1670Comparative Metagenomics of Polymicrobial Surface Organisms and Their Invasive Monomicrobial Analogs Indicates the Rate of Genetic Alterations in the Infectious Organisms not Influenced by the Local Microbiome

Background. Why only some bacteria isolated from mixed populations predominate or become infectious is incompletely understood, although ecological interactions of communities of bacteria referred to as the microbiome is gaining popularity as one explanation. We hypothesized that whole genome mapping (WGM) and sequencing (WGS) could reveal metagenomic differences pertinent to this phenomenon. Methods. From a collection of >20,000 isolates and clinical data, we identified patients who had the same species isolated from both a sterile site such as blood (monoculture), and a non-sterile (polymicrobial) site such as a wound or surveillance culture. These ‘paired isolates’ then underwent WGM and WGS to determine if genomic rearrangements and/or single nucleotide changes occur more frequently in pathogens isolates from mixed vs pure infection habitats. Results. WGM of 18 paired isolates did not reveal larger genomic rearrangements more frequently in polymicrobial than monomicrobial cultures. Further supporting these data at higher resolution, WGS did not reveal more subtle (i.e., single nucleotide variations (SNV) or point mutations) that were intrinsic to the pathogen or influenced by the ecology of the surrounding bacterial community. On rare cases, a stretch of DNA was found unique to an individual isolate within a pair, but this finding is not enough to substantiate a claim that presence of a pathogen in a microbiome environment is correlated with heritable genetic alterations relative to monoculture sites. There were no significant genomic differences between polymicrobial surface organisms and their invasive monomicrobial analogs. Conclusion. Interactions between the pathogen and the greater bacterial population did not influence the frequency in which large scale genomic rearrangements, SNVs, or point mutations accumulated. Rather, our data suggests that the influence of other nearby organisms on the pathogen was minor, if any, and supports the notion that pathogenicity is inborn to the organism itself regardless of the surrounding community. Disclosures. All authors: No reported disclosures.