Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with poor outcomes depending on patient’s conditions, clinical severity and type of infection, and treatment is challenging given the limited therapeutic options available. The aim of this study was to describe the clinical and microbiological characteristics of two outbreaks caused by CRAB in an intensive care unit (ICU). In addition, the mechanisms of resistance detected in these strains and the treatment chosen according to the available therapeutic options were analyzed. Overall, 28 patients were included. Ten patients (35.71%) had ventilator-associated pneumonia (VAP), ten (35.71%) had a bloodstream infection (BSI), and eight (28.57%) were only colonized. Recurrent infection occurred in 25% (5/20) of infected patients. Two different strains of A. baumannii were isolated from the index patient of the first outbreak. The first strain belonged to the ST85 and carried the bla_NDM-1 carbapenemase gene, while the second belonged to the ST2 and carried bla_OXA-23, and bla_OXA-66 carbapenemase genes. The phylogenetic analysis revealed that the ST2 strain was the cause of the major outbreak, and mutations in the AmpC gene were related to progressive increasing minimum inhibitory concentration (MIC) and finally, cefiderocol-resistance in one strain. The CRAB isolates from the second outbreak were also identified as ST2. Cefiderocol-resistant strains tests identified by the disc diffusion method were involved in 24% (6/25) of nosocomial infections. Using broth microdilution (BMD) ComASP^® only, 33.3% (2/6) of these strains were cefiderocol-resistant. All-cause ICU mortality was 21.4%. Conclusions: Cefiderocol is the first approved siderophore cephalosporin for the treatment of CRAB infections. Cefiderocol-resistant strains were related with bla_NDM-1 carbapenemase and mutations in the AmpC gene. Cefiderocol-resistant strains or that cannot be properly interpreted by disk diffusion, should be retested using BMD for definitive categorization.

Patients in burn intensive care units (BICUs) are at high risk of infections caused by multidrug-resistant pathogens, which can lead to hospital outbreaks. To investigate an outbreak caused by carbapenem-resistant Acinetobacter baumannii (CRAB) in a BICU at a tertiary care hospital in Madrid, Spain, using whole-genome sequencing (WGS) and antibiotic susceptibility testing. CRAB isolates were obtained from rectal swabs collected during routine epidemiological screening of BICU patients, as well as clinical and environmental samples collected throughout the outbreak. The genomes of the isolates were sequenced using Ion Torrent™ and MinION™ technologies. Antibiotic susceptibility testing was conducted by microdilution using the MicroScan NF50 panel. Susceptibility to cefiderocol was tested using disk diffusion and broth microdilution (ComASP®). The outbreak occurred between October 2022 and August 2023, affecting 26 patients (median age: 56 years, IQR 34–70). Genomic analysis identified the isolates as belonging to ST2/ST451 (Pasteur/Oxford schemes), carrying blaOXA−23 carbapenemase gene. Environmental sampling detected CRAB on 20 of 105 tested surfaces. The outbreak’s genomic evolution included the emergence of hypermucoid isolates and blaADC−73 mutants with increased cefiderocol minimum inhibitory concentrations (MICs). Novel mutations and combinations in blaADC−73 were observed, likely selected under cefiderocol pressure. Antibiotic susceptibility testing using the microdilution method was more sensitive in detecting these mutations. The outbreak ultimately necessitated the closure of the BICU for disinfection with high-concentration H2O2. WGS enabled detailed tracking of CRAB’s genomic evolution during the outbreak, identifying mutations associated with increased cefiderocol MICs. This information supported effective infection control measures, highlighting the utility of WGS in managing hospital outbreaks.

Millions of SARS-CoV-2 whole genome sequences have been generated to date. However, good quality data and adequate surveillance systems are required to contribute to meaningful surveillance in public health. In this context, the network of Spanish laboratories for coronavirus (RELECOV) was created with the main goal of promoting actions to speed up the detection, analyses, and evaluation of SARS-CoV-2 at a national level, partially structured and financed by an ECDC-HERA-Incubator action (ECDC/GRANT/2021/024). A SARS-CoV-2 sequencing quality control assessment (QCA) was developed to evaluate the network’s technical capacity. QCA full panel results showed a lower hit rate for lineage assignment compared to that obtained for variants. Genomic data comprising 48,578 viral genomes were studied and evaluated to monitor SARS-CoV-2. The developed network actions showed a 36% increase in sharing viral sequences. In addition, analysis of lineage/sublineage-defining mutations to track the virus showed characteristic mutation profiles for the Delta and Omicron variants. Further, phylogenetic analyses strongly correlated with different variant clusters, obtaining a robust reference tree. The RELECOV network has made it possible to improve and enhance the genomic surveillance of SARS-CoV-2 in Spain. It has provided and evaluated genomic tools for viral genome monitoring and characterization that make it possible to increase knowledge efficiently and quickly, promoting the genomic surveillance of SARS-CoV-2 in Spain.