Pseudomonas aeruginosa is a resilient Gram-negative pathogen frequently implicated in healthcare associated infections, particularly among immunocompromised individuals and those with chronic conditions such as cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), or cancer. It is well known for its high resistance to antibiotic treatment. This review briefly mentions P. aeruginosa’s resistance mechanisms, biofilm formation, and virulence factors, while primarily focusing on treatment challenges and recent advancements in therapeutic strategies aimed at overcoming resistance. Covered are novel non-antibiotic interventions such as quorum sensing inhibitors, quorum quenching agents, iron chelators, lectin and efflux pump inhibitors, as well as antimicrobial peptides and nanoparticles. Traditional medicine, phytochemicals, and probiotics are also evaluated. Additionally, this review explores the development of a viable vaccine, bacteriophage therapy, lactoferrin-hypothiocyanite combination, and topical use of electrochemical scaffolds. This review emphasizes the need for extensive safety studies and in vivo validation of these emerging non-antibiotic therapeutic strategies to determine their efficacy, pharmacological behavior, and clinical feasibility before they can be translated into practice. Many of these emerging treatments could play a vital role in future combination therapies by enhancing the efficacy of existing antibiotics and countering resistance and virulence mechanisms. Advancing these approaches from laboratory to clinical application remains a major challenge, making the development of approved therapies or vaccines a critical scientific and public health priority.

Klebsiella spp. are among the most prominent bacteria in nature and can be found in different environments, including soil, vegetation, and surface waters. The most important species of the Klebsiella genus is Klebsiella pneumoniae, which is recognized as an alarming opportunistic pathogen responsible for approximately 70% of human infections within their family. Due to their evolving hypervirulence and antimicrobial resistance, there is an increasing amount of research about the trends and mechanisms of virulence factors and epidemiology. Understanding pathogenetic mechanisms is important to advance diagnostic methods and treatment. In this review, we aim to summarize the available information and recent development in research of Klebsiella spp., specifically focusing on the trends in epidemiology, virulence factors, and the development of antimicrobial resistance.

Background and Objectives: Pseudomonas aeruginosa is a versatile, opportunistic pathogen responsible for a wide spectrum of infections, particularly in immunocompromised patients and those with disrupted epithelial barriers and chronic respiratory conditions. Its clinical significance is amplified by intrinsic and acquired antibiotic resistance, contributing to high mortality rates and treatment challenges. The bacterium’s pathogenic success stems from a multifaceted repertoire of virulence factors, including adhesins, pili, fimbriae, flagella, exopolysaccharides, biofilm-associated proteins, secreted toxins, proteases, lipases, phospholipases, rhamnolipids and redox-active metabolites. These factors are tightly regulated through complex networks, such as quorum sensing and c-di-GMP signaling, enabling dynamic adaptation to host environments and modulation of acute and chronic infection phenotypes. Biofilm formation and nutrient acquisition strategies further support survival in resource-limited conditions and protect against immune clearance and antibiotic pressure. Antibiotic resistance in P. aeruginosa limits therapeutic options. In addition, it may indirectly enhance virulence through modulation of stress responses and quorum sensing. P. aeruginosa’s pathogenicity emerges from the synergy between traditional virulence determinants and adaptive survival strategies, supporting long-term persistence, chronic infection, and resistance to host immunity and therapy. Materials and Methods: This narrative review is based on a comprehensive analysis of recent peer-reviewed literature focusing on virulence regulation, biofilm formation, nutrient acquisition strategies, and the interplay between antibiotic resistance and pathogenicity. Results: The reviewed evidence indicates that virulence expression in P. aeruginosa is highly dynamic and context-dependent, with regulatory networks integrating environmental signals to fine-tune pathogenic responses. A consistent finding across studies is the central role of biofilm-associated adaption in promoting persistence and antimicrobial tolerance. Moreover, the interaction between resistance mechanisms and global regulatory pathways appears to enhance bacterial fitness and long-term survival within the host. Conclusions: A deeper understanding of these interconnected mechanisms may facilitate the development of more effective anti-virulence and therapeutic strategies.

Background and Objective: Enterococci are typically found in a healthy human gastrointestinal tract but can cause severe infections in immunocompromised patients. Such infections are treated with antibiotics. This study addresses the rising concern of antimicrobial resistance (AMR) in Enterococci, focusing on the prevalence of vancomycin-resistant enterococcus (VRE) strains. Materials and Methods: The pilot study involved 140 Enterococci isolates collected between 2021 and 2022 from two multidisciplinary hospitals (with and without local therapeutic drug monitoring protocol of vancomycin) in Latvia. Microbiological assays and whole genome sequencing were used. AMR gene prevalence with resistance profiles were determined and the genetic relationship and outbreak evaluation were made by applying core genome multi-locus sequence typing (cgMLST). Results: The acquired genes and mutations were responsible for resistance against 10 antimicrobial classes, including 25.0% of isolates expressing resistance to vancomycin, predominantly of the vanB type. Genetic diversity among E. faecalis and E. faecium isolates was observed and seven potential outbreak clusters were identified, three of them containing sequence types ST6, ST78 and ST80. The prevalence of vancomycin resistance was highest in the hospital without a therapeutic drug-monitoring protocol and in E. faecium. Notably, a case of linezolid resistance due to a mutation was documented. Conclusions: The study illustrates the concerning prevalence of multidrug-resistant Enterococci in Latvian hospitals, showcasing the rather widespread occurrence of vancomycin-resistant strains. This highlights the urgency of implementing efficient infection control mechanisms and the need for continuous VRE surveillance in Latvia to define the scope and pattern of the problem, influencing clinical decision making and planning further preventative measures.

Objective: Hepatitis B virus (HBV) is a globally distributed infectious disease affecting the liver. This literature review aims to summarize all available relevant information on the PubMed database about HBV’s connection to the microbiome and to consider possible treatment adjuncts. Materials and methods: Database used: PubMed. Keywords used: “HBV”, “Hepatitis B”, “microbiome”. In the PubMed database, 179 research publications were identified using these keywords; 69 studies were excluded as they were irrelevant or retracted. Of the remaining, 110 were analyzed in this literature review, and four additional literature sources were used to supply background information and context. Information was summarized. The analysed studies in total included 14,814 participants (excluding animal studies), of whom 8564 were HBV-infected individuals. Results: Results characterizing abundance or decrease in specific bacterial, viral, and fungal species are heterogeneous; multiple studies support that the HBV patient oral and fecal microbiome is different from that in healthy controls (HCs) and varies throughout disease progression. The HBV seems to transform the microbiome negatively, leading to dysbiosis and decreased microbial diversity in most studies. Evidence links HBV microbiome changes with influence on HbeAg seroconversion, HBV-DNA load, metabolic pathways, liver cirrhosis, and hepatocellular carcinoma. The research proposes that members of microbiota could potentially promote or protect against liver injury in HBV. Four studies proposed that the plasma virome in HBV patients was primarily composed of members of the Anelloviridae. One study researched a parasite (Entamoeba gingivalis) in HBV patients. Two studies analyzed HBV patients’ fungal profiles. Conclusions: Microbiota research, although promising, at the present moment is heterogeneous. HBV patients’ microbiota is distinguishable from HCs, and multiple studies have tried to identify the HBV characteristic microbiome; however, more precise information is needed to draw conclusions. Fecal microbiota transplantation and probiotics have the potential to be therapy adjuncts for HBV patients, but more research is needed.