a search for alternative antimicrobials. Aureocin A53- and enterocin L50-like bacteriocins are potent antimicrobial agents that form daptomycin-like cationic complexes and have a similar cell envelope-targeting mechanism of action, suggesting their potential as next-generation antibiotics. However, to ensure their safe use, the mechanisms of resistance to these bacteriocins and cross-resistance to antibiotics need to be well understood. Here, we investigated the genetic basis of E. faecium's resistance to aureocin A53- and enterocin L50-like bacteriocins and compared it with that to antibiotics. First, we selected spontaneous mutants resistant to the bacteriocin BHT-B and identified adaptive mutations in the liaFSR-liaX genes encoding the LiaFSR stress response regulatory system and the daptomycin-sensing protein LiaX, respectively. We then demonstrated that a gain-of-function mutation in liaR increases the expression of liaFSR, liaXYZ, cell wall remodeling-associated genes, and hypothetical genes involved in protection against various antimicrobials. Finally, we showed that adaptive mutations or overexpression of liaSR or liaR alone results in cross-resistance to other aureocin A53- and enterocin L50-like bacteriocins, as well as antibiotics targeting specific components of the cell envelope (daptomycin, ramoplanin, gramicidin) or ribosomes (kanamycin and gentamicin). Based on the obtained results, we concluded that activation of the LiaFSR-mediated stress response confers resistance to peptide antibiotics and bacteriocins via a cascade of reactions, eventually leading to cell envelope remodeling. IMPORTANCE Pathogenic enterococci carry virulence factors and a considerable resistome, which makes them one of the most serious and steadily increasing causes of hospital epidemiological risks. Accordingly, Enterococcus faecium is classified into a top-priority ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group of six highly virulent and multidrug-resistant (MDR) bacterial pathogens for which novel antimicrobial agents need to be developed urgently. Alternative measures, such as the use of bacteriocins, separately or in combination with other antimicrobial agents (e.g., antibiotics), could be a potential solution, especially since several international health agencies recommend and support the development of such interventions. Nevertheless, in order to exploit their efficacy, more basic research on the mechanisms of cell killing and the development of resistance to bacteriocins is needed. The present study fills some of the knowledge gaps regarding the genetic basis of the development of resistance to potent antienterococcal bacteriocins, pointing out the common and divergent features regarding the cross-resistance to antibiotics.

Isolation and Characterization of Multidrug Resistant Bacterial Pathogens Present in Hospital Environment within Awka Metropolis

The contamination of hospital environment by bacterial organisms plays a vital role in the spread of nosocomial infections. This study was conducted to determine bacterial contamination, bacterial profiles, antibiotic susceptibility pattern and plasmid profiles of bacterial isolates from hospital air, water and fomite environment within Awka. This cross-sectional study was conducted at Crest Specialist Hospital, Regina Caeli Specialist Hospital and Nnamdi Azikiwe University (UNIZIK) Medical Centre, Awka. Using random sampling techniques (surface, air and water), culturing, Gram staining, antibiotic susceptibility test, biochemical tests and molecular identification, bacterial organisms from surrounding air, water and fomites were isolated and identified. A total of 112 samples were collected from the three hospitals. Of all the samples, 110 (98.2%) showed positive for bacterial growth. A total of 40 bacterial isolates underwent antibiotic sensitivity testing, of which 6 (15%) showed multidrug resistance. Bacterial organisms isolated from Regina Caeli Hospital showed the most resistance to the antibiotic drugs (41.8%), followed by Crest Specialist Hospital (30.9%) and then UNIZIK Medical Centre (27.3%). Interestingly, there was 100% sensitivity of isolates to ciprofloxacin, levofloxacin, ofloxacin, augmentin (amoxicillinclavulanate), rifampicin and septrin. Out of the six multidrug resistant isolates, Staphylococcus hominis strain PCP01, Myroides odoratimimus subsp. xuanwuensis strain M2S3B6 and Bacillus cereus strain DS-2 were identified using DNA sequencing and PCR. The three identified microorganisms are opportunistic pathogens. While S. hominis has no plasmid, both M. odoratimimus and B. cereus showed the presence of plasmids. With proper prevention practices such as; disinfection of hospital surfaces, proper personal hygiene of health care workers, special air handling and ventilation and wearing of facemask within the hospital environment, possibilities of nosocomial infections can be reduced drastically, especially in Africa. Keywords: Isolation, Characterization, Multidrug Resistant and Bacterial

Enhanced antibacterial activity of green ZnO NPs against multi-drug resistant bacterial pathogens from diabetic foot ulcer using Aristolochia indica

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Essential oil and phytoconstituent (Linalool) from Homalomena aromatica Schott. rhizomes exhibit antibacterial and synergistic effects with beta-lactam antibiotics against Carbapenem-resistant Enterobacteriaceae (CRE) and Methicillin Resistant S. aureus (MRSA) pathogens

Homalomena aromatica Schott. (HA) locally known as “Sugandhmantri” in India is a perennial herb commonly found in Assam, Northeast India and popular for its aromatic and medicinal properties. The main aim of this study was to determine the phytoconstituents of the essential oil (HA-EO) extracted from the rhizomes of Homalomena aromatica, purify its major phytoconstituent (HA-EOC-L) and examine the antibacterial activity. Further the study investigated the synergistic effect of both HA-EO and HA-EOC-L with beta lactam antibiotics against a panel of multi drug resistant (MDR) bacterial pathogens comprising CRE (Carbapenem resistant Enterobacteriaceae namely Escherichia coli & Klebsiella pneumonia genetically harboring NDM/OXA enzymes that deactivates major β-lactam antibiotics including carbapenem) and MRSA (Methicillin Resistant Staphylococcus aureus harboring mecA gene that encodes PBP2a protein and attributes to antibiotic resistance). Gas chromatography – Mass spectrometry (GC-MS) analyses of HA-EO displayed a total of 177 phytoconstituents with Linalool (mono-terpene alcohol) (38.6 %), terpinen-4-ol (9.5 %), gamma terpinene, and gamma muurolene (3.6 %) as the major class. The major phytoconstituent (Linalool) HA-EOC-L of this lot was purified by fractional distillation. In vitro investigation of the antibacterial activity of HA-EO and HA-EOC-L demonstrated its potential antibacterial activity with MIC 134–1075 µg/ml and 75–606 µg/ml against MDR bacteria (CRE & MRSA) respectively. Further, testing the combinatorial activity of HA-EO and HA-EOC-L with β-lactam antibiotics [(ceftriaxone-CRO (third generation cephalosporin) and meropenem-MEP (carbapenem)], by checkerboard test and time kill assay, demonstrated its synergistic effect towards MDR bacteria with HA-EOC-L showing better adjuvant activity with fractional inhibitory concentration index values (FICI) ranging from 0.13 to 0.49. The results emphasize the significant use of HA-EO and its constituent (HA-EOC-L) as an antibiotic-adjuvant agent to combat MDR infections propounded by the MRSA and CRE indicating HA with its beneficial secondary metabolites as a useful plant that can help human health, animal health besides food and cosmetic industry to combat MDR pathogens.

Antibiotic synergist OM19r reverses aminoglycoside resistance in multidrug-resistant Escherichia coli.

The continued emergence and spread of multidrug-resistant (MDR) bacterial pathogens require a new strategy to improve the efficacy of existing antibiotics. Proline-rich antimicrobial peptides (PrAMPs) could also be used as antibacterial synergists due to their unique mechanism of action. Utilizing a series of experiments on membrane permeability, In vitro protein synthesis, In vitro transcription and mRNA translation, to further elucidate the synergistic mechanism of OM19r combined with gentamicin. A proline-rich antimicrobial peptide OM19r was identified in this study and its efficacy against Escherichia coli B2 (E. coli B2) was evaluated on multiple aspects. OM19r increased antibacterial activity of gentamicin against multidrug-resistance E. coli B2 by 64 folds, when used in combination with aminoglycoside antibiotics. Mechanistically, OM19r induced change of inner membrane permeability and inhibited translational elongation of protein synthesis by entering to E. coli B2 via intimal transporter SbmA. OM19r also facilitated the accumulation of intracellular reactive oxygen species (ROS). In animal models, OM19r significantly improved the efficacy of gentamicin against E. coli B2. Our study reveals that OM19r combined with GEN had a strong synergistic inhibitory effect against multi-drug resistant E. coli B2. OM19r and GEN inhibited translation elongation and initiation, respectively, and ultimately affected the normal protein synthesis of bacteria. These findings provide a potential therapeutic option against multidrug-resistant E. coli.

Rosmarinus officinalis essential oils’ eradication of beta-lactamase and multidrug resistant clinical bacterial pathogens from hospital settings

Antibiotics have become increasingly ineffective in the face of bacterial resistance, particularly in hospitals. Interestingly, there is high demand for bioprospecting of secondary metabolites, particularly for treating multidrug-resistant clinical diseases. In fact, Rosemary has been used for its antiseptic properties dating back to antiquity. The aim of this research is to evaluate the effectiveness of Rosmarinus officinalis essential oil against multidrug-resistant clinical bacterial pathogens. Results showed promising antibacterial activity against seven bacteria: Escherichia coli, Enterobacter cloacae, Staphylococcus aureus, Serratia odorifera, Klebsiella pneumoniae, Klebsiella oxytoca, Aeromonas hydrophila with MIC values of 35.7, 17.85, 71.4, 8.9, 17.8, 285.7, 35.7 µg/ml respectively and MBC values of 142.8, 71.4, 285.7, 35.7, 71.4, 571.5,71.4 µg/ml respectively. This study suggests that Rosmarinus essential oil can be used as a therapeutic agent in the fight against a wide range of multi-resistant bacteria.

Comparison of myconanoparticles and myconanoemulsion incorporated biomaterials in controlling multidrug-resistant bacterial pathogens

Green nanotechnology plays a significant role in many domains, from medicine to agriculture. Antibiotic resistance has emerged in organisms because of the continuous and indiscriminate application of various antibiotics. MDR (Multi drug resistant) bacteria, including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus were found to be resistant to beta- lactam antibiotics. In this study, the aqueous extract of Colletotrichum siamense was used to engineer nanoparticles (CsNps) and tea tree oil-based nanoemulsion (CsNe). Engineered CsNps and CsNe were subjected to biophysical characterization by using UV visible spectroscopy, FESEM, EDAX, FT-IR, HRTEM, SAED, and zeta potential to determine the charge, size, stability, elemental composition, topography, etc., The CsNps and CsNe were screened to detect antimicrobial activity by the zone of inhibition, MIC, MBC, and biofilm inhibition to its test potential against pathogenic E. coli, K. pnuemoniae, A. baumannii, and S. aureus. In silico studies were performed to study the binding affinity of the virulence proteins of MDR pathogens with secondary metabolites of Colletotrichum siamense. The results of both in vitro and in-silico studies of nanoparticles and nano-emulsion were observed to be more promising than beta-lactam antibiotics. Hence, in near future, these endophytic fungi, C. siamense mediated nanoparticles (CsNps) and nanoemulsion (CsNe) can be employed to develop an alternative to beta lactam antibiotics against the MDR pathogens.

Prevalence and Detection of Multidrug Resistance Bacterial Strains Isolated from the Different Inanimate Surfaces of the Hospital Environment

Nosocomial infections or Hospital-acquired infections (HAI) influence the clinical outcomes in hospital in-patients and indicate a serious global concern in medicine. Fomites of hospital environments carry a deadly pathogen and transmit infectious diseases. The emergence of antimicrobial resistance (AMR) in the hospital environment has increased due to misuse and/or overuse of antibiotics. The present study was aimed to evidence the MDR bacterial pathogens from the fomites of the hospital environment. The study was conducted in Acute care hospital, in Cuddalore district, Tamil Nadu, India. Totally 65 samples were collected from the different areas of the hospital including Operation Theatre (OT), Orthopaedics Surgery (OS), Wound and emergency Unit (WEU), Intensive care unit (ICU), Dialysis Unit (DU), Special Ward (SW) from March 2022 to September 2022 and the samples were processed for the isolation of bacteria using Nutrient agar, Macconkey agar and Blood agar. Totally 84 isolates were identified in that 48 and 36 isolates were gram positive and gram-negative respectively. Bacillus spp, Staphylococcus aureus, Streptococcus spp, Micrococcus spp, E. coli, Salmonella spp and the proteus spp. were the common isolates of this study and most of them showed multidrug resistance. In gram-positive isolates Bacillus spp. (22%) was dominant followed by Staphylococcus aureus (21%) and in gram-negative bacterial isolates Salmonella spp. (17%) were dominant followed by E.coli (16%). Among the bacterial isolates, 18% showed multidrug resistance (MDR) followed by 3% and 2% of XDR and PDR respectively. All the studied surfaces of the hospital carried minimum bacterial contamination. So more hygienic practices and effective disinfection practices should be implemented in the studied hospital to prevent the spread of nosocomial infections.

Facile preparation and antibacterial activity of zinc oxide nanobullets

Bacterial infections and emergence of many multidrug resistant bacterial pathogens are serious threats to human health. Nanostructured metal oxides are now used as antibacterial additives in various products of everyday usage, but their mode of antibacterial action still remains unclear. ZnO nanobullets were synthesized using a surfactant-free and template-free simple chemical route and well characterized by using FESEM, TEM, HRTEM, XRD, Raman and UV-vis spectroscopy. FESEM and TEM revealed bullet-shaped ZnO nanostructures with average size 50 nm. XRD analysis confirmed hexagonal wurtzite structure of ZnO nanobullets with crystallite size of 24 nm. We explored the antibacterial effects of ZnO nanobullets on gram-negative (Escherichia coli) and gram-positive (Bacillus oceanisediminis), and investigated the underlying mechanism using morphological analysis by SEM, ROS scavenging by histidine, thiobarbituric acid reactive species (TBARS) assay, analysis of potassium ion leakage and Bradford assay. Our results demonstrated that ZnO nanobullets efficiently inhibited the growth of both Escherichia coli and Bacillus oceanisediminis bacteria. Furthermore, various biochemical and molecular assays have provided evidence that the strong antibacterial action of ZnO nanobullets can be attributed to ROS induced oxidative stress resulting in enhanced lipid peroxidation and cell membrane damage, which subsequently caused protein leakage. In summary, our results show that ZnO nanobullets exhibit a strong antibacterial activity against both Escherichia coli and Bacillus oceanisediminis under ambient lighting, which is exciting for practical applications.

Structural and Antibacterial Characterization of a New Benzamide FtsZ Inhibitor with Superior Bactericidal Activity and In Vivo Efficacy Against Multidrug-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant (MDR) bacterial pathogen of acute clinical significance. Resistance to current standard-of-care antibiotics, such as vancomycin and linezolid, among nosocomial and community-acquired MRSA clinical isolates is on the rise. This threat to global public health highlights the need to develop new antibiotics for the treatment of MRSA infections. Here, we describe a new benzamide FtsZ inhibitor (TXH9179) with superior antistaphylococcal activity relative to earlier-generation benzamides like PC190723 and TXA707. TXH9179 was found to be 4-fold more potent than TXA707 against a library of 55 methicillin-sensitive S. aureus (MSSA) and MRSA clinical isolates, including MRSA isolates resistant to vancomycin and linezolid. TXH9179 was also associated with a lower frequency of resistance relative to TXA707 in all but one of the MSSA and MRSA isolates examined, with the observed resistance being due to mutations in the ftsZ gene. TXH9179 induced changes in MRSA cell morphology, cell division, and FtsZ localization are fully consistent with its actions as a FtsZ inhibitor. Crystallographic studies demonstrate the direct interaction of TXH9179 with S. aureus FtsZ (SaFtsZ), while delineating the key molecular contacts that drive complex formation. TXH9179 was not associated with any mammalian cytotoxicity, even at a concentration 10-fold greater than that producing antistaphylococcal activity. In serum, the carboxamide prodrug of TXH9179 (TXH1033) is rapidly hydrolyzed to TXH9179 by serum acetylcholinesterases. Significantly, both intravenously and orally administered TXH1033 exhibited enhanced in vivo efficacy relative to the carboxamide prodrug of TXA707 (TXA709) in treating a mouse model of systemic (peritonitis) MRSA infection. Viewed as a whole, our results highlight TXH9179 as a promising new benzamide FtsZ inhibitor worthy of further development.

Interconnections of Pseudomonas aeruginosa Quorum-Sensing Systems in Intestinal Permeability and Inflammation.

Quorum sensing (QS) is a highly conserved microbial communication mechanism based on the production and sensing of secreted signaling molecules. The recalcitrant pathogen Pseudomonas aeruginosa is a problematic nosocomial pathogen with complex interconnected QS systems controlling multiple virulence functions. The relevance of QS in P. aeruginosa pathogenesis is well established; however, the regulatory interrelationships of the three major QS systems, LasR/LasI, MvfR (PqsR)/PqsABCD, and RhlR/RhlI, have been studied primarily in vitro. It is, therefore, unclear how these relationships translate to the host environment during infection. Here, we use a collection of P. aeruginosa QS mutants of the three major QS systems to assess the interconnections and contributions in intestinal inflammation and barrier function in vivo. This work reveals that MvfR, not LasR or RhlR, promotes intestinal inflammation during infection. In contrast, we find that P. aeruginosa-driven murine intestinal permeability is controlled by an interconnected QS network involving all three regulators, with MvfR situated upstream of LasR and RhlR. This study demonstrates the importance of understanding the interrelationships of the QS systems during infection and provides critical insights for developing successful antivirulence strategies. Moreover, this work provides a framework to interrogate QS systems in physiologically relevant settings. IMPORTANCE Pseudomonas aeruginosa is a common multidrug-resistant bacterial pathogen that seriously threatens critically ill and immunocompromised patients. Intestinal colonization by this pathogen is associated with elevated mortality rates. Disrupting bacterial communication is a desirable anti-infective approach since these systems coordinate multiple acute and chronic virulence functions in P. aeruginosa. Here, we investigate the role of each of the three major communication systems in the host intestinal functions. This work reveals that P. aeruginosa influences intestinal inflammation and permeability through distinct mechanisms.

Silver Nanoparticles: Bactericidal and Mechanistic Approach against Drug Resistant Pathogens.

This review highlights the different modes of synthesizing silver nanoparticles (AgNPs) from their elemental state to particle format and their mechanism of action against multidrug-resistant and biofilm-forming bacterial pathogens. Various studies have demonstrated that the AgNPs cause oxidative stress, protein dysfunction, membrane disruption, and DNA damage in bacteria, ultimately leading to bacterial death. AgNPs have also been found to alter the adhesion of bacterial cells to prevent biofilm formation. The benefits of using AgNPs in medicine are, to some extent, counter-weighted by their toxic effect on humans and the environment. In this review, we have compiled recent studies demonstrating the antibacterial activity of AgNPs, and we are discussing the known mechanisms of action of AgNPs against bacterial pathogens. Ongoing clinical trials involving AgNPs are briefly presented. A particular focus is placed on the mechanism of interaction of AgNPs with bacterial biofilms, which are a significant pathogenicity determinant. A brief overview of the use of AgNPs in other medical applications (e.g., diagnostics, promotion of wound healing) and the non-medical sectors is presented. Finally, current drawbacks and limitations of AgNPs use in medicine are discussed, and perspectives for the improved future use of functionalized AgNPs in medical applications are presented.

Repetitive Exposure to Bacteriophage Cocktails against Pseudomonas aeruginosa or Escherichia coli Provokes Marginal Humoral Immunity in Naïve Mice.

Phage therapy of ventilator-associated pneumonia (VAP) is of great interest due to the rising incidence of multidrug-resistant bacterial pathogens. However, natural or therapy-induced immunity against therapeutic phages remains a potential concern. In this study, we investigated the innate and adaptive immune responses to two different phage cocktails targeting either Pseudomonas aeruginosa or Escherichia coli-two VAP-associated pathogens-in naïve mice without the confounding effects of a bacterial infection. Active or UV-inactivated phage cocktails or buffers were injected intraperitoneally daily for 7 days in C57BL/6J wild-type mice. Blood cell analysis, flow cytometry analysis, assessment of phage distribution and histopathological analysis of spleens were performed at 6 h, 10 days and 21 days after treatment start. Phages reached the lungs and although the phage cocktails were slightly immunogenic, phage injections were well tolerated without obvious adverse effects. No signs of activation of innate or adaptive immune cells were observed; however, both active phage cocktails elicited a minimal humoral response with secretion of phage-specific antibodies. Our findings show that even repetitive injections lead only to a minimal innate and adaptive immune response in naïve mice and suggest that systemic phage treatment is thus potentially suitable for treating bacterial lung infections.

Global Transmission of the penA Allele 60.001–Containing High-Level Ceftriaxone-Resistant Gonococcal FC428 Clone and Antimicrobial Therapy of Associated Cases: A Review

Abstract Neisseria gonorrhoeae is a multidrug-resistant bacterial pathogen for which ceftriaxone is the only remaining recommended first-line therapy. However, ceftriaxone susceptibility has been waning in a number of countries over the last decade and ceftriaxone treatment failures have been reported, commonly as a result of sporadic high-level ceftriaxone-resistant strains. In recent years, N. gonorrhoeae strains associated with the high-level ceftriaxone-resistant FC428 clone or strains that acquired its main ceftriaxone resistance determinant, penA allele 60.001, have shown global transmission, resulting in ceftriaxone treatment failure in a number of cases. The FC428 clone was first encountered in Japan in 2015 and subsequently in China, Europe, Australia, North America and Southeast Asia afterward. Strains associated with the FC428 clone commonly display a ceftriaxone minimum inhibitory concentration of 0.5–1 mg/L. However, where penA alleles encountered in sporadic high-level ceftriaxone-resistant isolates induce an in vitro growth defect, penA allele 60.001 does not seem to affect in vitro growth. The limited impact of penA allele 60.001 on biological fitness might be associated with its successful global transmission. Although the FC428 clone displays high-level ceftriaxone resistance, most gonorrhea cases associated with this clone were still successfully cured with ceftriaxone when intramuscular or intravenous doses of 500 mg to 2 g were used. A successful alternative therapy seems to be ertapenem given at 1-g doses, although further clinical studies are required to validate ertapenem efficacy. This review summarizes the global transmission of strains associated with the FC428 clone and antimicrobial treatment of associated cases.

Synthetic peptides that form nanostructured micelles have potent antibiotic and antibiofilm activity against polymicrobial infections.

The emergence of multidrug-resistant bacterial pathogens is a growing threat to global public health. Here, we report the development and characterization of a panel of nine-amino acid residue synthetic peptides that display potent antibacterial activity and the ability to disrupt preestablished microbial biofilms. The lead peptide (Peptide K6) showed bactericidal activity against Pseudomonas aeruginosa and Staphylococcus aureus in culture and in monocultures and mixed biofilms in vitro. Biophysical analysis revealed that Peptide K6 self-assembled into nanostructured micelles that correlated with its strong antibiofilm activity. When surface displayed on the outer membrane protein LamB, two copies of the Peptide K6 were highly bactericidal to Escherichia coli. Peptide K6 rapidly increased the permeability of bacterial cells, and resistance to this toxic peptide occurred less quickly than that to the potent antibiotic gentamicin. Furthermore, we found that Peptide K6 was safe and effective in clearing mixed P. aeruginosa-S. aureus biofilms in a mouse model of persistent infection. Taken together, the properties of Peptide K6 suggest that it is a promising antibiotic candidate and that design of additional short peptides that form micelles represents a worthwhile approach for the development of antimicrobial agents.

Hybrid nanoparticles of tetraamino fullerene and benzothiadiazole fluorophore as efficient photosensitizers against multidrug-resistant bacteria

Antimicrobial photodynamic therapy has emerged as an innovative and promising alternative treatment for mitigating the prevalence of multidrug-resistant bacterial pathogens. Herein, a facile approach for the construction of stable hybrid nanoparticles based on the non-covalent conjugation of tetraamino fullerene with benzothiadiazole fluorophore is reported. Various characterization techniques were employed to verify the biocompatibility, structural, photophysical and photochemical properties of the as-synthesized hybrid nanoparticles. Such confined nanocompartment favored efficient energy or electron transfer between the fullerene and fluorophore, thus leading to 80.8 % fluorescence quenching and enhanced photodynamic therapy (PDT) efficiency. Compared with the individual fullerene, the resulting compact nanoparticles in water not only generated more hydroxyl radicals, but also exclusively produced a large amount of singlet oxygen, thereby creating an 18-fold increase in reactive oxygen species (ROS) yield. Therefore, 20 μg/mL of positively charged hybrid nanoparticles could selectively eliminate 99.9 % of methicillin-resistant Staphylococcus aureus (MRSA) and greatly inhibit their biofilm formation after merely 10 min of visible light exposure. These results offer new insights and strategies for the design of novel photosensitizers composed of fullerenes and light-harvesting dyes against multidrug-resistant bacterial and associated infections.

Identification and Characterization of Klebsiella pneumoniae from Farmed American Bullfrogs (Rana catesbeiana).

Klebsiella pneumoniae is a major cause of nosocomial infection and is considered a clinically important bacterium with antibiotic-resistant strains. There are few reports of K. pneumoniae infections in cultured aquatic animals, and no natural infection has been reported in amphibians. From September to October 2021, a high-mortality disease outbreak occurred in a pond-raised American bullfrog farm in Guangzhou, China. The infected bullfrogs were characterized by multiple organ congestive enlargement and inflammation. A pathogenic bacterium was isolated from the viscera of infected bullfrogs and confirmed to be K. pneumoniae by morphological, biochemical, and phylogenetic analyses. Infection experiments confirmed the virulence of the pathogenic strain against bullfrogs and tadpoles. A histopathological examination showed that the strain was harmful to multiple organs. Antibiotic resistance experiments indicated the isolate was a carbapenemase-producing multidrug-resistant K. pneumoniae (MDR-KP) strain. This study is the first report of K. pneumoniae infected American bullfrogs (Rana catesbeiana) and amphibians. These results will shed light on the pathogenicity of K. pneumoniae and help prevent and control K. pneumoniae infections in bullfrogs. IMPORTANCE Klebsiella pneumoniae is recognized as the most common multidrug-resistant bacterial pathogen in humans, and little is known about its pathogenicity in aquatic animals. Recently, K. pneumoniae was found to cause substantial mortality and morbidity in American farm frogs. This was the first report of K. pneumoniae infecting amphibians. In this study, we analyzed the biochemical, growth, and phylogenetic characteristics of the K. pneumoniae strain and described the symptoms and pathological features of infected bullfrogs and tadpoles; this will provide useful data for the prevention and control of infectious diseases, which has been suggested to decrease economic losses in bullfrog farming and reduce the potential threat to public health posed by K. pneumoniae.

Design, synthesis and evaluation of halogenated phenazine antibacterial prodrugs targeting nitroreductase enzymes for activation.

It is of great importance to develop new strategies to combat antibiotic resistance. Our lab has discovered halogenated phenazine (HP) analogues that are highly active against multidrug-resistant bacterial pathogens. Here, we report the design, synthesis, and study of a new series of nitroarene-based HP prodrugs that leverage intracellular nitroreductase (NTR) enzymes for activation and subsequent release of active HP agents. Our goals of developing HP prodrugs are to (1) mitigate off-target metal chelation (potential toxicity), (2) possess motifs to facilitate intracellular, bacterial-specific HP release, (3) improve water solubility, and (4) prevent undesirable metabolism (e.g., glucuronidation of HP's phenol). Following the synthesis of HP-nitroarene prodrugs bearing a sulfonate ester linker, NTR-promoted release experiments demonstrated prodrug HP-1-N released 70.1% of parent HP-1 after 16 hours (with only 6.8% HP-1 release without NTR). In analogous in vitro experiments, no HP release was observed for control sulfonate ester compounds lacking the critical nitro group. When compared to parent HP compounds, nitroarene prodrugs evaluated during these studies demonstrate similar antibacterial activities in MIC and zone of inhibition assays (against lab strains and clinical isolates). In conclusion, HP-nitroarene prodrugs could provide a future avenue to develop potent agents that target antibiotic resistant bacteria.