Microbial ecology of a specimen is evaluated using an approach (Level I) that utilizes nucleic acid amplification with specific gene primers that will identify panels of microorganisms and antibiotic-resistance factors generating a diagnostic report (optionally with quantification of each microorganism or antibiotic-resistance factor) and an approach (Level II) that utilizes universal or semi-universal primers to amplify conserved genes at a general or specific taxonomic level that are tagged specimen specifically using a genetic or chemical marker that is specific to the specimen from which it was derived, then sequencing the amplified products with highly-parallel, high-throughput technology to provide comprehensive sequences of the microbial population in the specimen followed by analysis of this sequence information and specific targeted information from Level I and/or Level II to generate a comprehensive analysis, interpretation, and/or diagnostic report.