Researchers detect evolutionary changes in the causative agent of pertussis in Barcelona

The research groups of Microbiology and Epidemiology and Public Health at the Vall d'Hebron Research Institute (VHIR) presented at the XX Congress of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) the results of a study assessing the possible causes for the increase in whooping cough (pertussis) in the Metropolitan Area of Barcelona. The research, which received the award for the best communication of the congress, stressed that in recent years there have been noticeable changes in the organism that might have affected the resurgence of the disease.

The winning paper examines the evolution of molecular epidemiology and antigenic profile of clinical isolates of Bordetella pertussis, which is the bacteria that causes whooping cough, an acute respiratory illness with a high capacity of transmission by air. The results revealed that from 2007 to 2015 mainly coexisted two populations of this bacterium: the first, which was the most prevalent until 2010, when it was gradually replaced by the second, which is currently circulating in our environment. This latter population is what caused in 2015 the number of cases to triple compared to the previous year.

The study's lead author, Dr. Juanjo González, emphasized that one of the most important results observed is that "the bacterium that causes whooping cough might have to adapt to the protective effect induced by acellular vaccine (DTPa) administered since 1998". In this sense, one of the main causes that are postulated that could be involved in the resurgence of whooping cough is the adaptation of B. pertussis to change their antigenic structures. This amendment would have allowed it to escape immunity induced by the vaccine DTPa, which was introduced in the immunization schedule in the late 90s, replacing the complete inactivated cell that was used until then and that showed adverse reactogenic effects. Coinciding with this change of vaccine, it has been observed how the reported cases of the disease have been progressively increasing.

Most cases of whooping cough are diagnosed in paediatric patients, but is particularly acute in children under 3 months of age. In these babies can be given particularly serious cases that require advanced life support and which can generate important consequences that persist throughout life. Despite being a disease that can be prevented with vaccination, it has one of the highest rates of incidence among all diseases preventable by immunization.

The study involved doctors Juanjo González Gema Codina, Maite Martín and Tomàs Pumarola from the research group and the Microbiology Service of the Hospital Vall d'Hebron Barcelona Campus, and with the collaboration of Dr. Magda Campins from the Service and Research Group of Preventive Medicine at Vall d'Hebron, and Dr. Mireia Jané, head of the Office of Surveillance and Emergency Response of the Public Health Agency of Catalonia. The work was presented by VHIR's researcher Alba Mir Cros, who is doing his doctoral thesis under the direction of Dr. González, in the conference which took place from 26 to 28 May in Barcelona.