Sepsis, severe sepsis and septic shock, systemic inflammatory response, and other related manifestations represent a relevant medical problem with high morbidity and mortality, despite the improvements in diagnosis, treatment, and preventive measures over the last few decades. The limited knowledge of the pathophysiology in association with the lack of in vitro diagnostic methods for the certain and quick determination of the causative microbiological agents and their antibiotic resistance means the condition is still critical and of high impact in health care. The current gold standard method to detect the sepsis-causing pathogens, which is based on blood culture, is still insufficiently sensitive and slow. The new culture-independent molecular biology-based techniques can lead to the identification of a broad range of microorganisms and resistance markers within a few hours and with high sensitivity and specificity; nevertheless, limitations of, for example, the polymerase chain reaction-based methods still hamper their application in the clinical routine. This review summarizes the in vitro diagnostic methods and their approach in the clinical diagnosis of the bloodstream infections, and explores their advantages and disadvantages at the current state of the art. A quick analysis of the future prospective in multiplex technologies for microbiological diagnosis of sepsis is also provided.