The goal of this clinical trial is to learn whether close microbiological monitoring without preventive antibiotics works as well as preventive treatment with ceftriaxone in adults receiving stem cell transplants. The study focuses on people with blood cancers or other conditions who need either autologous or allogeneic hematopoietic stem cell transplantation (HSCT). The main questions the study aims to answer are: What percentage of participants develop an infection when they do not receive preventive antibiotics compared with those who receive daily ceftriaxone? Does preventive ceftriaxone lower the chance of specific complications such as bloodstream infections, pneumonia, or severe sepsis? Researchers will compare two groups: one group will not receive preventive antibiotics one group will receive ceftriaxone once a day until their white blood cells recover or until signs of infection appear All participants will: have their body temperature monitored continuously starting one day before the transplant have blood, urine, or other samples collected if they develop fever or symptoms of infection receive standard medical care during and after the transplant start standard antibiotic treatment if they develop signs of infection This study will include 100 adults. The information collected will help determine whether skipping preventive antibiotics is safe in hospitals where bacteria often show resistance to commonly used drugs such as fluoroquinolones.