API 20E Biochemical Test Strip Simulation

Biochemical Tests for Bacterial Identification

Colony morphology and Gram stain offer initial clues, but biochemical tests are often necessary for specific bacterial identification.
Biochemical tests assess a bacterium's enzymatic or metabolic capabilities.
These tests involve observing color changes or gas production when bacteria interact with specific chemicals.
A series of biochemical tests and a dichotomous key are used to identify bacterial species.

Miniaturized test strips are commercially available, reducing the time and cost of traditional methods.
Plastic test strips contain wells or "pockets" with chemical reagents.
Unknown microbes are cultured in broth and used to inoculate the test wells.
After incubation (4-24 hours), color changes indicate test results, which are compared to positive/negative controls.
Test results create a profile of the unknown organism, which is compared to a library of results for known organisms.
Test strips can have 10-20 tests.

The API 20E strip (Analytical Profile Index) is used for standardized identification of Enterobacteriaceae and other Gram-negative bacillus bacteria.
Prior to API 20E testing, Gram staining is typically performed to confirm the presence of Gram-negative bacteria.
The strip contains 20 microtubules with dried chemicals for 20 tests.
A liquid suspension of bacteria is added to each compartment to react with the chemicals.
After overnight incubation at 37 degrees Celsius, color changes are observed, and identification is made using charts of known bacterial species reactions.
The API test strip is discussed in the Microbiology OpenStax textbook in Chapter 8: Microbial Metabolism (pages 301-302).

The lab session involves using simulated bioMerieux API 20E test strip data to identify an unknown bacterial sample.
Students act as clinicians, using the API test strip and case study information to identify the bacterial species causing a patient's illness.