Final answer:
Serological testing, molecular analysis like PCR ribotyping, biochemical tests, and antibiotic susceptibility testing are recommended tools for identifying specific bacterial strains after species determination.
Step-by-step explanation:
The best diagnostic tools for identifying specific strains of bacteria after the species has already been determined include serological testing, molecular analysis such as PCR ribotyping, biochemical tests, and antibiotic susceptibility testing. Serological testing, including ELISA, is used to identify highly pathogenic strains, but it usually requires confirmation with DNA testing or culture. PCR ribotyping and rep-PCR are molecular techniques commonly used for strain identification, as they are precise and allow for the differentiation between strains at the genetic level. The use of biochemical tests, like those included in the various API strips, and antibiotic susceptibility tests can also yield a metabolic profile that may be used to identify specific bacterial strains. For example, S. aureus can be confirmed with a coagulase test, while E. coli, Salmonella, and Shigella can be differentiated using a TSI test.