ABSTRACT The type VI secretion system (T6SS) is a widespread bacterial nanomachine involved in interbacterial competition and environmental adaptation. Its distribution and evolutionary significance in Acinetobacter baumannii is not fully understood. Here, we investigated the ST19 lineage, revealing a near-complete absence of the T6SS across 159 genomes from diverse geographic and clinical origins. Comparative genomic analysis showed that the T6SS locus in ST19 is frequently disrupted, with some isolates harboring insertions of mobile genetic elements, while in others, the region is fragmented or unresolved. To assess whether T6SS loss is associated with broader genomic changes, we analyzed 8,218 publicly available A. baumannii genomes. Interestingly, T6SS-negative genomes did not exhibit increased acquisition of accessory genetic material. Instead, they carried fewer antimicrobial resistance genes (8.06 vs 10.56 per genome), fewer virulence genes (101.8 vs 132.5 per genome), and comparable plasmid replicon content relative to T6SS-positive genomes. However, T6SS-negative genomes exhibited a higher number of insertion sequences (IS) per genome compared to T6SS-positive genomes (mean ~12.3 vs ~9.0 IS elements per genome, respectively). Ancestral state reconstruction of the frmRAB and the putative chlorite dismutase genes within ST19 revealed identical distribution patterns and strong phylogenetic conservation, with 7 inferred state transitions indicating limited evidence for independent gain or loss events. Our results suggest that T6SS loss represents a lineage-specific evolutionary trajectory characterized by loss of the T6SS locus and reduced accessory genome, suggesting an alternative ecological strategy.

As antimicrobial resistance continues to rise and the development of new antimicrobials lags, we face an urgent threat where routine infections could become life-threatening. Armed conflicts, like the Russian war on Ukraine, intensify this crisis by accelerating the emergence and spread of resistant organisms across regions and borders. Phage Support Ukraine (Phage Sp UKR) is a collaborative effort to provide phages targeting circulating pathogens in Ukraine for delivery of personalized phage therapies. Within this context, we received multidrug-resistant bacterial isolates belonging to a number of different species. We here focus on Klebsiella pneumoniae , the most concerning pathogen with regard to prevalence, virulence and antibiotic resistance. Among the K. pneumoniae isolates, we identified sequence types (ST) 39, 101, 147, 307 and 395, as well as a predominating clonal group—CG10146 (ST23 KL57), first detected in Moscow—carrying a hybrid virulence-resistance plasmid encoding NDM-1 and aerobactin. Over two years (2023–2025), this clonal group expanded and acquired pan-resistance. When tested in virulence assays, only one isolate (ST395) displayed hypervirulence in a Galleria mellonella though not in a mouse infection model. Several phages isolated from Ukrainian sewage were able to lyse these K. pneumoniae strains, including strains obtained from soldiers displaced in Belgium, Germany, and Latvia. Bacterial resistance was observed during in vitro testing. However, some phage-resistant isolates had mutations in virulence factors, including one that completely lost its hybrid plasmid, resulting in restored antibiotic susceptibility. Strategies like Phage Sp UKR are essential to prevent the selection, persistence, and global spread of these MDR clones. ### Competing Interest Statement The authors have declared no competing interest.

Acinetobacter baumannii is a critical, opportunistic pathogen due to its multi- to pandrug-resistance including resistance to last-resort antibiotics such as carbapenems. While A. baumannii can acquire environmental DNA through multiple mechanisms including natural competence, one of the most common is acquisition via plasmids by conjugation. One of the challenges for conjugation is an active Type VI Secretion System (T6SS), which kills nonkin bacteria and therefore inhibits the conjugation. The acquisition of resistance genes has helped the spread of resistant clones of A. baumannii. The most prominently disseminated clones belong to specific sequence types [(ST), Pasteur scheme], namely ST1, ST2, ST10, ST15, ST25, ST79 and ST85 with the ST2 being the most detected ST. While ST1 and ST2 were thoroughly studied, there are new emerging clones whose genetic background facilitating the rise is still unknown or poorly understood. One of the rising clones is A. baumannii ST19, recently reported to be frequently occurring in Georgia and Ukraine. In this study, we have whole-genome sequenced three isolates of A. baumannii ST19 which were then assessed for biofilm production and virulence in the Galleria mellonella in vivo infection model. Further 156 A. baumannii ST19 genomes were obtained from public repositories. In total, 157/159 genomes revealed loss of ompA and T6SS locus, which was in 56/157 genomes (35,7%) replaced by ΔTn 9 carrying chloramphenicol and ΔTn 10 carrying tetracycline resistance genes and formaldehyde and chlorite resistance genes. Hindered T6SS-loss-mediated contact-killing might promote the acquisition of genetic material supporting the success of the A. baumannii ST19 lineage. Importance Acinetobacter baumannii is a nosocomial pathogen with immense potential to become multidrug- to pan-drug-resistant, driven in part to its capacity to acquire DNA from the environment through conjugation and natural competence. Conjugation might however be hindered by an active type VI secretion system (T6SS), which kills nonkin bacteria. In A. baumannii ST19, the absence of the T6SS enables the co-existence and conjugation of nonkin bacteria. This, together with the reduced metabolic burden of lacking T6SS and further acquisition of antibiotic and non-antibiotic resistance traits, might enable the emergence of a successful, resistant, and potentially high-risk A. baumannii lineage ST19.

The growing threat of antimicrobial resistance (AMR) is a critical issue for both civilians and the military. With each successive conflict, pathogens become more resistant, making the management of infections in casualties increasingly challenging. To better understand the scope and characteristics of conflict-related AMR, a comprehensive literature search was conducted in the PubMed database in April 2025, using defined search terms related to war casualties and antimicrobial resistance. We screened and included 117 relevant publications, comprising original research articles, reviews, case series, case reports, editorials, and commentaries, published in English or French, with no date restriction. This narrative review synthesizes current evidence on multidrug-resistant bacteria most commonly isolated from war casualties, their associated resistance mechanisms, and the microbiological diagnostic tools available at various levels of the military continuum of care (Roles 1–4). It also presents strategies for preventing cross-contamination and infection in resource-limited combat settings and provides practical, field-adapted recommendations for clinicians, from first responders to specialized care providers, aiming to improve infection management in armed conflict zones and mitigate the spread of AMR.

As antimicrobial resistance continues to rise and the development of new antimicrobials lags, we face an urgent threat where routine infections could become life-threatening. Armed conflicts, like the war on Ukraine, intensify this crisis by accelerating the spread of resistant organisms across regions and borders. Phage therapy or the use of bacteriophages (phages), the viruses of bacteria, as a therapeutic has reemerged as a viable treatment for difficult to treat multidrug resistant (MDR) infections. Our Belgian consortium, led primarily by the Queen Astrid Military Hospital (QAMH), has been dedicated to treating patients, culminating in a landmark publication that documents 100 consecutive cases of phage therapy. 1 Phage Support Ukraine (Phage SP UKR) is a collaborative effort led by QAMH in partnership with our group at KU Leuven to provide phages targeting circulating pathogens and enable a military hospital in Kyiv to effectively deliver personalized phage therapies. As part of this initiative, we received from this hospital in Kyiv bacterial isolates belonging to a number of species, but decided to focus here on Klebsiella pneumoniae , the most concerning pathogen with regard to prevalence, virulence and antibiotic resistance. Strains were sequenced using both Illumina (short-read) and Nanopore (long-read) technologies to characterize their genomic content, including antibiotic resistance and virulence factors. Antibiograms were also conducted in accordance with standard protocols. Strains were assessed for hypervirulence using Galleria mellonella and a mouse model of pneumonia. Phages were isolated from Ukrainian wastewater, sequenced and characterized for therapeutic effectiveness. Among these K. pneumoniae isolates we identified MDR sequence types (ST)39, 307 and 395 and one predominating clonal group—CG10146 first detected in Moscow, Russia—carrying a hybrid virulence and antibiotic resistance plasmid encoding the carbapenemase NDM-1 and aerobactin. When tested in virulence assays, only one isolate (ST395) was hypervirulent in a G. mellonella though not in a mouse model of infection. Several phages were isolated that could lyse these K. pneumoniae strains, including those isolated from soldiers displaced in Belgium, Germany, and Latvia. Bacterial resistance was observed during in vitro testing; however, some phage-resistant isolates had mutations in virulence factors, including one that lost its hybrid plasmid, resulting in re-sensitivity to antibiotics. As we continue to receive isolates for surveillance, new strains emerging from Ukraine this year have been identified as pan-drug resistant (PDR). However, they have also been found to be susceptible to the phages isolated to date. These phages show high potential as a therapeutic against MDR and PDR strains of K. pneumoniae . As part of this initiative, QAMH will provide these phages as well as equipment for the group in Kyiv to work with these phages and the training needed to implement phage therapy in Ukraine. Strategies like Phage SP UKR are essential to prevent the selection, persistence, and global spread of these drug-resistant clones. Pirnay JP, Djebara S, Steurs G, Griselain J, Cochez C, De Soir S, et al . Personalized bacteriophage therapy outcomes for 100 consecutive cases: a multicentre, multinational, retrospective observational study. Nat Microbiol . 2024; 9 (6):1434–53. Abstract A24 Figure 1 Phage SP UKR. A schematic outlining the goals of this project, which include: 1. Pathogen characterization, 2. Phage isolation and characterization, and 3. Delivery of phages to Ukraine The authors declare no conflict of interest.

This study investigated the presence of tick-borne encephalitis virus (TBEV) in ticks collected in Belgium between 2018 and 2024, as well as the occurrence of Rickettsia spp. in ticks sampled in 2024. A total of 3739 ticks from 17 locations, of which 16 in Flanders and 1 in Wallonia, were collected from vegetation and tested in 510 pools for TBEV by RT-PCR. Sampling locations were selected based on potential exposure risk, including proximity to human TBE cases, evidence of TBEV antibodies in animals, or near the border between Belgium and the Netherlands. No TBEV RNA was detected in this collection. The 2432 ticks collected in 2024, were tested in 324 pools for Rickettsia spp. by PCR. Spotted Fever Group (SFG) rickettsiae were found in half of the pools, corresponding to an estimated prevalence of 10 %. Rickettsia helvetica was the predominant species, with an estimated prevalence of 8 %, while two pools (1.26 %) tested positive for R. felis. These results contribute to the understanding of tick-borne disease epidemiology in Belgium. Continuous monitoring is recommended to evaluate the impact of environmental changes on Belgian tick populations and pathogen circulation.

Antimicrobial susceptibility testing (AST) by disk diffusion provides an accurate image of bacterial growth, enabling the detection of culture purity, heterogeneous growth, and antibiotic interactions. However, this manual method is time-consuming and visual interpretation is prone to errors. To overcome these disadvantages, the Radian® In-Line Carousel (Copan, Brescia, Italy) was launched, which is a WASPLab® module dedicated to full automation of (pre)-analytical steps as well as interpretation of disk diffusion AST. However, until now, no evaluation of Radian® against manual disk diffusion has been performed. We assessed the categorical agreement (CA) between standardized disk diffusion (reference method) and Radian® using EUCAST 2021 breakpoints. We tested 135 non-duplicate strains, selected from the National EUCAST challenge panel, clinical strains, and external quality controls. The strains included Enterobacterales (n = 63), Enterococcus faecalis (n = 3), Enterococcus faecium (n = 10), Pseudomonas aeruginosa (n = 16), Staphylococcus aureus (n = 19), coagulase-negative staphylococci (n = 4), and Streptococcus spp. (n = 20). Furthermore, we explored antibiotic disk thermolability in the WASP Radian® carousel by testing 10 ATCC® strains up to 7 days. The observed CA was 95.3

Schistosomiasis is a parasitosis caused by trematodes of the genus Schistosoma. Humans are infected when coming into contact with freshwater containing the parasites’ infective stages, which are amplified through freshwater-dwelling snails acting as intermediate hosts. Schistosomiasis has posed significant problems for troops exposed to freshwater in endemic regions ever since the Napoleonic wars. Schistosomiasis has substantial differences in clinical presentation, depending on the type of parasite, intensity of infection and reinfection, clinical form, and disease stage. It can remain undiagnosed for long periods of time, with well-known long-term morbidity and mortality risks. The diagnosis of schistosomiasis depends on its stage and relays on several tests, all with limitations in sensitivity and specificity. The diagnostic gold standard is the detection of eggs in urine, feces, or tissue biopsies, but this can raise problems in patients such as military personnel, in which the worm burden is usually low. Praziquantel is the drug of choice for schistosomiasis. Currently, there is no available commercial vaccine against any Schistosoma parasite. Avoiding freshwater exposure is the best prevention. Herein, we review the clinical presentation, diagnosis, treatment, and prevention of schistosomiasis in the military. This information may decrease the impact of schistosomiasis on this particular professional group.

IntroductionAntimicrobial resistance is a growing problem that necessitates the development of new therapeutic options. Cefiderocol and aztreonam (AT) are often the last active β-lactams for treating metallo-β-lactamases (MBL)-producing Gram-negative bacilli. In these difficult-to-treat bacterial strains, AT resistance is frequently attributed to the co-occurrence of other resistance mechanisms. In the case of β-lactamases they can often be inhibited by avibactam. In the present study, we evaluated the use of the double-disc synergy test (DDST) as a screening tool for the detection of synergy between AT-avibactam (ATA). We validated both the Gradient Diffusion Strips (GDSs) superposition method and the commercially available Liofilchem’s ATA GDS.Materials and methodsWe tested AT susceptibility in combination with ceftazidime-avibactam for 65 strains, including 18 Serine-β-Lactamase (SBL)- and 24 MBL-producing Enterobacterales, 12 MBL-producing P. aeruginosa, and 11 S. maltophilia isolates. Interpretation was done with EUCAST breakpoints (version 13.0), AT breakpoints being used for ATA. The accuracy and validity of the GDSs superposition method and ATA GDS were evaluated using an AT GDS applied on Mueller Hinton Agar plates supplemented with avibactam (MH-AV). A DDST was performed to screen for synergy between antibiotic combinations.ResultsUsing MH-AV, all SBL- and MBL-positive Enterobacterales were susceptible or susceptible at increased exposure to the combination AT-avibactam. In contrast, only 2 out of the 12 (17%) P. aeruginosa strains and 9/11 (82%) of the S. maltophilia strains were susceptible- or susceptible at increased exposure for the combination of AT-avibactam. The DDST detected all synergies, demonstrating a 100% sensitivity and 100% negative predictive value for all bacterial strains.ConclusionThe DDST is a sensitive tool for screening for antibiotic synergy. Unlike S. maltophilia and SBL- and MBL-positive Enterobacterales, most MBL-positive P. aeruginosa strains remain resistant to AT-avibactam. ATA GDS should be preferred for MIC determination of the AT-avibactam combination, while the GDSs superposition method can be used as an alternative to the commercial test.

Intestinal helminthic infections are not uncommon in Western Europe, mainly due to modern travel, emigration and globalization. Moreover, some helminthic infections are endemic in Western Europe and are part of the everyday clinical practice. The hepatogastroenterologist should therefore recognize and manage these patients or at least refer them to appropriate reference centers. Signs and symptoms are often unspecific or even absent. Discerning the disease at an early stage avoids expensive diagnostic testing, life-threatening complications and in some cases even further spread of the disease. This review article aims to guide the hepatogastroenterologist when suspecting a helminthic infection by addressing the most prevalent symptoms, summarizing the most probable associated helminthic entities, highlighting practical steps in diagnosis and available treatments.

This case report describes a 60-year-old female patient suffering from systemic sclerosis, for which she received immunomodulatory drugs. Her first SARS-CoV-2-positive nasopharyngeal sample was obtained in the emergency department, on 31 January 2022. Whole genome sequencing confirmed infection with Omicron BA.1.1. Her hospital stay was long and punctuated by many complications, including admission to the intensive care unit. At the beginning of April 2022, she started complaining of increased coughing, for which another SARS-CoV-2 RT-qPCR test was performed. The latter nasopharyngeal swab showed a strongly positive result. To support the theory of healthcare-associated reinfection, whole genome sequencing was performed and confirmed reinfection with Omicron BA.2. Since this patient was one of ten positive cases in this particular ward, a hospital outbreak investigation was performed. Whole genome sequencing data were available for five of these ten patients and showed a cluster of four patients with ≤2 small nucleotide polymorphisms difference.

We report 3 confirmed autochthonous tick-borne encephalitis cases in Belgium diagnosed during summer 2020. Clinicians should include this viral infection in the differential diagnosis for patients with etiologically unexplained neurologic manifestations, even for persons without recent travel history.

Background: Biotin has been reported to be a leading cause of interference on several immunoassay platforms using the streptavidin-biotin immobilization system. While biotin interferences have now been well characterized for several assays, only few data are available on their impact on serological markers of infectious viral diseases. Methods: Overall, 10 healthy volunteers (HVs) received a single 100 mg dose of biotin to evaluate its effect on hepatitis B serological markers. Blood samples were taken several times before and after biotin intake. In addition, spiking experiments were applied to investigate biotin's impact on anti-HIV/p24 Ag and anti-HCV antibody levels. Several procedures designed to overcome this interference were evaluated. Results: Biotin intake resulted in a false-negative anti-HBs immunological status (< 10 mIU/mL) in 40.0% of cases. According to our anti-HBc and anti-HBe results, biotin intake was associated with 90.0% and 80.0% of false positive results, respectively. At the theoretical biotin peak concentration following a 100 mg intake, 50.0% and 66.6% of anti-HIV and anti-HCV results were false negatives, respectively. All the procedures evaluated to overcome the interference were proven effective. Conclusion: HBV, HCV, and HIV serological markers are likely to be highly sensitive to biotin. Our data confirm that the scope of biotin interference is broader than commonly described.