Rapid an Accurate Detection of Whooping Cough in Clinical Samples with the Vivalytic Bordetella

Background

Despite a high vaccination coverage in the EU, whooping cough is not only present in Europe, but is dramatically on the rise in the post-pandemic era. Several countries reported outbreaks or increasing numbers in 2023/24^1,2:

• Denmark: Infection cases 4-fold higher in 2023 (compared to 2022)
• Spain: Infection cases 7-fold higher in 2023 (compared to 2022)
• United Kingdom: 553 cases in January 2024 (2023 858 per annum; 7-fold)
• Croatia: 6.261 cases reported in the first 3 months in 2024

The main cause of whooping cough is Bordetella pertussis (Bpt), however, Bordetella parapertussis (Bpa) and Bordetella holmesii (Bho) can also cause infection. Therefore, rapid and accurate diagnostic tools are still necessary for their detection in clinical specimen. The Vivalytic instrument is a new PCR platform using either multiplex RT PCR or microarray for detection of nucleic acids from microbes. The easy-to use cartridge system can be applied in the micro lab or as point-of-care test (POCT).

Methods

411 nasopharyngeal specimens (all in Copan eNAT™ swabs) collected from symptomatic patients in Croatia were tested in our lab.
All 411 samples were pre-characterized with the reference test.
In addition, we received 11 positive samples from a hospital in Split (Croatia).
To accurately validate the new Vivalytic Bordetella assay (Bosch Healthcare Solutions, Waiblingen, Germany) we used 150 spiked samples:
50 samples of each virulent species Bordetella pertussis (Bpt), B. parapertussis (Bpa) and B. holmesii (Bho) were spiked with 3 different inocula, low, medium and high (20/50/200 10e3 copies/mL). All 561 samples were compared to the Bordetella Speciation Plus Toxin-OSR (BioGX, Amsterdam/NL) as reference test, which also covers all three virulent Bordetella species. To achieve comparable results both tests were performed within 72 hours.
Discrepant results were tested with a third party test: RIDA Gene Bordetella.

Results

In the 411 Croatian samples we detected 10 Bordetella positive specimens with Vivalytic (2,4%) and 8 with BioGX assay (1,9%).
The Vivalytic Bordetella cartridge showed a very high concordance to the reference test 97.7% The positive percent agreement (PPA) was 97.9%. As the positivity rate of the specimen set was rather low, we received additional positive samples (n=11) from a hospital in Split (Croatia). All swabs gave positive results for Bordetella pertussis in the Vivalytic, 100% PPA. Within the 150 spiked samples the PPA was >98% for all tests and >95% for the challenging low inocula samples. Time-to result was only 45min for the Vivalytic test compared to 150min for the comparator assay.
The rate of invalid results of the Vivalytic assay was very low 0,6%.

Conclusion

The Vivalytic Bordetella cartridge demonstrated excellent concordance with a sensitive reference test and delivered accurate and rapid results. The assay is suitable for hospital labs and for outpatients’ settings due to its easy use and short time-to report.
Easy-to use PCR systems with rapid results are suitable also for smaller hospitals and outpatient department. Early identification of infected patients will help to intercept transmission of the current re-emerging whooping cough epidemics.

¹ECDC Weekly Communicable Disease Threats Report, Week 51/2023
²Smout E., etal.; BMJ 2024: 385:q736, epub 02 April 2024