Jul 2026· Iraqi Journal of Science· 0 citations· 36 references
TL;DR
The dynamic expression of UPEC's stress response mechanisms are emphasized and the central role of Bar/UvrY in modulating pathoadaptive mechanisms under antibiotic stress is outlined.
Abstract
Uropathogenic Escherichia coli (UPEC) remains the most common etiologic agent of community-acquired urinary tract infections (UTIs), largely due to its extensive virulence arsenal and adaptive regulatory mechanisms. In this study, we examined the phenotypic regulation of major virulence factors—hemolysin production, biofilm, swarming motility, and adhesion—under exposure to sub-inhibitory concentrations of Ceftazidime, an extended-spectrum β-lactam antibiotic. The transcriptional response of the BarA/UvrY two-component regulatory system was also examined to unravel its role in response to antibiotic stress. Using an extensive range of microbiological, molecular, and phenotypic tests, we unveiled differential profiles of virulence traits. Exposure to sub-MICs Ceftazidime markedly diminished hemolytic activity, biofilm formation, and adhesive capacity, with swarming motility exhibiting almost complete inhibition. Moreover, quantitative real-time PCR (qRT-PCR) analysis revealed variable transcriptional responses of BarA and UvrY in the tested isolates, with the recovery of BarA expression noted after prolonged exposure to antibiotics. These findings emphasize the dynamic expression of UPEC's stress response mechanisms and outline the central role of Bar/UvrY in modulating pathoadaptive mechanisms under antibiotic stress.
Pseudomonas aeruginosa is a bacterium with high antimicrobial resistance to several drugs including carbapenems. Recently, resistance to cefiderocol (FDC), a new siderophore cephalosporin, has been reported despite its rare use in clinical practice. Therefore, this study aimed to investigate the dynamics of different resistance mechanisms in P. aeruginosa that evolve under FDC pressure, as well as the interactions between these mechanisms in evolutionary trajectories to guide clinical medication. P. aeruginosa ATCC 27853 was continuously induced with subinhibitory concentrations of cefiderocol in vitro to generate strains with different resistance levels. Phenotypic adaptability and molecular regulatory networks during the evolution of resistance were systematically elucidated using growth curves, pairwise competition assays, transcriptomics, RT-qPCR and efflux inhibition assays. The minimum inhibitory concentration (MIC) of the induced FDC-resistant strain increased from 0.125 to 64 μg/mL. Simultaneously, the growth rate and peak declined below those of the parental strain. The pairwise competition assay showed that the relative fitness of resistant strains versus parental strains was < 1 in LB and ID-CAMHB broths. Transcriptome analysis revealed that the MIC of the induced FDC-resistant strain was related to the dose of efflux pumps, together with a layer-by-layer regulation of gene expression, to adapt to environmental stress. In the initial resistant strain, efflux pumps were slightly upregulated, and energy metabolism was downregulated. Conversely, in the strain with a MIC of 64 μg/mL, efflux pumps were significantly up-regulated and drove bacterial reprogramming to induce resistance, particularly the RND efflux pump component oprM, along with multiple ABC transporters. RT-qPCR validated the significant upregulation of oprM, opuC, and opuBD (p < 0.05), confirming their central role. Furthermore, in the presence of the efflux pump inhibitor phenyl-arginine β-naphthylamide (PAβN), the resistant strains exhibited significantly reduced MICs for FDC. In conclusion, these data indicate that multiple mechanisms of action are involved in the antibacterial activity of P. aeruginosa against FDC. Notably, the evolution of resistance was associated with the dose-dependent upregulation of core efflux pumps, complemented by stage-specific global physiological remodeling; however, it also came at a fitness cost.
Ting Zhang, Hanxu Hong, Jun Wang et al.· Frontiers in Microbiology· 0 citations
The Type VI secretion system (T6SS) is a multi-component transmembrane apparatus that is crucial for substance acquisition and pathogenicity of bacteria. In this study we investigated Acinetobacter baumannii, a causative agent of bacteremia, to explore the mechanisms of T6SS in drug resistance and pathogenicity by contrasting virulence, drug sensitivity, conjugation, transformation, competition, and cell adhesion capacities. A total of 136 non-repetitive A. baumannii strains were collected, and 80.1% of patients received treatment in intensive care unit. Forty strains (29.4%) were classified as hypervirulent A. baumannii (hvAB), which exhibited a higher prevalence of the virulence gene abaI, a reduced capacity for biofilm formation, and a lower prevalence of the outer membrane protein gene carO. T6SS-positive strains exhibited enhanced antimicrobial resistance, elevated frequencies of resistance genes (blaOXA-23-like, blaTEM, adeB, adeR, adeS) and the virulence gene csuE. Differences were observed between strains with T6SS deletion and those with an intact T6SS concerning the HigAB toxin-antitoxin system and the RSF1010-like IncQ plasmid. T6SS may down-regulate the expression of effector genes due to the insertion sequence ISAba13. The critical role of the T6SS in the drug resistance and pathogenicity of A. baumannii necessitates strengthened surveillance and the prompt implementation of effective measures.
Jun Li, Mengli Tang, Zhaojun Liu et al.· Scientific Reports· 0 citations
Uropathogenic Escherichia coli (UPEC) strains are the primary cause of urinary tract infections and pose a serious clinical problem due to their remarkable genetic variability, diverse virulence traits, and rapidly increasing antibiotic resistance. In this study, five clinical UPEC isolates (EC3, EC149, EC164, EC179, and EC256) were deeply investigated to better understand their pathogenic potential. The strains differed substantially in genome architecture, mobile genetic elements, plasmid composition, virulence factors composition, and antibiotic resistance profiles, illustrating the highly dynamic nature of UPEC populations. Of particular concern was the detection of plasmids linked to resistance against “last-resort” antibiotics, emphasizing the growing epidemiological risk associated with these pathogens. To address the limitations of conventional therapy, five lytic bacteriophages active against the analyzed UPEC strains were isolated and thoroughly characterized. Comparative genomic and phylogenetic analyses revealed that all phages represent previously undescribed species belonging to the genera Hanrivervirus, Warwickvirus, Nonavirus, Kagunavirus, and Vectrevirus. Functional assays demonstrated pronounced differences in host range and infectivity. Among them, phage vB_EcoS-149_4M emerged as the most promising candidate, combining broad antibacterial activity with high stability and a favourable safety profile, including the absence of toxin or antibiotic resistance genes and no detectable cytotoxicity toward human cell lines. Taken together, these findings highlight both the complexity and clinical threat posed by UPEC strains and the substantial potential of carefully selected bacteriophages as effective and precise antimicrobial tools. In effect, this multi-faceted approach provides a strong foundation for the development of precision phage therapy against multidrug-resistant UPEC infections.
Wojciech Wesołowski, Grzegorz Czerwonka, Katarzyna Zegadło et al.· Scientific Reports· 0 citations
ABSTRACT Uropathogenic Escherichia coli (UPEC) often causes recurrent urinary tract infections, where biofilms and persister cells can promote recalcitrance. This study evaluated whether secretion-system marker genes associate with antimicrobial susceptibility, biofilm formation, and biofilm-associated persistence in clinical urinary isolates. A total of 71 isolates were screened by PCR for fimH and markers of secretion systems: type I (hlyA), type II (gspD), type V (ag43), and type VI (hcp). Minimum inhibitory concentrations (MICs) were measured by Etest, biofilm biomass by crystal violet assay, and persister survival in strong biofilm producers after antibiotic challenge. fimH was detected in 91.5% isolates; gspD and ag43 were common (71.8% and 80.3%), while hlyA and hcp occurred in 32.4% and 46.5%. Marker co-occurrence was frequent, with 19.7% carrying all four secretion markers, and 8.5% with no secretion markers detected. A total of 81.7% isolates formed biofilm, including 18.3% strong producers. Individual marker prevalence did not differ across biofilm categories. Carriage of hlyA and hcp was associated with lower MIC distributions for selected antibiotics (including fosfomycin, ciprofloxacin, and ampicillin-sulbactam), whereas gspD and ag43 showed no consistent MIC associations. The biofilm category was linked to non-susceptibility to ampicillin-sulbactam, but not the other agents tested. Strong biofilm producers showed biphasic killing consistent with persister formation, and hcp carriage tended to align with higher ciprofloxacin survival. These findings map secretion-system markers in clinical UPEC and suggest that a type VI secretion system may track with biofilm-associated persistence. IMPORTANCE Recurrent urinary tract infections (rUTI) often relapse after antibiotic treatment because bacteria can generate persister cells—temporary survivors that tolerate antibiotics without being genetically resistant. Clinicians, therefore, lack markers that flag isolates likely to persist. In 71 clinical urinary Escherichia coli isolates, this study surveyed genes encoding several secretion systems, molecular machines that help bacteria interact with each other and with host tissues. These markers were widespread and frequently co-occurred, but they did not track with stronger biofilm formation. However, a type VI secretion system marker (hcp) was associated with higher survival during ciprofloxacin exposure in strong-biofilm isolates, linking virulence-associated machinery with biofilm-associated persistence. Genetic signatures that reflect persistence, rather than routine resistance, could help prioritize follow-up testing and support development of strategies that target hard-to-eradicate rUTI infections. Recurrent urinary tract infections (rUTI) often relapse after antibiotic treatment because bacteria can generate persister cells—temporary survivors that tolerate antibiotics without being genetically resistant. Clinicians, therefore, lack markers that flag isolates likely to persist. In 71 clinical urinary Escherichia coli isolates, this study surveyed genes encoding several secretion systems, molecular machines that help bacteria interact with each other and with host tissues. These markers were widespread and frequently co-occurred, but they did not track with stronger biofilm formation. However, a type VI secretion system marker (hcp) was associated with higher survival during ciprofloxacin exposure in strong-biofilm isolates, linking virulence-associated machinery with biofilm-associated persistence. Genetic signatures that reflect persistence, rather than routine resistance, could help prioritize follow-up testing and support development of strategies that target hard-to-eradicate rUTI infections.
Paulina Soból, Weronika Kęsek, Maja Kirzyc et al.· Microbiology spectrum· 0 citations
Deletion of fabR reduced host cell adherence, increased serum sensitivity, enhanced IgG deposition, and decreased vitronectin binding compared with the wild-type strain, and ΔfabR mutants from multiple NTHi strains showed increased metabolic activity, indicating a conserved role for FabR in metabolic regulation.
Martina Janoušková, Yu-Ching Su, Sandra Jonsson et al.· Journal of Infectious Diseas...· 0 citations
Introduction Vibrio cholerae relies on two-component signal transduction systems to adapt to the host intestinal microenvironment. This study investigated the role and regulatory mechanism of the BaeS/BaeR two-component system in intestinal colonization and antimicrobial peptide resistance. Methods A baeS/baeR deletion mutant and complemented strain were constructed in the O1 El Tor clinical isolate EL2382. Intestinal colonization, Caco-2 cell adhesion, histopathological analysis, transcriptomic profiling, qRT-PCR, western blotting, electrophoretic mobility shift assays, chromatin immunoprecipitation-qPCR, and antimicrobial peptide resistance assays were performed. Results Expression of baeS and baeR was markedly induced during intestinal colonization and adhesion to Caco-2 cells. The ΔbaeS/baeR mutant exhibited significantly impaired bacterial adhesion and in vivo colonization, accompanied by reduced histopathological scores, and these phenotypes were restored by genetic complementation. Transcriptomic analysis identified salX (VC2553), which encodes an ABC transporter involved in antimicrobial peptide homeostasis, as a key downstream target of BaeS/BaeR. BaeR bound to the salX promoter and activated its transcription, and deletion-mapping electrophoretic mobility shift assays localized a putative BaeR-responsive sequence to 5′-TTCTTTTT-3′ within the −10/−35 spacer region. Similar to the ΔbaeS/baeR mutant, the salX mutant exhibited reduced resistance to human defensin 5 and impaired intestinal colonization. L-arginine exposure was associated with dose-dependent activation of the BaeS/BaeR pathway and BaeS/BaeR-dependent induction of salX, although a direct physical interaction between L-arginine and BaeS was not established. Discussion These findings identify an L-arginine-associated BaeS/BaeR–SalX regulatory pathway that promotes antimicrobial peptide resistance and intestinal colonization by V. cholerae, providing new insight into host cue-associated regulation of bacterial colonization fitness.
Qiushi Wang, Xiaoya Guo, Yongquan Shi et al.· Frontiers in Cellular and In...· 0 citations
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