Azithromycin versus penicillin for early syphilis.

n engl j med 354;2 www.nejm.org january 12, 2006 203 is likely to be the cause of bacterial vaginosis and that Koch’s postulates for disease causation are inadequate for describing potential causal relationships in this syndrome. Bacterial vaginosis probably results from infection with complex communities of bacteria that consist of metabolically interdependent (syntrophic) species. Diseases caused by uncultivated microbes or communities of microbes are not amenable to the application of Koch’s postulates in their original formulation2; therefore, we must build a case for causation on the basis of a concordance of scientific evidence.3 David N. Fredricks, M.D.