Simplifying Microbiological Testing

The technology is based on monitoring changes in the chemical characteristics of a microbial liquid growth medium in which the target microorganisms grow and are detected by optically sensitive reagents (color or fluorescence). The reagents change their spectral patterns as metabolic processes take place. These changes are detected by optical sensors and monitored at predetermined time intervals. The key to the technology is the monitoring of these changes in a detection zone found at the bottom of the test vial and separated from an incubation zone by a membrane or porous material, thereby eliminating the masking of the optical pathway by the product and microbial turbidity. The signal is relatively constant until the numbers of microorganisms reach a threshold value; thereafter, there are accelerating changes in the color and fluorescence signals.

The sensitivity of the BioLumix system is a single viable cell of bacterium or fungi per sample vial. One bacterial cell is usually detected in 8-14 hours while a single yeast cell can be detected in 20-24 hours. Although the system can detect as little as one cell per vial, organisms must first grow to a level exceeding a pre-determined, specific detection threshold. That threshold for bacteria is ~100,000 cells/ml and the threshold for yeast/mold is ~10,000 cells/ml. The time to detection depends on the initial concentration of organisms in the product sample. Therefore, highly contaminated samples rapidly detect, providing rapid warning of contamination.

A wide array of tests are available, including total viable count (or total aerobic count), coliform, E. coli, the combined testing of coliform and E. coli in a single vial, yeast, mold, lactic acid bacteria, Enterobacteriaceae, sanitation monitoring, shelf-life predictions, challenge test, and spoilage flora. The organisms can be incubated in the BioLumix instrument at predetermined temperatures from 15°C to 65°C, enabling optimal growth of a variety of flora.

The BioLumix system has direct applications with foods (meat, dairy, seafood, beverages, salad dressings, chocolate, desserts, frozen foods, fruits and vegetables, and soy products), cosmetic and toiletry (shampoos, detergents, tooth paste, creams, lotions, etc), nutraceuticals, and applications in non-sterile pharmaceutical products.

For liquid products, 1 to 5 ml of product (depending on the test) can be added directly to the test vial. For solid products, 1 to 5 ml of a 1:10 dilution (depending on the test) can be added directly to the vial.

It only takes 3 easy steps to perform a test: (1) Inoculate the ready-to-use vial with the sample, swab, or filter; (2) Place the vial in the BioLumix instrument; and, (3) record the sample in the Windows®-based software.

Most vials have a shelf life of 6 months at room temperature. Some supplements may need to be refrigerated.

The BioLumix instrument is capable of conducting 32 concurrent tests at a single temperature. Up to 32 instruments can be attached to one computer. There is random access to each location and various assays can be run in the same instrument. Each instrument has the shape of a drawer and each drawer of 32 tests has independent temperature control. All instruments can have a temperature test range of 15-65 +/-0.2°C. The physical size of the BioLumix instrument is 16cm x 36cm x 65cm (6¼” x 14½” x 26¾”) and weighs 10 kg (22 pounds).

A standard curve or calibration can be prepared for a given product or group of products if the products are processed similarly and are expected to have the same flora.

Presence/absence endpoints may be applied if few organisms are expected (<10 CFU). In that case, calibration is not recommended. A more simple approach using the presence/absence endpoint is performed after the product has been diluted in appropriate detection medium.

Dilute-to-specification protocol requires diluting the sample to the specification limit required for product action or release. If there is growth, the sample fails; if there is no detection the sample passes, since the counts are below the specification limit.

Functional sterility includes the type of test where there is no allowable number of microorganisms and the product is not expected to contain any living cells. Therefore, in a functional sterility application, a pre-incubation time is incorporated into the protocol. The pre-incubation time is based on the target microflora. After pre-incubation, a sub-sample of the pre-incubation broth is transferred to vials containing the appropriate growth medium for testing.