Molecular identification of bacteria by fluorescence-based PCR-single- strand conformation polymorphism analysis of the 16S rRNA gene

Abstract

PCR-single-strand conformation polymorphism (PCR-SSCP) analysis is a rapid and convenient technique for the detection of mutations and allelic variants. We have adapted this technique for the identification of bacteria by PCR with fluorescein-labeled primers chosen from the conserved regions of the 16S rRNA gene flanking a variable region. The PCR product was denatured, separated on a nondenaturing gel, and detected by an automated DNA sequencer. The mobility of the single-stranded DNA is sequence dependent and allows the identification of a broad panel of bacteria. A single nucleotide difference in the amplified region was sufficient to obtain different PCR-SSCP patterns. The simultaneous amplification of multiple polymorphic regions by multiplex PCR with subsequent multiplex SSCP increased the discriminatory power of PCR- SSCP. A broad range of gram-negative and gram-positive bacteria were tested by PCR-SSCP, including, e.g., Escherichia coli, Enterobacter spp., Klebsiella spp., Haemophilus spp., Neisseria spp., Staphylococcus spp, Streptococcus spp., Enterococcus spp., and Bacillus spp. In total, a panel of 178 strains of bacteria representing 51 species in 21 genera was examined. Although a limited number of strains from each species were tested, the strains tested gave species-specific patterns, with only one exception: Shigella species were indistinguishable from E. coli. PCR is a sensitive technique; as few as 10 CFU of E. coli was sufficient to produce PCR-SSCP patterns suitable for identification. The whole fluorescence PCR-SSCP procedure takes approximately 8 h for the detection and identification of low numbers of bacteria. Fluorescence PCR-SSCP seems to be a promising method for the differentiation of a broad range of pathogens found in usually sterile clinical sites, such as blood and cerebrospinal fluid.