Diagnosis of bacterial vaginosis by a new multiplex peptide nucleic acid fluorescence in situ hybridization method

PeerJ. 2015 Feb 17;3:e780. doi: 10.7717/peerj.780. eCollection 2015.


Bacterial vaginosis (BV) is one of most common vaginal infections. However, its diagnosis by classical methods reveals low specificity. Our goal was to evaluate the accuracy diagnosis of 150 vaginal samples with research gold standard methods and our Peptide Nucleic Acid (PNA) probes by Fluorescence in situ Hybridization (FISH) methodology. Also, we described the first PNA-FISH methodology for BV diagnosis, which provides results in approximately 3 h. The results showed a sensitivity of 84.6% (95% confidence interval (CI), from 64.3 to 95.0%) and a specificity of 97.6% (95% CI [92.6-99.4%]), demonstrating the higher specificity of the PNA-FISH method and showing false positive results in BV diagnosis commonly obtained by the classical methods. This methodology combines the specificity of PNA probes for Lactobacillus species and G. vaginalis visualization and the calculation of the microscopic field by Nugent score, allowing a trustful evaluation of the bacteria present in vaginal microflora and avoiding the occurrence of misleading diagnostics. Therefore, the PNA-FISH methodology represents a valuable alternative for BV diagnosis.

Keywords: Bacterial vaginosis; Biofilms; Fluorescence in situ hybridization (FISH); Gardnerella vaginalis; Lactobacillus spp.; Peptide Nucleic Acid Probe (PNA probe).

Grant support

This work was supported by European Union funds (FEDER/COMPETE) and by national funds (FCT) under the project FCOMP-01-0124-FEDER-008991 (PTDC/BIA-MIC/098228/2008). António Machado was funded by the FCT individual fellowship SFRH/BD/62375/2009. Other fundings came from the FCT Strategic Project PEst-OE/EQB/LA0023/2013, the Project NORTE-07-0124-FEDER-000027, co-funded by the Programa Operacional Regional do Norte (ON.2–O Novo Norte), QREN, FEDER, and the project FCOMP-01-0124-FEDER-008991 (RECI/BBB-EBI/0179/2012). Nuno Cerca is an Investigador FCT (Portuguese national funds). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.