Comparison of pulsed field gel electrophoresis patterns of Bordetella pertussis isolates from unvaccinated children with severe or mild pertussis

Background. The clinical spectrum of pertussis ranges from mild cough illnesses of short duration to typical illness with paroxysmal cough, whooping and posttussive vomiting. We performed comparative genotyping of Bordetella pertussis isolates from children in Germany with severe or mild pertussis. Methods. Pulsed field gel electrophoresis (PFGE) of genomic DNA, digested with the restriction endonucleases XbaI and SpeI, was used to determine the profiles of strains isolated from 31 unvaccinated children with severe symptoms of pertussis (with hospitalization and/or complications) compared with isolates from 32 matched children with mild symptoms. Results. No significant differences in PFGE patterns were found in B. pertussis strains isolated from children with severe vs. mild illness. Conclusions. Differences in virulence of circulating B. pertussis strains can be absent or might not correlate with specific PFGE patterns. Other methods should be evaluated to identify differences in virulence.