Clinical Manifestations and Molecular Characterization of Pertactin-deficient and Pertactin-producing Bordetella pertussis in Children, Philadelphia 2007 – 2014.

B. pertussis strains lacking expression of pertactin, a bacterial adhesin and vaccine target, are emerging. There are limited data on disease manifestations of mutant strains in children. We sought to compare clinical manifestations of pertactin-deficient and pertactin-producing B. pertussis infection in infants and describe corresponding molecular characteristics.
METHODS:
 Molecular characterization of archived B. pertussis isolates (January 2007 – March 2014) included Western blot analysis, pulse-field gel electrophoresis (PFGE), PCR and pertactin gene sequencing. Medical record review compared epidemiologic and clinical courses of pertactin-producing and pertactin-deficient B. pertussis infections.
RESULTS:
 60 of 72 B. pertussis isolates were viable for analysis. Cohort median age was 95 days, 90% received ≤1 dose of vaccine, 72% were hospitalized. Pertactin deficiency was first noted in 2008 and increased over time (68% overall prevalence). There were no statistically significant differences in presenting symptoms/signs, hospitalization, intensive care, respiratory support or laboratory results related to pertactin expression. Illness length was shorter in pertactin-deficient group (mean difference 3.2 days, p=0.04); no difference was noted in subgroup of infants <4 months. Molecular analyses identified 11 PFGE profiles (CDC002 predominant, 47%). In 41 pertactin-deficient strains, sequencing identified 2 STOP codon and 3 IS481 locations disrupting the prn gene. Mutations and nucleotide positions were not unique to PFGE type, nor clustered in time.
CONCLUSIONS:
 In this cohort of predominantly unimmunized infants, clinical disease was not different for infection with pertactin-deficient or pertactin-producing B. pertussis. Molecular analyses demonstrated remarkable PFGE strain diversity, with multiple mechanisms and molecular sites of pertactin inactivation.

Authors:Vodzak J1, Queenan AM2, Souder E1, Evangelista AT3, Long SS1.
Journal:Clin Infect Dis. 2016
Link:http://www.ncbi.nlm.nih.gov/pubmed/27624959