Will cultures survive? The role of molecular tests in diagnostic bacteriology

PCR-based diagnostics for infectious diseases: uses, limitations, and future applications in acute-care settings

Molecular diagnostics are revolutionising the clinical practice of infectious disease. Their effects will be significant in acute-care settings where timely and accurate diagnostic tools are critical for patient treatment decisions and outcomes. PCR is the most well-developed molecular technique up to now, and has a wide range of already fulfilled, and potential, clinical applications, including specific or broad-spectrum pathogen detection, evaluation of emerging novel infections, surveillance, early detection of biothreat agents, and antimicrobial resistance profiling. PCR-based methods may also be cost effective relative to traditional testing procedures. Further advancement of technology is needed to improve automation, optimise detection sensitivity and specificity, and expand the capacity to detect multiple targets simultaneously (multiplexing). This review provides an up-to-date look at the general principles, diagnostic value, and limitations of the most current PCR-based platforms as they evolve from bench to bedside.

Sepsis Syndrome

A clinical syndrome including fever, leukocytosis, elevated cardiac output, and reduced systemic vascular resistance has been associated with severe infection (i.e., sepsis). However, during the last 15 years, many patients have demonstrated all of the findings that have traditionally been associated with “sepsis” but have not had demonstrated sources of infection. This led to the term “sepsis syndrome” to refer to that population of patients who appeared to have a physiologic and metabolic response associated with, but who did not have, severe infection. More commonly called the systemic inflammatory response syndrome (SIRS), the sepsis syndrome is now associated with the nonspecific systemic activation of the human inflammatory cascade by any of a number of clinical events. The management of the SIRS patient has been ineffective because of incomplete definition of the mechanisms responsible for the syndrome. It is argued that all of the biological mechanisms that are operative in a simple wound and are beneficial are negative for the host when activated systemically. Thus, SIRS is seen in three separate scenarios at present: (1) invasive infection; (2) dissemination of microbes secondary to failure of host defense mechanisms; and (3) severe activation of inflammation by injury, shock, severe soft tissue inflammation, and other noninfectious but proinflammatory events. Newer treatment strategies will need to focus not on the inciting event itself but on better control of the complex responses of the host.