%0 Journal Article
%T Q&A: What is a pathogen? A question that begs the point
%A Liise-anne Pirofski
%A Arturo Casadevall
%J BMC Biology
%D 2012
%I BioMed Central
%R 10.1186/1741-7007-10-6
%X Yes. But it's more complicated than that. First of all, a factor or product that confers pathogenicity in a normal host cannot be identified for many microbes. Second, properties conferring pathogenicity depend as much on the host as they do on the microorganism: encapsulated bacteria are pathogenic because they have a polysaccharide coat that prevents phagocytic cells from seeing them, and thereby avoid immediate elimination by the innate immune system of the host. Even toxins are damaging because they disrupt essential host functions. However, it was developments in the 20th century that clearly obliterated the hope of ever drawing a clear and unequivocal line of distinction between pathogens and non-pathogens. Beginning in the 1950s the introduction of broad spectrum antimicrobial agents, immunosuppressive therapies, newer types of surgery, including organ transplantation and joint replacement, implantable devices and indwelling catheters, each of which alters host-microbe interactions, turned out to create conditions in which the host became vulnerable to microbes that were previously considered non-pathogenic. As a result, it became apparent that many microbes previously considered non-pathogenic, or rarely pathogenic, such as Staphylococcus epidermis and Candida albicans, could cause serious disease.Right. Antibiotics make people more vulnerable to microbe-mediated damage because they alter the microbiota, or the normal microbial flora, and the balanced relationships between the microbes that reside in the mucosal niches in the body and the host structures that support these communities. Surgery can have the same effect by removing or altering normal mucosal and cutaneous barriers to infection. So the effects of antibiotics and surgery enhance the pathogenicity of microbes that do not ordinarily cause damage or disease in normal microbial communities, or intact mucosal and cutaneous surfaces, by making the host more susceptible to damage or invasion.In part. M
%U http://www.biomedcentral.com/1741-7007/10/6