Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases

Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases 9th edition PDF free download – The human microbiota can be defined as all microorganisms (approximately 90 trillion bacteria, archaea, eukaryotic microbes, and viruses) residing in the human body; the human microbiome consists of the genes and gene products (RNA, proteins, metabolites) produced by resident microbial communities. The advent of high-throughput DNA and RNA sequencing technologies and computational methodologies has enabled scientists to systematically catalog the global set of microorganisms—cultured and uncultured—in a heretofore unparalleled manner. Different body habitats contain microbial communities and microbiomes that differ by microbial composition and function (metabolic modules and pathways). As a result, each body habitat is composed of characteristic bacterial species and other microbial taxa that are adapted to each body site. Differences in microbial composition yield differences in metabolic capacity and aggregate function of the human microbiome. Traditional notions have been challenged, such as the ideas first put forth in Koch’s postulates, whereby microbes were viewed as pathogens and as sole etiologic agents of infectious diseases. Such a “foe” view neglects our earliest sightings of oral and fecal microbes with Anton van Leeuwenhoek’s microscopes, where it was observed that animalcules (microorganisms) reside in a symbiotic and likely mutually beneficial relationship with the host. We now appreciate that the microbial genome exceeds the human genome by at least 250-fold, and the cellular count of resident microbiota matches and slightly exceeds the human cell count.1 Our concepts regarding the relative abundance and ubiquity of diverse human pathogens are growing more profoundly with advances in the science of the human microbiome. Abundance refers to the relative quantity of microbes within each individual or body site, whereas ubiquity refers to the presence of the same microbes in different individuals.