Search Results (1,884)

Essential oils (EOs) are complex plant-derived products known for their broad-spectrum antibacterial activity. This study aims to evaluate the chemical composition of eight essential oils-EOs (Caryophylli aetheroleum, Menthae aetheroleum, Origani aetheroleum, Rosmarini aetheroleum, Salviae aetheroleum, Melaleucae aetheroleum, Limonis aetheroleum, and Curcumae aetheroleum) and to evaluate their antibacterial and antibiofilm activity against five opportunistic pathogens with biofilm-forming potential (methicillin-susceptible and methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli, and Klebsiella pneumoniae). GC-MS was used to determine the chemical composition of the EOs, and antibacterial activity was evaluated using broth microdilution to determine the minimum inhibitory concentration and minimum bactericidal concentration. Biofilm inhibition was assessed by a crystal violet assay. Oxygenated monoterpenes and phenolic compounds were dominant in Origani, Menthae, Rosmarinus, Melaleucae, and Caryophylli aetheroleum. Potent inhibitory effects against the tested bacterial strains were observed for clove, tea tree, oregano, and rosemary EOs. The antimicrobial efficacy of EOs is closely linked to their chemical composition. Tea tree and oregano EOs exhibited the broadest spectrum of antimicrobial activity, while peppermint and curcuma oils were the least potent. Cytotoxicity thresholds from the literature suggest that some effective EO concentrations exceed safe mucosal limits, particularly in continuous high-dose applications, but short-contact delivery systems or adjunctive use with different agents may mitigate safety concerns. These findings support further investigation into their therapeutic applications in oral health products. Full article

Background/Objectives: Bacteroides species are key members of the human gut microbiota but can act as opportunistic pathogens. This study investigated the genomic features of clinical Bacteroides isolates from southern Thailand. Methods: Sixteen isolates were collected from body fluids, tissues, and pus at Songklanagarind Hospital (2022–2024). Whole-genome sequencing was performed on the BGI platform, followed by genome assembly, annotation, average nucleotide identity (ANI), pairwise single-nucleotide polymorphism (SNP) analysis, antimicrobial resistance (AMR) gene profiling, plasmid prediction, virulence screening, and phylogenetic analysis. Results: ANI and SNP analysis revealed two clusters: one comprising B. ovatus, B. intestinigallinarum, and B. thetaiotaomicron, and another mainly B. fragilis with one B. hominis isolate. All isolates were resistant to ampicillin, cephalothin, and penicillin; six B. fragilis strains were resistant to all tested antibiotics. The β-lactamase gene cepA was detected in all B. fragilis isolates, and plasmids were predicted in two genomes. Three virulence types (capsule formation, lipopolysaccharide modification, and stress response) were identified. Phylogenomic analysis confirmed species-level assignments and revealed underrecognized lineages, emphasizing the value of genome-based approaches for accurate classification. Conclusions: Clinical Bacteroides isolates display diverse resistance and virulence profiles, highlighting the importance of strain-level genomic surveillance. Full article

Background/Objectives: Klebsiella spp., particularly K. pneumoniae, are major opportunistic pathogens in healthcare settings driven by carbapenemase- and ESBL-producing strains. We assessed antimicrobial resistance and biofilm formation abilities in Klebsiella spp. from a Brazilian tertiary hospital and related environments and characterized capsular types. Methods: Over six months (July–December 2023), 303 carbapenem-resistant Klebsiella spp. were collected from clinical specimens (n = 198), ICU/non-ICU surfaces (n = 79), hospital sewage (n = 22), and stream water (n = 4). Species were identified by MALDI-TOF. Susceptibility testing covered eight antibiotic classes, focusing on carbapenems and polymyxin B. Biofilm formation was quantified by crystal violet, and capsular typing used wzi/K-locus approaches. Results: Most isolates (70.95%) had meropenem MICs ≥ 128 μg/mL, while 77.6% (n = 235) remained susceptible to polymyxin B. Resistance profiles largely consisted of extensive drug resistance (95.4%), with 1.3% exhibiting pandrug resistance, including isolates from bed rails. Biofilm formation was detected in 96.7% of isolates, mainly weak (67.6%) or moderate (28%), with 4.4% being strong producers. Among the Klebsiella isolates analyzed, 21 K types were identified with an uneven distribution dominated by K64, followed by K24, K173, and K50. K75 was the only K type detected across all sources—clinical isolates, bed-rail surfaces (non-ICU), wastewater, and fluvial water. Conclusions: Carbapenem-resistant Klebsiella spp. exhibited widespread resistance, with residual susceptibility to aminoglycosides, ceftazidime–avibactam, and polymyxins. Environmental reservoirs—hospital surfaces, sewage, and stream water—harbored resistant biofilm producers, reinforcing their role in persistence and dissemination. K-typing revealed concentrated distribution (predominantly K64) and cross-source K75. These findings underscore the urgency of integrated strategies combining molecular surveillance, antimicrobial stewardship, and environmental control. Full article

Nontuberculous mycobacteria (NTM) represent a heterogeneous group of environmental opportunistic pathogens that have emerged particularly in immunocompromised individuals and patients with underlying pulmonary disorders. NTM infections primarily affect the lungs, but can also manifest as lymphadenitis, skin and soft tissue infections, and disseminated disease. This retrospective study took into consideration 425 NTM-positive samples collected between May 2011 and December 2023, analyzed by sample type, sex, and age group (0–17, 18–49, 50–65, >65 years). Antimicrobial susceptibility analysis was performed on the 223 NTM strains with greater pathogenic power and most frequently isolated, from 2016 to 2023. Pulmonary NTM disease (NTM-PD) infections were most prevalent in patients over 65 years (52.1%), while extrapulmonary NTM disease (NTM-EPD) occurred most frequently in the 0–17 age group (56.4%). Women were slightly more affected (54.4%) than men (45.6%), with the highest incidence in female individuals over 65 years old. The most frequently isolated NTM species was the Mycobacterium avium complex (MAC) (47% of isolates). Antimicrobial susceptibility testing of 223 isolates from 2016 to 2023 revealed species-specific resistance patterns, with high susceptibility to clarithromycin in MAC (94.7%) and Mycobacterium chelonae (100%), but notable resistance in Mycobacterium abscessus complex (MABC). The increasing incidence of NTM infections underscores the need for improved diagnostic techniques and targeted treatment strategies. Full article

Intra-abdominal infections (IAIs) remain among the most challenging problems in surgical clinical practice. They range from uncomplicated appendicitis to life-threatening peritonitis, demanding rapid diagnosis, timely source control, and appropriate antibiotic therapy. Antibiotics are crucial to manage patients with complicated IAIs. Antibiotics should always be prescribed appropriately, ensuring the correct spectrum, timing, duration, and dosage. Appropriate prescribing within hospitals enhances treatment success and patient safety, while also reducing the risk of opportunistic infections such as Clostridioides difficile and lowering the likelihood of selecting resistant pathogens. Over recent decades, antimicrobial resistance has escalated into a worldwide public health threat. The rapid rise in multidrug-resistant organisms, especially Gram-negative bacteria, has created a pressing global concern. The objective of this narrative review is to describe (a) when antibiotics should be used in patients with IAIs; (b) which antibiotics should be selected in patients with IAIs; (c) how they should be managed in patients with IAIs; and (d) how long they should be administered in patients with IAIs. Full article

Exopolysaccharides (EPSs) are important extracellular metabolites secreted by microorganisms. Klebsiella pneumoniae is an opportunistic pathogen widely distributed in the environment, host mucosal and intestinal surfaces, and EPS from Klebsiella pneumoniae are of significant interest. Conventional studies have mainly focused on hypervirulent strains, whereas comprehensive investigations of non-hypervirulent strains and their EPS functionalities remain limited. This study employed ST678-type Klebsiella pneumoniae CGMCC 31459 as the model to investigate genomic characteristics, EPS structural features, and biological activities. Its genome comprises one chromosome and four plasmids, functionally enriched in carbohydrate metabolism genes, including abundant glycoside hydrolases and glycosyltransferases essential for EPS biosynthesis. Virulence and antimicrobial resistance assessments confirmed the absence of typical hypervirulence loci, indicating genetic stability with low pathogenic and resistance potential. EPS-KP is a weakly acidic, branched heteropolysaccharide composed of glucose, galactose, mannose, and glucuronic acid. EPS-KP exhibited significant antioxidant and anti-aging activities, with a 77.47% (5 mg/mL) superoxide anion scavenging rate and a 30.9% (200 μg/mL) lifespan extension in Caenorhabditis elegans, accompanied by enhanced SOD/CAT enzyme activity and reduced lipofuscin accumulation. This integrated genomic and biochemical analysis provides new insights into the safe, non-hypervirulent Klebsiella pneumoniae strain and its functional EPS, highlighting its potential for biotechnological applications. Full article

Streptococcus pneumoniae is a major opportunistic pathogen and a leading cause of severe infections in infants under two years of age. Human milk oligosaccharides (HMOs), key bioactive components of breast milk, possess immunomodulatory and antimicrobial properties. In this study, the antipneumococcal effects of HMOs are investigated across multiple S. pneumoniae serotypes, focusing on concentration-dependent activity and underlying mechanisms. Growth inhibition and bacterial viability were evaluated using growth curve analysis and colony-forming unit (CFU) assays. HMOs inhibited pneumococcal growth in a concentration-dependent manner, with suppression observed at 1.5–2.5 mg/mL and complete killing at 5 mg/mL for all serotypes. Nonencapsulated strains were more sensitive, with inhibition at 1 mg/mL. In the CFU assays, killing occurred at 1.25–5 mg/mL depending on the strain. At physiologically relevant colostrum concentrations (20–25 mg/mL), HMOs achieved complete bactericidal effects across all the tested strains. In contrast, lactose at equivalent doses showed no measurable antimicrobial activity, confirming the specificity of the observed effects. Overall, HMOs exhibit serotype-independent antipneumococcal activity, possibly through interference with bacterial adhesion or metabolic disruption. These findings suggest a potential role for HMOs as adjunctive agents in the prevention of pneumococcal infections in vulnerable populations, such as infants, and warrant further in vivo studies to validate these effects and explore clinical applications. Full article

COVID-19 can cause long-term symptoms, such as a post-infection syndrome, known as Long-COVID. Among the symptoms present during this period, the most reported are gastrointestinal symptoms. This study discusses the effects of changes in the gut microbiota of post-COVID-19 patients. SARS-CoV-2 infection is associated with significant alterations in gut microbial composition, disturbing its homeostasis and promoting a reduction in the abundance of beneficial symbiotic bacteria and an increase in the abundance of opportunistic pathogens. Furthermore, the composition of the gut microbiota may play a role in the prognosis of patients with post-COVID-19 infection. The microbiota of the intestinal tract and the respiratory tract influence each other; therefore, the gut–lung axis has attracted increasing interest in understanding COVID-19. Moreover, the brain–gut axis has been studied, since there have been reports of anxiety and depression along with post-COVID-19 gastrointestinal symptoms. Treatments options for intestinal dysbiosis in Long-COVID patients include probiotics, prebiotics, and fecal microbiota transplantation. These treatments may serve as an approach to improve gastrointestinal symptoms during Long-COVID, increasing microbiome diversity, strengthening the integrity of intestinal barrier functions, and consequently influencing the treatment of COVID-19. Full article

Antimicrobial resistance (AMR) is a major public health threat that urgently requires alternative strategies to address this challenge. Klebsiella spp. are among the most important clinical pathogens and a leading cause of opportunistic nosocomial infections, with high morbidity and mortality associated with strains resistant to last-line antimicrobials such as carbapenems. Bacteriophages are considered a promising therapeutic option for treating infections caused by Klebsiella strains. Hence, the aim of this work was to isolate and characterize a phage capable of infecting carbapenem-resistant Klebsiella strains. The phage KpCCP1 was isolated using the double layer agar method (DLA), from the influent of a wastewater treatment plant, which was characterized through phenotypic and genomic analyses. Morphological characteristics were determined using TEM, and its host range was evaluated against a collection of 133 Klebsiella strains. Its whole genome was sequenced using the Illumina NovaSeq X Plus platform and then assembled and annotated. VICTOR was used for phylogenetic analysis of the isolated phage, and VIRIDIC to compare its genome with those of its closest relatives. KpCCP1 is a tailed dsDNA lytic phage with a genome size of 177,276 bp and a GC content of 41.82%. It encodes 292 ORFs, including two tRNA genes. Phage KpCCP1 is a member of the Slopekvirus genus in the Straboviridae family. It is capable of infecting 22 carbapenem-resistant Klebsiella strains, including K. pneumoniae and K. michiganensis. Notably, it does not contain virulence or antibiotic resistance genes and harbors putative anti-CRISPR genes, therefore representing a promising candidate for phage therapy against clinically critical Klebsiella strains. Full article

Archaea, one of the three domains of life, are increasingly recognized as consistent, though often underappreciated, members of the human microbiome, yet their roles in health and disease remain poorly understood. Unlike bacteria, no archaeal species have been conclusively identified as primary mammalian pathogens, but their widespread presence across diverse body sites suggests potential indirect contributions to host physiology and pathology. Current evidence is synthesized on archaeal diversity and habitat specificity across multiple human-associated sites, encompassing the gastrointestinal, aerodigestive, and urogenital tracts as well as the skin. Methanogens dominate the lower gastrointestinal tract (LGT), where they influence fermentation dynamics and methane production, while members of the class Nitrososphaeria are prevalent on the skin and upper aerodigestive tract (UAT), reflecting ecological specialization. Variability in archaeal composition across niches highlights possible links to disease processes: methanogens have been associated with irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), obesity, and colorectal cancer (CRC); Methanobrevibacter oralis is enriched in periodontal disease; and archaea have been detected in the lungs of cystic fibrosis patients. Although archaea lack canonical bacterial virulence factors, they may contribute indirectly through metabolic cross-feeding, immune modulation, synergy in polymicrobial infections, and alteration of host–microbiome network dynamics. This review explores the emerging concept of the human “archaeome”, evaluates current evidence for archaeal involvement in disease, and highlights emerging technologies, such as bacteria-MERFISH and multi-omics profiling, that enable translational applications including microbiome diagnostics, therapeutic targeting, and microbiome engineering. Full article

Aspergillus species are major opportunistic pathogens responsible for invasive aspergillosis, with antifungal resistance posing increasing challenges to their treatment worldwide. We investigated the antifungal susceptibility and genomic features of Aspergillus isolates from sterile clinical specimens collected at a tertiary hospital in Thailand between January and December 2023. In total, 24 isolates were identified via culture and tested for amphotericin B and voriconazole susceptibility using CLSI M38 broth microdilution, and whole-genome sequencing was performed on selected isolates to characterize resistance mechanisms. Aspergillus fumigatus was the most frequent species (54%), followed by A. flavus (29%) and other less common species. Voriconazole exhibited potent activity against most isolates, although two A. fumigatus strains showed elevated MICs (2–4 µg/mL), meeting resistance thresholds. One isolate (CUAFU23) was confirmed to harbor the cyp51A TR34/L98H mutation, marking the first identification of this canonical azole resistance mechanism in a clinical specimen from Thailand and supporting earlier environmental findings of azole-resistant A. fumigatus carrying the same allele. Genomic profiling of CUAFU23 further revealed subtle but distinct shifts in domain composition compared with susceptible strains, suggesting broader adaptive changes. The above findings underscore the emergence of azole-resistant A. fumigatus in Thailand and highlight the importance of ongoing surveillance using combined phenotypic and molecular approaches. Full article

Candida species are common commensals within the human microbiome but can transition opportunistically to pathogenic states when host–microbe homeostasis is disrupted. Their ability to adhere to mucosa and implanted medical devices, form thick biofilms, and invade epithelial tissues makes candidiasis particularly harmful in immunocompromised and elderly populations. This review examines the reported antifungal activity of common probiotic genera such as Lactobacillus, Bacillus, Bifidobacterium, and Saccharomyces across the oral cavity, gastrointestinal tract, and vaginal tract. The probiotic mechanisms of action, such as competitive exclusion, secretion of antifungal metabolites, and immunomodulation, are explored in detail, and research methodologies are scrutinised to assess the robustness of current evidence. This review compiles evidence from a variety of studies and clinical trials showing certain probiotic strains and formulations have the ability to significantly decrease Candida colonisation and reduce candidiasis symptom prevalence. Although outcomes vary greatly between probiotic strains tested, species of Candida targeted, and specific site of infection, it is clear that selected probiotic species and their secreted substances can have prominent anti-Candida effects and promote tangible clinical improvements. Future directions for the field of probiotic study are suggested, including the roles of prebiotics, postbiotics, and synbiotic formulations to enhance probiotic efficacy against candidiasis. Full article

Background/Objectives: Staphylococcus sciuri, traditionally regarded as a commensal organism in animals and the environment, is increasingly recognized as a potential opportunistic pathogen with zoonotic significance. Its genomic reservoir of methicillin resistance homologues further raises concern regarding its role in antimicrobial resistance dissemination. This study describes the first documented case of S. sciuri isolated from the urinary bladder of a domestic rabbit (Oryctolagus cuniculus) in Romania, emphasizing its clinical relevance and antimicrobial profile. Methods: A seven-year-old intact female rabbit presenting with apathy, dysuria, and hematuria underwent clinical evaluation, ultrasonography, and cystocentesis. The aspirated intravesical content was subjected to bacterial culture, MALDI-TOF MS identification, and antimicrobial susceptibility testing via the VITEK 2 system. Results: Pure colonies of Gram-positive cocci were identified as S. sciuri with high confidence. Antimicrobial susceptibility testing revealed susceptibility to β-lactams, aminoglycosides, glycopeptides, linezolid, rifampicin, fusidic acid, tigecycline, and trimethoprim-sulfamethoxazole, while resistance was observed against fluoroquinolones, macrolides, lincosamides, and tetracycline, indicating a multidrug-resistant phenotype. Treatment with trimethoprim-sulfamethoxazole combined with ultrasound-guided bladder lavage and supportive therapy resulted in complete clinical recovery within 10 days. Conclusions: This case highlights the pathogenic potential of S. sciuri in domestic rabbits and its capacity to exhibit multidrug resistance. The findings underscore the necessity of including rabbits in antimicrobial resistance surveillance programs and reinforce the importance of culture and sensitivity testing in guiding the therapeutic management of exotic companion animals. Full article

Bats are widely recognized as reservoirs of diverse bacterial pathogens with important implications for human health. Recent zoonotic disease outbreaks have intensified interest in bat microbiomes, with high-throughput sequencing increasingly used to assess microbial diversity. In this article, we review literature from the past five years on bacterial species associated with bats and their potential clinical relevance. Using automated searches and manual filtering, we extracted data from 47 peer-reviewed studies. Most research has focused on guano samples, though interest in skin microbiomes is rising, particularly in relation to Pseudogymnoascus destructans, the agent of white-nose syndrome. China leads in the number of publications, followed by the United States, and amplicon sequencing remains the predominant metagenomic method. Across studies, 4700 bacterial species were reported, including several known human pathogens capable of aerosol transmission or opportunistic infections in immunocompromised individuals. Many of these taxa are classified as global priority targets for antimicrobial drug development by the World Health Organization and the U.S. Centers for Disease Control and Prevention. Given the clinical severity of diseases linked to some species, bats should be integrated into epidemiological surveillance systems. However, the lack of standardized reporting practices significantly limits the comparability and utility of bat microbiome data for robust ecological and epidemiological analyses. Full article

Stenotrophomonas maltophilia (S. maltophilia) is a multidrug-resistant opportunistic pathogen. There are an increasing number of case reports on S. maltophilia infections in recent years, and the species is becoming a public health concern. Many studies have focused on profiling and pangenome of the species, particularly on their antibiotic resistance and virulence genes. However, there is a lack of studies on mobile genetic elements (MGEs), a subset of pangenome that significantly contributes to the diversity, stability, and plasticity of a population. In this study, 20 genomes of S. maltophilia were downloaded from the NCBI Genome database. The genomes were subjected to profiling of MGEs, their impact on the population structures, and the evaluation of evolutionary trends of the core genomes. The cataloguing of MGEs indicated active horizontal gene transfer events in the S. maltophilia’s population. Multiple virulence and drug resistance genes were predicted within and outside of the MGEs. We observed multiple chromosomal rearrangements in the genomes, most likely caused by MGEs, affecting up to approximately 50% of a single genome sequence. A high number of linkage disequilibrium sites were also predicted in the core genomes. This study provides insights into stability in the core and plasticity in the accessory regions in the S. maltophilia population. Full article