Breast cancer is one of the most frequently diagnosed malignancies and remains the leading cause of cancer-related death among women worldwide. Emerging evidence implicates the microbiota to be a potential contributor to its pathogenesis and progression. This review summarizes emerging evidence of microbial alterations across various body niches in breast cancer patients, including gut, breast tissue, nipple aspirate fluid (NAF), oral cavity, skin, urinary and reproductive tracts, and blood. Reductions in commensal taxa such as Faecalibacterium, Bifidobacterium, Lachnospira, Akkermansia, and Sphingomonas, along with an increase in pro-inflammatory genera like Prevotella, Fusobacterium, and Desulfovibrio, may promote breast tumor development and progression through multiple pathways including modulation of estrogen metabolism, production of microbial metabolites, and immunoregulation. The presence of cross-niche overlaps and possible translocation of microbiota between niches through the bloodstream suggests the existence of a complex interconnected oral–gut–breast microbiota axis. Progress in the field will depend on integrative multi-omics, translational approaches, and longitudinal studies to give a clearer mechanistic understanding of microbiota–host interactions to develop feasible microbiota-based biomarkers and therapeutic strategies in breast cancer.

Wastewater surveillance has proven to be a cost-effective, non-invasive method for monitoring the spread and evolution of SARS-CoV-2, yet its value during today’s low-incidence phase is still being defined. Between August 2023 and July 2024, 42 composite wastewater samples were collected in Perugia, Italy and analyzed using RT-qPCR and whole-genome sequencing to identify circulating SARS-CoV-2 lineages. In parallel, clinical samples (respiratory tract samples) were collected and analyzed, allowing for direct comparisons to confirm the robustness of the wastewater findings. The sewage viral loads ranged from 8.9 × 10⁵ to 4.9 × 10⁷ genome copies inhabitant⁻¹ day⁻¹, outlining two modest community waves (September–December 2023 and May–July 2024). Sequencing resolved 403 Omicron lineages and revealed three successive subvariant phases: (i) XBB.* dominance (August–October 2023), when late-Omicron XBB subvariants (mainly EG.5.* and XBB.1.5) accounted for almost all genomes; (ii) a BA.2.86/JN surge (November 2023–March 2024), during which the BA.2.86 subvariant, driven mainly by its JN descendants (especially JN.1), rapidly displaced XBB.* and peaked at 89% in February 2024; and (iii) KP.* takeover (April–July 2024), with JN.1-derived KP subvariants rising steadily and KP.3 reaching 81% by July 2024, thereby becoming the dominant lineage. Comparisons of data from wastewater and clinical surveillance demonstrated how the former presented a much higher diversity of circulating viral lineages. Importantly, some subvariants (including BA.2.86*) were detected in wastewater weeks to months prior to clinical identification, and for longer periods. Taken together, the obtained data validated wastewater surveillance as an effective early warning system, especially during periods of low infection prevalence and/or limited molecular testing efforts. This methodology can thus complement clinical surveillance by offering valuable insights into viral dynamics at the community level and enhancing pandemic preparedness.

Serratia marcescens complex bacteria are recognized causes of outbreaks in neonatal intensive care units. We investigated a cluster of VIM-producing Serratia spp. in the Neonatal Unit of Azienda Ospedaliera di Perugia, Italy, using epidemiological surveillance, antimicrobial susceptibility testing, environmental sampling, and whole-genome sequencing (WGS). In November 2024, ten neonates were colonized and/or infected with Serratia. Eight carried VIM-producing isolates, including two patients with bloodstream infections. Nine VIM-producing Serratia isolates were recovered because one patient yielded both a rectal and a blood culture isolate; one non-VIM-producing bloodstream isolate was also available and included for comparison. WGS showed that the ten isolates, initially identified as S. marcescens by routine diagnostic methods, belonged to two species within the S. marcescens complex: seven Serratia bockelmannii ST388 isolates and three ST382-like Serratia sarumanii isolates. All VIM-producing Serratia spp. isolates carried bla_VIM-1 and bla_SHV-12 and showed multidrug-resistant phenotypes. bla_VIM-1 was also detected in Escherichia coli, Citrobacter freundii, and Pseudomonas putida isolates from the same ward. A shared IncA-ST12 replicon suggested possible horizontal dissemination of a related mobile resistance element. Environmental and healthcare-worker screening did not detect Serratia. These findings highlight the value of WGS for distinguishing clonal transmission from dissemination of mobile resistance determinants during complex healthcare-associated outbreaks.

New beta-lactam/beta-lactamase inhibitor combinations (BL/BLICs) are licensed for Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) infections. However, data regarding their efficacy against bacterial biofilms and the potential of synergistic combinations remain limited. This study evaluated their efficacy on planktonic and biofilm forms of KPC-Kp isolated from catheter-related bloodstream infections (CRBSIs), correlating findings with genomic and clinical data. Twelve KPC-3-harboring isolates (ST512, n = 7; ST307, n = 3; ST101, n = 2) were characterized via whole-genome sequencing. Ceftazidime/avibactam (CAZ/AVI), meropenem/vaborbactam (MEM/VAB), and imipenem/relebactam (IMI/REL) were tested alone or combined with fosfomycin (FOS), cefepime (FEP), meropenem (MEM), or imipenem (IMI) using checkerboard assays. All BL/BLICs alone showed significant, comparable efficacy against biofilm-producing strains. However, combination testing revealed heterogeneous synergistic profiles. CAZ/AVI combined with MEM, IMI, or FEP achieved 100% synergy in both planktonic and biofilm states. MEM/VAB-based combinations demonstrated consistent synergy (50–100%), whereas IMI/REL showed higher synergistic rates in biofilm than in planktonic forms. Conversely, FOS-based regimens were significantly less effective against biofilms. These findings provide a clinical rationale for selecting optimized dual regimens to eradicate biofilms, offering a critical therapeutic strategy to preserve vascular devices when catheter removal is unfeasible.

Serratia marcescens complex bacteria are recognized causes of outbreaks in Neonatal Intensive Care Units (NICU). We investigated a cluster of VIM-producing Serratia spp. in the NICU of Santa Maria della Misericordia Hospital, Perugia, through a retrospective epidemiological and genomic analysis integrating clinical and surveillance data, antimicrobial susceptibility testing, environmental screening, and whole-genome sequencing (WGS). In November 2024, VIM-producing Serratia was isolated from eight neonates, of whom five developed clinical infections, including two bloodstream infections. Nine VIM-producing Serratia isolates recovered from these eight neonates and one non-VIM-producing isolate from a bloodstream infection (used for comparison) were analysed. Routine MALDI-TOF MS identified all isolates as S. marcescens, whereas WGS resolved them into two genomic lineages: seven S. bockelmannii ST388 isolates and three S. sarumanii ST382-like isolates. All VIM-producing Serratia carried bla_VIM-1 and bla_SHV-12 and showed multidrug-resistant phenotypes. Long-reads sequencing reconstructed complete, and almost identical, IncA-ST12 plasmids in all nine VIM-producing Serratia isolates; the plasmids carried bla_VIM-1 and bla_SHV-12 together with additional resistance determinants. Environmental, water, and healthcare-worker screening did not identify a Serratia reservoir. No new VIM-producing Serratia infections occurred after the November cluster. These findings show how WGS complements routine MALDI-TOF MS and rapid carbapenemase testing by providing the taxonomic, epidemiological, and plasmid-level resolution needed to investigate complex healthcare-associated outbreaks.