Final answer:
If two microorganisms are mixed when inoculating an API strip, it would result in blended reactions making it difficult to accurately interpret results and identify the individual species.
Step-by-step explanation:
If two microorganisms (MOs) were growing on a MacConkey plate and both were inoculated into the saline when setting up the API strip, the results could be inaccurately represented. The API strip is designed to identify bacteria based on a series of biochemical tests, each producing a distinct reaction according to the bacterium's enzymes and metabolic characteristics.
If two different microorganisms are mixed, the resulting biochemical reactions would be a blend of the responses from both organisms, making it difficult to accurately interpret which reaction corresponds to which organism.
This co-inoculation could lead to erroneous identification because the API system relies on a database of known patterns of individual bacteria to determine the species. If multiple species are present, the pattern produced would not match the known patterns of any single species, potentially resulting in an incorrect identification.
For instance, if Micrococcus luteus and Enterococcus faecalis were both included in the inoculum for an API strip, one might see reactions indicative of both Gram-positive cocci and enterococci, thus confounding the test outcomes.
Therefore, it is vital to isolate individual colonies of a single microorganism prior to API strip inoculation to ensure accurate identification. In practice, to avoid such cross-contamination, microorganisms are typically isolated and purified through streaking on a suitable agar medium to obtain single colonies before being subjected to further identification procedures.