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 Biochemical Tests

• 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.

API 20E Test Strip

• 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).

Lab Session Simulation

• 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.