Multidrug-resistant Enterobacterales (MDRE) are an emerging threat to global health, leading to rising health care costs, morbidity and mortality. Multidrug-resistance is commonly caused by different β-lactamases (e.g., ESBLs and carbapenemases), sometimes in combination with other resistance mechanisms (e.g., porin loss, efflux). The continuous spread of MDRE among patients in hospital settings and the healthy population require adjustments in healthcare management and routine diagnostics. Rapid and reliable detection of MDRE infections as well as gastrointestinal colonization is key to guide therapy and infection control measures. However, proper implementation of these strategies requires diagnostic methods with short time-to-result, high sensitivity and specificity. Therefore, research on new techniques and improvement of already established protocols is inevitable. In this review, current methods for detection of MDRE are summarized with focus on culture based and molecular techniques, which are useful for the clinical microbiology laboratory.

Purpose: This study aims to evaluate the performance of two latest generation matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems in routine laboratory settings, focusing on turnaround time (TAT), time to results (TTR), hands-on time, and identification rate. Methods: We conducted a time and motion study on three workflow scenarios to simulate different laboratory settings. Overall, 618 bacterial isolates from a tertiary hospital’s laboratory were processed using the VITEK MS PRIME (bioMérieux) and the MALDI Biotyper sirius (Bruker Daltonics) and their corresponding databases VITEK IVD Database 3.2 and MBT reference library 12. Results: The target preparation process showed no significant difference in TAT, but the Biotyper workflow had a shorter hands-on time by 3 to 6 min. In the measurement process, TTR was three to five times shorter for the Biotyper sirius while hands-on time was significantly shorter for VITEK MS PRIME (approximately 1.5 min per target). The identification rate without retesting was 97.9% for VITEK MS PRIME and 98.9% for Biotyper sirius. Both systems achieved 100% agreement at genus and 96.2% at species level. Conclusion: Both systems exhibited excellent identification rates for routine bacterial isolates. Due to its high speed, the Biotyper sirius is suited for laboratories with high sample throughput and a workflow designed for processing larger batches. The VITEK MS PRIME, with its “load and go” system accommodating up to 16 targets, reduces hands-on time, making it a reasonable choice for laboratories with fewer identifications overall but a higher number of targets and a workflow designed for parallel processing on different workstations.

Widespread antimicrobial resistance in Gram-negative bacteria (GNB), particularly carbapenem resistance, represents a major clinical challenge. Cefiderocol is a novel siderophore cephalosporin active against all carbapenemase classes. We evaluated the in vitro activity of cefiderocol and other antibacterial agents (ceftazidime/avibactam, ceftolozane/tazobactam, colistin and meropenem) against GNB isolates collected in Germany (2013-2018) as part of two multinational studies. Antimicrobial susceptibility testing was performed by broth microdilution. Minimum inhibitory concentrations were interpreted according to EUCAST breakpoints. Cefiderocol had high activity against GNB isolates (N = 2298), encompassing both Enterobacterales (n = 1562) and non-fermenter species (n = 736), and maintained high activity against carbapenem-resistant strains (n = 211). The activity of cefiderocol against Enterobacterales was equivalent to that of ceftazidime/avibactam and colistin, while ceftolozane/tazobactam was somewhat less active. Against non-fermenter species, cefiderocol displayed equivalent activity to colistin; both of these agents were more active than ceftazidime/avibactam and ceftolozane/tazobactam. Colistin had similar activity to cefiderocol against the majority of species. These patterns of activity were echoed in carbapenem-resistant isolates. The high activity of cefiderocol was independent of infection site, whereas other antibacterial agents demonstrated slightly lower activity against isolates causing pneumonia compared with those from other key infection sites. Cefiderocol exhibited consistently high in vitro activity against a variety of GNB isolates collected in Germany, including resistant phenotypes, across multiple infection sites. These data suggest that cefiderocol is an effective choice of antibacterial agent in patients with GNB infection, regardless of species and resistance phenotype to other agents.

Purpose: This study assessed the impact of EUCAST’s Rapid Antimicrobial Susceptibility Testing (RAST) on empirical therapy and its clinical usability in routine bloodstream infection management. Methods: This retrospective single-center, observational study compared two four-month periods before and after RAST implementation (Feb–May 2023 vs. Feb–May 2024) at Oldenburg Medical Center. Patients with monomicrobial bloodstream infections due to Escherichia coli , Klebsiella pneumoniae , Pseudomonas aeruginosa , or Acinetobacter baumannii were included. Primary outcome: duration of empirical antimicrobial therapy. Secondary outcomes: turnaround time and categorical agreement between RAST with VITEK 2, including major errors (ME) and very major errors (VME). Surrogate-based interpretation was used for ATU results, particularly for piperacillin-tazobactam. Results: In total 126 patients were included (66 in 2023, 60 in 2024). After RAST, empirical therapy duration was significantly shorter (40.5 h vs. 73.3 h, p < 0.001). Median time to RAST result was 15.8 h, significantly shorter than by VITEK 2 (33.9 h, p < 0.0001), reducing time to first susceptibility result by 9.6 h ( p < 0.00001). Concordance with VITEK 2 was excellent: 100% for cefotaxime, meropenem, and piperacillin-tazobactam, 96.4% for ceftazidime, 95.2% for ampicillin. ATU results occurred mainly for piperacillin-tazobactam and were partly resolved through surrogate-based interpretation. Conclusion: RAST significantly shortened empirical therapy duration and accelerated susceptibility reporting with high agreement to VITEK 2. However, antibiotic-specific uncertainty and incomplete translation of early results into therapeutic action indicate that the clinical impact of RAST depends on structured interpretation and integration into antimicrobial stewardship workflows.