Melting of the Ribosomal RNA Gene Reveals Bacterial Species Identity: A Step toward a New Rapid Test in Clinical Microbiology

Abstract

Effective treatment of bacterial infections ideally requires the rapid and accurate detection and identification of the causative organism. Among the procedures currently used in clinical microbiology laboratories, the most precise method of detecting bacteria is growth in a culture. Although at least 8 h of incubation are required, diagnostic culture indicates the presence of living and therefore potentially infectious organisms and provides the material for subsequent antibiotic susceptibility testing. Starting with a pure culture or single colonies of the grown organisms, species identification is usually accomplished by a comprehensive determination of phenotypic profiles including Gram stain results, morphology, growth requirements, biochemical or biophysical properties, and when available, specific antigen or agglutination tests. This method has been automated over the past few years and has become a cost-effective way to identify the majority of bacterial pathogens. Because most of the phenotypic and biochemical properties are determined by the metabolism of actively growing cells, analysis requires a considerable number of pure organisms, and differentiation down to species level may require hours or days of subculture in the presence of various substrates and/or selective media. For slow-growing or nonreactive bacterial species, the results are often delayed. Moreover, accurate identification is compromised when common bacterial species present with uncommon phenotypes, or when unusual species are encountered whose phenotypic profiles are not yet covered by the database. The advent of in vitro nucleic acid amplification and, more recently, the introduction of rapid-cycle real-time PCR technology has led to substantial improvements in the diagnosis of infectious disease (1)(2). By eliminating the need for subculturing the target organisms before their definitive identification, nucleic acid amplification– based procedures can provide highly desired same-day results, and genotypic methods have evolved as objective, rapid, and accurate ways for bacterial species identification in modern clinical microbiology. Driven by a …