The escalating challenge of antibiotic resistance underscores the urgent need to develop novel antimicrobial agents with innovative mechanisms of action. This study investigates the potential of quinoline derivatives as inhibitors of two critical microbial targets: DNA gyrase (PDB ID: 2XCT) and dihydropteroate synthase (PDB ID: 5U10). A library of 22 quinoline-based compounds was subjected to molecular docking to assess their binding affinities and interactions with these essential enzymes.

CMPD1 and CMPD2 emerged as promising candidates. CMPD1 exhibited a binding affinity of -9.3 kcal/mol with DNA gyrase, forming stabilizing hydrogen bonds with ARG 98 and ASP 85, while CMPD2 displayed a binding affinity of -8.8 kcal/mol with the same target. Against dihydropteroate synthase, CMPD1 and CMPD2 showed binding affinities of -9.0 kcal/mol and -8.5 kcal/mol, respectively, leveraging pi-pi stacking and hydrogen bonding interactions with critical active-site residues. The structure-activity relationship (SAR)-driven library design incorporated electron-donating (-OCH₃) and electron-withdrawing (-Cl) groups, strategically enhancing the binding specificity and affinity of these compounds.

In addition to docking, in silico ADMET profiling confirmed favorable pharmacokinetic properties for the lead compounds. CMPD1 demonstrated high gastrointestinal absorption and zero Lipinski’s rule violations, while CMPD2 demonstrated acceptable absorption with only one rule violation, highlighting their potential for oral bioavailability and safety.

These findings underscore the potential of quinoline scaffolds as novel agents to combat antibiotic resistance. This study highlights the utility of computational tools in identifying promising drug candidates, paving the way for experimental validation, and developing quinoline-based therapies to address the global antibiotic resistance crisis.

Introduction: The global increase in antibiotic-resistant bacteria, particularly multidrug-resistant strains, is diminishing antibiotic effectiveness. Livestock animals serve as reservoirs for these bacteria, threatening public health via the food chain and environmental contamination. Klebsiella pneumoniae is a significant pathogen, linked to fatal human infections, veterinary concerns, and multidrug resistance. This study aimed to phenotypically and genotypically characterize Klebsiella spp. isolated from fecal samples of four cattle breeds, Holstein–Friesian and three native Portuguese breeds—Barrosã, Cachena, and Minhota—in the Northern Region of Portugal.

Methods: A total of 640 fecal samples were collected from 40 farms, pooled by age group (8 calves and 8 cows per farm) and inoculated on MacConkey and HiCrome Klebsiella Selective agar. Klebsiella spp. isolates (43 out of 63) representing breeds/age groups were selected for antibiotic susceptibility testing (CLSI guidelines) and PCR assays for identification and detection of resistance genes.

Results: All 43 isolates were identified as Klebsiella pneumoniae and showed resistance to at least one antibiotic, with 100% of them being resistant to ampicillin. Barrosã and Cachena isolates displayed resistance only to ampicillin, while 17% (calves) and 13% (cows) of Minhota isolates demonstrated resistance to amoxicillin+clavulanic acid and tetracycline, respectively. Holstein-Friesian isolates exhibited resistance to multiple antibiotics, including amoxicillin+clavulanic acid (20%), cefotaxime (50%), aztreonam (30%), ciprofloxacin (20%), gentamicin (10%), tetracycline (80%), and trimethoprim+sulfamethoxazole (50%), all obtained from calves. Multidrug resistance was observed in 14% isolates, all from Holstein-Friesian cattle. ESBL activity was detected in 21% of the 43 K. pneumoniae isolates. From 42 tested isolates, the bla_SHV gene was detected in 67% of isolates, followed by sul2 (43%), aac(3′)-IV (43%), bla_TEM (33%), bla_CTX-M (14%), tetB (10%) and aac(6′)-Ib- cr (10%), with a higher prevalence in calves.

Conclusions: This work underscores, for the first time, the presence of multidrug-resistant K. pneumoniae in native Portuguese cattle breeds, highlighting potential risks to food safety and public health.

Acknowledgements: CoRECattle-GI2-CESPU-2022, EnteroGEN_GI2-CESPU_2023, FCT/MCTES-UIDB/50006/2020 and UIDP/50006/2020.

Background: Antibiotics have been known as "miracle drugs" for good reason, but due to their overuse, most antibiotic bacterial combinations now have higher frequencies of resistance. Plants have been discovered to be synergistic enhancers, meaning that they may not possess any antimicrobial qualities alone but can increase the effectiveness of conventional medications.

Methodology

Successive extraction with sonication-aided maceration was used to prepare ethyl acetate (EA), methanol (M), and aqueous (Aq) extracts of C. arvense, which were subjected to chromogenic assays for phytochemical evaluation and antioxidant activity. Antibacterial activity was determined using disc diffusion and microbroth dilution assays. Synergistic evaluation of the extracts and mechanistic insights were provided using the checkerboard method, time–kill kinetics, and protein estimation studies.

Results

The aqueous extract exhibited the highest percent recovery (7.33%), the highest total phenolic (16.95±0.16 µg GAE/mg of extract) and flavonoid contents (10.925±0.13 µg QE/mg of extract), and a notable antioxidant capacity (102.86±0.01 µg AAE/mg of extract) and reducing power (121.5±0.03 µg AAE/mg of extract) and significant radical scavenging activity (18.2±0.09%). The extracts showed noteworthy antibacterial activity (MIC = 500 μg/ml). The checkerboard method revealed total synergism, with 4- and 16-fold reductions in the MICs of the C. arvense extracts and cefixime, leading to a time-dependent reduction in bacterial growth. Together with the cell membrane damage brought on by cefixime, the synergistic combinations resulted in greater inhibition of bacterial proteins. Our findings suggest that the C. arvense aqueous extract showed the maximum synergistic activity and could be a potential candidate for the treatment challenges of global multidrug resistance.

Conclusion

This research highlights the promising antibacterial efficacy of C. arvense extracts, demonstrating their potential in combination with cefixime to inhibit bacterial growth. This study underscores the potential to integrate C. arvense extracts with conventional antibiotics, offering a novel approach to combating infectious diseases.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant challenge in managing acute wound infections due to its high resistance to conventional antibiotics. The persistence of these infections not only complicates treatment but also increases the likelihood of chronicity. This study investigates the potential of the blue-light photoactivated berberine-gentamicin (Ber-Gen) combination as a novel strategy to enhance bacterial inactivation and overcome antibiotic resistance in S. aureus.

Methods: A clinical strain of MRSA isolated from a diabetic foot ulcer was used. The antibacterial activity of Ber and Gen was screened individually and in combination. The photodynamic activity of the Ber was assessed using a light-emitting diode (LED) system with blue light (420 nm), at 30 mW/cm² (light doses of 9, 18, 27 J/cm²). The photodynamic activity of the Ber-Gen combination was evaluated after 6 h of incubation by the reduction of the culturability (colony forming units (CFU)/mL).

Results: Ber significantly enhanced Gen activity, exhibiting a potentiating effect against MRSA. Blue-light activation of Ber (420 nm, 18 J/cm²) reduced its bactericidal concentration by 80-fold. The photodynamic activation of the Ber-Gen combination (420 nm, 10 min, 18 J/cm²) resulted in a ≈9-log CFU/mL reduction in S. aureus culturability, with a 2048-fold decrease in the bactericidal concentration of Gen.

Conclusion: The dual approach of antimicrobial photodynamic inactivation combined with phytochemical-antibiotic combinations demonstrated a strong synergistic effect, effectively reducing S. aureus culturability and restoring the efficacy of Gen against MRSA. This approach shows promise as an innovative solution for managing antibiotic-resistant infections.

Background: Quorum sensing (QS) is a bacterial intercellular communication mechanism mediated by extracellular signalling molecules that regulate gene expression. The las system, consisting of LasI and LasR, is a fundamental QS component in Pseudomonas aeruginosa and plays a crucial role in the formation and maintenance of biofilms as well as in the regulation of virulence factors. Phenolic acids such as sinapic acid are plant secondary metabolites that exhibit antibacterial properties and low toxicity. The aim of this study was to evaluate the potential of sinapic acid as inhibitors of the las-QS system in P. aeruginosa, focussing on their effects on biofilm structure and virulence factor production.

Methods: The inhibitory effect of sinapic acid on the las system was evaluated using bioreporter strains and bioluminescence-based assays. The architecture of the biofilm was analysed using optical coherence tomography (OCT), while the production of virulence factors (pyoverdine, pyocyanin, total proteases, lipases, and gelatinases) and motility was analysed by absorbance measurement and plate agar method.

Results: Sinapic acid inhibited las QS activity by 90 % at a concentration of 1000 µg mL^-1. The production of N-3-oxododecanoyl-homoserine lactone, the autoinducer of the las system, was reduced by 60 % at a concentration of 6.25 µg mL^-1. This phenolic acid significantly disrupted the biofilm architecture and reduced the biofilm thickness from 25 µm to 14 µm. In addition, sinapic acid significantly reduced the production of important virulence factors and impaired bacterial swarming motility.

Conclusion: Sinapic acid demonstrated strong inhibitory effect on the las QS system, leading to a disruption of the biofilm structure and reduced virulence of P. aeruginosa. These findings support their potential as antipathogenic and antivirulence agents for the treatment of biofilm-associated infections.

Antibiotic-resistant pathogens, such as methicillin resistant Staphylococcus aureus (MRSA), pose significant challenges in managing chronic wound infections. Antibacterial photodynamic inactivation (aPDI) has emerged as an alternative to antibiotics by offering localized and resistance-independent bacterial elimination. Natural compounds with photosensitizing properties are particularly attractive due to their biocompatibility and sustainability. Therefore, this study investigates the potential of aPDI using riboflavin (RB), a vitamin and vital micronutrient commonly found in various animals and plants. RB is known to be a promising natural photosensitizer, capable of causing bacterial cell damage by reactive oxygen species (ROS) generation. Additionally, the potential synergistic combinations with the commonly used wound antiseptics, namely octenidine dihydrochloride (OCT) and polyhexamethylene biguanide (PHMB) against S. aureus clinical strain (MJMC568-B: MRSA) was assessed. The approach aimed to improve antiseptic effiency by reducing the necessary concentrations. The antibacterial efficacy of RB, OCT and PHMB were determined independently by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The photodynamic activity of RB was assessed by irradiating with blue light (420 nm) using a light-emitting diode (LED) system and quantification through colony-forming unit (CFU) analysis. An evaluation of the potential synergistic interactions of RB-mediated aPDI, with OCT and PHMB was conducted by a disk diffusion assay, and a checkerboard assay. The results highlight the potential of combining aPDI with antiseptics to achieve enhanced antibacterial effects against S. aureus. This dual approach could offer a promising solution for managing chronic wound infections, reducing the reliance on traditional antibiotics, and mitigating the risk of resistance development.

Acknowledgments: This work was supported by:Project InnovAntiBiofilm(ref. 101157363) financed by European Commission(Horizon-Widera 2023-Acess-02/Horizon-CSA); LEPABE, UIDB/00511/2020((DOI: 10.54499/UIDB/00511/2020)) and UIDP/00511/2020(DOI: 10.54499/UIDP/00511/2020); ALiCE, LA/P/0045/2020(DOI: 10.54499/LA/P/0045/2020); funded by national funds through the FCT/MCTES(PIDDAC; Lisbon, Portugal). Lília S. Teixeira acknowledges individual PhD fellowship from FCT(2023.04774.BDANA).

Introduction: Antimicrobial resistance is a critical concern, especially in immunocompromised cancer patients, where multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections limit treatment options. This study investigates the resistance profiles of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli isolated from cancer patients at a tertiary hospital.
Methods: Clinical isolates from urine, blood, and sputum samples were collected from a tertiary hospital in Abu Dhabi. Antibiotic susceptibility testing was conducted using the disc diffusion method according to CLSI guidelines. Isolates were classified as CRE, MDR, or XDR based on resistance profiles. Genomic DNA was extracted using the Promega Kit, and whole-genome sequencing was performed on the Illumina platform. Resistance genes were identified using ResFinder, and plasmid incompatibility types were determined with PlasmidFinder. The genetic context of resistance genes, including IS elements and transposons, was assessed using ISfinder. Data analysis focused on resistance profiles, plasmid types, and potential clonal transmission.
Results: A total of six P. aeruginosa, three K. pneumoniae, three E. coli, and additional isolates of Aeromonas dhakensis, Salmonella enterica, and Stenotrophomonas maltophilia were analyzed. P. aeruginosa isolates exhibited widespread resistance, including blaNDM-1 (carbapenem resistance), aph(3')-IIb (aminoglycoside resistance), and tet(A) (tetracycline resistance). K. pneumoniae isolates carried blaOXA-181 and blaCTX-M-15. E. coli strains harbored blaNDM-5 and blaCTX-M-15, along with aminoglycoside and fluoroquinolone resistance genes, with blaNDM-5 located on plasmids (MGEs) together with other resistance genes, facilitating their spread. Additional isolates included Aeromonas dhakensis from a leukemia patient, Salmonella enterica with IncFIB/IncFII plasmids from a breast cancer patient, and MDR Stenotrophomonas maltophilia from a cervical cancer patient.
Conclusion: This study highlights the prevalence of MDR and XDR pathogens in cancer patients and the significance of plasmid-mediated gene transfer in resistance. Improved infection control and novel therapeutic strategies are critical to addressing these complex resistance mechanisms.

A high-risk clone is defined as being globally distributed, associated with multiple antimicrobial resistance determinants, able to colonise and persist in the host, capable of effective transmission between hosts, has enhanced pathogenicity and fitness, and can cause severe and/or recurrent infections. Since 2024, third-generation cephalosporin-resistant (3GC-R) E. coli has been included in the critical group of the WHO Bacterial Priority Pathogens List. This study aimed to determine the presence of high-risk clones among the highest priority critically important antimicrobials (HPCIA)-resistant E. coli isolated from fresh pork meat from butcher shops in La Plata, Buenos Aires, Argentina. Whole genome sequencing was performed on 85 HPCIA-resistant E. coli isolates, obtained from 46 butcher shops in La Plata. Of these, 27 belonged to nine clones described as High Risk: ST101 (n=5), ST10 (n=4), ST48 (n=4), ST744 (n=4), ST23 (n=3), ST58 (n=2), ST88 (n=2), ST117 (n=2) and ST410 (n=1) and 12 of them were 3GC-R. Resistance was mediated by bla_CTX-M-55 (n=7), bla_CTX-M-14 (n=4) and bla_CMY-2 (n=1). E. coli harbouring bla_CTX-M-55 belonged to ST10, ST23, ST58, ST88 and ST117. These were also fosfomycin-resistant mediated by fosA3 (n=3) and fosL1 (n=2), and potentially ciprofloxacin-resistant by plasmid-mediated quinolone resistance genes qnrB19 and qnrS1 (n=4). E. coli harbouring bla_CTX-M-14 (n=4) belonged to ST23 and ST101 and were potentially ciprofloxacin-resistant due to qnrS1 carriage. E. coli harbouring bla_CMY-2 belonged to ST48, and all were fluoroquinolone-resistant, with one carrying qnrS1 (n=1). The detection of high-risk clones in food products underscores the risk of transmission and highlights the urgent need for control strategies to mitigate the spread of pathogens implicated in cross-contamination and food safety, highlighting the importance of implementing good manufacturing practices.

1. Introduction

• Background:
• Antimicrobial resistance (AMR) poses a significant global health threat, increasing morbidity, mortality, and healthcare costs.
• The WHO has recognized the urgency of this issue and emphasized the need for multi-sectoral collaboration to combat AMR.
• Significance:
• Antibiotic Stewardship Programs (ASPs) are crucial for mitigating AMR by optimizing antibiotic use, reducing unnecessary prescriptions, controlling infection spread, and improving patient outcomes.
• Effective ASPs can contribute to preserving the effectiveness of existing antibiotics for future generations.
• Research Question:
• What are the primary obstacles encountered in the successful implementation and long-term sustainability of ASPs within healthcare settings?
• 2. Methods

• Literature Review:
• A comprehensive literature review was conducted using major databases (PubMed, Scopus, Web of Science, Embase, and the Cochrane Library).
• Relevant articles were identified using a combination of relevant keywords.
• Data were systematically extracted from selected articles, including information on the types of challenges encountered, strategies to overcome these challenges, and the outcomes of implementation strategies.
• Data Analysis:
• Qualitative analysis was conducted to identify and categorize common themes and patterns in the challenges encountered during ASP implementation.
• If applicable, quantitative analysis was performed to further analyze and interpret the extracted data.
• 3. Results

• Key Challenges identified were as follows:
• Resource Limitations;
• Organizational Barriers;
• Patient-Related Factors;
• External Pressures.

Microbial systems play a crucial role in the synthesis of the chiral drugs and drug intermediates, contributing significantly to the pharmaceutical industry. Chirality refers to the existence of two non-superimposable mirror-image molecules (enantiomers), which can have vastly different biological activities. In many cases, one enantiomer may be therapeutically active, while the other could be ineffective or even harmful. Thus, the ability to produce chiral compounds with high specificity is essential in modern medicine. Functional microorganisms and enzyme (derived biocatalysts) have great potential in the biotransformation of synthetic chemicals in drugs with high enantiomeric, chemical and regional selectivity. The Chiral feature is an important factor in the efficacy and safety of many therapeutic drugs. Biocatalysis is becoming a major sub-component in the toolbox of medicinal chemistry. In fact, many intermediates of important therapeutic agents have been successfully synthesized by biocatalysis. Currently, about 57% of drugs on the market are chiral drugs, and about 99% of pure natural products are chiral compounds. Here, we have summarized various biocatalytic systems capable of synthesizing chiral drugs and intermediates and discussed their potential applications in the pharmaceutical industry. With the emphasis on green chemistry, the further development and use of biocatalysis in drug production is expected to increase.