Clinical Implications of Bacteremia Caused by Non- Compared with Those of Bacteremia.

This study aimed to compare clinical characteristics, antimicrobial susceptibility, and 28-day mortality between patients with bacteremia (ABB) and non- bacteremia (NBAB) after rapid matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) species identification. We retrospectively reviewed the clinical data of adult ABB and NBAB patients over >7 years. Multivariate logistic regression was used to identify the risk factors for 28-day mortality. Of 273 episodes of species bacteremia, 224 (82.1%) were ABB and 49 (17.9%) were NBAB. NBA isolates were predominantly (49%), with smaller proportions of , , , and others. The primary sites of infection in NBAB cases were the intra-abdomen, urinary tract, intravascular catheters, and lungs. While only 4.0% of isolates were susceptible to carbapenem, 87.8% of non- isolates were susceptible. Multivariate analysis revealed that low carbapenem resistance was independently associated with NBAB. Additionally, a higher Pitt bacteremia score, septic shock, continuous renal replacement therapy, inappropriate empirical antibiotic therapy, and thrombocytopenia were independent risk factors for the 28-day mortality in patients with ABB. Although less common than ABB, NBAB cases are increasing and exhibit lower carbapenem resistance. Rapid MALDI-TOF MS identification enables timely and appropriate antibiotic treatment. The key factors driving the 28-day mortality include illness severity, septic shock, renal replacement therapy, inappropriate antibiotics, and thrombocytopenia, highlighting the need for early risk assessments and tailored management. Ongoing surveillance and species-specific strategies are essential for combating resistant infections.