Acta Microbiol. Hell., Volume 70, Issue 4 (December 2025) – 10 articles

The European catfish (Silurus glanis, Linnaeus 1758), commonly known as the wels catfish, is one of the largest freshwater fish in Europe and an ecologically and economically important species in both natural ecosystems and aquaculture. Its broad native distribution, together with the rapid growth of farming practices, increases concerns about pathogen dissemination and their potential impact on biodiversity, animal health, and potential risks to human healthcare. This review is based on a structured literature search following PRISMA recommendations for narrative reviews and summarizes current knowledge on the main pathogen groups affecting S. glanis—viruses (ranaviruses, alloherpesviruses), bacteria (Aeromonas spp., Edwardsiella spp.), protozoan and metazoan parasites (Ichthyophthirius multifiliis, Thaparocleidus spp., Eustrongylides spp., Contracaecum larvae), and oomycetes (Saprolegnia spp., Branchiomyces spp.). Within the One Health approach, particular attention is given to zoonotic pathogens such as Aeromonas spp., Edwardsiella tarda, and helminths like Eustrongylides and Contracaecum, which may cause risks to human health through contaminated water or consumption of raw or undercooked fish. The review integrates findings from field surveys, regional case studies such as those from the Danube basin, and data from the authors’ doctoral research. Because the wels catfish is increasingly cultivated and serves as an apex predator in natural habitats, its effective disease management is critical for both aquaculture and wild populations, and also for the food chains at all. Strengthened surveillance, health monitoring, and biosecurity measures are essential preventing the introduction and spread of pathogens into new hosts and habitats. Through the underlining of major catfish pathogen groups, this review highlights key challenges within the One Health approach and underscores the need for integrated health monitoring, biosecurity, and environmental management strategies. Full article

Malassezia spp. has been recognized among neonatal intensive care unit (NICU) patients’ commensals and pathogens, accounting for a significant number of invasive fungal infections. The Random Amplified Polymorphic DNA (RAPD) may be used for Malassezia spp. strains typing from clinical isolates, demonstrating high resolution and specificity. Herein, we propose a retrospective analysis of Malassezia spp. isolates, aiming to investigate their identity and transmission pathways. Moreover, we documented Malassezia spp. prevalence within the University Hospital Policlinico of Catania, Italy. The analysis collected a total number of 16 M. pachydermatis and categorized them into four different clusters, hypothesizing a horizontal transmission. Although the essential role of microbiological sample cultures, our data suggested further environmental surveillance protocols to prevent NICU patients’ colonization due to the Malassezia spp. persistence and adhesion within healthcare surfaces. Full article

Linezolid (LZD) is an oxazolidinone antibiotic effective in the treatment of infection with Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The decline in susceptibility to linezolid is a concern for antimicrobial chemotherapy. In this study, the prevalence of the LZD minimum inhibitory concentration (MIC) of 2 mg/L (LZD-MIC2), which represents a slightly high value within a range of susceptibility for S. aureus (≤4 mg/L), was investigated retrospectively for staphylococcal species from different sources. We collected the records of LZD MIC of Staphylococcus/Mammaliicoccus that had been obtained in our previous studies on isolates from patients, healthy individuals, and foodstuff. Prevalence of isolates showing LZD-MIC2 was analyzed depending on the type of staphylococcal species and S. aureus clones. In clinical isolates, methicillin-susceptible S. aureus (MSSA) and S. argenteus showed significantly higher LZD-MIC2 rates (20.0% and 21.5%, respectively) than MRSA (7.3%). Among clinical and colonizing isolates of MSSA, LZD-MIC2 was more commonly found in CC1 (ST188, ST2990, etc.), CC8, CC15, ST30, ST97, and ST121 than other lineages. In S. argenteus isolates, which were mostly methicillin-susceptible, there was no significant difference in the LZD-MIC2 prevalence among the three genotypes. The LZD-MIC2 was detected in 18.3% of coagulase-negative staphylococci (CoNS), with S. saprophyticus, S. pasteuri, and M. sciuri showing higher prevalence (30–57%) than other species. The present study revealed that the prevalence of the LZD-MIC2 is different depending on staphylococcal species/types, as they are more common in specific MSSA lineages and some CoNS species. Full article

West Nile Virus (WNV), a mosquito-borne flavivirus first identified in Uganda in 1937, has emerged over the past quarter century as a major global public health threat. Since its introduction into North America in 1999, WNV has become the leading cause of arboviral neuroinvasive disease, with recurrent outbreaks continuing across Europe, Africa, and the Americas. This review provides a comprehensive overview of the microbiology, epidemiology, and clinical impact of WNV. We discuss the molecular biology of the virus, highlighting its genomic organization, replication strategies, and the structural and non-structural proteins that underpin viral pathogenesis and immune evasion. The complex enzootic transmission cycle, involving Culex mosquitoes and diverse avian reservoir hosts, is examined alongside ecological and climatic determinants of viral amplification and spillover into humans and equines. The clinical spectrum of WNV infection is outlined, ranging from asymptomatic seroconversion to West Nile fever and life-threatening neuroinvasive disease, with particular emphasis on risk factors for severe outcomes in older and immunocompromised individuals. Current approaches to diagnosis, supportive management, and vector control are critically reviewed, while challenges in vaccine development and the absence of effective antiviral therapy are underscored. Finally, we address future research priorities, including therapeutic innovation, predictive outbreak modeling, and genomic surveillance of viral evolution. WNV exemplifies the dynamics of emerging zoonotic diseases, and its persistence underscores the necessity of a coordinated One Health approach integrating human, animal, and environmental health. Continued scientific advances and public health commitment remain essential to mitigate its enduring global impact. Full article

Severely burned patients are at high risk of local and systemic infections due to skin barrier loss. Their clinical management is complex and requires coordinated intensive care and infection prevention strategies. Diagnosing infective endocarditis (IE) in this population is particularly difficult due to overlapping symptoms and limited diagnostic specificity. Common pathogens include Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. We conducted a retrospective cohort study on 543 patients with burns affecting >18% of total body surface area (TBSA), admitted to our Burn Intensive Care Unit (BICU) from 2019 to 2024. The incidence of infective endocarditis was 1.47%, involving aortic (75%), mitral (12.5%), and tricuspid (12.5%) valves. Pathogens identified included S. aureus, Klebsiella pneumoniae, A. baumannii, and P. aeruginosa. This incidence is significantly higher than that in the general population. Mortality reached 50%, with an overall 3-month mortality of 75%. The literature on IE in burn patients is scarce, and the role of antibiotic prophylaxis remains controversial. Infective endocarditis in burn patients, although rare, represents a severe complication with high mortality. Early diagnosis and coordinated multidisciplinary care are essential to improve patient outcomes. Full article

The COVID-19 pandemic resulted in high morbidity and mortality, as well as severe social and economic disruption globally. Since the pandemic began in 2019, the severe acute respiratory syndrome, coronavirus 2, has undergone numerous changes, resulting in the emergence of new variants and subvariants. The emergence of new variants of the virus poses a challenge to scientists. There is currently no SARS-CoV-2 variant meeting the criteria of variants of concern, whereas the only variant of interest is JN.1, and there are six variants under monitoring: LP8.1, NP1.8.1, XEC, KP.3, KP.3.1.1 and the latest, XFG (Stratus). Although the latter appears to be more transmissible than the others, genomic evidence indicates that it is less aggressive than some recent variants. Nevertheless, continuous genomic surveillance of COVID-19 is still important to detect any new variants that could threaten public health. Numerous therapeutic strategies, such as drugs, vaccines, and nutritional supplements, are being used to treat COVID-19. This narrative review is an overview of COVID-19 and its various facets, from the number of cases to the therapies used, the current variants, and the ongoing clinical trials, specifically focusing on the most recent studies. Full article

Genome editing technologies, including CRISPR/Cas9, TALENs, and ZFNs, offer promising approaches to disrupt HPV oncogenes E6 and E7, thereby restoring tumor-suppressor pathways. In this review, we summarize recent preclinical findings demonstrating selective apoptosis and tumor regression in HPV-positive cell and animal models, as well as early-phase clinical studies exploring local CRISPR-based therapies. We also compare the relative strengths and limitations of major editing platforms, discuss delivery strategies, and highlight their potential integration with immunotherapy and conventional treatments. While preclinical studies show encouraging efficacy (e.g., up to 60% tumor regression in xenograft models and marked reactivation of p53/pRb pathways), translation into routine practice remains limited by challenges such as efficient delivery, minimizing off-target effects, long-term safety, cost, and ethical considerations. Continued optimization of high-fidelity nucleases, tissue-specific delivery systems, and genotype-tailored guide RNAs will be essential. Genome editing therefore represents a potential future addition to the therapeutic landscape of HPV-related diseases, but substantial barriers must be addressed before clinical implementation. Full article

Dermatophilosis, caused by the Gram-positive, filamentous bacterium Dermatophilus congolensis, is an important skin disease that adversely affects cattle health and productivity. It also affects other domestic and wild animals and occasionally humans. This review provides a detailed overview of the molecular characteristics and resistome profile of D. congolensis, highlighting recent advances in genomic research. We examine the bacterium’s genome architecture, including its genome size, GC content, gene composition, and phylogenetic placement within the Actinomycetales. Key virulence factors are discussed, including proteolytic enzymes, hyphal invasion, zoospore motility, and the gene products of nasp and agac, emphasizing their roles in tissue invasion, pathogenesis, and diagnostic detection. Furthermore, we analyze resistome, focusing on identified antibiotic resistance genes, diverse resistance mechanisms such as efflux pumps and beta-lactamases, and the contribution of mobile genetic elements to horizontal gene transfer. The implications of these molecular insights for accurate diagnosis, effective treatment, and antibiotic stewardship in cattle production are critically evaluated. Finally, we highlight future research priorities aimed at deepening our understanding of D. congolensis biology and improving strategies for disease control. This review underscores the importance of integrating molecular surveillance with antimicrobial monitoring to safeguard cattle health and promote sustainable livestock management. Full article

Worldwide, polymicrobial infections (PMIs) account for an estimated 20–50% of severe clinical infection cases, with biofilm-associated and device-related infections reaching 60–80% in hospitalized patients. This review discusses the clinical burden of major infections in which PMIs are almost inevitable, such as diabetic foot infections, intra-abdominal infections, pneumonia, and biofilm-associated device infections. Globally, the PMI landscape is diverse; however, the Indian subcontinent is a PMI hotspot where high comorbidities, endemic antimicrobial resistance, and underdeveloped diagnostic capacity elevate the risks of poor outcomes. Existing diagnostic like culture-based methods, PCR panels, sequencing, and biomarker-based assays are constrained by sensitivity, turnaround times (TATs), and high costs. Vulnerable populations, particularly neonates, the elderly, immunocompromised patients, and socioeconomically marginalized groups, show case-fatality rates 2-fold higher than monomicrobial infections in similar settings. Emerging diagnostic solutions include CRISPR-based multiplex assays, artificial intelligence-based metagenomic platforms, and sensitive biosensors with point-of-care applicability. These technologies show potential in reducing the TAT (<2 h) with high accuracy (>95%). However, their translation to real-world settings depends critically on affordability, integration into healthcare pathways, and supportive policy. This will provide equitable diagnostic access, particularly in low- and middle-income countries (LMICs). Full article

Age-related impaired wounds often become infected with bacteria, leading to substantial mortality and morbidity in the elderly. The decline in androgen levels with increasing age is believed to exacerbate inflammation during wound infections. Despite its well-documented anti-inflammatory activities in wound repair, little is known about the effect of age-related androgen deprivation on bacterial phagocytosis in impaired chronic wounds. The aim of this study was to investigate the effect of age-related testosterone deprivation on the phagocytic functions of THP-1 monocyte-derived macrophages to eliminate Gram-positive and Gram-negative bacteria in vitro. Host–pathogen interaction experiments were conducted to quantify the macrophage-mediated clearance of two common wound-associated bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, under in vitro environments that model testosterone levels representative of those found in elderly males, healthy young adults and testosterone replacement therapy (TRT). Testosterone and its metabolite 5α-dihydrotestosterone (DHT) significantly dampened the macrophage-mediated phagocytosis of both MRSA and P. aeruginosa in a dose-dependent manner (p < 0.05). Blockade of the androgen receptor (AR) using enzalutamide confirmed that testosterone mediates bacterial clearance through binding to the AR. Blocking the conversion of testosterone to DHT through stimulation of macrophages with the 5-α-reductase inhibitor finasteride reversed the testosterone-mediated effects on bacterial clearance, which confirmed that testosterone could potentially dampen the innate phagocytic responses in macrophages through conversion to DHT. Novel findings in this study suggest that the selective manipulation of the AR and/or blockade of testosterone–DHT conversion may provide effective therapeutic treatments to combat wound infections in the elderly. Full article