Acta Microbiologica Hellenica

Background: The clinical significance of Helicobacter pylori (H. pylori) infection in acute non-variceal upper gastrointestinal bleeding (NVUGIB) remains uncertain, particularly regarding short-term outcomes beyond rebleeding. Methods: We conducted a single-center retrospective cohort study of consecutive adults admitted with acute NVUGIB to Hatyai Hospital, Thailand, between January 2016 and December 2020. H. pylori status was determined during the index hospitalization using rapid urease testing and/or histopathologic examination of gastric biopsy specimens obtained during upper gastrointestinal endoscopy. The primary outcome was 30-day all-cause mortality. Secondary outcomes included in-hospital mortality, rebleeding, requirement of packed red blood cell transfusion, and length of hospital stay. Multivariable regression analyses were performed to adjust for potential confounders. Results: Among 933 patients, 289 (31.0%) were H. pylori-positive and 644 (69.0%) were H. pylori-negative. The H. pylori-positive group was younger, predominantly male, and had lower rates of cirrhosis and prior proton pump inhibitor use. They also more often had peptic ulcer bleeding and underwent earlier endoscopy. H. pylori positivity was independently associated with lower 30-day mortality (adjusted odds ratio 0.39, 95% confidence interval 0.18–0.84), but not with rebleeding, requirement of transfusion, or length of stay. Conclusions: H. pylori positivity was associated with lower short-term mortality in acute NVUGIB, although this finding may reflect baseline clinical differences rather than a direct effect on bleeding severity. Full article

Background: The vagina undergoes important changes across the life course that are shaped not only by hormonal transitions but also by shifts in the vaginal microbial environment. Despite growing interest in the vaginal microbiome, research has disproportionately centered reproductive-aged populations, leaving the aging vagina comparatively understudied. Objective: This article examines the aging vagina through a life-course lens, with emphasis on microbial and clinical transitions associated with midlife and older adulthood. Key Content: The article highlights menopause-related changes and approaches for reducing stigma and missed clinical opportunities. Particular attention is given to menopause-related declines in estrogen, reduced glycogen availability, increased vaginal pH, and accompanying changes in microbial balance, as well as their relationship to dryness, irritation, genitourinary symptoms, and susceptibility to adverse outcomes. The article also provides health professionals with a practical educational framework for symptom recognition, patient communication, vaginal health assessment, menopause-related education, stigma reduction, and prevention of missed clinical opportunities. Conclusions: Positioning the aging vagina within life-course and microbial-health frameworks can strengthen prevention, improve symptom recognition, and support more age-inclusive, informed, and responsive care for older women. Full article

Introduction: In recent years, antibiotic resistance has increased a lot due to inappropriate prescribing practices, presenting a critical global health challenge. There is evidence of inappropriate prescription practices by dental practitioners in Saudi Arabia. Aim: This scoping review of the published literature aimed to report on the knowledge levels and practice of antibiotic prescriptions among dental practitioners in Saudi Arabia. Methods: Three databases (PubMed, ProQuest and Scopus) were searched for relevant studies; eligible studies (primary research conducted in Saudi Arabia) were organized into three broad domains: knowledge among dental students, knowledge levels among dentists, and prescribing practice among dentists. The quality of the included studies was assessed with the Newcastle–Ottawa Scale. Results: Of the 407 search records, 22 were eligible for inclusion. Almost all studies (n = 21) were cross-sectional in design. Most of the included studies assessed the knowledge among dental students, interns and practicing dentists. Two studies were analyzing medical records and antibiotic prescribing patterns, whereas only one study was implemented as a clinical audit whose measures resulted in positive outcomes (i.e., decrease in prescriptions and increase in awareness). Most of the studies revealed a low level of knowledge and inappropriate prescription patterns among dental students and interns. Conclusions: Since only one study evaluated an interventional approach (clinical audit) that resulted in a significant reduction in inappropriate prescriptions, future research should focus on measurements and interventions to increase awareness and reduce inappropriate prescriptions. Full article

Early-onset infection caused by Streptococcus agalactiae (Group B Streptococcus, GBS) may occur during gestation or delivery and can lead to severe neonatal sepsis, meningitis, or pneumonia. Discordant GBS infections in twin gestations are rare. We report a fatal case of early-onset GBS infection in dichorionic–diamniotic twins conceived via IVF and delivered by caesarean section at 32 weeks’ gestation due to discordant fetal growth and abnormal Doppler indices in Twin A (Umbilical Artery PI = 1.4; Middle Cerebral Artery PI = 1.5). Twin A had Apgar scores of 3, 5, and 5 and rapidly developed tachycardia, respiratory distress, and systemic infection, while Twin B, with Apgar scores of 7, 8, and 9, remained clinically stable. Both infants were admitted to the NICU and underwent routine blood, urine, and cerebrospinal fluid testing. Despite the prompt initiation of parenteral ceftriaxone and respiratory support, Twin A deteriorated rapidly and died within 28 h. GBS was isolated from Twin A’s blood culture, and maternal placental tissue and high vaginal samples collected before antibiotic administration also grew GBS, with all isolates demonstrating identical antimicrobial resistance profiles. Molecular analysis revealed matching rib1 and alp2/3 gene patterns in isolates from the mother and Twin A. Maternal anovaginal immunochromatography at delivery was positive, whereas screening cultures obtained at 29 weeks’ gestation were negative. This case highlights the limitations of culture-based GBS screening in high-risk pregnancies and preterm deliveries and underscores the potential value of molecular assays and point-of-care testing to improve detection of S. agalactiae throughout pregnancy and the peripartum period. Emerging preventive strategies, including modulation of the genital microbiome and maternal vaccination aligned with WHO recommendations, may further reduce the burden of neonatal GBS disease. Full article

Leptospirosis is a zoonotic disease caused by spirochetes of the genus Leptospira, primarily transmitted via direct or indirect contact with contaminated rodent urine. Human disease ranges from a mild, flu-like illness to severe, life-threatening Weil’s disease. Although the incidence of leptospirosis in Greece is not high, the Ionian Islands Region, including Corfu Island, presents the highest average frequency of cases in the country. A retrospective study of 11 confirmed cases in Corfu between 2015 and 2025 was conducted. The infections recorded during this period occurred from autumn to spring, exclusively affecting male patients in rural settings; notably, 90.9% of cases were attributed to occupational exposure. No association with urban or tourist areas was found. Although the incidence of the disease decreased by 42.1% compared to the previous decade (2005–2014), the case fatality ratio reached 27.3%, considerably above the average of 2.6% in Europe (during 2010–2022). The study underscores the need for enhanced clinical awareness and targeted preventive measures in Corfu, mainly among patients with at-risk occupations. Timely preparedness is needed especially in the face of ongoing climate change. Full article

People living with HIV (PLWH) receiving effective antiretroviral therapy (ART) continue to exhibit chronic immune activation and systemic inflammation despite virological suppression. The viral envelope glycoprotein gp120, which binds the CD4 receptor and mediates viral entry, has been implicated in pro-inflammatory and pro-apoptotic effects in neuronal and endothelial cells. Although gp120 is expressed on the viral surface, its oligomeric structure and its ability to form immune complexes with circulating antibodies may reduce the sensitivity of standard detection assays in serum. Soluble gp120 has been associated with increased levels of pro-inflammatory cytokines, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β), as well as chemokines. These mediators may contribute to blood–brain barrier dysfunction, endothelial injury, vascular smooth muscle alterations, and subsequent neurodegenerative and cardiovascular complications. Importantly, gp120 shedding may persist due to viral reservoirs and intermittent reactivation, even during ART. Fostemsavir inhibits the interaction between gp120 and CD4, preventing viral entry and potentially limiting gp120-mediated pathogenic effects. Beyond antiviral activity, this mechanism suggests a potential role in attenuating gp120-mediated inflammation. This review discusses the biological effects of gp120 and the rationale for targeting it therapeutically in PLWH. Full article

Clostridioides difficile infection (CDI) remains a major cause of healthcare-associated morbidity and mortality, particularly among older adults and patients with recent healthcare exposure, underscoring the need for early risk stratification and accurate prognostic assessment. This retrospective observational study evaluated clinical, laboratory, and therapeutic factors associated with disease severity and in-hospital mortality, and assessed the predictive performance of the ATLAS score and the Charlson comorbidity index. A total of 101 adult inpatients with laboratory-confirmed CDI admitted to a Portuguese tertiary care hospital were included. Data were extracted from clinical records and analysed using comparative statistics, multivariable logistic regression, and Kaplan–Meier survival analysis. Advanced age, elevated white blood cell count, renal dysfunction, and prior exposure to multiple antibiotic classes were independently associated with increased disease severity and mortality. The ATLAS score demonstrated good discriminative ability, particularly for short-term mortality, and showed higher sensitivity compared with the Charlson comorbidity index. These findings provide additional evidence on clinical and laboratory factors associated with severe CDI and in-hospital mortality, while supporting the utility of the ATLAS score as a practical tool for early risk stratification in hospitalised patients. Full article

The COVID-19 pandemic necessitated rigorous infection control protocols across hospital environments, particularly in nutrition services. UV-C light emerged as a viable option due to its shortest wavelength, conferring the greatest capacity for nucleic acid (DNA/RNA) penetration in both microorganisms and human cells. We aim to develop and validate an alternative method for decontaminating food carts using UV-C light. A prototype box was created to cover the meal transport carts, with UV-C lamps strategically positioned for irradiation and decontamination. To validate this technology, four different hygiene protocols were compared: Group 1, positive control, with no sanitization procedure; Group 2, cleaned using the standard protocol of the University Hospital of UFS (HU/UFS) with 70% ethanol solution; Group 3, negative control, cleaned using the standard HU/UFS protocol with 70% ethanol and neutral detergent; and Group 4, exposed to UV-C light irradiation for 10 min after food transport. Microbiological samples were collected from 15 distinct points on the carts. Samples were collected using sterile swabs moistened with 0.85% saline solution and incubated in BHI broth at 37 °C for 24 h for presence/absence testing. Positive samples were plated on selective media (CLED, SS, MacConkey and Blood agar), incubated at 37 °C for 24–48 h, and evaluated for colony-forming unit (CFU) count. A statistically significant association was found between the hygiene method and the presence of microbial contamination (p < 0.001), based on both bacterial plate counts and BHI broth growth. Carts sanitized with 70% alcohol showed a lower probability of contamination compared to the control group (alcohol + detergent), while unsanitized carts showed a higher risk. UV-C light treatment resulted in complete absence of bacterial growth. UV-C disinfection demonstrated superior effectiveness in eliminating microorganisms, indicating a promising alternative to traditional methods. Full article

Chlamydia is the most common sexually transmitted infection (STI) worldwide. In 2020, the global prevalence was estimated to be 4.0% among women and 2.5% among men aged 15 to 49 years. In more than 80% of cases, the infection is asymptomatic, thereby increasing the risk of subsequent infections. Complications in women can include chronic pain, pelvic inflammatory disease, and an increased risk of ectopic pregnancies. Chlamydia trachomatis (CT) infections can be diagnosed using several techniques, including cell culture, immunofluorescence, enzyme immunoassays, and polymerase chain reaction (PCR). PCR is regarded as the gold standard for screening and detection of CT. We conducted a three-year retrospective study from January 2022 to December 2024, collecting 4241 cervicovaginal swab samples from outpatient gynecology patients. The overall prevalence of CT in our study was 2.02%. An increase in CT detection during the study period was observed: from 24 cases (1.7%) in 2022 to 30 cases (2%; p = 0.64) in 2023 and 32 cases (2.35%; p = 0.26) in 2024. The highest proportion of cases was observed in the 20–24 and 25–34 age groups. Notably, 7 out of 10 cases were asymptomatic. Risk factors for chlamydial infections include behavioral factors, such as having multiple sexual partners and engaging in risky sexual practices, as well as social and lifestyle influences. Full article

Parvovirus B19 is a DNA virus. Most parvoviruses infect animals; Parvovirus B19 infects humans. Parvovirus B19 is mainly transmitted through respiratory droplets during close contact, but additional routes such as transmission through contaminated blood products and vertical transmission from mother to fetus have also been documented. Infections occur throughout the year, with a seasonal increase between late winter and early summer. Clinical symptoms depend on age, and on patients’ immune status. Healthy, immunocompetent individuals experience asymptomatic or mild infections including a febrile rash; serious complications rarely appear, such as rheumatoid-like arthritis or acute myocarditis. Clusters of myocarditis cases following Parvovirus B19 infections appeared in a daycare in Thessaloniki in 2024. To molecularly and phylogenetically characterize Parvovirus B19 strains detected during a pediatric outbreak associated with elevated troponin levels and myocarditis in Northern Greece, and to compare these strains with isolates from adult cases with mild symptoms in order to explore potential associations between viral genetic variability and cardiac involvement. MinION sequencing protocol was performed for nine whole blood samples, seven belonging to children with myocarditis, and two to adults presenting mild symptoms. Statistical analysis was performed with QualiMap 2.3 and relevant tools. Phylogenetic analysis identified distinct viral groups originating from the samples investigated. A distinct branch was formed by the reference genome and the ones of the adults’ samples, while samples from children with myocarditis provided discrete branches differing from the reference one. The findings demonstrate a clear association between Parvovirus B19 infection and myocarditis in the pediatric cases analyzed. The detected viral strains, including variants identified in several samples, support the role of Parvovirus B19 as a contributing factor in post-infectious cardiac involvement. Although these results reinforce the clinical relevance of Parvovirus B19 in childhood myocarditis, expanding the sample size would allow for a more robust characterization of circulating strains and confirmation of the observed patterns. Full article

Genitourinary infections caused by Candida spp. and other yeasts have increased in incidence, and the emergence of resistant isolates to commonly prescribed antifungals is becoming more frequent. Thus, the purpose of this study was to characterize the physiological characteristics of 38 yeast isolates (Candida albicans [n = 32], Candida tropicalis [n = 3], and Nakaseomyces glabratus [n = 3]) recovered from genitourinary infections to better understand the diversity of their physiological profiles, their virulence factors, and their role in pathogenicity. In addition, an experimental study was conducted to determine the minimum inhibitory concentration (MIC) of the isolates using the M27-A3 microdilution method described by the Clinical Laboratory and Standards Institute. Clinical isolates of Candida spp. studied showed in vitro susceptibility to both fluconazole and clotrimazole, the latter having greater antifungal activity due to its lower MIC₅₀. Statistically significant differences were found between the MICs obtained for fluconazole and clotrimazole, with the latter showing the highest in vitro activity. Therefore, the clinical use of clotrimazole is recommended, as is the ongoing need for this type of analysis to monitor changes in susceptibility profiles over time. Full article

The emergence and dissemination of antimicrobial resistance (AMR) are driven by complex, interconnected mechanisms involving microbial communities, environmental factors, and human activities, with climate change playing a pivotal and accelerating role. Rising temperatures, altered precipitation patterns, and other environmental disruptions caused by climate change create favorable conditions for bacterial growth and enhance the horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs). Thermal stress and environmental pressures induce genetic mutations that promote resistance, while ecosystem disturbances facilitate the stabilization and spread of resistant pathogens. Moreover, climate change exacerbates public and animal health risks by expanding the range of infectious disease vectors and driving population displacement due to extreme weather events, further amplifying the transmission and evolution of resistant microbes. Livestock agriculture represents a critical nexus where excessive antibiotic use, environmental stressors, and climate-related challenges converge, fueling AMR escalation with profound public health and economic consequences. Environmental reservoirs, including soil and water sources, accumulate ARGs from agricultural runoff, wastewater, and pollution, enabling resistance spread. This review aims to demonstrate how the Mediterranean’s strategic position makes it an ideal living laboratory for the development of integrated “One Health” frameworks that address the mechanistic links between climate change and AMR. By highlighting these interconnections, the review underscores the need for a unified approach that incorporates sustainable agricultural practices, climate mitigation and adaptation within healthcare systems, and enhanced surveillance of zoonotic and resistant pathogens—ultimately offering a roadmap for tackling this multifaceted global health crisis. Full article

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