Bacteria, Volume 5, Issue 2 (June 2026) – 17 articles

Pseudomonas aeruginosa, an opportunistic pathogen, is a major threat to hospital infection control and global public health due to its strong environmental adaptability, complex virulence systems, efficient biofilm formation capability, and widespread multidrug resistance. Traditional single-target antibiotics are often inadequate for clinical treatment. The research into Plant-Derived Bioactive Compounds for combating P. aeruginosa infections is reviewed, highlighting their advantages (many of which are extensively studied in Traditional Chinese Medicine) over conventional antibiotics. The antimicrobial mechanisms of these compounds include the inhibition of bacterial quorum sensing (QS) systems to suppress virulence factor expression rather than direct anti-bactericidal effects, delaying the development of resistance. The abundant natural medicinal plants and their diverse chemical structures provide ample material for active compound screening to identify unique chemical compositions with specific binding to pathogen targets. Plant-Derived Bioactive Compounds exhibit excellent safety profiles, targeting bacterial-specific pathways or host immune regulation, resulting in minimal off-target toxicity. Plant-Derived Bioactive Compounds exert anti-P. aeruginosa effects via inhibition of QS systems to reduce pathogenicity by disrupting intercellular signaling, suppressing biofilm formation/maturity to overcome biofilm-associated resistance, directly interacting with bacterial structure. Plant-Derived Bioactive Compounds are promising treatments for drug-resistant P. aeruginosa infections, providing lead compounds for novel anti-infective drug development. Full article

Background: The rapid rise in antimicrobial resistance (AMR) represents one of the most pressing global health challenges of the 21st century, threatening antibiotic effectiveness, compromising clinical outcomes, and undermining healthcare systems. Understanding how resistant pathogens emerge and spread across human, animal, and environmental sectors is essential for effective global response. Main body: This review evaluates traditional and advanced AMR detection methodologies, including phenotypic assays, molecular diagnostics, whole-genome sequencing (WGS), metagenomics, and biosensor-based technologies. It also highlights the role of bioinformatics tools, surveillance databases, and integrated platforms that support real-time analysis. Genomic surveillance provides unparalleled resolution for characterizing resistance mechanisms, transmission patterns, and evolutionary trajectories of multidrug-resistant organisms. Techniques such as WGS and metagenomics allow timely and precise identification of resistance genes, improving outbreak detection and strengthening antimicrobial stewardship. Despite these advantages, the adoption of genomic surveillance faces barriers in low- and middle-income countries, including high costs, limited infrastructure, insufficient technical expertise, and the lack of standardized data frameworks. Conclusions: Genomic surveillance is a transformative tool for combating AMR and strengthening global health systems. Effective implementation requires sustained investment, capacity-building, coordinated cross-sector collaboration, and commitment to the One Health approach to ensure equitable access and long-term global impact. Full article

L. angustifolia is a perennial shrub native to the Mediterranean region with multiple medicinal properties. In this study, we report on the chemical composition of L. angustifolia essential oil (LEO), its antibacterial, antibiofilm, and antioxidant activities against ten clinical isolates. Chemical constituents of LEO were identified using Gas Chromatography-Mass Spectrometry (GC–MS). Its antibacterial activity was evaluated in vitro against Gram-positive and Gram-negative bacteria using disk diffusion and broth microdilution methods. A growth inhibition assay was performed to determine the bacterial growth spectrophotometrically. The antibiofilm activity was assessed using a Crystal Violet assay. Finally, the activities of oxidative stress indicators, including Superoxide dismutase (SOD) and Catalase (CAT), were evaluated. GC–MS findings of the essential oil revealed the predominance of Linalool as the major compound. Antimicrobial tests demonstrated activity against Acetobacter aceti, Acinetobacter baumannii, Enterococcus faecium, Escherichia coli, Methicillin-resistant Staphylococcus aureus, Proteus vulgaris, Klebsiella pneumonia, Staphylococcus aureus, Staphylococcus haemolyticus and Stenotrophomonas maltophilia. Furthermore, LEO modulated bacterial growth over time, inhibited biofilm formation and eradicated pre-formed ones. Additionally, LEO significantly decreased the activities of the antioxidant enzymes SOD and CAT. Our findings demonstrated the therapeutic potential of LEO against pathogenic strains and broad antibacterial efficacy. Full article

Saline ecosystems, including saline lakes, are indeed major hotbeds of microbial novelty, harboring diverse and largely unexplored microbes. The sebkha of Lake Naïla (Morocco), an ecologically protected area registered under the Ramsar Convention in 1998, remains largely unexplored. Isolation using three different selective media enabled seven phenotypically distinct actinobacterial isolates to be obtained. Molecular characterization, based on 16S RNA gene sequencing, was used to identify strains as members of the genera Streptomyces, Nocardiopsis, and Prauserella. Three strains showed antimicrobial potential against pathogenic microorganisms, with Streptomyces sp. strain 43 exhibiting the most potent effects. Additionally, all isolates displayed plant-growth-promoting (PGP) traits, including phosphate solubilization, auxin (IAA) synthesis, siderophore secretion, and ammonia production. Notably, Nocardiopsis sp. strain 42 produced the highest IAA levels (282 μg/mL), while Streptomyces sp. strain 39, Streptomyces sp. strain 43, and Streptomyces sp. strain 48 excelled in phosphate solubilization. GC-MS profiling of Streptomyces sp. strain 43 revealed a complex metabolite repertoire, including 1,2-propanediol and nonanal, highlighting the strain’s versatile secondary metabolism. These findings highlight that the sebkha of Lake Naïla represents a rich source of halophilic actinobacteria with promising dual potential for antimicrobial and biofertilizer applications. The findings provide a solid basis for new perspectives on biotechnology applications and sustainable agriculture. Full article

Shiga toxin-producing Escherichia coli (STEC) is a major zoonotic foodborne pathogen associated with severe human illnesses, including hemorrhagic colitis and hemolytic uremic syndrome. While ruminants are traditionally recognized as the primary reservoirs, increasing evidence suggests that poultry production systems may also contribute to the dissemination of pathogenic and antimicrobial-resistant E. coli through the food chain. However, the extent of this contribution and its relevance to human infection remain incompletely understood. This review provides a critical synthesis of the virulence mechanisms, epidemiology, and antimicrobial resistance (AMR) of E. coli, with particular emphasis on STEC in poultry production systems. Key virulence determinants, including Shiga toxins (Stx1 and Stx2), the locus of enterocyte effacement, and plasmid-encoded factors, are discussed in relation to their roles in host colonization and disease progression. Transmission pathways within poultry production and processing environments are examined, highlighting critical points of contamination from farm to consumer. The increasing prevalence of multidrug-resistant and extended-spectrum β-lactamase-producing E. coli in poultry underscores significant public health concerns. However, variability in epidemiological data and limitations in current surveillance systems complicate the interpretation of transmission dynamics. Current and emerging control strategies, including biosecurity measures, alternative antimicrobial interventions, and processing hygiene, are evaluated alongside their practical limitations under commercial conditions. Overall, this review identifies key knowledge gaps and emphasizes the need for integrated, evidence-based approaches within a One Health framework to better define zoonotic risks and develop sustainable control strategies. Full article

Background: Urinary tract infections (UTIs) are among the most common bacterial infections worldwide and represent a significant public health concern due to their high prevalence and increasing antimicrobial resistance. This study aimed to systematically review the epidemiology, uropathogens, and resistance patterns of UTIs in Portugal over the last decade. Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines. A literature search was performed in April 2026. A total of 425 records were identified. After removal of duplicates and preliminary exclusions, 121 records were screened by title and abstract. Following application of eligibility criteria, 41 full-text articles were assessed, of which 13 met the criteria for detailed eligibility assessment. Six studies met the inclusion criteria and were included in the final qualitative synthesis. Results: The included studies consistently reported a higher prevalence of UTIs in females and, in some cases, in older populations. Escherichia coli was identified as the predominant uropathogen across all studies, followed by Klebsiella pneumoniae, Proteus spp., and Enterococcus spp. A consistently high prevalence of antimicrobial resistance was observed, particularly against commonly used antibiotics such as ampicillin and trimethoprim–sulfamethoxazole. The presence of extended-spectrum β-lactamase (ESBL)-producing strains was also reported, especially in healthcare-associated infections, which exhibited higher resistance profiles compared to community-acquired infections. Conclusions: The available evidence suggests that UTIs in Portugal are predominantly caused by enterobacteria, particularly Escherichia coli. However, the limited number and heterogeneity of studies highlight the need for cautious interpretation. Further multicenter and methodologically robust studies are required to better characterize national epidemiological patterns and antimicrobial resistance trends. Full article

Biosurfactant production by hydrocarbon-degrading bacteria is strongly influenced by the nature and concentration of available carbon substrates, which determine hydrocarbon bioavailability and microbial metabolic responses. In this study, five Bacillus subtilis strains isolated from weathered oil-contaminated sites in Qatar were evaluated for growth and biosurfactant activity using diesel fuel, fresh corn oil, and five-times-overheated corn oil as sole carbon sources. Cultures were grown in mineral salts medium under controlled conditions, and biosurfactant production was assessed through emulsification activity (EA), solubilization activity (SA), and colony-forming unit counts. All strains grew on the tested substrates but exhibited distinct strain-specific responses. Fresh corn oil supported the highest biomass production with values up to 3.3 × 10⁷ CFU mL⁻¹, whereas the strongest emulsification activity yield was observed in diesel cultures at low carbon loading (59 ± 2.3 EU g⁻¹ carbon. Five-times-overheated corn oil maintained more stable emulsification activity across a broader concentration range, indicating tolerance to oxidized hydrocarbons and adaptation to chemically altered substrates. Increasing hydrocarbon concentrations led to progressive declines in EA and SA, indicating inhibitory effects at high substrate loads. Overall, biosurfactant production did not correlate directly with biomass, highlighting the importance of substrate properties in regulating functional output. These findings demonstrate that substrate composition and concentration are key determinants of biosurfactant performance in B. subtilis isolates and support the potential use of waste oils as low-cost feedstocks for biotechnological and bioremediation applications. Full article

Background: Antibiotic misuse and prescribing errors are significant concerns in clinical practice, contributing to unnecessary antibiotic exposure, increased adverse effects, rising healthcare costs, and the escalation of antibiotic resistance. Understanding the prevalence, patterns, and risk factors of these prescription errors is essential for improving patient safety and healthcare efficiency in the future. Aim: Our aim was to evaluate the prevalence, patterns, and risk factors of antibiotic prescription errors in Saudi Arabia. Methods: A comprehensive search of three databases (PubMed, Scopus and ProQuest) was conducted to identify eligible cohort and cross-sectional studies in Saudi Arabia published up to January 2025. Studies that reported on error rates of antibiotic prescription errors and those that did not provide quantitative data were excluded. The primary outcome was the prevalence and patterns of inappropriate antibiotic use, while the secondary outcomes included the pooled prevalence of specific errors (i.e., selection, dose, duration, etc.). The quality of the studies was assessed using the Newcastle–Ottawa scale. This review was registered in PROSPERO (CRD42024611747). Results: Fourteen eligible cohort (n = 2) and cross-sectional (n = 12) studies conducted in Saudi Arabia were included in the review. Two studies reviewed medical records and orders of patients. Patient selection varied from emergency department to intensive care units and outpatients. The pooled prevalence of antibiotic prescription errors was 42.7% [95% CI: 37.5–47.8], with common errors including dosage (29.3%), duration (24.3%), selection (15%) and frequency (11.1%) errors. However, there was a high heterogeneity among the results. Overall, the quality assessment revealed a low risk of bias, except for one study with a high risk of bias. Conclusions: These findings highlight the high prevalence of antibiotic prescription errors. Future efforts should strengthen antibiotic stewardship, enhance clinician training, and ensure adherence to evidence-based guidelines to reduce prescription errors and combat antibiotic resistance. Full article

Enterococcus lactis is increasingly recognized as an emerging mastitis pathogen, yet the functional basis of its virulence and associated health risks remain poorly defined. This study presents an integrated genomic and phenotypic characterization of E. lactis strain EL-A150 isolated from bovine subclinical mastitis. Whole-genome sequencing revealed a 2.49 Mb circular chromosome encoding multiple genes associated with adhesion (acm, bepA, fms, sagA), biofilm formation (empB, empC) and antimicrobial resistance, including determinants related to aminoglycosides and macrolides. Phenotypic assays demonstrated rapid growth, strong biofilm-forming capacity and high adhesion to bovine mammary epithelial cells, while internalization remained low and intracellular persistence was transient. Comparative genomic analyses confirmed the taxonomic placement of the strain within the E. lactis clade (ANI up to 99.5% against reference genomes) and revealed a limited resistome composed of chromosomally encoded genes, with no detectable plasmids or major mobile genetic elements. Collectively, these findings demonstrate that E. lactis EL-A150 possesses a coordinated set of traits conducive to intramammary colonization, supporting its classification as an opportunistic pathogen. The convergence of virulence potential and clinically relevant antimicrobial resistance within a single isolate underscores a One Health concern and highlights the need for surveillance frameworks that integrate functional validation with genomic risk assessment. Full article

Leuconostoc suionicum strain JNUCC 76 (=CH10) was isolated from cherry blossom flowers (Prunus yedoensis) collected on Jeju Island, Republic of Korea, representing a flower-associated strain of L. suionicum. To clarify its taxonomic position and genomic characteristics, whole-genome sequencing was performed using a hybrid PacBio–Illumina approach. The complete genome was assembled into a single circular chromosome of 2.20 Mb with a GC content of 36.8% and high sequencing depth, indicating a high-quality, closed genome assembly. Genome annotation revealed a compact gene repertoire dominated by functions related to carbohydrate transport and metabolism, amino acid utilization, and core cellular processes, consistent with adaptation to plant-derived, sugar-rich environments. Genome-based phylogenomic analyses using average nucleotide identity (ANI), digital DNA–DNA hybridization (dDDH), and Genome BLAST Distance Phylogeny (GBDP) placed strain JNUCC 76 within the species L. suionicum. Genome-based metrics clearly exceeded the accepted species thresholds, supporting the assignment of the strain to L. suionicum. Secondary metabolite gene cluster analysis identified a limited number of low-complexity and precursor-oriented biosynthetic gene clusters, including RiPP-like, type III polyketide synthase, and terpene-precursor clusters, suggesting that the ecological fitness of the strain relies primarily on primary metabolism rather than extensive secondary metabolite production. Overall, this study expands current knowledge of flower-associated Leuconostoc lineages and provides a high-quality genomic framework for future comparative and functional studies. The genomic features of strain JNUCC 76 highlight floral environments as underexplored reservoirs of lactic acid bacteria diversity and support further evaluation of flower-derived Leuconostoc strains as potential postbiotic or fermentation-based resources for cosmetic and related biotechnological applications. Full article

Iron (Fe) and zinc (Zn) are essential micronutrients for plant metabolism; however, their bioavailability in tropical soils is often limited by low solubility and complex mineral interactions. Root-associated bacteria may enhance micronutrient availability through siderophore production and the solubilisation of insoluble mineral forms. This study aimed to functionally characterise three bacterial isolates from rice roots—Bacillus siamensis TUR07-02b, Priestia aryabhattai SMNCH17-07, and Priestia megaterium SMBH14-02—under controlled in vitro conditions. Siderophore activity was evaluated qualitatively using Chrome Azurol S (CAS) agar, where percentages represent halo-based indices relative to colony diameter, and quantitatively using the CAS–shuttle assay, expressed as percent siderophore units relative to an uninoculated reference. Zinc solubilisation was assessed in solid media as halo-based indices and in liquid media as Zn-equivalent signals (mg L⁻¹) obtained by spectrophotometry. All strains produced siderophores, with P. aryabhattai showing the highest qualitative index (167%), while P. aryabhattai and B. siamensis showed statistically similar activity in liquid medium (~23%). Zinc solubilisation was substrate-dependent: B. siamensis showed the broadest solubilisation spectrum in solid media, whereas P. aryabhattai achieved the highest Zn-equivalent signals for ZnCO₃ and Zn₃(PO₄)₂ after 20 days. These results demonstrate strain-specific functional differences and represent a preliminary screening method based on relative in vitro estimations. Full article

The aim of the study was to evaluate the biotechnological potential of thermophilic microorganisms isolated from chernozem soil during composting of poultry manure. The efficiency of the strains was determined by their effect on organic matter degradation, humification intensity, and nitrogen accumulation. The correlation between the quality indicators of the composting process was assessed with the gross values, taking into account the proportion of compost fractions. The strains were identified as: Aeribacillus pallidus KCTC 3564^T (cellulolytic), Neobacillus sedimentimangrovi FJAT-2464^T, Aeribacillus composti N.8^T, Caldifermentibacillus hisashii N-11^T (nitrogen fixers), Acinetobacter pittii CIP 70.29^T, and Pseudomonas plecoglossicida NBRC 103162^T (nitrifies). It was found that all the bacteria increase the proportion of small fractions by 19.0–19.9%. The gross content of humic acids increases under the influence of nitrifiers (15.5%) and nitrogen fixers (5.5%). The total nitrogen content increases under cellulolytics (13.8%) and nitrogen fixers (20.2%). The smallest fraction (≤0.25 mm) in nitrogen fixers and nitrifying variants has the greatest bioreclamation properties, by 16.4% (p < 0.001) and 12.9% (p < 0.001). Targeted microbial strains provide the direction of the transformation processes during biocomposting. It can also be concluded that assessing the quality of composting based on the fraction distribution can be a promising element of the biofermentation process monitoring. Full article

Acinetobacter baumannii remains a significant nosocomial infectious agent, with its ability to acquire antimicrobial resistance posing a global public health concern. Over time, substantial knowledge has been amassed regarding A. baumannii in human clinical cases. Recently, research has shifted to non-human A. baumannii. Therefore, the current work aimed to investigate the occurrence of A. baumannii carrying carbapenem resistance genes in broiler chickens via molecular detection and its public health significance. Two hundred cloacal swabs were collected from broiler chickens and grouped into 40 pools. DNA extraction was conducted on these pools, followed by molecular detection of the A. baumannii bla_OXA-51-like gene. Among the 40 pools, 31 (77.5%) tested positive for the bla_OXA-51-like gene and were further screened for additional carbapenemase genes, including bla_OXA-58, bla_OXA-23, and bla_OXA-24. The bla_OXA-58 gene was identified in eight pools (25.8%), whereas bla_OXA-23 and bla_OXA-24 were not detected. Subsequently, partial DNA sequencing was performed on two PCR amplicons of the A. baumannii bla_OXA-51-like gene derived from broiler chickens, followed by a phylogenetic analysis. The analysis revealed genetic similarity between the A. baumannii sequences obtained in this work and those retrieved from humans, birds, animals, and environmental sources. In conclusion, the occurrence of A. baumannii harboring genes coding for carbapenem resistance in broiler chickens highlights a potential new path of transmission, which may require further investigation to better understand the dynamics of transmission and to guide effective strategies for preventing and controlling A. baumannii infections. Full article

Bacteria adapted to elevated temperatures are commonly associated with geothermal environments and are recognized for their functional diversity. In this study, cultivable bacteria were isolated from a geothermal spring in northern Sinaloa, Mexico, and characterized through physicochemical analysis, molecular identification, growth kinetics, and functional screening. The isolates were identified as Bacillus licheniformis (strains J1, J3, and J8) and Brevibacillus borstelensis (strains J6 and J9). Growth analyses showed that, in nutrient broth at 45 °C, the evaluated strains exhibited specific growth rates ranging from 1.25 to 1.78 h⁻¹ and short doubling times between 23 and 33 min, with B. borstelensis J6 displaying the highest rate. At 50 °C, μmax values ranged from 0.77 to 1.08 h⁻¹, indicating sustained growth at elevated temperatures. Functional assays demonstrated extracellular proteolytic, amylolytic, and cellulolytic activities, mainly associated with B. licheniformis strains, in addition to tolerance to the pesticides fluazinam and benomyl. Antagonistic tests showed that B. licheniformis J8 inhibited the phytopathogenic fungi Sclerotinia sclerotiorum and Sclerotium rolfsii, while qualitative mineral solubilization assays indicated the ability of selected isolates to mobilize phosphate and potassium. These findings highlight geothermal ecosystems as valuable reservoirs of thermotolerant bacteria with enzymatic versatility and environmental relevance, supporting further molecular and process-optimization studies. Full article

Antimicrobial resistance [AMR] is a silent yet intensifying global threat, with particularly severe consequences in tropical and subtropical ecosystems, where high ecological connectivity, extensive antimicrobial use, and inadequate sanitation create ideal conditions for the persistence and spread of antimicrobial resistance genes [ARGs]. Within the One Health framework, migratory birds warrant special attention because they traverse tropical AMR hotspots, linking contaminated aquatic, agricultural, and peri-urban environments along established flyways. Evidence from tropical and subtropical regions indicates that migratory birds frequently carry clinically relevant AMR-associated pathogens, including extended-spectrum β-lactamase-producing Escherichia coli, multidrug-resistant Salmonella enterica, and fluoroquinolone- and macrolide-resistant Campylobacter spp. These findings suggest that migratory birds primarily function as ecological sentinels and geographic redistributors of antimicrobial resistance, reflecting environmental contamination and ecological connectivity between human-dominated and natural ecosystems, while evidence for long-term reservoir status remains context-dependent. Addressing the complex interface among AMR, migratory birds, and ARGs requires integrative surveillance strategies that explicitly incorporate wildlife into existing health systems. Genomic and metagenomic monitoring of migratory bird populations, combined with cross-sectoral data sharing, can provide early warning signals of emerging resistance patterns and inform evidence-based interventions. Understanding the ecological role of migratory birds in tropical ecosystems is therefore essential for designing effective One Health strategies to mitigate transboundary AMR risks and preserve the long-term efficacy of antimicrobial therapies. Full article

In today’s environment, rapid, reliable, and accurate bacterial detection is essential for protecting public health while preserving and ensuring the safety of food, water, and agricultural and environmental systems. Over the years, electrochemical sensors have gained widespread attention as viable candidates due to their rapid response, high sensitivity and selectivity, adaptability and portability, and low manufacturing cost. This facilitates their integration into various sectors, including healthcare and diagnostic applications, food safety and agriculture, and water and environmental monitoring. While these achievements represent tremendous progress, some of the challenges that need to be overcome include stability, batch-to-batch reproducibility, manufacturability, performance reliability, and the lack of point-of-care (POC) implementation for the utilization of these sensors for real-sample bacterial analysis. However, in the future, it is expected that with continued efforts made towards improving durability, standardization, and manufacturability, electrochemical bacterial sensors will be pivotal to the advancement of efficient bacterial diagnostics across various fields. This review presents major developments in modern electrochemical sensing technologies, which include, but are not limited to: electrochemical sensor and biosensor surface modifications, nanomaterials, the integration of artificial intelligence (AI) and machine learning (ML), and the emergence of wearable systems, for bacterial detection and monitoring. Additionally, their utilization in the aforementioned sectors is discussed. The integration and sustained use of these advanced electrochemical sensors for bacterial detection and surveillance can significantly enhance global safety and public well-being. Full article