Background: Whooping cough is an acute respiratory disease caused by Bordetella pertussis. Despite developed vaccination programs, there has been a rise in pertussis notifications in Australia with an epidemic occurring between 2008 and 2012. The rise in incidence has been associated with pathogen adaption and the use of an acellular vaccine (ACV) that only targets 3-5 antigens. Recent studies have shown that B. pertussis readily forms biofilms, and this may lead to greater persistence in the respiratory tract. However, the proteins involved with biofilm formation and persistence in B. pertussis are not fully understood. The aim of this study was to use proteomic analysis to determine differences in protein expression between biofilm and planktonic cells of a recent Australian epidemic strain.
Method: L1423, a clinical isolate from the 2008-2012 Australian B. pertussis epidemic, was grown in THIJS media to 96 h in biofilm and 12 h in planktonic conditions. The proteins were extracted and label free liquid chromatography tandem mass spectrometry (LC-MS/MS) with spectral counts was used to identify and quantify the expressed proteins. Fold change < 0.8 and > 1.2 were considered downregulated and upregulated, respectively. Significance was assigned as p < 0.05 and q < 0.05.
Results and conclusion: There were 969 proteins identified with 590 proteins differentially expressed between biofilm and planktonic cells. There was a downregulation of proteins associated with de novo synthesis and an upregulation in central metabolism and nutrient transport in biofilms cells which may allow B. pertussis to persist under nutrient limiting conditions. Upregulation of toxins (pertussis toxin, dermonecrotic toxin and adenylate cyclase toxin) associated with immune modulation and downregulation of pertactin and type 3 secretion system proteins may increase immune evasion. Together, these proteomic changes in metabolism and virulence could increase the persistence of biofilm cells in the host.