Eikenella corrodens is a facultative anaerobic Gram-negative bacillus, part of the normal oropharyngeal flora, with opportunistic pathogenic potential particularly in immunocompromised hosts. The progression from localized intracranial infections such as cerebritis and subdural empyema to secondary bloodstream infection represents a rare but clinically significant pathway, especially in immuno-compromised patients. Here, we report a case of secondary E. corrodens bacteremia following left temporal cerebritis and ipsilateral subdural empyema in a 50-year-old man with advanced nasopharyngeal carcinoma treated with nivolumab. The patient presented neurological deficits and systemic inflammatory response, suggesting for a bacterial infection. Neuroimaging confirmed the intracranial infectious foci and blood cultures identified E. corrodens via MALDI-TOF MS and 16S rRNA gene sequencing. We discuss how cancer-associated immune dysregulation and immune checkpoint inhibition could modulate host susceptibility and clinical presentation of infection, potentially facilitating microbial dissemination across compromised blood–brain barriers. Additionally, we examine the cases of E. corrodens bacteremia secondary to CNS and head and neck infections. This case underscores the importance of heightened clinical vigilance for secondary bacteremia in oncologic patients with CNS infections and highlights the need for integrated microbiological and radiological assessment to optimize outcomes.

Legionella pneumophila (Lp) remains one of the major causes of community- and hospital-acquired pneumonia, yet its diagnosis and source attribution continue to pose significant challenges. Here, we describe the case of an immunocompromised patient who developed Legionnaires’ disease during hospitalization. Following activation of the hospital’s internal surveillance system, Lp and Legionella anisa (L. anisa) were recovered from multiple water distribution points using a simplified culture-based protocol. Whole-genome sequencing (WGS) demonstrated that all environmental isolates belonged to a single clonal strain, whereas the clinical isolate was genetically unrelated, thereby excluding the hospital water system as the source of infection. Although not implicated in the patient’s disease, the detection of both Lp and L. anisa within the plumbing system highlighted underlying structural contamination and the potential masking effect of non-L. pneumophila species during culture-based surveillance. These findings support the integration of conventional microbiological methods with high-resolution genomic tools to enhance surveillance accuracy, support outbreak investigations, and strengthen public health responses. Overall, this case underscores the value of WGS as a decisive tool for source attribution, including the robust exclusion of a suspected nosocomial source, in complex clinical and environmental scenarios.

Background/Objectives: Antimicrobial resistance (AMR) represents a major global health challenge, driving the need for rapid and accurate diagnostic tools. Novel molecular assays, including multiplex PCR and DNA microarray-based systems, have emerged to detect antimicrobial resistance genes (ARGs) alongside bacterial identification. Methods: In this study, we evaluated the performance of the HybriSpot12 PCR AUTO (HS12a) system and the MDR Direct Flow Chip (MDR-FC) Kit—an automatic microarray assay based on reverse hybridization—for the detection of ARGs directly from positive blood culture (PBC) samples. A total of 111 Gram-negative bacterial isolates (92 Enterobacterales, 14 Acinetobacter baumannii, and 6 Pseudomonas spp.), previously characterized by whole-genome sequencing (WGS), were each used to generate a PBC, which was then analyzed with the HS12a/MDR-FC assay. Results: We demonstrated perfect agreement for the detection of macrolide resistance genes across all bacterial species and high agreement for genes conferring resistance to sulfonamides and β-lactams. In contrast, aminoglycoside resistance genes showed only moderate agreement, with minor discrepancies observed in Klebsiella pneumoniae and Escherichia coli, largely attributable to specific SNP variations. Conclusions: The HS12a/MDR-FC assay includes 51 ARGs, though not all were represented in our isolate set, and some false negatives were observed. Despite these limitations, its broad coverage and rapid turnaround remain advantageous compared to other rapid assays with fewer targets. Future refinements should aim at broader gene coverage, inclusion of key mutations, and detection of emerging variants, making this approach a promising tool for rapid AMR surveillance and antimicrobial stewardship.