Laboratory diagnosis of pertussis: A survey on provincial public health laboratory methods

Pertussis, a vaccine preventable respiratory illness caused by the bacterium Bordetella pertussis (B. pertussis), has been a nationally reportable disease in Canada for over 100 years; however, cases resurged in Canada and globally in 2023-2024.

To examine the breadth and depth of pertussis strain surveillance currently being carried out across Canada.

A survey was sent to all ten provincial public health laboratories inquiring how pertussis was diagnosed or identified in the laboratory, including the polymerase chain reaction (PCR) diagnostic methods, bacteriological culture, identification and strain characterization such as molecular typing and antibiotic susceptibility testing.

Nine of the ten provincial laboratories provided responses. Five provincial laboratories reported performing bacteriological culture, and some only from specimens that tested positive by PCR. Long-term storage of submitted and historical specimens took place in six laboratories. Identification of B. pertussis was commonly done through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, though immunochemical and PCR-based methods were also used. One laboratory conducted antibiotic susceptibility testing in specific circumstances. No laboratory performed fimbriae serotyping or examined expression of other pertussis vaccine antigens. One laboratory used whole-genome sequencing for outbreak investigation. The PCR diagnostics were performed in eight of the responding laboratories and always include IS481 and pIS1001 gene targets. Some laboratories also reported using other gene targets to identify and distinguish between B. pertussis, B. parapertussis, B. holmesii and B. bronchiseptica.

Given the global increase in pertussis, with the emergence of macrolide-resistant and pertactin-deficient strains, strain characterization should be added to the Canadian national pertussis surveillance program.