Is Bordetella pertussis co-infecting SARS-CoV-2 patients?

Dear Editor,

Bordetella pertussis (B. pertussis) is a gram-negative respiratory coccobacillus that still represents a significant (yet largely preventable) cause of morbidity and mortality worldwide. It is well known that an infection with B. pertussis does not confer long-lasting protective immunity; this is also true in case of vaccination, as the antibody levels progressively wane. While B. pertussis is generally considered a potentially life-threatening agent in children with less than 3 months of life, there has been increasing evidence that other categories of patients can also be severely affected by the disease, especially seniors.

As a result, some authors have recently hypothesized the possibility of overlooking a coinfection with B. pertussis in patients diagnosed with SARS-CoV-2 pneumonia. The clinical symptoms of these two diseases are in fact partially overlapping; moreover, Bordetella pertussis infections are frequently associated with respiratory viruses, including other types of human coronaviruses.

Therefore, we aimed to screen for B. pertussis 10 adult patients admitted to the Intensive Care Unit (ICU) of our large tertiary university hospital for the management of severe SARS-CoV-2 pneumonia.

All patients underwent serologies for B. pertussis, while 8 were also screened through PCR assays on a nasopharyngeal swab, as molecular testing is the gold standard diagnostic for this disease. These patients were found to have negative PCR for B. pertussis DNA (Table 1). Furthermore, although the interpretation of Bordetella pertussis’ serologies is challenging in the vaccine era, there was no serologic evidence of recent infection in our cohort.

Table 1

Results of Bordetella pertussis testing in 10 COVID-19 patients admitted to the ICU.

Patient	DNA*	IgM§	IgG§	IgA§
1	NEG	2.2	18.8	2.7
2	NEG	9.1	2.1	1.5
3	NEG	3.6	10.9	6.4
4	NEG	0.9	2.5	1.9
5	NEG	6	48.1	2.6
6	NEG	0.5	27.6	7.9
7	–	3.9	5.9	4.5
8	–	0.6	2.9	3.8
9	NEG	1	10.1	3.9
10	NEG	1.3	10	6.5

PCR assays on nasopharyngeal swab.

Serological tests for B. pertussis.

Based on this limited, yet insightful experience, we believe that a coinfection with B. pertussis in patients affected by SARS-COV-2 is rather unlikely. Consequently, we would not recommend for these patients an extensive screening for B. pertussis.

Funding

None.

Authors’ contributions

All authors contributed equally to data collection and manuscript writing.

Conflicts of interest

The authors declare no conflicts of interest.