Methicillin-resistant Staphylococcus aureus (MRSA) nasopharyngeal carriage is a major global health concern linked to severe infections and transmission. However, comprehensive evidence on the burden of MRSA carriage, antimicrobial resistance, and associated risk factors in Ethiopia remains limited. This study aimed to estimate pooled prevalence, resistance pattern, and determinants of nasopharyngeal MRSA carriage. PubMed, ScienceDirect, Scopus, Web of Science, Google Scholar, and gray literature were searched for cross-sectional studies published between January 2015 and December 2025. Two groups of reviewers screened studies based on predefined criteria. The risk of bias was assessed using the Joanna Briggs Institute tool. Pooled prevalence and resistance proportions were estimated using a random-effects model, and pooled odds ratios (ORs) were calculated using the Mantel-Haenszel method. Heterogeneity and publication bias were assessed, and a sensitivity analysis was conducted. A total of 1040 records were identified, and 20 studies (6869 participants) were included. The pooled carriage prevalence was 7.3% (95% CI, 5.0-10.8), with substantial heterogeneity (I2 = 95.5%). Resistance was highest to tetracycline (55.75%) and lowest to clindamycin (12.66%). Increased odds of carriage were associated with prior hospitalization (OR, 3.49) and antibiotic use (OR, 2.35). Inconsistent variable coding across included studies limited the inclusion of other potential risk factors. Evidence of publication bias was detected, suggesting that the pooled prevalence should be interpreted with appropriate caution. The findings indicate a considerable burden of MRSA and highlight the need for strengthened antimicrobial stewardship, improved surveillance, and targeted prevention efforts in higher-risk populations. This review was registered in PROSPERO (CRD420251047192).
Increasing evidence indicates that alterations in the gastrointestinal microbiota are associated with the initiation and progression of gastrointestinal cancers. Abundant evidence suggests that gastrointestinal microbiota dysbiosis plays an important role in the development of gastrointestinal cancers by producing proinflammatory and immunosuppressive signals. This review examines the role of microbiome dysbiosis in the pathogenesis of gastrointestinal malignancies. The composition of the microbiota varies greatly among individuals and depends on various factors such as age, diet, lifestyle, genetics, medications, and environmental factors. Given this diversity, a comprehensive characterization of the gastrointestinal microbiota is crucial to elucidate its role in carcinogenesis. Therefore, investigating the microbial composition of the host gastrointestinal tract can provide important information about the status of gastrointestinal cancers.
This study provides the first metagenomic assessment of microbial diversity from the tea rhizosphere of the Kangra valley. Tea rhizosphere soil samples were collected from 4 locations (Dharamshala, Baijnath, Palampur, and Joginder Nagar) of the Kangra valley. DNA extracts of rhizosphere samples were analysed for bacterial and Archaeal diversity using amplicon sequencing (V3-V4) region of the 16S rRNA gene and Fungal diversity using ITS1 and ITS2 regions. Baijnath and Palampur samples showed the highest bacterial richness, while Dharamshala and Palampur had the highest fungal richness. Proteobacteria was a dominant phylum in all the rhizosphere samples, followed by Firmicutes, Actinobacteria, Acidobacteria, and Bacteroidetes. A total of 11 fungal phyla were identified among all the locations, with abundance of Ascomycota and Basidiomycota. For the Archaea domain, uncultured archaeon and Aeropyrum camini were the most common found among all the locations. A small fraction (< 0.5%) of Bacillus and Pseudomonas species were observed among all the locations. Alpha and beta diversity indices displayed notable differences within and between microbial diversities. Soil factors were variably associated with microbial diversity, with nitrogen positively aligned with fungal diversity, while EC and K were associated with Archaeal diversity. Soil pH and OM% showed moderate associations with bacterial diversity. These findings provided valuable and comprehensive insights into tea rhizosphere microbial ecology and could be used to better understand microbial functions and their role in plant health.
Intrinsically disordered proteins (IDPs) are biological macromolecules lacking a well-defined structure under normal physiological conditions. These proteins can be essential for both eukaryotic and prokaryotic cells, yet bacterial IDPs are significantly understudied. In this review, we highlight the functional importance of intrinsic disorder across a range of microbial phenomena, including effector secretion, desiccation tolerance, and the bacterial stress response. Given the emergence of structural disorder in key mechanisms of bacterial fitness, we propose bacterial intrinsic disorder as a novel linkage to antimicrobial resistance (AMR). We highlight areas of research where further study of bacterial IDPs could provide new insights into microbial evolution. Functional disorder introduces a new paradigm to the challenge of AMR, identifying novel targets for antimicrobial therapy.
Livestock wound infections are a major challenge in veterinary medicine due to the increasing prevalence of bacterial pathogens and antimicrobial resistance. This study evaluated the phytochemical composition and antibacterial activity of selected medicinal plants traditionally used for the treatment of livestock wound infections. A total of 250 livestock wound samples were processed using standard bacteriological methods, resulting in the identification of 216 bacterial isolates. The predominant bacterial pathogens included Staphylococcus aureus (19.2%), Escherichia coli (13.6%), Staphylococcus epidermidis (12.0%), Streptococcus agalactiae (9.2%), Salmonella Typhimurium (9.2%), Klebsiella pneumoniae (8.0%), Enterococcus faecalis (7.6%), and Proteus mirabilis (7.6%). Methanol, ethanol, and aqueous extracts of Withania somnifera, Achyranthes aspera, Verbascum sinaiticum, Aloe vera, and Capparis zeylanica were evaluated for antibacterial activity using the agar well diffusion method. Phytochemical screening revealed the presence of alkaloids, flavonoids, tannins, saponins, steroids, and phenolic compounds in most plant extracts. Among the tested plants, Withania somnifera exhibited strong antibacterial activity against Staphylococcus aureus, with inhibition zones ranging from 21 to 24 mm, while Achyranthes aspera demonstrated notable activity against E. coli, producing inhibition zones of 13-17 mm. Overall, Gram-positive bacteria were more susceptible to the plant extracts than Gram-negative bacteria. These findings suggest that the investigated medicinal plants possess significant antibacterial potential and may serve as promising alternative therapeutic agents for the management of livestock wound infections.
Basal cell carcinoma (BCC) is the most common malignant skin tumor. Skin-resident lipophilic Malassezia yeasts are associated with various cutaneous disorders, while their correlative patterns and potential biological effects in BCC tissues remain insufficiently defined. We used RT-qPCR screening of archived FFPE BCC specimens and metagenomic sequencing of three paired fresh tumor and peritumoral tissues to characterize tissue-associated Malassezia colonization. M. globosa was the most abundant species in FFPE samples and was also detectable in fresh tissues. In vitro functional assays (CCK-8, EdU) in HaCaT keratinocytes and A-431 epidermoid carcinoma cells showed that 12 h stimulation with optimal concentrations of M. globosa (1.2 × 107 CFU/mL) and M. yamatoensis (1.6 × 107 CFU/mL) significantly promoted epithelial cell proliferation. Transcriptome sequencing and subsequent RT-qPCR validation further showed that both strains significantly upregulate pro-inflammatory genes (IL-1β, IL-6, TNF-α) and oxidative stress-related genes (SOD1, SOD2) in these cell lines. Collectively, our findings describe a correlative association between Malassezia colonization and BCC lesions and offer preliminary in vitro mechanistic clues.
This study aimed to analyse antimicrobial resistance (AMR) in bacterial isolates from subgingival biofilms of patients with periodontitis and supragingival biofilms of orally healthy individuals, and to explore the association between biofilm-forming capacity and AMR. Three hundred and forty-seven bacterial isolates from 44 patients were analysed. Bacterial isolates were obtained from subgingival/supragingival biofilm and identified using MALDI-TOF mass spectrometry. Antibiotic susceptibility was evaluated by the Kirby-Bauer test, the E-test, and a β-lactamase activity assay, and biofilm formation capacity was assessed using the gentian violet assay. The 44 participants (median age 28.0 [25.0; 55.0]) were stratified into untreated generalised stage III/IV periodontitis (n = 21) and orally healthy (n = 23) groups. Among 347 isolates, 74.4% formed biofilms. AMR was generally higher in isolates from orally healthy subjects (77.7% vs. 59.1% in periodontitis patients, p < 0.001) and females (73.2% vs. 60.6% in males, p = 0.026). Multivariate binary logistic mixed models linked biofilm formation to AMR (OR: 1.66 CI: [1.12, 2.49]; p = 0.045 for severe biofilm formers and OR: 1.93 CI: [1.31, 2.83]; p = 0.004 for moderate biofilm formers). Phenotypic antimicrobial resistance was thus commonly detected throughout the cohort and was at least as frequent in orally healthy participants as in patients with periodontitis. Because the orally healthy group was substantially younger, this contrast is confounded by age and smoking and cannot be interpreted as an independent effect of periodontal status. Furthermore, this study might indicate that biofilm-forming isolates may exhibit increased antibiotic resistance.
Humans have historically been considered the only natural host of typical enteropathogenic Escherichia coli (tEPEC), a cause of human infantile diarrhoea. Recent findings of bat-specific tEPEC in two Australian bat species (Pteropus poliocephalus and Pteropus conspicillatus) revealed that these Pteropus spp. are also tEPEC hosts. tEPEC pathogenicity is associated with key virulence factors including intimin (eae) and the bundle-forming pilus (bfp) operon, which contains the bfpA gene. This study characterised 63 tEPEC isolates from five Australian Pteropus spp.; four from mainland Australia (P. poliocephalus, P. conspicillatus, P. alecto and P. scapulatus) and one from Christmas Island (P. natalis). The 63 tEPEC isolates included 10 novel tEPEC strains and eight previously identified Pteropus tEPEC strains. Faecal DNA samples (n = 386) from the five Australian Pteropus spp. were screened for eae and bfpA genes to identify tEPEC-positive samples. The estimated true prevalence of tEPEC ranged from 14.2% to 37.0% across the five Pteropus spp. Typing of 119 bfpA alleles (63 tEPEC isolates and 56 faecal DNA samples) from the five Pteropus spp. identified 27 bfpA allele types, 24 of which belonged to bat-specific bfpA lineages. Bat-specific bfpA alleles were shared between tEPEC strains, Pteropus spp. and across regions, including the geographically isolated P. natalis endemic to Christmas Island. This study reveals that diverse bat-specific tEPEC strains and bfpA types have evolved in Pteropus spp. and have been circulating among populations for an extensive period, thereby confirming that all Australian Pteropus spp. are natural tEPEC hosts.
This study aimed to assess the genetic diversity and potential epidemiological overlap of Staphylococcus aureus using molecular (spa and SCCmec typing) and phenotypic characterization of 108 isolates obtained along the farm-to-fork continuum (dairy and meat chains) and 50 human clinical isolates. Forty-four spa types, including 17 novel patterns, were identified, with t11284 and t127 predominating among animal-related MRSA and clinical MRSA, respectively. Six SCCmec types (I-VI) were detected in the majority of isolates (85.2%), with SCCmec IVa prevalent in farm-to-fork isolates (67%) and SCCmec III dominant in clinical isolates (28%). Spa repeat-based MST analysis revealed a heterogeneous distribution of isolates across clusters, with identical spa types detected in multiple source categories, indicating genetic relatedness rather than direct transmission events. Overall, 54.6% of isolates exhibited a multidrug-resistant phenotype. Farm-to-fork isolates showed mainly β-lactam resistance (≥ 85%), whereas clinical MRSA exhibited broader resistance profiles, including high fluoroquinolone resistance (≥ 92%). PVL was detected in 41 isolates (38%), predominantly in MRSA, and was associated with SCCmec IV/V and diverse spa types. Toxin genes (tst-1, sea, seb, and sed) were mainly confined to clinical MRSA, suggesting source-associated distribution of virulence determinants. Biofilm formation was observed in 49 isolates (45.3%), more frequently among farm-to-fork isolates. Our study demonstrate marked genetic and phenotypic diversity of S. aureus across farm-to-fork and human clinical sources and suggest the presence of shared genetic lineages among isolates from different sources. The results support the importance of integrated One Health surveillance for monitoring antimicrobial-resistant and virulent S. aureus populations across interconnected ecological compartments.
Multidrug-resistant members of the Enterobacter cloacae complex (ECC) are increasingly linked to difficult-to-treat infections and biofilm-mediated antimicrobial tolerance. Here, two lytic phages, vB_EhoIP_HHH and vB_EluM_RZH, displaying podovirus-like and myovirus-like morphology, respectively, were isolated from the River Chelt. HHH has a 39,582 bp genome (51.2% GC, 63 ORFs), while RZH has a 174,197 bp genome (39.4% GC, 314 ORFs), with neither genome carrying antimicrobial resistance, virulence or lysogeny-associated genes. VIRIDIC and VICTOR analyses placed HHH within Kayfunavirus and RZH within Karamvirus, supporting their classification as distinct species. Both phages demonstrated rapid adsorption, short latent periods and stability across physiological pH and temperature ranges. A phage cocktail targeting MDR ECC strain was evaluated with EDTA against established biofilms. Crystal violet assays showed the greatest biomass reduction at MOI 10 with 0.5-0.75 mM EDTA. Bliss independence analysis revealed localized synergy within this window but significant overall antagonism at higher EDTA concentrations. CFU enumeration confirmed greater activity against 24 h than 48 h biofilms. The optimized combination also reduced recoverable bacteria in a fibroblast infection model while maintaining low LDH release. These findings identify two novel lytic Enterobacter phages and support a narrow EDTA concentration window for enhanced phage-mediated antibiofilm activity.
Scorpions are ancient arachnids of medical and ecological importance; they prey on insects and other arthropods while serving as prey to birds and reptiles. In this study, we reported for the first time on the characterization of the gut intestinal microbiome of Hottentotta tamulus native to northeastern Pakistan. The scorpions were identified on a morphological basis and the Cytochrome c oxidase subunit 1 gene sequence, while the gut microbiome was characterized through full-length 16S rRNA (V1-V9) Nanopore sequencing. The gut microbiota exhibited low to moderate alpha diversity with Chao1 and Shannon indices of 126 ± 90.54 and 0.85 ± 0.21, respectively. The intestinal microbial community was dominated by the phyla Firmicutes (79.48%-90.43%), followed by Proteobacteria (9.46%-20.48%), whereas Actinobacteriota (0.03%-0.11%) and Bacteroidota (0.00%-0.01%) were present at very low relative abundance. The functional profiling identified 23 notable pathways involved in energy metabolism, biomolecule synthesis, the biodegradation of various xenobiotics, and nucleotide metabolism, highlighting the role of the gut microbiome in metabolic homeostasis. The dominance of Bacillus and Mycoplasma in gut microbial communities may enhance host adaptation to low-resource environments.
Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation and compromised epithelial barrier integrity. Emerging evidence demonstrates that gut microbiota-derived tryptophan metabolites serve as endogenous ligands for the aryl hydrocarbon receptor (AhR), initiating protective signaling cascades that restore mucosal homeostasis. This review synthesizes current mechanistic insights into how microbial tryptophan catabolites including indole-3-aldehyde, indole-3-propionic acid, indole-3-lactic acid, and indole-3-acetic acid activate AhR to enhance epithelial barrier function. However, this protective capacity is specific to activation by physiological, low-affinity microbial ligands and should not be generalized to AhR signaling irrespective of ligand identity, dose, or duration of exposure. Key bacterial producers include Lactobacillus species (L. reuteri and L. plantarum), Clostridium sporogenes, and Allobaculum species. AhR activation by these metabolites triggers multiple downstream pathways, including AMP-activated protein kinase (AMPK) activation, which promotes autophagy and mitochondrial homeostasis; nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant responses; nuclear factor-κB (NF-κB) inhibition, which reduces pro-inflammatory cytokine production; and interleukin-22 (IL-22) induction, which supports epithelial regeneration. These signaling events converge to upregulate tight junction proteins, preserve mucus layer integrity, and reduce actomyosin-mediated permeability through decreased myosin light chain phosphorylation. Preclinical studies demonstrate AhR-dependent barrier restoration, with protective effects abolished by AhR antagonists. Despite these preclinical findings, their therapeutic utility in IBD remains to be established in human interventional studies. Importantly, the protective effects of AhR are highly context-dependent, as kynurenine pathway ligands and sustained receptor activation may exert immunosuppressive or pro-tumorigenic effects, highlighting the importance of ligand selectivity in therapeutic development.
Given the critical role of the bap gene in biofilm formation of Acinetobacter baumannii, this study aimed to evaluate the efficacy of green-synthesized silver nanoparticles (AgNPs) derived from Nepeta pogonosperma and Astrodaucus persicus (Boiss) in reducing the expression of this gene and inhibiting biofilm production in clinical isolates of A. baumannii. AgNPs were synthesized using the leaf extracts of the plants and characterized using standard techniques. The minimum inhibitory concentration of the AgNPs was determined by the microbroth dilution method. Biofilm production and the anti-biofilm effects of the nanoparticles were assessed using a microtiter plate assay. Quantitative real-time PCR was employed to evaluate bap gene expression levels before and after treatment with the AgNPs. The AgNPs significantly inhibited biofilm formation in A. baumannii. Furthermore, a marked reduction in bap gene expression was observed following treatment. Moreover, 90% and 10% of the isolates showed up to 60% and 61%-80% of biofilm disruption after treatment with A. persicus AgNP, respectively. In addition, 80%, 15%, and 5% of the isolates showed up to 60%, 61%-80%, and more than 80% of biofilm disruption after treatment with N. pogonosperma AgNP, respectively. Green synthesis of silver nanoparticles represent a promising strategy to counteract antimicrobial resistance. The AgNPs investigated in this study demonstrated significant potential in inhibiting biofilm formation and reducing bap gene expression in strong biofilm-producing clinical isolates of A. baumannii. Further research is warranted to elucidate the underlying mechanisms and optimize the clinical application of these nanoparticles.
A significant increase of vancomycin-resistant Enterococcus faecium (VREfm) infections was observed in South-Eastern Austria since 2024. The prolonged outbreak is caused by a novel vanB-VREfm clone (ST117/CT7799, "VREfmstyr"). This study characterizes the atypical difficult-to-detect resistance phenotype and assesses the genomic relatedness of the isolates. Patient and outbreak characteristics were investigated including whole genome sequencing of the isolates. Sensitivity of broth microdilution (BMD), gradient tests (GT), disk diffusion (DD), and automated susceptibility testing (VITEK2) was compared. The performance of commercial screening media was evaluated. From sporadic detections in early 2024 case numbers began to rise during the year. In 30/31 (97%) of all cases, intra-hospital transmission was considered likely and an association with invasive procedures was identified in most cases. Core genome multilocus sequence typing revealed only six allelic differences between VREfmstyr isolates collected in a 12-month period, all belonging to the E. faecium ST117/CT7799 lineage. BMD detected vancomycin resistance (MIC > 4 mg/L) in no more than 16/31 (52%) of isolates after 24 h incubation, while GT and DD misclassified all isolates. Only prolonged incubation improved the performance of these assays. VITEK2 analysis, however, correctly classified all 31 isolates. Of four commercially available VRE-screening agars, only one was capable of detecting VREfmstyr after 24 h incubation. The emergence and clonal dissemination of VREfm ST117/CT7799 reveals a serious diagnostic gap as commonly used diagnostic algorithms fail to reliably detect this resistance phenotype. Our findings should help to further evaluate the true geographical distribution and clinical significance of this novel VREfm clone.
Antimicrobial resistance (AMR) constrains effective treatment and carries implications for infection control, surveillance, and public health. The World Health Organization (WHO) priority bacterial pathogen framework has intensified the need for diagnostic innovation by redefining research priorities around organisms combining high disease burden with complex resistance profiles. Molecular diagnostics have accordingly moved beyond culture-based workflows, integrating rapid pathogen identification, resistance-marker detection, genomic surveillance, and clinical decision support. The present study conducted a bibliometric mapping of the literature on WHO priority pathogens. Rather than addressing resistance at a general level or a single pathogen or technology, it integrates priority pathogens, molecular platforms, and resistance markers within a single framework, tracing their joint thematic and temporal evolution along an explicit pathogen-platform-marker axis. Scopus-indexed articles and reviews (2000-2025) were retrieved, yielding 1746 publications after screening adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Analyses used Bibliometrix/Biblioshiny, R, and VOSviewer. The literature expanded markedly after 2018, led by China and the United States. Methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis, Enterococcus faecium, and the Enterobacterales-carbapenemase axis constituted the principal thematic cores, whereas conventional polymerase chain reaction (PCR)/nucleic acid amplification testing (NAAT) and whole-genome sequencing were the dominant platforms. Overall, the field has evolved from pathogen detection into an AMR-centered translational domain encompassing resistance prediction, genomic epidemiology, surveillance, and clinical decision support. Diagnostic development, stewardship, and surveillance depend on hybrid workflows coupling rapid marker-targeted assays with genome-based characterization, delivering actionable resistance within clinically meaningful timeframes, and extending coverage to underrepresented pathogens and platforms.
Studies have demonstrated that arbuscular mycorrhizal fungi (AMF) can alter the rhizosphere microbial communities during exposure to tetracycline, thereby alleviating the adverse effects of antibiotics. We hypothesized that Funneliformis mosseae (F. mosseae) reshapes soil metabolite composition and associated-microbial pathways under tetracycline stress and that these metabolite changes are associated with the rhizosphere microbial communities. To test this hypothesis, microbiological profiling with metabolomics approaches were carried out to investigate how AMF reshape rhizosphere metabolite profiles in soybeans undergoing tetracycline stress. Specifically, inoculation with F. mosseae altered the soil metabolite profiles, with 34 differential metabolites identified, including 14 upregulated and 20 downregulated compounds, mainly amino acids, sugar phosphates, fatty acids, polyphenols, triterpenes, and heterocyclic compounds. In addition, 19 differential metabolic pathways were identified and classified into four metabolic clusters: polyunsaturated fatty acids and oxidative stress-related metabolism, carbon source and energy metabolism, amino acid and sulfur-containing metabolism, and secondary metabolism and defense responses. The correlation analysis between soil metabolites and published rhizosphere microbial data revealed 14 metabolites, including Trehalose-6-phosphate, increased with bacterial abundance, while five metabolites decreased; similarly, four metabolites increased and three decreased with fungal abundance. Correlation network analysis further indicated that 16 differential metabolites were significantly associated with 8 differential bacterial genera, and 12 differential metabolites were significantly associated with six fungal genera. Overall, our findings demonstrated that F. mosseae plays a crucial role in regulating microbial metabolism and interactions in tetracycline-contaminated soils, providing valuable insights into the mechanisms by which AMF alleviate tetracycline-induced stress in soils.
ABSTRACT Acinetobacter baumannii is a major multidrug‐resistant nosocomial pathogen, and new antimicrobial strategies are urgently needed. Green‐synthesized silver nanoparticles (AgNPs) have emerged as promising candidates because of their broad antibacterial activity and potentially improved biocompatibility. This systematic review evaluated the antibacterial effects of pure, plant‐mediated AgNPs against A. baumannii isolates. PubMed, Scopus, and Web of Science were searched from database inception to October 5, 2025 according to PRISMA guidelines. Eligible studies were original English‐language reports assessing pure green‐synthesized AgNPs against A. baumannii. Sixty‐three studies met the inclusion criteria. Green AgNPs were generally active against A. baumannii and more often showed stronger effects than the corresponding plant extracts. The most commonly proposed mechanisms were reactive oxygen species generation, membrane and cell–wall disruption, increased permeability, and damage to proteins, lipids, or DNA. Biofilm data were limited but suggested promising inhibitory potential. Toxicity findings were mixed, ranging from good biocompatibility to cytotoxicity in sensitive cell models. Plant‐mediated AgNPs show credible antibacterial potential against A. baumannii, but standardized synthesis, rigorous characterization, biofilm‐focused testing, and in vivo safety studies are still needed before clinical translation.
ABSTRACT ClpX functions as a component of the ClpXP protease, a conserved intracellular protease that regulates protein turnover, stress responses, and virulence in multiple bacterial species. Our lab has established that clpX is necessary for resistance to cell envelope targeting antibiotics, such as penicillin and daptomycin in Bacillus anthracis Sterne. Previous microarray data identified the msrA/B gene encoding a bifunctional methionine sulfoxide reductase as upregulated in the ΔclpX mutant. Methionine sulfoxide reductases (Msr) repair oxidatively damaged proteins by reducing methionine sulfoxide residues back to methionine. While Msr enzymes are primarily associated with oxidative stress, cell wall antibiotics induce expression of msrA1 and msrB in S. aureus. Here, we investigated the role of MsrA/B in oxidative and cell envelope stress. Our results show that although hydrogen peroxide and paraquat induce msrA/B expression, the ΔmsrA/B strain was not susceptible to either oxidant, whereas the ΔclpX strain was sensitive to both. We also found that loss of msrA/B conferred penicillin‐specific sensitivity, but, unlike ΔclpX, increased sensitivity was not seen with other cell wall or cell membrane targeting antibiotics. Inactivation of the catalytic cysteine of either Msr domain of MsrA/B failed to complement, suggesting that the reducing activity of MsrA/B is required for penicillin resistance. These findings indicate that while MsrA/B contributes to penicillin resistance, other proteins in the ClpXP modulon must also play a role in oxidative and cell envelope stress.
ABSTRACT Polyethylene terephthalate (PET) waste represents a major environmental challenge due to limited recycling solutions. Thermophilic bacteria from geothermal environments harbor diverse enzymatic machinery adapted to extreme conditions, offering promising biocatalysts for plastic degradation; however, biological resources from Peru and other South American countries remain scarce. We characterized four bacterial strains isolated from two geothermal sites in Cajamarca, Peru, screened for PET hydrolysis at 50°C. Whole‐genome sequencing using hybrid assembly achieved near‐complete circular genomes. GTDB‐Tk classification identified three species: Neobacillus thermocopriae (strain 19A), Bacillus licheniformis (strains 16P and BI2), and Brevibacillus agri (strain BI8). Quantitative assays revealed that strain 16P achieved the highest mass loss (0.598%), followed by strain BI8 (0.449%). ATR‐FTIR analysis of the incubated sheets showed a significant reduction of the ester carbonyl index in strains 16P, 19A, and BI8 relative to both non‐incubated PET and an abiotic control, whereas strain BI2 did not differ from the controls, indicating preferential modification of ester bonds at the sheet surface. Genome mining and structure‐based homology searches identified multiple candidate enzymes similar to validated PETases and carboxylesterases, including PETase46‐like homologs in strains BI8 and 16P and a terephthalate‐active carboxylesterase homolog in strain 16P. Molecular docking supported the conservation of catalytic geometry and substrate‐binding sites in these candidates. This work represents one of the first systematic genomic and structural characterizations of putative PET‐hydrolases in Peruvian geothermal bacteria, expanding knowledge of extremophile diversity and advancing thermostable enzymes for sustainable plastic waste management.
ABSTRACT Urinary tract infections are highly prevalent diseases with a broad spectrum of clinical manifestations. This study investigates the influence of two key abiotic factors, pH and salinity, on the growth and antibiotic susceptibility of Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and a clinical E. coli isolate obtained from a human urine sample. Growth kinetics and gentamicin susceptibility were evaluated across a pH range (4.5–11.0) and NaCl concentrations (0–1000 mM) using Luria–Bertani and Mueller–Hinton (MH) media. In parallel, real urine was analyzed, and urine‐mimicking MH media were prepared by adjusting pH and salinity independently and in combination. Gentamicin susceptibility was strongly influenced by environmental conditions. Salinity pre‐exposure increased E. coli and P. aeruginosa resistance from 23.0 to 19.0 mm and from 25.5 to 18.5 mm at 800 mM, respectively. Direct pH modification enhanced gentamicin activity at extreme pH (up to 34.33 mm in E. coli and 33.5 mm in P. aeruginosa). In standard MH medium, the clinical E. coli isolate exhibited a 32.5‐mm inhibition zone and a gentamicin minimum inhibitory concentration (MIC) of 4 µg/mL. Under urine‐mimicking conditions, the inhibition zone decreased to 22.5 mm, while the MIC increased eightfold to 32 µg/mL, indicating a marked reduction in gentamicin efficacy under physiologically relevant urinary conditions. These findings demonstrate that environmental stress profoundly influences gentamicin efficacy and suggest that this effect may involve physiological adaptations, including RpoS‐mediated stress responses, membrane remodeling, and osmoprotective mechanisms previously described in the literature.
