Kate Johnson

September 22, 2015

SAN DIEGO — The recent increase in outbreaks of whooping cough might not be related to the common Bordetella pertussis pathogen, but instead to a lesser-known but related species, data from a recent Minnesota outbreak suggest.

Although Bordetella parapertussis has been shown to cause similar clinical manifestations, vaccination against B pertussis does not protect against B parapertussis, said Vytas Karalius, MPH, who is a medical student at the Mayo Clinic in Rochester, Minnesota.

"Symptoms alone may not enable a distinction between the two, which supports testing for both when a patient presents with whooping cough symptoms," Karalius explained here at the Interscience Conference of Antimicrobial Agents and Chemotherapy 2015.

Karalius and his colleagues conducted an analysis of all patients at the Mayo Clinic tested for both B pertussis and B parapertussis from 2012 to 2014. All tests were done using nasopharyngeal swabs and real-time polymerase chain reaction (PCR) assays.

During the final quarter of 2014, there was a marked increase in the rate of B parapertussis infection.

Parapertussis on the Rise

"There were 31 cases in 2014, and 25 of them — 81% — were between the months of October and December," Karalius reported.

The average age of the patients was 6 years, although two patients were younger than 1 year, and 20% reported exposure to pertussis.

The fact that symptoms were similar to those of pertussis underscores the importance of specific testing.

"Not all tests for pertussis detect B parapertussis," said senior author Robin Patel, MD, also from the Mayo Clinic. If patients are being assessed for B pertussis and B parapertussis, then the test used should detect both, she told Medscape Medical News.

For the 25 patients treated for B parapertussis during the last quarter of 2014, the mean duration of symptoms before the diagnostic visit was 2.6 weeks.

Table. Clinical Presentation of B parapertussis

Clinical Presentation Percent
Posttussive vomiting 40
Coryza 40
Apnea or sleep disturbance 32
Sore throat 12


"It's important to know that 100% of our patients were vaccinated against B pertussis, leading us to believe that vaccination is not protective against B parapertussis," Karalius reported. "It may be beneficial to consider targeting B parapertussis in the development of future vaccines."

These findings might have something to do with the switch from the whole-cell to the acellular form of the pertussis vaccine, said session moderator Keith Klugman, MD, PhD, from Emory University in Atlanta.

"In theory, the whole-cell vaccine previously used in the United States, and still used in developing countries, could offer some protection against parapertussis," he told Medscape Medical News.

Mr Karalius and Dr Klugman have disclosed no relevant financial relationships. Dr Patel reports holding patents on PCR assays for B pertussis and B parapertussis.

Interscience Conference of Antimicrobial Agents and Chemotherapy (ICAAC) 2015. Presented September 18, 2015.


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