EDITORIAL Accentuate the ( Gram ) positive

In the last two decades, Gram-positive bacteria have become the most common organisms associated with bacteremia and sepsis [1]. Moreover, clinically-significant resistance to each class of conventional antibiotics has been shown by at least one Gram-positive species, posing an additional public health challenge [2, 3]. In June 2009 in Stockholm, the 140th Nobel Symposium continued a traditional focus on scientific fields in which breakthroughs were occurring, and was dedicated to "Acute Infections Caused by Gram-Positive Bacteria". This lively forum, expertly chaired by Profs. Anna Norrby-Teglund of the Karolinska Institute and Gunnar Lindahl of Lund University, brought together renowned investigators from more than a dozen countries to present cutting edge investigations on the virulence mechanisms of the leading Gram-positive bacterial pathogens and their interactions with the human immune system. Many new collaboration were found and audiences of scientists, both young and established, were inspired to contemplate new opportunities for translational studies to address the ongoing medical challenges. This special issue of the Journal of Molecular Medicine presents eight invited topical reviews from featured speakers of the 140th Nobel Symposium to further showcase this exciting area of contemporary human infectious disease research. Streptococcus pneumoniae (SPN) is a leading agent of pneumonia, meningitis and sepsis throughout the world, affecting primarily those individuals at either extreme of the age spectrum. Recent analysis of World Health Organization data indicate that SPN is responsible for 11% of all deaths in children from 1 month to 5 years of age [4]. Coincidently, SPN has one of the most cherished histories in molecular biology research, being the experimental model in which Frederick Griffith demonstrated the principle of transformation [5] and in which Oswald Avery and colleagues demonstrated that DNA was the genetic material [6]. Like all the leading Gram-positive bacterial pathogens of humans, SPN commonly colonizes the human host without causing symptoms (carrier state) or generates milder, self-limited mucosal infections. The question of why bugs so innocent to most, can produce life-threatening invasive infections in a few, remains something of guiding paradox for researchers in the Gram-positive field. Jeffrey Weiser of the University of Pennsylvania proposes that many of the virulence factors promoting invasive SPN infection themselves provide adaptive advantages during the commensal state, either by meeting metabolic demands, resisting local mucosal immune responses, or allowing SPN to outcom-pete other members of the local flora [7]. The mechanisms of SPN invasion to produce lower respiratory tract, pneumonia, and …