Rapid Microbiological Methods and the PAT Initiative - Numerous new RMM systems are available to replace traditional testing methods - BioPharm International


Rapid Microbiological Methods and the PAT Initiative
Numerous new RMM systems are available to replace traditional testing methods

BioPharm International
Volume 18, Issue 12

Colorimetric Detection of Carbon Dioxide Production

Type of Technology: Growth-based.

Premise of Technology: As microorganisms grow, they produce carbon dioxide. In this technology, the test samples are placed in culture bottles for monitoring. The samples are incubated, agitated, and monitored for the presence of microorganisms. These systems use colorimetric detection of CO2 production from the growth of organisms. Some of the systems commercially available detect color change, flag a positive test sample, and notify the user. These systems are often considered to be non-invasive microbial detection systems and can accommodate a large number of samples. Although these systems are commonly used clinically for blood cultures, Genzyme received approval from the FDA in 2004 to use this method (with the BacT/Alert System) for sterility testing.

Commercial Systems Available: BacT/Alert (bioMerieux) and ESP Microbial Detection System (AccuMed).

Other: This technology may be useful for slow-growing organisms, e.g., mycobacteria.7

Concentric Arcs of Photovoltaic Detectors with Laser Scanning

Type of Technology: Combination.

Premise of Technology: The system comprises five concentric arcs of photovoltaic detectors, in an orb-like platform. The sample being evaluated is suspended in a liquid or gas inside a vial or sample collection device, which is placed near the center of the orb. A laser beam of red, solid-state composition is passed through the sample. The scattered light intensities generate a spectrum that is compared to a library of known scatter patterns, i.e., using a statistical classification algorithm. Contamination can be identified in seconds. This light-scattering pattern becomes a fingerprint-type of identification for the microorganism. The pattern includes the size of the particle, the shape of the particle, and the optical characteristics. Light patterns are evaluated at multiple angles to detect and differentiate the size of the microorganism almost instantaneously. Identification occurs within a few milliseconds after the particle passes through the beam.9

Commercial Systems Available: MIT System (MicroImaging Technologies, Inc.).

Other: This system was recently granted a US patent. Product claims include enumeration of microorganisms present, determination of the size of microorganisms present, identification of the microorganisms, and the ability to handle mixed cultures.9


Type of Technology: Growth-based.

Premise of Technology: This is similar to impedance methods, with measurement taken in conductance.

Commercial Systems Available: Bactometer (bioMerieux), BacTrac (Sy-Lab), RABIT (Don Whitley Scientific Ltd), and the Malthus Microbial Detection System (Malthus Diagnostics, Inc.).

Conventional Methods with Computer-Aided Imaging

Type of Technology: Growth-based.

Premise of Technology: Many conventional methods for processing samples can be used for testing, and using advanced image-analysis software can significantly reduce the incubation and enumeration time required. Commercial software programs are available that can be customized for use with current methods. With this technology, images are collected using a charge-coupled device camera. The collected images are digitized on a computer, using image processing software that has programming capabilities (alternatively, some systems collect the data directly with a digital camera); the digitized picture is processed to detect colonies present, and the separated colonies are counted. Depending on the system used, one can obtain movie-like presentations of colony growth, overgrowth, and confluence, if present. These systems use either a fluorescent staining procedure, cellular epifluorescence, or autofluorescence as a method of cellular detection. This technology can be used as a series of commercially available products used together to achieve the desired enumeration, or as a combined industrialized (automated) system that performs these tasks.

Commercial Systems Available: COVASIAM10 (University of Mexico) and Growth Direct (Genomic Profiling Systems).

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