László Orosz

Background/Objectives: Surveillance of local antibiotic resistance plays a critical role in guiding empirical antibiotic therapies in emergency departments (EDs). This study aimed to collect and analyze a five-year period of prevalence and AMR rates among “ESKAPE” pathogens in a tertiary-care ED setting. Methods: This retrospective observational study included a complete census of microbiological specimens collected from patients presenting to the emergency department between 1 January 2019 and 31 December 2023. Data was retrieved from the MedBakter laboratory information system. Non relevant isolated and duplications were excluded. Only the first isolates per patient per phenotype were included in the final dataset. Results: The final dataset contained 6510 isolates. The most frequent isolates were E. coli (2717, 41.7%), K. pneumoniae (715, 11.0%), and P. mirabilis (696, 10.7%) followed by E. faecalis (662, 10.2%). Prevalence of multi-drug resistance (MDR) was 23.26% among “ESKAPE” pathogens, with highest prevalence in M. morganii (79.6%), P. stuartii (78.5%) and S. marcescens (77.1%). Difficult-to-treat resistance (DTR) was found in 32 isolates, while extensive drug resistance (XDR) was found in 5 isolates. The prevalence of other high-priority MDR bacteria was 12.4% for MRSA and 4.7% for VRE, while among Gram-negative bacteria the prevalence of carbapenem-resistant Enterobacterales was 0.52%. The prevalence of cephalosporin-resistant Enterobacterales varied greatly between 0 and 33%. Conclusions: Despite these important AMR trends, the cumulative antibiogram, according to the World Health Organization (WHO)-issued Access, Watch and Reserve (AWaRe) classification, revealed room for empirical antibiotic choices that spare Watch and Reserve agents. The results will aid the revision of the local antibiotic guidelines.

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a major therapeutic challenge due to its extensive antibiotic resistance. This study examined how bacteriophage exposure affects the genome, proteome and antibiotic susceptibility of a clinical MRSA isolate. Methods: The MRSA isolate was exposed to the PYOFAG bacteriophage cocktail, and small colony variants (SCVs) of the surviving bacteria were compared with the untreated parental strain by phenotypic testing, whole-genome sequencing, comparative proteomics, and transmission electron microscopy. Results: Phage exposure induced marked remodeling in MRSA, including altered growth, colony morphology, and increased susceptibility to various antibiotics, especially β-lactams and aminoglycosides. Genomic analysis identified multiple mutations and the loss of two genomic regions, including changes in tarS, a gene linked to wall teichoic acid glycosylation, phage adsorption, and β-lactam resistance. Proteomic analysis revealed broad changes in metabolic, stress-response, and cell-envelope-associated pathways. Transmission electron microscopy showed a significant reduction in cell wall thickness after phage treatment. Conclusions: Bacteriophage exposure drives phenotypic and molecular adaptation in MRSA and may create evolutionary trade-offs that weaken resistance mechanisms. These findings support the potential of bacteriophages as both direct antibacterial agents and modulators of antibiotic susceptibility.

This retrospective study analysed 14,625 isolates of the six major hospital-associated ‘ESKAPE’ pathogens ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa , and Enterobacter spp.) collected between 2002 and 2024 in a Hungarian tertiary-care centre. Antimicrobial resistance was assessed using the antibiotic resistance index (ARI), multidrug resistance (MDR) ratios, and resistance instability index (RII). A. baumannii and E. faecium showed the highest resistance burdens and instability. Age showed a significant monotonic association with resistance (Spearman r = 0.88), with peaks in infants, middle-aged women, and the elderly. Species-specific age trends varied, with a negative correlation seen in Enterobacter spp. Hierarchical clustering grouped pathogens by resistance trajectory rather than taxonomy. Pairwise resistance distances confirmed divergence between Gram-positive and Gram-negative species. Resistance to aminoglycosides and sulphonamides showed the highest year-to-year variability, as quantified by the RII, particularly in A. baumannii and E. faecium. Vector autoregressive (VAR) modelling predicted continued MDR increases in these species. A strong correlation was found between ARI and RII (Pearson r = 0.85, p = 0.032). These findings underscore the importance of integrating resistance magnitude and volatility in surveillance.

Background/Objectives: Antimicrobial resistance (AMR) is an escalating global threat driven by antibiotic misuse and bacterial adaptation. Efflux pumps are major contributors to multidrug resistance in Escherichia coli, as they expel antibiotics and reduce their intracellular activity. This study examined efflux-mediated resistance in extended-spectrum beta-lactamase (ESBL)-producing E. coli and evaluated the potential of several efflux pump inhibitors (EPIs)—promethazine (PMZ), thioridazine (TZ), carbonyl cyanide m-chlorophenyl hydrazine (CCCP), reserpine (RES), and phenyl-arginine-β-naphthylamide (PAβN)—as therapeutic adjuncts. Methods: Antibacterial and anti-biofilm activities of EPIs were tested using broth microdilution, real-time fluorimetry, and crystal violet assays, while ceftriaxone–PMZ interactions were assessed by checkerboard analysis. Results: TZ and CCCP showed strain-specific antibacterial activity, whereas PMZ, RES, and PAβN did not exert any effect. PMZ, TZ, and especially CCCP effectively inhibited efflux pump function, while RES and PAβN were less active. Biofilm inhibition varied between strains, with PMZ and TZ producing moderate reductions. We observed a quite weak synergism between ciprofloxacin, ceftriaxone, and PMZ; however, the result was not significant. Conclusions: Overall, the results highlight the central role of efflux pumps in ESBL-producing E. coli and indicate that EPIs can reverse resistance (e.g., PMZ) and exhibit potent anti-biofilm activity and show additive interactions with antibiotics. However, further studies are needed to optimize their safety, pharmacokinetics, and antibiotic pairing for potential clinical use.

Multidrug-resistant Pseudomonas aeruginosa is a major cause of healthcare-associated infections, particularly in high-burden clinical settings where rapid tools to capture clinically relevant resistance and virulence phenotypes are needed. In this study, we applied an integrated whole-genome sequencing (WGS) and Fourier-transform infrared (FTIR) spectroscopy approach to evaluate genotype–phenotype relationships in multidrug-resistant P. aeruginosa isolates collected during the COVID-19 pandemic. High-quality WGS data were used to characterize antimicrobial resistance determinants, mobile genetic elements, and virulence gene repertoires, while FTIR spectroscopy provided culture-based phenotypic fingerprints reflecting cell envelope composition. Genomic analyses revealed a conserved efflux-centered intrinsic resistance backbone, variably supplemented by acquired β-lactamases and aminoglycoside-modifying enzymes, alongside a largely conserved core virulome with heterogeneity driven primarily by type III secretion system effector profiles. Comparison of FTIR- and WGS-derived distance matrices revealed a weak but statistically significant global association, indicating a non-linear relationship between genomic relatedness and phenotypic similarity. Cluster-level concordance was strongly scale-dependent, with high agreement emerging only at finer clustering resolutions, consistent with FTIR capturing phenotypic variation linked to regulatory, metabolic, and cell envelope adaptations rather than deep phylogenetic structure. Together, these findings show that multidrug resistance and virulence in P. aeruginosa are shaped by a modular genomic architecture that manifests as distinct, measurable phenotypic states. The observed scale-dependent concordance supports FTIR spectroscopy as a rapid, cost-effective phenotypic screening tool for outbreak-oriented surveillance, complementing WGS in integrated antimicrobial resistance monitoring workflows.

Background/Objectives: Bacteriophage therapy represents a promising strategy to combat multidrug-resistant pathogens, such as Escherichia coli. In this study, we explored the effects of a bacteriophage infection on an Extended Spectrum Beta-Lactamase (ESBL) positive E. coli isolate. Methods: We used next generation sequencing, proteomics and phenotypic screens to investigate the effect of bacteriophage infections on E. coli metabolism and resistance phenotypes. Results: The bacteriophage infection led to notable alterations in colony morphology, indicating profound changes in bacterial metabolism. Proteomic analysis revealed significant shifts in protein expression, with 65 proteins upregulated and 246 downregulated post-infection. The downregulated proteins were involved in various metabolic pathways, including nucleic acid, protein and lipid metabolism, and iron acquisition. Bacteriophage treatment also led to increased bacterial membrane permeability. Altogether, these alterations in bacterial metabolism and membrane permeability may lead to a general reduction in antibiotic resistance. Indeed, the bacteriophage-infected E. coli exhibited increased sensitivity to various classes of antibiotics, including beta-lactams, fluoroquinolones, trimethoprim-sulfamethoxazole, and aminoglycosides. Conclusions: Our findings highlight the potential of bacteriophage therapy as an adjunct to existing antibiotics, enhancing their efficacy against resistant strains.

Intravascular catheter-associated infections pose a significant threat to the health of patients because of biofilm formation. Hence, it is imperative to exploit cost-effective approaches to improve patient compliance. With this aim, our present study reported the potential of an antimicrobial polymeric gel coating of chitosan (CS) and chlorhexidine (CHX) on the marketed urinary catheters to minimize the risk of biofilm formation. The study involved the implementation of the Quality by Design (QbD) approach by identifying the critical parameters that can affect the coating of the catheter’s surface in any possible way. Later, design of experiments (DoE) analysis affirmed the lack of linearity in the model for the studied responses in a holistic manner. Moreover, in vitro studies were conducted for the evaluation of various parameters followed by the antibiofilm study. The coating exhibited promising release of CHX in the artificial urinary media together with retention of the coating on the catheter’s surface. Therefore, this study aims to emphasize the importance of a systematic and quality-focused approach by contributing to the development of a safe, effective, and reliable catheter coating to enhance intravascular catheter safety.