The rapid identification method, the Rapid Sepsityper protocol with a specific MBT-Sepsityper module (Bruker Daltonics), based on the MALDI Biotyper platform, accurately identified 93.5% (116/124) of microorganisms at the species level in the 124 flagged blood culture samples from patients with monomicrobial bloodstream infections. Gram-negative bacilli (95.6%, 43/45) had a higher identification rate than Gram-positive cocci (93.3%, 70/75) and yeasts (75%, 3/4). The Rapid Sepsityper protocol displayed poor identification performance for polymicrobial samples.

Staphylococcus argenteus is an emerging pathogen that is recognized as non-pigmented Staphylococcus aureus. However, the molecular characteristics of S. argenteus and its virulence factors have not been well studied. The present study analyzed 96 isolates of S. argenteus recovered from blood. Identification of S. argenteus was based on results of MALDI-TOF MS and lacking crtM gene. All 96 isolates were methicillin-susceptible. Multilocus sequence typing (MLST) revealed four sequence types: ST2250 (n = 72), ST2793 (n = 12), ST1223 (n = 10), and ST2198 (n = 2). All 72 ST2250 isolates harbored CRISPR loci with polymorphism of direct repeats and spacers, but no other STs carried CRISPR loci. To date, ST2793 isolates have rarely been reported in other countries. Collagen-binding adhesin gene (cna) and staphylococcal enterotoxin type C (sec) were detected in 12 (100%) and 8 (67%) ST2793 isolates, respectively. ST1223 has been reported as food poisoning pathogens, and enterotoxin gene clusters (egc) were detected in all 10 isolates, while seb gene was detected in three isolates. Two ST2198 isolates carried bone sialoprotein-binding protein gene (bbp), belonging to agr type IV. Our focus on the heterogeneity of molecular characterization in four ST types of S. argenteus revealed that S. argenteus had been isolated as early as 2000. Each ST type of S. argenteus harbors particular genetic markers that may contribute to their virulence.

The increasing emergence of multidrug-resistant (MDR) bacteria has been recognized as a public health threat worldwide. Hospitalized patients and outpatients are commonly infected by non-fermenting Gram-negative bacilli (NFGNB), particularly the Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ACB) and Pseudomonas aeruginosa. Antimicrobial agents are critical for treating the nosocomial infections caused by NFGNB. The aim of this study was to assess antimicrobial resistance and the use of antimicrobial agents. The bacterial isolates of 638,152 specimens from both inpatients and outpatients, retrieved from 2001 to 2008 at a medical center in central Taiwan, were examined for their susceptibility to various antimicrobial agents, including cefepime, imipenem, ciprofloxacin, gentamicin, amikacin, meropenem, and levofloxacin. Administrated prescriptions of the monitored antibiotics were analyzed using the Taiwan National Health Insurance Research Database (NHIRD). Our results show that the defined daily doses (DDDs) for cefepime, imipenem, and ciprofloxacin increased with time, and a trend toward reduced antimicrobial sensitivities of both ACB and P. aeruginosa was noticeable. In conclusion, the antimicrobial sensitivities of ACB and P. aeruginosa were reduced with the increased use of antibiotics. Continuous surveillance of antibiotic prescriptions and the prevalence of emerging resistance in nosocomial infections is warranted.

A novel coagulase-negative Staphylococcus strain (NTUH-S172^T) was isolated from human blood culture in Taiwan with preliminary identification of Staphylococcus saprophyticus . 16S rRNA gene analysis and multilocus sequence analysis (MLSA) showed that NTUH-S172^T was most closely related to Staphylococcus haemolyticus . The average nucleotide identity and digital DNA–DNA hybridization values with the whole genome sequence were <95 % and<70 % when compared to the related species. Strain NTUH-S172^T could be distinguished from S. haemolyticus by urease production and from Staphylococcus borealis by nitrate reduction. In addition, the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) spectrum of NTHU-S172^T was significantly different from that of S. haemolyticus , which could be used in clinical identification. In conclusion, it is proposed that this isolate represents a novel species, named Staphylococcus taiwanensis sp. nov., with type strain NTUH-S172^T (=BCRC 81315^T=JCM 34726^T).

Cefiderocol (FDC) is a siderophore cephalosporin approved for the treatment of infections caused by multidrug-resistant Gram-negative bacilli (MDR-GNB), including carbapenem-resistant (CR) isolates. However, interpretation criteria for both broth microdilution (BMD) and disk diffusion (DD) methods differ among Clinical and Laboratory Standards Institute (CLSI), European Committee on Antimicrobial Susceptibility Testing (EUCAST), and U.S. Food and Drug Administration (FDA) guidelines. This study aimed to assess the categorical agreement (CA) between minimum inhibitory concentrations (MICs) determined by the BMD method and inhibition zone diameters measured by the DD method for FDC, using different interpretive breakpoints across various Gram-negative bacilli (GNB) isolates. A total of 1,170 GNB isolates were collected, including CR and carbapenem-susceptible (CS) isolates of Escherichia coli , Klebsiella pneumoniae , Klebsiella oxytoca , Enterobacter cloacae complex, Pseudomonas aeruginosa , and Acinetobacter baumannii-calcoaceticus complex. Isolates of Stenotrophomonas maltophilia , Burkholderia cepacia , and Elizabethkingia anophelis —which are not categorized by carbapenem susceptibility—were also included. The CA and error rates (minor error, major error, and very major error) were calculated using MIC interpretation as the reference. Among CR isolates, CA based on CLSI breakpoints ranged from 90.0% to 100% across species. U.S. FDA criteria showed comparable performance, except for A. baumannii-calcoaceticus complex, where CA was lower (63.0%). In contrast, EUCAST breakpoints demonstrated greater variability, with CA ranging from 66.7% to 100%. Among CS isolates, CA was generally high (≥87.5%) across most standards and species, with exceptions including EUCAST in the E. cloacae complex (63.0%) and U.S. FDA in A. baumannii-calcoaceticus complex (73.7%). In conclusion, CLSI breakpoints demonstrated the highest consistency between DD and BMD methods. IMPORTANCE: Cefiderocol is one of the few remaining treatment options for infections caused by carbapenem-resistant Gram-negative bacilli (GNB). Accurate interpretation of susceptibility testing is essential for guiding effective therapy. However, discrepancies among breakpoints established by the Clinical and Laboratory Standards Institute, the European Committee on Antimicrobial Susceptibility Testing, and the U.S. Food and Drug Administration may result in inconsistent interpretations, particularly when using the disk diffusion (DD) method, which is more practical in many clinical laboratories. This study compares the categorical agreement between broth microdilution and DD method interpretations for Gram-negative bacilli across multiple guidelines and highlights the potential for misclassification. It also provides susceptibility data for Burkholderia cepacia and Elizabethkingia anophelis , for which established interpretive criteria are currently lacking.

Sequence type 59 (ST59) is the dominant type of community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Previously, we reported that ST59 MRSA harbors enterococcal IS1216V-mediated multidrug-resistant composite transposons MES_PM1 or MES_6272-2. The MES were found to have a mosaic structure, largely originating in enterococci and partly native to S. aureus. The current study aimed to track the origin of the MES and how they disseminated from enterococci to ST59 S. aureus. A total of 270 enterococcal isolates were analyzed, showing that two ST64 Enterococcus faecalis isolated in 1992 and 11 clonal complex 17 Enterococcus faecium harbored MES_PM1-like and MES_6272-2-like structures, respectively. Sequence analysis revealed that ST64 E. faecalis strain N48 acquired the MES_PM1-like structure on the plasmid pEflis48. The pEflis48 harbored the enterococci-originated region (erythromycin, kanamycin, and streptomycin resistances) and the S.aureus-originated region (chloramphenicol resistance) of MES_PM1 but was separated by the replication region of the plasmid. Homologous recombination between the two direct repeats of IS1216V resulted in excision of the replication region of the plasmid to regenerate MES_PM1. The p4780-1 and pV19 of E. faecium carried MES_6272-2-like structures with IS1216V, albeit with multiple insertions by other insertion sequences. The findings show that IS1216V plays important roles in bidirectional gene transfer of multidrug resistance between enterococci and S. aureus.