A novel, species-specific PCR assay for identifying Lactobacillus fermentum

Objectives:

Lactobacillus fermentum is a Gram-positive, anaerobic bacillus found in the oral cavity, gastrointestinal tract and female genital tract.  Traditional methods for identifying L. fermentum can be time-consuming, unreliable and often give rise to ambiguous results. The aims of this study were to develop a novel PCR assay specific for L. fermentum and apply this protocol to investigate the prevalence of this organism in clinical samples.

Methods:

PCR primers specific for L. fermentum were derived by comparing the 16S rRNA sequence of L. fermentum to the 16S rRNA sequences of other Lactobacillus species. Sequences unique at their 3’ ends to L. fermentum were identified and used as primers.  PCR was carried out on Lactobacillus type strains, oral bacterial type strains, supragingival plaque samples from healthy patients and archival pus samples from dentoalveolar abscesses.  The products were then analysed by agarose gel electrophoresis.

Results:

The specificity of the primers was demonstrated by amplification of a PCR product of 330-bp with L. fermentum and not with any of the test strains of Lactobacillus speciesor the other oral bacteria analysed.  None of the 36 supragingival plaque samples and 19 pus samples analysed were PCR-positive for L. fermentum.

Conclusions:

L. fermentum is rarely found in supragingival plaque of healthy subjects and is not an aetiological agent in dentoalveolar abscesses.  PCR is a rapid, specific and reliable method for the identification of L. fermentum and itsuse is also recommended in analysis of other types of clinical specimens for the presence of L. fermentum.